http://www.eetindia.com/CAT_1800006_networkinghttp://www.eetindia.com/CA T_1800006_networkingdesign.HTM?refer=google_cpc&gclid=CMHE9ueB6Y4CFQfIbgodJmYODQ ref:- http://en.wikipedia.org/wiki/Computer_network#Definition A computer network is composed of multiple connected computers that communicate over a wired or wireless medium to share data and other resources. For instance, a home computer network may consist of two or more computers that share files and a printer using the network. The size and scalability of any computer network are determined both by the physical medium of communication and by the software controlling the communication (i.e., the protocols the protocols). ). Computer networks may be classified according to the network topology upon which the network is based, such as Bus network , Star network , Ring network , Mesh network , Star bus network , Tree or Hierarchical topology network , etc. Network Topology Topology signifies the way in which intelligent devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, hu b, the network has a Star topology topolog y, rather than a Bus Topology. Topology. In this regard the visual and operational characteristics of a network are distinct.
By network layer Computer networks may be classified according to the network layer at which they operate according to some basic b asic reference models that are considered to be standards in the industry such as the seven layer OSI layer OSI reference model and the four layer Internet layer Internet Protocol Suite model. In practice, the great majority of networks use the Internet Protocol (IP) as their network layer. Some networks, however, h owever, are using IP Version Version 6 IPv6 IPv6,, usually in coexistence with IPv4 IPv4.. IPv6 use is often experimental. it is an interconnection of a group of computers in other words. A network as simple as two computers linked with a crossover cable has several points at which the network could fail: either network interface, and the cable. La rge networks, without careful design, can have many points at which a single failure could cou ld disable the network. When networks are critical the general rule is that they should have no single point of failure. The broad factors that can bring down networks, according to the Software Engineering Institute [3] at Carnegie-Mellon University: 1. Attacks : these include software attacks by various miscreants (e.g., malicious hackers, computer criminals) as well as physical destruction of facilities. 2. Failures: these are in no way wa y deliberate, but range from human error in entering commands, bugs in network element executable code, failures of electronic
components, and other things that involve deliberate human action or system design. 3. Accidents : Ranging from spilling coffee into a network element to a natural disaster or war that destroys a data center, these are largely unpredictable events. Survivability from severe accidents will require physically diverse, redundant facilities. Among the extreme protections against both accidents and attacks are airborne command posts and communications relays[4], which either are continuously in the air, or take off on warning. In like manner, systems of communications satellites may have standby spares in space, which can be activated and brought into the constellation.
Why Networking ?? Network Criteria Networking Basics a.) LAN(Local Area Network) b.) MAN(Metropolitan Area Network) c.) WAN(Wide Area Network) Types of Connection Topologies Transmission Media N/W Interface Card N/W Connectivity Devices • •
• • • • •
• • • • • • • • •
INTRODUCTION NEED OF NETWORKS NETWORK CLASSIFICATION CLASSIFICATION NETWORK DEVICES NETWORK TOPOLOGIES NETWORK SOFTWARE APPLICATIONS CONCLUSION BIBLIOGRAPHY
A computer computer network is a system for communication among two or o r more computers. TOPICS TO BE COVERED • • • •
INTRODUCTION TYPES TOPOLOGIES OSI MODEL
• • • •
HARDWARE PROTOCOLS SECURITY(FIREWALL) FUTURE ASPECTSRED
NETWORKING & NETWORK COMPONENTS • • • • • • • •
INTRODUCTION TYPES OF NETWORK NETWORK RELATIONSHIP RELATIONSHIP FEATURES OF NETWORK OSI MODEL NETWORK HARDWARE COMPONENT CONCLUSION BIBLIOGRAPHY
FUTURE ASPECTS OF NETWORKING NEEDS OF NETWORKING 1 - RESOURCE SHARING . 2 - HIGH RELIABILITY . 3 - COMMUNICATION MEDIUM
CONTENTS: • • • • •
VIRTUAL PRIVATE NETWORK(VPN) GIGABIT ETHERNET COMMON USES ADVANTAGES DISADVANTAGES
http://freecomputerebooks.blogspot.com/2007/05/free-computer-networking-ebooks.html http://more-networking.blogspot.com/2007/02/computer-networks-and-internets.html
There are many different computing and networking technologies -- some available today, today, some just now emerging, some well-proven, some quite experimental. Understanding the computing dilemma more completely involves
recognizing technologies; especially since a single technology by itself seldom suffices, and instead, multiple technologies are usually necessary n ecessary.. This document describes a sampling of technologies of various types, by using a tutorial approach. It compares the technologies available in the thre e major technology areas: application support, transport networks, and subnetworking. In addition, the applicability of these technologies within a particular situation is illustrated using a set of typical customer situations. This document can be used by consultants and system designers to better understand, from a business and technical perspective, the options available to solve customers' networking problems.
http://basic-networking.blogspot.com/2007/08/computer-network-devices-andcomponent.html
A Computer network is comprised of different devices to share, transmit, and boost the signal, voice and data. Network devices or components are the physical parts connected to a network. There is a large number of the network devices and are increasing daily. The basic network devices are: Individual Computers, Server Server,, Hub Hub,, Switch Switch,, Bridges Bridges,, Routers Routers,, Modems Modems,, Printers, DSL Modems & Routers, Gateways Gateways,, Network Interface Cards, Cards , Cabling & Wireless access point. point . The following is a overview of each of these network devices. INDIVIDUAL COMPUTERS: The personal computer is usually a desktop computer, a work station or a laptop. The personal computers are most widely used in any organization or for personal use. The individual computers are the most common types of the microcomputers. SERVER: A server is a computer on a network, which process request and is used to share the data and resources among the other computers in a network. A server stores all the necessary information and provides the different services like, workstation computer’s logon access, internet sharing, print sharing, disk space sharing etc. There are different types of servers e.g File and print server, database server, proxy server, Fax server, backup server etc. A database server stores all the data and software, which may related to the certain database and it allows other network devices to access and process the database queries. A file server is used to store the data of any user on the network and a print server manages one or more printers in a network. Similarly a network server is a server
that manages the network traffic. NETWORK INTERFACE CARD: CARD : Network interface cards are attached with the computer or other network devices and are used to provide the connectivity between the two computers. Each network card is specifically designed for the different types of the network like Ethernet, FDDI, Token Ring and Wireless Networks. The Network card operates on the first and second layers of the OSI models i.e Physical layer and datalink layer specifications. NIC basically defines the physical connection methods and the control signals that provides the timings of the data transfer over the network. HUBS:: Hub is a simplest network device. The function of the hub is broadcasting HUBS i.e data is forwarded towards the all ports of a hub, regardless of whether the data was intended for the particular systems in the network or not. Computers in a network are connected to a hub with a twisted pair (CAT5) cables. There are two types of the hubs. 1. Active Hubs. 2. Passive Hubs. SWITCHING HUB: The Switching hub (also called “switch” is the most advance shape of the basic hub. In a basic hub all the computers are connected with the hub and the speed of the network is defined by the slowest computer network card connected. For example if you have 10/100 Mbps cards in a network and only one card of 10Mbps speed then the system cannot run faster than the 10 Mbps. Now if you have a switching hub in a network, it will allow all the faster connections in the network to remain at the higher speed and still interact with the 10Mbps system. SWITCHES: Switch is a intelligence device than hub. Switch is a layer 2 device. Swith provides the same function as a hub or a bridge but it has the advance functionality of connecting the two computers together temporarily. Switch contains the switch matrix or switch fabric that can connect and disconnect ports. Unlike hubs, switch only transmit or forwards the data to the destined computer and it does not broadcasts the data to all its ports. MODEMS: Modems are the devices, which are used to translate the digital data into the analog format and vice versa. It performs the two main functions. Modulation and demodulation. A modulated data can travel across the
conventional telephone lines. The modem modulates the signals at the sending end and demodulates at the receiving end. Modems are required for different types of the access methods such ISDN, DSL and 56K data modem. Modem can be the internal devices that plug into the expansion slots in a system or can be external devices that plug into the serial or USB ports. ports . In Laptops, PCMCIA cards are used for this purpose and many new laptops having the built in integrated modems. The specialized devices are designed for use in the systems such as handheld computers. In ISPs where the large scaled modems are required, rackmounted modems are used. ROUTERS: Routers route the data between two logically and physically different networks. A Router has the capability to determine the destination address for the data and hence provides the best way for the data to continue its journey. Router gets this capability through its software called routing software. Unlike Switches and Bridges, which use hardware configured MAC address to determine the destination of the data, router uses logical network address such as IP address to make the decision in determining the destination of the data. GATEWAY: A gateway performs the function of translating the data from one format to another format without changing the data itself. A gateway can be a device, system, software. A computer with two NIC cards can function as a gateway. Router acts as a gateway e.g a router that routes the data from a IPX network to a IP network is technically a gateway. The same can be said of translational switch converts from a Ethernet network to a token ring network. CABLES: There are two most common types of the cables. 1. 10baseT and 10base2. 10baseT is a four paired cable. 10baseT has further two types 1. UTP (unshielded twisted pair) and 2. STP (shielded twisted pair. STP is most secure cable covered with the silver coated twisted paper to protect the cable. On the other end Thin 10base2 looks like the copper coaxial cabling that often used to connect TV sets and VCR. 10baseT/Cat5 cables are most commonly used cables to connect the computers. It has the connector, (like a telephone connector) called RJ45 connector. Twisted pair cables are ideal for the small, medium or large networks.
http://en.wikipedia.org/wiki/Computer_network#By_network_topology By network layer Computer networks may be classified according to the network layer at which they operate according to some basic b asic reference models that are considered to be standards in the industry such as the seven layer OSI layer OSI reference model and the four layer Internet layer Internet Protocol Suite model. In practice, the great majority of networks use the Internet Protocol (IP) as their network layer. Some networks, however, h owever, are using IP Version Version 6 IPv6 IPv6,, usually in coexistence with IPv4 IPv4.. IPv6 use is often experimental. it is an interconnection of a group of computers in other words. A network as simple as two computers linked with a crossover cable has several points at which the network could fail: either network interface, and the cable. La rge networks, without careful design, can have many points at which a single failure could cou ld disable the network. When networks are critical the general rule is that they should have no single point of failure. The broad factors that can bring down networks, according to the Software Engineering Institute [1] at Carnegie-Mellon University: 1. Attacks : these include software attacks by various miscreants (e.g., malicious hackers, computer criminals) as well as physical destruction of facilities. 2. Failures: these are in no way wa y deliberate, but range from human error in entering commands, bugs in network element executable code, failures of electronic components, and other things that involve deliberate human action or system design. 3. Accidents : Ranging from spilling coffee into a network element to a natural disaster or war that destroys a data center, these are largely unpredictable events. Survivability from severe accidents will require physically diverse, redundant facilities. Among the extreme protections against both accidents and attacks are airborne command posts and communications relays[2], which either are continuously in the air, or take off on warning. In like manner, systems of communications satellites may have standby spares in space, which can be activated and brought into the constellation.
[edit edit]] Dealing with Power Failures One obvious form of failure is the loss of electrical power. Depending on the criticality and budget of the network, protection from power failures can range from simple filters against excessive voltage spikes, to consumer-grade Uninterruptible Power Supplies(UPS) Supplies (UPS) that can protect against loss of commercial power for a few minutes, to independent generators with large battery banks. Critical installations may switch from commercial to internal power in the event of a brownout,where the voltage level is below
the normal minimum level specified for the system. Systems supplied with three-phase electric power also suffer brownouts if one or more phases are absent, at reduced voltage, or incorrectly phased. Such malfunctions are particularly damaging to electric motors. Some brownouts, called voltage reductions, are made intentionally to prevent a full power outage. Some network elements operate in a manner to protect themselves and shut down gracefully in the event of a loss of power. These might include noncritical application and network management servers, but not true network elements such as routers routers.. UPS may provide a signal called the "Power-Good" signal. Its purpose is to tell the computer all is well with the power supply and that the computer can continue to operate normally. If the Power-Good signal is not present, the computer shuts down. The Power-Good signal prevents the computer from attempting to operate on improper voltages and damaging itself To help standardize approaches to power failures, the Advanced Configuration and Power Interface (ACPI) specification is an open industry standard first released in December 1996 developed by HP, HP, Intel, Microsoft, Phoenix and a nd Toshiba Toshiba that defines common interfaces for hardware recognition, motherboard and device configuration and power management.
[edit edit]] By scale Computer networks may be classified according to the scale: Personal Area Network (PAN),, Local Area Network , Campus Area Network , Metropolitan area network (MAN), (PAN) network (MAN), or Wide or Wide area network (W network (WAN). AN). As Ethernet increasingly is the standard interface to networks, these distinctions are more important to the network administrator than the end user. Network administrators administrators may have to tune the network, based on delay dela y that derives from distance, to achieve the desired Quality of Service (QoS). Controller Area Networks are a special niche, as in control of a vehicle's engine, a boat's electronics, or a set of factory robots.
[edit edit]] By connection method Computer networks may be classified according to the hardware technology that is used to connect the individual devices in the network such as Ethernet Ethernet,, Wireless LAN, LAN, HomePNA,, or Power HomePNA or Power line communication. communication.
[edit edit]] By functional relationship Computer networks may be classified according to the functional relationships which exist between the elements of the network, for example Active Networking, Networking, Client-server and Peer-to-peer Peer-to-peer (workgroup) (workgroup) architectures.
[edit edit]] By network topology
Main article: Network article: Network Topology Computer networks may be classified according to the network topology upon which the network is based, such as Bus network , Star network , Ring network , Mesh network , Star bus network , Tree or Hierarchical topology network , etc. Network Topology Topology signifies the way in which intelligent devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, hu b, the network has a Star topology topolog y, rather than a Bus Topology. Topology. In this regard the visual and operational characteristics of a network are distinct.
[edit edit]] By protocol Computer networks may be classified according to the communications protocol that is being used on the network. See the articles on List of network protocol stacks and List of network protocols for more information.
[ edit edit ] Types of networks: Below is a list of the most common types of computer networks in order of scale.
[edit edit]] Personal Area Network (PAN) Main article: Personal article: Personal area network A personal area network (PAN) (PAN) is a computer co mputer network used for communication among computer devices (including telephones and an d personal digital assistants) close to one person. The devices may or may not belong to the person in question. q uestion. The reach of a PAN PAN is typically a few meters. PANs PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink). Personal area networks may be wired with computer buses such as USB and FireWire FireWire.. A wireless personal area network (WPAN) (WPAN) can also be made possible po ssible with network technologies such as IrDA and Bluetooth Bluetooth..
[edit edit]] Local Area Network (LAN) Main article: Local article: Local Area Network A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on o n Ethernet technology. The defining characteristics of LANs, in contrast to WANs WANs (wide area networks), include their much higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines.
Hosts can be made part pa rt of a specific LAN can be defined by setting their address to one within the address range of the LAN subnet This can be done by manual configuration, or by configuring DHCP DHCPDynamic Dynamic Host Configuration Protocol autoconfiguration to give the host an address in the appropriate range. Currently standardized LAN technologies operate at speeds up to 10 Gbit/s. IEEE has projects investigating the standardization of 100 Gbit/s, and possibly 40 Gbit/s. Inverse multiplexing is commonly used to build a faster aggregate from slower physical streams, such as bringing 4 Gbit/s aggregate stream into a computer or network element with four 1 Gbit/s interfaces.
[edit edit]] Campus Area Network (CAN) Main article: Campus Area Network A network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus , industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN, so it is called a CAN. This term is most often used to discuss the implementation of networks for a contiguous area. In the past, when layer 2 switching (i.e., bridging (i.e., bridging (networking) was cheaper than routing,, campuses were good candidates routing ca ndidates for layer 2 networks, until they grew to very large size. Today, Today, a campus may use a mixture of routing and bridging. The network elements used, called "campus switches", tend to be optimized to have many Ethernet interfaces rather than an arbitrary mixture of Ethernet and WAN WAN interfaces.
[edit edit]] Metropolitan Area Network (MAN) Main article: Metropolitan Area Network A network that connects two or more Local Area Networks or CAN together but does not extend beyond the boundaries bo undaries of the immediate town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN
[edit edit]] Wide Area Network (WAN) Main article: Wide Area Network A WAN WAN is a data d ata communications network that covers a relatively broad geographic area (i.e. one country to another and one continent to another continent) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN WAN technologies generally function at the lower three layers of the OSI reference model: model: the physical layer , the data link layer , and the network layer .
The highest data rate commercially available, as a single bitstream, on WANs WANs is 40 Gbit/s, principally used between large service providers. Wavelength Division Multiplexing,, however, can put multiple 10 or 40 Gbyte/s Multiplexing Gb yte/s streams onto the same optical fiber.
[edit edit]] Global Area Network (GAN) Main article: Global Area Network Global area networks (GAN) specifications are in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is "handing off" the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial Wir Wireless eless local area a rea networks (WLAN) is the [3]. INMARSAT has defined a satellite-based Broadband Global Area Network (BGAN). Network (BGAN). IEEE mobility efforts focus on the data link layer and make assumptions about the media. Mobile IP is a network layer technique, developed by the IETF IETF,, which is independent of the media type and can ca n run over different media while still keeping the con nection.
[edit edit]] Internetwork Main article: Internetwork article: Internetwork Two or more networks or network segments connected using devices that operate at layer 3 (the 'network' layer) of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, com, or governmental networks may also be defined as an internetwork. In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them: • • •
Intranet Extranet "The" Internet
Intranets and extranets may or may not have hav e connections to the Internet. If connected conn ected to the Internet, the intranet or extranet is normally n ormally protected from being accessed from the Internet without proper authorization. The Internet itself is not considered to be a part of the intranet or extranet, although the Internet may serve as a portal for access to portions of an extranet.
[edit edit]] Intranet Main article: Intranet article: Intranet
An intranet is a set of interconnected networks, using the Internet Protocol and uses IP based tools such as web browsers, that is under the control of a single a dministrative entity. entity. That administrative entity closes the intranet to the rest of the world, and an d allows only specific users. Most commonly, an intranet is the internal network of a company or other enterprise.
[edit edit]] Extranet Main article: Extranet article: Extranet A extranet is network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, usually, but not necessarily, necessarily, trusted organizations or entities (e.g., a compan y's customers may be provided access to some part of its intranet thusly creating an extranet while at the same time the customers may not be b e considered 'trusted' from a security standpoint). Technically, echnically, an extranet may also be categorized as a CAN, MAN, WAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN, because an extranet must have at least one connection with an outside network.
[edit edit]] Internet, The Main article: Internet article: Internet A specific internetwork, consisting of a worldwide interconnection of governmental, academic, public, and private networks based upon the Advanced Research Projects Agency Network (ARP Network (ARPANET) ANET) developed by ARPA of the of the U.S. Department of Defense – also home to the World Wide Web (WWW) and referred to as the 'Internet' with a capital 'I' to distinguish it from other generic internetworks. obtained from address registries that control assignments. Service providers and large enterprises also exchange information on the reachability of their address ranges through the Border Gateway Protocol. Protocol.
[ edit edit ] Basic Hardware Components All networks are made up of o f basic hardware building blocks to interconnect network nodes,, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In nodes addition, some method of connecting conn ecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). cable). Less common are microwave links (as in IEEE 802.11) 802.11) or optical cable ("optical ("optical fiber "). ").
[edit edit]] Network Interface Cards Main article: Network article: Network card A network card, network adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer
n etworking medium and provides a low-level network . It provides physical access to a networking addressing system through the use of MAC of MAC addresses. addresses. It allows users to connect to each e ach other either by b y using cables or wirelessly.
[edit edit]] Repeaters Main article: Repeater article: Repeater A Because repeaters work with the actual physical signal, and do not attempt to interpret the data being transmitted, they operate on the Physical layer, the first layer of the OSI model.BY model .BY HAYTECH
[edit edit]] Hubs Main article: Network article: Network hub A hub contains multiple ports. When a packet arrives at one port, it is c opied the packets to all the ports of the hub. When the packets are copied, the destination address in the frame does not change to a broadcast address. It does this in a rudimentary way, way, it simply [4] copies the data to all of the Nodes connected to the hub.
[edit edit]] Bridges Main article: Network article: Network bridge A network bridge connects multiple network segments at the data link layer (layer layer (layer 2) of the OSI model. model. Bridges do not promiscuously copy traffic to all ports, as does a hub. but learns which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received. Bridges learn the association of ports and addresses ad dresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived. Bridges come in three basic types: t ypes: 1. Local bridges: bridges: Directl Directly y connect connect local local area area networks networks (LANs) (LANs) 2. Remote bridges bridges:: Can be used used to create create a wide area networ network k (WAN) (WAN) link link between between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced by routers. 3. Wireless ireless bridges: bridges: Can be used used to join join LANs or connect connect remote remote stations stations to LANs LANs
[edit edit]] Switches Main article: Network article: Network switch Switches are a marketing term that encompasses routers and b ridges, as well as devices that may distribute traffic on load or by application content (e.g., a WebURL Web URL identifier). Switches may operate at one or more OSI layers, including physical including physical,, data link , network , or transport or transport (i.e., end-to-end). end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch. switch. Overemphasizing the ill-defined term "switch" often leads to confusion when first trying to understand networking. Many experienced network designers and operators recommend starting with the logic of devices dev ices dealing with only one protocol level, not all of which are covered by OSI. Multilayer device selection is an advanced topic that may lead to selecting particular implementations, but multilayer switching is simply not a realworld design concept.
[edit edit]] Routers Main article: Router article: Router Routers are the networking device that forwards data packets along networks by using headers and forwarding tables to determine the best path to forward the packets. pack ets. Routers work at the network layer (layer layer (layer 3) of the OSI model. model. Routers also provide interconnectivity between like and unlike media.[5] This is accomplished by examining the Header of a data packet.[6] They use routing protocols such as Open Shortest Path First (OSPF) to communicate with each other and configure the best route between any two hosts. A router is connected to at least two networks, commonly two LANs or WANs WANs or a LAN and its ISP's network. Some DSL and Cable Modems have been integrated with routers for home consumers.
[ edit edit ] Building a simple computer network A simple computer network may be constructed from two computers by adding a network adapter (( Network adapter Network Interface Controller (NIC)) (NIC) ) to each computer and then connecting them together with a special cable called a crossover cable. cable. This type of network is useful for transferring information between two computers that are not normally connec ted to each other by a permanent network connection or for basic home networking applications. Alternatively, Alternatively, a network between two computers can be established without dedicated extra hardware by using a standard connection such as the RS-232 serial port on both computers, connecting them to each other via a special crosslinked null modem cable. Practical networks generally consist of more than two interconnected computers and generally require special devices in addition to the Network Interface Controller that each computer needs to be equipped with. Examples of some of these special devices are hubs, switches and routers.
[ edit edit ] Ancillary equipment used by networks To keep a network operating, to diagnose failures or degradation, and to circumvent problems, networks may have a wide-ranging amount of ancillary equipment.
[edit edit]] Providing Electrical Power Individual network components may have surge protectors - an appliance designed to protect electrical devices from voltage spikes. Surge protectors attempt to regulate the voltage supplied to an electric device by either blocking or shorting to ground voltage above a safe threshold.[5] Beyond the surge protector, network elements may have uninterruptible power supplies (UPS),, which can be anywhere from a line-charged battery to take the element through a (UPS) brief power dropout, to an extensive network of generators and large battery banks that can protect the network for hours or days of commercial power outages.
[edit edit]] Monitoring and Diagnostic Equipment Networks, depending on their criticality and the skill set available among the operators, may have a variety of temporarily or permanently conne cted performance meaasurement and diagnostic equipment. Routers and bridges intended more for the enterprise or ISP market than home use, for example, usually record the amount of traffic and errors experienced on their interfaces. Diagnostic equipment, to isolate failures, may be nothing more complicated than a spare piece of equipment. If the problem disappears when the spare is manually replaced, the problem has been diagnosed. More sophisticated and expensive installations will have spare elements that can automatically replace a failed unit. Failures can be made transparent to user computers with techniques such as the Vi Virtual rtual Router Redundancy Red undancy Protocol (VRRP), as specified in RFC 3768. 3768.
http://more-networking.blogspot.com/2007/02/networking-fundamentals-v40.html
Networking Fundamentals, v4.0 By Brian Brown Networks are an interconnection of computers. These computers can be linked together using a wide variety varie ty of different cabling types, and for a wide variety of different purposes. The basis reasons why computers are networked are
•
•
•
to share resources (files, printers, modems, fax machines) to share application software (MS Office) increase productivity (make it easier to share data amongst users)
Take for example a typical office scenario where a number of users in a small business require access to common information. As long as all user computers are connected via a network, they can share their files, exchange mail, schedule meetings, send faxes and print documents all from any point of the network. It would not be necessary for users to transfer files via electronic mail or floppy disk, rather, rather, each user could access all the information they require, r equire, thus leading to less wasted time and hence he nce greater productivity. productivity. Imagine the benefits of a user being able to directly di rectly fax the Word document they are working on, rather than print it out, then feed it into the fax machine, dial the number etc. Small networks are o often ften called Local Area Networks [LAN]. A LAN is a network allowing easy access to other computers or peripherals. The typical characteristics of a LAN are, •
•
•
•
•
physically limited ( less than 2km) high bandwidth (greater than 1mbps) inexpensive cable media (coax or twisted pair) data and hardware sharing between users owned by the user
http://physinfo.ulb.ac.be/cit_courseware/networks/default.htm,, http://physinfo.ulb.ac.be/cit_courseware/networks/default.htm
BASIC NETWORK CONCEPTS Networks are an interconnection of computers. These computers can be linked together using a wide variety of different cabling types, and for a wide variety of different purposes. The basis reasons why computers are networked are • • •
to share resources (files, printers, modems, fax machines) to share application software (MS Office) increase productivity (make it easier to share data amongst users)
Take for example a typical office scenario where a number of users in a small business require access to common information. As long as all user computers are connec ted via a network, they can share their files, exchange mail, schedule meetings, send faxes and print documents all from any point of the network.
It would not be necessary nece ssary for users to transfer files via electronic mail or floppy disk, rather, each user could access all the information they require, thus leading to less wasted time and hence hen ce greater productivity. Imagine the benefits of a user being be ing able to directly fax the Word Word document they are working on, rather than print it out, then feed it into the fax machine, dial the number etc. Small networks are often called Local Area Networks [LAN]. A LAN is a network allowing easy access to other computers or peripherals. The typical characteristics of a LAN are, • • • • •
physically limited (< 2km) high bandwidth (> 1mbps) inexpensive cable media (coax or twisted pair) data and hardware sharing between users owned by the user
BASIC NETWORK COMPONENTS There are a number of components which are used to build networks. An understanding of these is essential in order to support networks. This is a discussion on some of the elements which make up a network [LAN].
Network Adapter Cards A network adapter card plugs into the workstation, providing the conn ection to the network. Adapter cards come from many different manufacturers, and support a wide variety of cable media and bus types [ISA, MCA, EISA, PCI, PCMCIA]. For an explanation about various bus types, click here. click here.
New cards are software configurable, using a software program to configure the resources used by the card. Other cards are PNP [plug and Play], which automatically configure their resources when installed in the computer, co mputer, simplifying simplifying installation. With an operating system like Windows 95, auto-detection of new hardware makes network connections simple and quick. On power-up, the computer detects the new ne w network card, assigns the correct resources to it, and then installs the networking software required for c onnection to the network. All the user need do is assign the network details like computer name. For Ethernet or 10BaseT or 10BaseT cards, each card is identified by a twelve digit hexadecimal number. This number uniquely identifies the computer. These network card numbers are used in the Medium Access [MAC] Layer to identify the destination for the data. When talking to another computer, the data you send to that computer is prefixed with the number of the card you are sending the data to. This allows intermediate devices in the network to decide in which direction the data should go, in order to transport the data to its correct destination. A typical adapter card looks like,
A PCMCIA adapter card, suitable for connecting to a portable laptop computer to a network, looks like,
Peripheral cards associated with EISA and MCA are are normally self configuring. The major problem arises with cards for the ISA bus (found in the majority of AT AT type computers and clones). This is because the cards are configured by the user (using either jumpers or a software program). Users make mistakes, and often configure cards so that they conflict with other cards already present in this system. This causes intermittent or immediate non-operation of the computer system. For instance, a networking card that is allocated the same resources as a serial communications program may function perfectly, except when the user is logged into the network and then tries to use the serial port, at which time the machine will crash. Resources Used By Peripheral Cards We have already mentioned that resources used by ISA peripheral cards must not be shared (two cards cannot use the same). So what are the resources used by peripheral cards? Essentially, Essentially, there are FOUR resources which are user configurable for peripheral cards. Some cards may only use one (a port location(s)), others may require all four.
The FOUR resources are 1. Input/Output Port Address In the PC, the port numbers used by peripheral cards range from 200h to 3FFh. The I/O port address is used by the PC to communicate with the peripheral card (issue commands, read responses, and perform data transfer). 2. Interrupt Request Line The interrupt request line is used by the card ca rd to signal the processor that the card requires the processors attention. ISA peripherals cannot share the same interrupt request line, and IRQ2 in AT/2386/486 AT/2386/486 computers should not n ot be used (there are others which must also not be used). IRQ2 to IRQ15 appear on the ISA bus. bus. 3. Direct Memory Request Line The DMA request line is used to transfer data between the peripheral card a nd the computers memory at high speed. DMA channel 0 cannot be used, as it is reserved for system use. 4. Buffer Memory Address Some peripheral cards prefer to use memory space rather than an I/O port address to transfer data to the processor. This memory space occupied by the peripheral card appears in the main system memory RAM area available to the processor (usually between C0000h to EFFFFh). Care must be taken to ensure this space is not being used for other purposes pu rposes (like shadow RAM, EMS for windows, VBGA BIOS). This space is also sometimes used by a remote b oot Eprom, which is used for diskless workstations which download the operating system from the server at boot time.
So How Do Peripheral Cards Work? Peripheral cards require a software driver to function. This software driver provides the interface between the card and the operating system, making the services provided by the card available to the user.
The software driver is normally configured to match the resource settings of the card. This is done by a con figuration utility, utility, and stored either in the executable file, or a separate file (like .ini or .cfg). It is obviously important for the configuration settings in the software driver to match those configured on the peripheral card. The resources used by the card are either set by jumpers (or slide switches). New cards can also be configured using a software program, rather than by manually setting jumpers on the card. Where cards are software configurable, the cards retain their configuration when the power is turned off. The software driver provides the follow functions • • • •
initialization routine interrupt service routine procedures to transmit and receive data procedures for status, configuration and control
The basic operation looks something like, • • • • •
card receives data card generates interrupt by asserting interrupt request line processor responds to interrupt request and jumps to service routine service routine instructs processor to read data from port location interrupt service routine releases processor to continue previous work
The major problem is assigning values va lues of these resources which are already being used by either the system or another peripheral card . It is therefore handy to know what the resources are which are used by common peripheral devices. The following tables identify these. Common I/O Port Addresses
Port Port Addre Address ss Periph Periphera erall 200-207h
Game I/ I/O Ad Adaptor
210-217h
XT Expansion Unit
220h
SoundBlaster
278-27Fh
LPT2
2E8-2EFh
COM4
2F8-2FFh
COM2
30000-30F 30Fh
Color Video Adaptor
320-32F
XT Hard Disk
330h
SoundBlaster MIDI
378-37Fh
LPT1
3A03A0-3A 3A9h 9h
IBM IBM Syn Synch chro rono nous us Adap Adapto tor r
3B03B0-3B 3BF Fh
Monoc onochr hrom omee Video ideo
3E8-3EFh
COM3
3F0-3F7h
Floppy Di Disk
3F8-3FFh
COM1
Common Interrupts
IRQ Line Line Periph Periphera erall 2
EGA/VGA
3
COM2
4
COM1
5
LPT2, Bus mouse, Network
6
Floppy Disk
7
LPT1
13
Co-Processor
14
AT Disk Controller Common Memory Addresses
Address
Peripheral
A0000A0000-BFF BFFFF FFh h EGA/VG EGA/VGA A B0000-B B0000-B7FF 7FFFh Fh Monochr Monochrome ome B8000 B8000-B -BFF FFFF FFh h CGA CGA C8000-C C8000-CFF FFFFh FFh XT Disk Disk F4000F4000-FF FFFF FFFh Fh AT ROM BIOS BIOS F8000F8000-FF FFFF FFFh Fh PC/XT PC/XT ROM BIOS BIOS Common DMA Lines
DMA Line Periph Periphera erall
0
Memory Circuitry
1
Spare
2
Floppy Drive
Installing A Peripheral Card This section discusses basic techniques for installing peripheral cards. By following standardized procedures, this will help to minimize damage to the system or peripheral card, and reduce the possibility of incorrect installation.
1. Determine the resources used by the computer Use the previous tables to determine the interrupts, memory and port addresses used by the current hardware in the computer. 2. Read the install manual Check the disk for a read.me file (and read it). Read the manual and take note of the jumper switches used by the card. Identify where these are located on the card. 3. Determine resources to be used by the card Allocate resources to the card which do not conflict with existing hardware. 4. Observe electrostatic protection in handling the card Use a wrist strap and ground yourself properly before handling the card. Handle the card by the edges. Do not touch the components or edge connector. Use electrostatic bags or an electrostatic mat. 5. Configure the card jumpers Set the jumpers on the card 6. Insert the card Remove the system base unit cover and insert the card into a spare peripheral bus slot. Observe electrostatic precautions. 7. Load the software driver If the card was provided with a software driver, install the software driver. This might involve running an INSTALL INSTALL program, or copying the drivers to the hard disk. It might also mean adding the driver name to the config.sys file (DEVICE=xxxxx.sys). 8. Configure the driver software If the driver software needs to be configured (specify which resources the card is using), this information might be stored in a separate file (.ini or .cfg). Often, when installing the software, it will ask for configuration details. These must be the same as the hardware jumpers used by the card. 9. Test card (run diagnostics where provided) If the card was provided with diagnostic software, run that now to test the card and driver. This is a good way to test if the installation was done correctly. 10. Test the machine Test some of the other software packages on the system (like networking, serial communications and printing) to see if they still work. If they don't, this indicates a probable conflict con flict of resources. In Windows 95 or NT, run the diagnostic program to check for interrupt and resource conflicts (MSD or WINMSD). WINMSD).
Summary of Installing Network Cards in Servers and Workstations • • • • • •
ISA cards are a problem check what resources are already being used do not share resources between two cards interrupts can only be shared on EISA and MCA cards run the diagnostics software after installation if the computer hangs, remove one board at a time until the problem disappears
Brief Guide to BUILDING WIRING The following is a very brief overview of the components that make up the wiring standards for commercial buildings. The objectives of such standards is to •
• •
define a generic voice and an d data wiring system that is multi-purpose and multivendor help minimize cost of administration simplify network maintenance and changes
A building wiring system covers a number nu mber of different elements • •
horizontal wiring backbone wiring
Horizontal Wiring The horizontal wiring extends from the wall outlet to the system center (telecommunications closet). It includes the • • •
the wall outlet the horizontal cable cables used to interconnect components componen ts [cross-connects or patch cables] in the telecommunications closet (TC)
Some general features of the horizontal wiring scheme are • • • • • •
uses star star topology topology limit of 90 meters (295') from TC to wall outlet limit of 3 meters (10') to connect from wall outlet to PC patch cords and cross-connect leads are limited to 6 meters (20') minimum of two outlets per user (phone+data) standardized media, Outlet A=4pair 100ohm UTP, UTP, Outlet B=same or 2 pair 150ohm STP
Backbone Wiring The backbone wiring system interconnects telecommunication closets, equipment rooms and entrance facilities (i.e., the outside world). Some general features are • • •
• •
star topology maximum of two hierarchical levels interconnections between any two TC must not go through more than 3 cross connects use of recognized media adherence to distance limitations
BRIDGES Bridges interconnect Ethernet segments. Most bridges today support filtering and forwarding, as well as Spanning Tree Algorithm. The IEEE 802.1D specification is the standard for bridges.
During initialization, the bridge learns about the network and the routes. Packets are passed onto other network segments based on the MAC layer. Each time the bridge is presented with a frame, the source address is stored. The bridge builds up a table wh ich identifies the segment to which the device is located on. This internal table is then used to determine which segment incoming frames should be forwarded to. The size of this table is important, especially if the network has a large number o f workstations/servers. The advantages of bridges are • •
•
•
•
•
increase the number of attached workstations and network segments since bridges buffer frames, it is possible to interconnect different segments which use different MAC protocols since bridges work at the MAC layer, they are transparent to higher level protocols by subdividing the LAN into smaller segments, overall reliability is increased and the network becomes easier to maintain used for non routable protocols like NETBEUI like NETBEUI which must be bridged [see also here]] here help localize network traffic by only forwarding data onto other segments as required (unlike repeaters)
The disadvantages of bridges are • • •
•
•
the buffering of frames introduces network delays bridges may overload during periods of high traffic bridges which combine different MAC protocols require the frames to be modified before transmission onto the new segment. This causes delays in complex networks, data may be sent over redundant paths, and the shortest path is not always taken bridges pass on broadcasts, giving rise to broadcast storms on the network
Transparent bridges bridge s (also known as spanning tree, IEEE 802.1 D) make all routing decisions. The bridge is said to be transparent (invisible) to the workstations. The bridge will automatically initialize itself and configure its own routing information after it has been enabled.
Bridges are ideally used in environments where there a number of well defined workgroups, each operating more or less independent of each other, with occasional access to servers outside of their localized workgroup or network segment. Bridges do not offer performance improvements when used in diverse o r scattered workgroups, where the majority of access occurs outside of the local segment. The diagram below shows two separate network segments connected via a bridge. Note that each segment must have a unique network address number in order for the bridge to be able to forward packets pack ets from one segment to the other.
Ideally, Ideally, if workstations on network segment A needed access to a server, the best place to locate that server is on the same segment as the workstations, as this minimizes traffic on the other segment, and avoids the delay incurred by the bridge. A bridge works at the MAC Layer by Layer by looking at the destination address and forwarding the frame to the appropriate segment upon which the destination computer resides.
Summary of Bridge features • • •
operate at the MAC layer (layer 2 of the OSI model) can reduce traffic on other segments broadcasts are forwarded to every segment
• • • • •
• •
•
most allow remote access and configuration often SNMP (Simple Network Management Protocol) enabled loops can be used (redundant (redundan t paths) if using spanning tree algorithm small delays introduced fault tolerant by isolating fault segments and reconfiguring paths in the event of failure not efficient with complex networks redundant paths to other networks are not used (would be useful if the major path being used was overloaded) shortest path is not always chosen by spanning tree algorithm
HUBS There are many types of hubs. Passive hubs are simple splitters or combiners that group workstations into a single segment, whereas active hub s include a repeater function and are thus capable of supporting many more connections.
Nowadays, with the advent of 10BaseT, 10BaseT, hub concentrators are being very popular. These are very sophisticated and offer significant features which make them radically different from the older hubs which were available during the 1980's. These 10BaseT hubs provide each client with exclusive access to the full bandwidth, band width, unlike bus networks where the bandwidth is shared. Each workstation plugs into a separate port, which runs at 10Mbps and is for the exclusive use of that workstation, thus there is no contention to worry about like in Ethernet. These 10BaseT hubs also include buffering of packets and filtering, so that unwanted packets (or packets which contain errors) are discarded. SNMP management is also a common feature.
In standard Ethernet, all stations are connected to the same network segment in bus configuration. Traffic Traffic on the bus is controlled using the CSMA (Carrier Sense Multiple Access) protocol, and all stations share the ava ilable bandwidth. 10BaseT Hubs dedicate the entire bandwidth to each port (workstation). The workstations attach to the hub using UTP. UTP. The hub provides a number of ports, which are logically combined using a single backplane, which often runs at a much higher data rate than that of the ports.
Ports can also be buffered, to allow packets to be held in case the hub or port is busy. And, because each workstation has it's own port, it does not contend with other workstations for access, having the entire bandwidth available for it's exclusive use. The ports on a hub all appear as one Ethernet segment. In addition, hubs can be stacked or cascaded (using master/slave configurations) together, to add more ports per segment. As hubs do not count co unt as repeaters, this is a better option for adding more workstations than the use of a repeater. repeater. Hub options also include an SNMP (Simple Network Management Protocol) agent. This allows the use of network management manage ment software to remotely administer and configure the hub. Detailed statistics related to port usage and bandwidth are often available, allowing informed decisions to be made concerning the state of the network. In summary, summary, the advantages for these newer 10BaseT hubs are, • • • • •
each port has exclusive access to its bandwidth (no CSMA/CD) hubs may be cascaded to add additional ports SNMP managed hubs offer good management tools and statistics utilize existing cabling and other network components becoming a low cost solution
Virtual Networking In virtual networking, workgroups can be created on demand. Users can be located anywhere on the network. Using software management, the network components (switches) are configured to recognize a number of defined workstations (by MAC address) as belonging to their own domain.
Any traffic generated by these workstations can be sent to any other workstation in that domain. Workstations outside that domain are unable to see any packets (including broadcasts) that belong to the secure domain. Obviously, Obviously, this has enormous implications for developing secure networks. Multiple virtual workgroups can exist, like email and www server. Users can belong to more than one virtual do main, thereby administration is centralized and security is maintained. The use of switch tech nology makes this possible.
NETWORK TOPOLOGY Topology refers to the way in which the network of computers is connected. Each topology is suited to specific tasks and has its own advantages and disadvantages. The choice of topology is dependent upon • • • •
type and number of equipment being used planned applications and rate of data transfers required response times cost
There are FOUR major competing topologies • • • •
Bus Ring Star FDDI
Most networking software support all topologies.
Bus Topology • • • • • •
all workstations connect to the same cable segment commonly used for implementing Ethernet at 10mbps the cable is terminated at each end wiring is normally done point to point a faulty cable or workstation will take the entire LAN down two wire, generally implemented using coaxial cable during the 1980's
The bus cable carries the transmitted message along the cable. As the message arrives at each workstation, the workstation computer checks the destination address contained in the message to see if it matches it's own. If the address does not match, the workstation does nothing more.
Ring Topology • • • • • •
workstations connect to the ring faulty workstations can be bypassed more cabling required than bus the connectors used tend to cause a lot of problems commonly used to implement token ring at 4 and 16mbps four wire, generally STP or UTP
Star Topology • •
•
all wiring is done from a central point (the server or hub) has the greatest cable lengths of any a ny topology (and thus uses the most amount of cable) generally STP or UTP, four wire
Star Topology: Topology: Summary
Advantages
Disadvantages
Easy to add new workstations
Hub failure cripples all workstations connected to that hub
Centralized control
Hubs are slighty more expensive than thin-Ethernet
Centralized network/hub monitoring
FDDI Topology • • • •
100mbps normally implemented over fiber optic (fast-Ethernet, UTP) dual redundancy built in by use of primary and secondary ring automatic bypassing and isolation of faulty nodes
Fiber Distributed Data Interface FDDI is based on two counter rotating 100-Mbit/sec token-passing rings. The rings consist of point to point wiring between nodes which repeat the data as it is received.
The primary ring is used for data transmission; the secondary is used for data transmission or to back up the primary ring in the event of a link or station failure. FDDI supports a sustained transfer rate of about 80Mbps, a maximum of 1000 connections (500 nodes) and a total distance of 200 kilometers end to end. There is a maximum distance of 2 kilometers between active nodes. FDDI Station Types There are two main types of stations, class A which attach directly to dual rings; or class B which attach to a station acting as a concentrator.
A concentrator is a specialized workstation that attaches to the ring and has multiple ports that allow attachment of other devices in a physical star configuration. These may be cascaded.
http://viewzoft.com/projecttopics/databasesearchresults.asp?textfield=networking&Subm it=Search Chat server is a standlone application that is made up the combination of two-application, server application (which runs on server side) and client application (which runs on client side). This application is using for chatting in LAN. To start chatting you must be connected with the server after that your message can broadcast to each and every client. For making this application we are using some core java features like swing, collection, networking, I/O Streams and threading also. In this application we have one server and any number of clients (which are to be communicated with each other). For making a server we have to run the MyServer.java file at any system on the network that we want to make server and for client we have to run MyClient.java file on the system that we want to make client. For running whole client operation we can run the Login.java. Understand and get the chat server application by following steps : Features and Limitations of the Application Some features of the application are as follows : This application is used for sending messages from one client to all clients. In this, server takes a message from the sender client and sends it to all clients. If any client wants to join the chatting then he runs the client application on client side, enters the login name and hits the login button and starts the chatting with every client. If any client joins the chatting system then the message “User_Name has Logged in” comes on the message list box of every client window. Same like this, if any client exit from the chatting then the message “User_Name has Logged Out” comes on the message list box of every client window. In this we are maintaining the list of user names (client name) also. After creating the connection with server, client sends the user name to server and server store it in the arraylist and sends this arraylist to all clients. Same like this when any client has logged out then server remove this name from the arraylist and send this updated arraylist to every client. For creating the Client side application firstly creates the login frame it consist one textfield and the login button. After hitting the login button it shows the next frame that Client Frame and it consist one textfield for writing the message and one send button for sending it. And two list boxes, one is for showing the all messages and another list box is use to show the all user names. This frame has one more button that is Logout button for terminating the chat.
The idea of networking is probably p robably as old as telecommunications itself. Consider people living in the Stone Age, when drums may have been used to transmit messages between individuals. Suppose caveman A wants to invite caveman B over for a game of h urling rocks at each other, but they live too far apart for B to hear A banging his drum. What are A's options? He could 1) walk over to B's place, 2) get a bigger drum, or 3) ask C, who lives halfway between them, to forward the message. The last option is called networking . Of course, we have come a long way from the primitive p rimitive pursuits and devices of our forebears. Nowadays, we have computers talk to each other over vast assemblages of wires, fiber optics, microwaves, and the like, to make an appointment for Saturday's soccer match.[1] match.[1] In the following description, we will deal with the means and ways by which this is accomplished, but leave out the wires, as well as the soccer part.
We will describe three types of networks in this guide. We We will focus on TCP/IP most heavily because it is the most popular popu lar protocol suite in use on both Local Loc al Area Networks (LANs) and Wide Area Networks (WANs), (WANs), such as the Internet. We will also take a look at UUCP and IPX. UUCP was once commonly used to transport news and mail messages over dialup telephone connections. It is less common today, but is still useful in a variety of situations. The IPX protocol is used most commonly in the Novell NetWare environment and we'll describe how to use it to connect your Linux machine into a Novell network. Each of these protocols are networking protocols and are used to carry data between host computers. We'll discuss how they are used and introduce you to their underlying principles. We define a network as a collection of hosts of hosts that are able to communicate with each other, often by relying on the services of a number of dedicated hosts that relay data between the participants. Hosts are often computers, but need not be; one can also think of X terminals or intelligent printers as hosts. Small agglomerations of hosts are also called sites called sites.. Communication is impossible without some sort of language or c ode. In computer networks, these languages are collectively referred to as protocols as protocols.. However, you shouldn't think of written protocols here, but rather of the highly formalized code of behavior observed when heads hea ds of state meet, for instance. In a very similar fashion, the protocols used in computer networks are nothing but very strict rules for the exchange of messages between two or more hosts.
Other Network Types Most other network types are configured similarly to Ethernet. The arguments passed to the loadable modules will be different and some drivers may not support more than one card, but just about everything else is the same. Documentation for these cards is /usr/src/linux /Documentation/n /Documentation/networki etworking/ ng/ directory of generally available in the /usr/src/linux the Linux kernel source.
Network Introduction Data Networking continues to evolve. The demand for a High-Speed Network Infrastructure has been growing at an alarming rate. Just a few short years ago, 4 Mbps (Million bits per second) Token Ring and 10 Mbps Ethernet shared networks were the norm. Now they can’t keep up with the growing demands from end-users. End-user applications and files are growing in size and number. This is an introduction to networking terminology and network infrastructure. For an introduction to Local Area Networks (LANs), please see What is a LAN? One of the early types of networking topologies was Token Ring. Token Ring uses a
token passing access method. In token passing, collisions between packets are prevented by assuring that only one station ca n transmit at any given time. This is accomplished by passing a special packet, called a token, from one station to another in a ring topology. topology. (To learn more about ring topologies, please see What is a LAN?) LAN?) When a station gets the token, it can transmit a packet, which travels in one direction around the ring. When the packet pack et passes by the station it is addressed to, it is copied. The packet continues to travel around the ring until it returns to the sending station, which removes it and sends the token on to the next station on the ring. Another popular network technology is Fiber Distributed Data Interface (FDDI). FDDI provides data transport at 100Mbps. Originally, FDDI networks required fiber-optic cable, but today they can accommodate twisted-pair cable twisted-pair cable as well. Fiberwell. Fiberoptic cable is still preferred in many FDDI networks because it can be used over twisted-pair cable. FDDI uses a token passing access much greater distances than twisted-pair cable. method and is usually configured in a ring topology. FDDI is used primarily as a backbone , a segment of network that links several individual LANs together in building or campus environments. One of the most common types t ypes of networks is Ethernet . Originally, Originally, Ethernet cables coaxial (similar to cable TV wires), but now twisted-pair cables twisted-pair cables (similar to were coaxial (similar telephone wires) are more common. Fiber-optic common. Fiber-optic cables are used for higher speeds and greater distances than copper wires are capable of providing. One version of Ethernet, called 10BASE-T, consists of twisted-pair of twisted-pair cables cables and can transmit data at 10Mbps (10 million bits per second). Another version, Fast Ethernet is 10 times faster than 10 Base-T. Base-T. Two of the common types of Fast Ethernet are 100Base-T and 100Base-FX . 100BASE-T consists of twisted-pair of twisted-pair cabling cabling similar to 10Base-T except the cables have to be of a higher quality to transmit the data reliably, and the distance limitation is 100 meters. 100Base-FX is Fast Ethernet that runs over fiber-optic fiber-optic cabling. The fiber-optic cable extends the distance to 2,000 meters over Multi-mode cable. The newest version of Ethernet is called Gigabit Ethernet and it can transmit data at twisted-pair cable or fiber fiber1000Mbps . Gigabit Ethernet can use either Category 5 twisted-pair cable optic cable to transmit the signals. Soon, 10 Gigabit Ethernet will be available. It will only use fiber-optic use fiber-optic cables. 10 Gigabit Ethernet will primarily be used for backbone applications. Ethernet can support both bus and star topologies. (To learn more about bus and star topologies, please see What is a LAN?) LAN?) The most popular is the star topology, which makes use of a central hub or switch through which all information is passed. All stations on the network are connected to the hub or switch and can "sense" packets as they are sent across the wire. Because each station can send a packet at any time, collisions between packets do occur occu r. These are common and are corrected
instantaneously. Ethernet networks are replacing Token Ring and FDDI networks daily. daily. Ethernet with its speed, simplicity and low cost has won the war of the LAN. Many sites are migrating their legacy networks to Ethernet. Hubs (also referred to as repeaters or concentrators ) are a very important part of the networking process. Hubs are wiring concentrators, which make use of structured wiring to wiring to connect stations on a LAN. They contain user ports into which each station's cable is connected. Many hubs are called intelligent , or manageable or manageable,, which means that each of the ports on the hub can be configured, monitored, enabled, and disabled by a network operator from a hub management console.
There are three different types of hubs: •
•
•
A stand-alone hub is, as the term implies, a single unit un it with a fixed number of ports. Stand-alone hubs usually include some method of linking them to other stand-alone hubs. A stackable hub looks and acts like a stand-alone hub except that several of them can be stacked together, usually joined by short lengths of cable. When they are linked together, they can be managed as a single unit. A modular hub consists of modules of modules that each act like a stand-alone hub, but like the stackable hubs they can be managed as a single unit. Modular hubs consist of a chassis and the modules that go into the chassis. The chassis links the modules together with an internal backplane and handles the management of individual modules.
All of these hubs can be linked together to broaden the network. In order to create an internetwork (linking LANs together), other more complex devices are used. •
•
•
Bridge - device that connects two or more networks and forwards packets among them. Usually, bridges operate at the physical network level. For example, an Ethernet bridge connects two physical Ethernet cables and forwards from one cable to the other exactly those packets that are not local. Bridges differ from repeaters because bridges store and forward complete packets while repeaters forward electrical signals. They differ from IP Gateways or IP Routers because they use physical addresses instead of IP addresses. Routers - use Network use Network Layer Protocol Information within each packet to route it from one LAN to another. This means that a router must be able to recognize all of the different Network Layer Protocols that may be used on the networks it is linking together. Switches - devices with multiple ports, each of which can support an entire Ethernet, FDDI or Token Ring segment. With a different segment connected to each of the ports, p orts, it can switch packets between them as a s needed. In effect,
a switch acts like a very fast multi-port bridge because packets are filtered based on the destination address. A new network technology, technology, called Asynchronous Transfer Mode (ATM), (ATM), is based on the switch concept. Switches are starting to replace hubs and routers in many installations. Switching technology is increasing the efficiency and speed of networks. This technology is making current systems more powerful, while at the same time facilitating the migration to faster networks. Switching directs network traffic in a very v ery efficient manner. It sends information directly from the port of origin to only o nly its destination port. Switching increases network performance, enhances flexibility and eases moves, adds and changes. change s. Switching establishes a direct line of communication between two ports and maintains multiple simultaneous links between various ports. It proficiently manages network traffic by reducing media sharing, traffic is contained to the segment for which it is destined, be it a server, power user or workgroup.
There are many different types of Switches , some common examples are: •
•
•
•
man y port varieties. Anywhere Unmanaged switch : These switches come in many from 4 to 24 ports. Unmanaged switches are inexpensive, but lack features for management. Comparable to an unmanaged hub, except they have the speed of a switch . Workgroup switch: Similar to unmanaged switch, except provide management of the unit. Sometimes provide Gigabit ports to uplink to larger backbone switches . Stackable switch : Usually has a proprietary cable to interconnect them together. It allows a stack of switches to only use one IP address for management. Some use Gigabit links to interconnect them and to uplink them to backbone switches . Chassis Switch, Backbone Switch or Core Switch : Usually support Layer 3 switching, along with Layer 2 switching and many high level protocols. The Chassis have blades similar to high-end routers. So you can mix and match different interfaces for connecting different types of networks together.
Layer 2 switches (The Data-Link Layer) operate using physical network addresses. Physical addresses, also known as link-layer, hardware, or MAC-layer addresses, identify individual devices. Most hardware devices are permanently assigned this number during the manufacturing process. Switches operating at Layer 2 are very fast because they’re the y’re just sorting physical addresses, but they usually aren’t very smart—that is, they don’t look at the data packet v ery closely to learn anything more about where it’s it’s headed. Layer 3 switching (The Network Layer) and all of its related terms (e.g. multilayer switching, IP switching, routing switches, etc.) was introduced as the router-killer. router-killer. Layer 3 switching attempts to reduce the performance p erformance bottlenecks associated with traditional routers. Layer 3 switches use network or IP addresses that identify
locations on the network. They read network addresses more closely than Layer 2 switches—they identify network locations as well as the physical device. dev ice. A location can be a LAN workstation, a location in a computer ’s memory, memory, or even a different packet of data traveling through a network. Switches operating at Layer 3 are smarter than Layer 2 devices and incorporate routing functions to actively calculate the best way to send a packet to its destination. But although they’re smarter, they may not be as fast if their algorithms, fabric, and processor don’t support high speeds. Layer 4 (The Transport Layer) of the OSI Model coordinates communications between systems. Layer 4 switches are capable of identifying which application protocols (HTTP, SMTP, FTP, and so forth) are included with each packet, and they use this information to hand off the packet to the appropriate higher-layer software. Layer 4 switches make packet-forwarding decisions based not only on the MAC address and IP address, but also on the application to wh ich a packet belongs. Because Layer 4 devices enable you to establish priorities for network traffic based on application, you can assign a high priority to packets belonging to vital in-house applications such as Smartstream, with different forwarding rules for low-priority packets such as generic HTTP-based Internet traffic. Layer 4 switches also provide an effective wire-speed security shield for your network because any compan y- or industry-specific protocols can be confined to only authorized switched ports or users. This security feature is often reinforced with traffic filtering and forwarding features.
Hubs vs. Switches Traditional Ethernet LANs run at 10Mbps over a common bus-type design. Stations physically attach to this bus through a hub, repeater or concentrator , creating a broadcast domain. Every station is capable of receiving all transmissions from all stations, but only in a half-duplex mode. This means stations canno t send and receive data simultaneously. simultaneously. Nodes on an Ethernet network transmit information following a simple rule: they listen before speaking. In an Ethernet environment, only one node on the segment is allowed to transmit at any time due to the CSMA/CD protocol (Carrier Sense Multiple Access/Collision Access/Collision Detection). Though this manages packet collisions, it increases transmission time in two ways. First, if two nodes begin speaking at the same time, the information collides; they both must stop transmission and try again later. Second, once a packet is sent from a node, and Ethernet LAN will not transfer any other information until that packet reaches its endpoint. This is what slows up networks. Countless hours have been lost waiting for a LAN to free up. When a single LAN station is connected to a switched port it may operate in fullduplex mode. Full-duplex does not require collision detection, there is a suspension of MAC protocols. A single device resides on that port, and therefore no collisions will be encountered. Full-duplex switching enables traffic to be sent and received simultaneously. simultaneously. (Hubs between a workgroup and a switch will not run full-duplex, because the hub is governed g overned by collision detection requirements. The workgroup
connected to the hub is unswitched Ethernet). The bottom line is a 24 port 100Mbps hub is only capable of sharing the full 100Mbps with all 24-ports, which averages out to 4.16Mbps for each port. While at the same time a 24-port 100Mbps Switch has 24 individual 100Mbps ports. The switch is capable of 2400Mbps or 2.4 Gigabits per second. Also a switch can operate in full-duplex mode, so it has a theoretical throughput of 4800Mbps or 4.8 Gbps. Virtual LANs (VLANs)
When something is virtual it appears to be real, but it is not. A virtual LAN, or large network. It is actually a collection of multiple VLAN, appears to be one large networks. While these networks are physically connected, logically they are separate. The protocol of each can be different. A switch can control and regulate traffic of a number of networks (creating a virtual LAN), but it cannot connect a user on one VLAN with a user on another. A router is required for that kind of connection. A switched switched virtual LAN is a broadcast domain connecting a group of LANs at wire speed. Ethernet switches have evolved from creating VLANs based on port assignment. They can now create VLANs based on MAC addressing and network addressing. This enables VLANs to be divided into closed logical user groups, called subnets, determined by administrative ad ministrative controls. An Ethernet VLAN can be established through software, allowing a network administrator to group a number of switch ports into a high bandwidth, low-latency switched workgroup. For network management identification purposes, each virtual LAN gets a unique network number. VLANs function on a bridge architecture, switching and transmitting data by media access control (MAC) source and destination addresses. Traffic between virtual LANs is filtered, secured and managed b y a router at the software level, separate from the virtual LAN switching logic.
Wireless networking can prove to be very useful in public places – libraries, guest houses, hotels, cafeterias, and schools are all places where one might find wireless access to the Internet. From a financial point of o f view, view, this is beneficial to both the provider and the client. The provider would offer the service for a charge – probably on a pay pa y per use system, and the client would be able to take advantage of this service in a convenient location; away from the office or home. A drawback of wireless Internet is that the QoS (Quality of Service) is not guaranteed and if there is any interference with the link then the connection may be dropped.
Types of Wireless Networks WLANS: Wireless Local Area Networks
WLANS allow users in a local area, such as a university campus or library, to form a network or gain access to the internet. A temporary network can be formed by b y a small number of users without the need of an access point; given that they do not need access to network resources. WPANS: WPANS: Wireless Personal Pe rsonal Area Networks
The two current technologies for wireless personal area networks are Infra Red (IR) and Bluetooth (IEEE 802.15). These will allow the connectivity of personal devices within an area of about 30 feet. However, IR requires a direct line of site and the range is less. WMANS: Wireless Metropolitan Area Networks
This technology allows the connection of multiple networks in a metropolitan area such as different buildings in a city, city, which can be an alternative or backup to laying copper or fibre cabling. WWANS: WW ANS: Wireless Wide Area Networks
These types of networks can be maintained over large areas, such as cities or coun tries, via multiple satellite systems or antenna sites looked after by an ISP. ISP. These types of nd systems are referred to as 2G (2 Generation) systems. Below is a table indicating the range that wireless data networks can handle: Metres
Network
0-10 0-100 0-10000
Personal Area Network Local Area Network Wide Area Ne Network
http://compnetworking.about.com/od/p2ppeertopeer/a/p2pintroduction.htm Introduction to Peer to Peer (P2P) Networks and Software Systems P2P networking has generated tremendous interest worldwide among both Internet surfers and computer networking professionals. P2P software systems like Kazaa and Napster rank amongst the most popular software applications ever. Numerous businesses and Web sites have promoted "peer to peer" technology as the future of Internet networking. Although they have actually existed for many years, P2P technologies promise to radically change the future of networking. P2P file sharing software has also created much controversy over legality and "fair use." In general, experts disagree on various details of P2P and precisely how it will evolve in the future.
Traditional Peer to Peer Networks The P2P acronym technically stands for peer for peer to peer . Webopedia defines P2P as "A type of network in which each workstation has equivalent capabilities and responsibilities.
Ultimate Guide to Networking: Part One BY:- Michael Furdyk
What is a Network? A network is simply a group of two or more Personal Computers linked together. What Types of Networks Exist? Many types of networks exist, but the most common types of networks are Local-Area Networks (LANs), and Wide-Area Networks (WANs). In a LAN, computers are connected together within a "local" area (for example, an office or home). In a WAN, computers are farther apart and are connected via telephone/communication lines, radio waves, or other means of connection. How are Networks Categorized? Networks are usually classified using three properties: Topology, Topology, Protocol, and Architecture. Topology specifies the geometric arrangement of the network. Common topologies ar e a bus, ring, and star. star. You can check out a figure showing the three common types of network topologies here. here. Protocol specifies a common set of rules and signals the computers on the network use to communicate. Most networks use Ethernet, but some networks may use IBM's Token Ring protocol. We recommend Ethernet for both home and office networking. Architecture refers to one of the two major types of network architecture: Peer-to-peer or client/server. client/server. In a Peer-to-Peer networking configuration, there is no server, server, and computers simply connect with eachother in a workgroup to share files, printers, and Internet access. This is most commonly found in home configurations, and is only practical for workgroups of a dozen or less computers. In a client/server network, there is usually an NT Domain Controller, Controller, which all of the computers log on to. This server can provide various services, including centrally routed Internet Access, mail (including e-mail), file sharing, and pr inter access, as well as ensuring security across the network. This is most commonly found in corporate configurations, where network security is essential.
Local-Area Networks Originally, only medium to large-sized businesses could afford the cost of networking hardware. In the last decade, prices have rapidly dropped as new technology has developed, and it is now possible to grab a basic 4-PC 10Base-T home networking kit for under $150. The affordable price and added convienence of having a LAN has made it commonplace to see networks in many homes and off ices. Each PC in a LAN is able to access shared files and devices anywhere on the LAN. This makes the sharing of expensive devices, such as laser printers or large removable storage dri ves, a cost-effective alternative to purchasing a device for every user. If you decide to use Ethernet for your LAN (which we recommend you do), you can choose from 10Base-T (10 million bits per second, or 10 Mbps) or 100Base-T (100 million bits per second, or 100 Mbps), which is usually refered to as Fast Ethernet . 10Base-T is used mostly for home and small office networks, because it offers both affordability (around $20-30 for a network card, and $80 for an 8-port hub) and decent performance. For large businesses, a 100Base-T solution may be required if there are a large number of PCs connected to the network, or if large amounts of data is frequently transferred.
There are three different types o f cabling for Ethernet networ ks. Unshielded Twisted Pair (UTP) is the most popular type of cabling, and the one we recommend because of its wide availibility and low price. The other two types are coax ial and Shielded Twisted Pair (STP). STP cable provides more shielding against outside Electromagnetic Interference (EMI) than UTP, UTP, but is more expensive. We've never had any problems with EMI, so we suggest the cheaper UTP. UTP. Coaxial uses much thicker and more expensive cable, and must be run in a ring configuration, from PC to PC, unlike Twisted Twisted Pair, Pair, which is run directly from each computer to a port on the hub, making wiring more conv ienent in most cases. Ethernet networks require a Hub, a hardware device that all PCs on a network are connected to by cabling. The hub manages receiving and transmitting data from networked devices. Hubs come in many different port configurations, but you will probably need a 4, 8, or 12 port hub, depending on the number o f PCs you want to connect together. together. Each port supports a single 10Base-T 10Base-T connection from a PC or peripheral. If you're using Coaxial cable, you need to find a hub with one Coax ial port and minimal Twisted Pair ports. There are both Manageab le Hubs, which allow advanced configuration of Hub properties via a software package, and Standard Hubs, which are cheaper, cheaper, and usually used fo r home or small office networ ks. We recommend purchasing a standard hub, since the extra features included in Manageable Hubs are not useful for a home or small office network. Since you will probably purchase a standard hub, we'll discuss the three types of standard hubs next.
Standard Hubs When thinking about what type of Standard Hub you want to purchase, you need to think about what you will be doing with your network in the near future. Will you be adding many more devices to your network? If so, you need to make sure your hub can handle network expansion.
Standalone Hubs Standalone hubs are single products with a number of ports. Standalone hubs usually include some method of linking them to other standalone hubs for network expansion. Standalone hubs are usually the least expensive type of hub, and are best suited for small, independent workgroups, departments, or offices, typically with fewer than 12 users per LAN. Stackable Hubs Stackable hubs work just like standalone hubs, except that several of them can b e "stacked" (connected) together, together, usually by short lengths of cable. When they are connected together, they act like a modular hub, because they can be managed as a single unit. These hubs are ideal if you want to start with a minimal investment, but realize that your LAN will grow.
Modular Hubs Modular hubs are popular in networks because they are easily expanded and always have a management option. A modular hub is purchased as a chassis, or card cage, with multiple card slots, each of which accepts a communications card, or module. Each module acts like a standalone hub, and usually has 12 twisted pair ports. Modules supporting different types of network cabling, like coaxial or token ring, can also be purchased. If you are building a home or small office network, you will probably want to purchase a standalone or stackable hub. For a medium to large sized company, a Modular hub will probably fit your needs more efficiently. Next, we'll take a look at other types of network hardware, like routers, bridges, and switches.
Bridges, Routers, and Switches Bridges and routers are dev ices used for linking different LANs or LAN segments together. together. There are many companies that have LANs at various offices across the world. Routers were originally developed to allow connection of remote LANs across a wide area network (WAN). Bridges can also be used for this purpose. By setting up routers or bridges on two different lans LANs and connecting them together, a user on one LAN can access resources on the other LAN as if they were on the local LAN.
Sample Network Layout With a LAN Switch, Courtesy of Bay Networks
There are maximums on distances between workstations and hubs, hubs and hubs, and stations connected to a single LAN. You can exceed these maximums by linking two LAN segments (groups of users/devices) together using a Bridge or Router. Router. Bridges Bridges are simpler and less expensive then routers. Bridges make a simple do/don't decision on which packets to send across two segments they connect. Filtering is done based on the destination address of the packet. If a packet's destination is a station on the same segment where it originated, it is not forwarded. If it is destined for a station on another LAN, it is connected to a different bridge port and forwarded to that port.
Routers Routers are more complex and more expensive than bridges. They use information wi thin each packet to route it from one LAN to another, and communicate with each other and share information that allows them to determine the best route through a complex network of many LANs. Switches Switches are another type of device used to link several LANs and route packets between them. A switch has multiple ports, each of which can support either a single station or an entire Ethernet or Token Ring LAN. With a different LAN connected to each of the ports, it can switch packets between LANs as needed.
