UMTS Architecture and Element Functionalities
UMTS Architect ure and Element Functionalities
Contents 1 2 2.1 2.2 2.3 2.4 3 3.1 3.2 4 4.1 4.2 5 5.1 5.2 6 7
Introduction User equipment Architecture Terminal Equipment Mobile Termination UICC UTRAN Node B Radio Network Controller Core Network General Architecture for UMTS R.99 UMTS R.4 Architecture Transport technologies ATM IP Exercises Solution
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
3 7 8 10 10 10 13 14 16 19 20 34 41 42 53 63 67
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UMTS Architecture and Element Functionalities
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
1
Introduction
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
3
UMTS Architecture and Element Functionalities
A Universal Mobile Telecommunications System (UMTS) network can be visualized from different angles, such as from the point of view of the user plane, control plane, or the function of each subsystem. In this module we will look at UMTS from the latter angle, where the focus is on the different network elements within the network. The UMTS network architecture can be divided into four subsystems: •
User Equipment
•
Radio Access Network
•
Core Network including the network elements for service groups
•
Network Management Subsystem.
This separation will allow modularity in the composition of networks. The objective is to be able to combine any 3G CN with any 3G RAN. In addition, technical enhancements and updates of individual modules will be able to be introduced more easily, quicker and at less expensively due to the separation of functions. Each subsystem can be further divided into separate technologies. For example, the RAN (Radio Access Network) is compromised of different air interface technologies, such as GSM EDGE Radio Access Network (GERAN), UMTS Terrestrial Radio Access Network (UTRAN) and future solutions such as WLAN, 1ExTREME and 4G. The core network is today clearly divided into: •
Circuit Switched (CS) domain.
•
Packet Switched (PS) domain.
The network elements of the circuit switched domain are offering CS bearer services. They are inherited from GSM: MSC/VLR and GMSC. The packet switched domain is responsible to offer PS bearer services. Based on GPRS core network elements, the PS bearer services are currently non-real time services. But standards are on the way to enhance this infrastructure, so that also real-time services can be served via the PS domain transmission infrastructure. The CS and PS domains share some network elements. These common CS and PS domain network elements are the HLR, AC, and EIR. A set of service platforms was specified in GSM. These are now – in an enhanced version – also available in UMTS. Network elements for service groups include CAMEL, text telephony, Location Based Services (LBS) network elements. As can be seen service provisioning is partly located in the core network and contains all the service-enabling platforms that support the multitude of 3G services that an operator can offer.
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
APSE
IN/SCE
HLR
PSTN/ISDN
BSC MSS
GCS Gateway Control Server
A
GSM
BICC CS- 2, SIP- T H.248
A
RNC
H.248
MGW
MGW
Other PLMN
IP/ATM Backbone
Iu- CS
WCDMA External IP networks GGSN SGSN
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 1 Mobile general architecture
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
5
UMTS Architecture and Element Functionalities
The UMTS specifications stipulated that the new air interface and system capabilities should reuse the existing 2G systems, such as GSM and GPRS. Therefore, it is envisaged that operators can quickly rollout network once the equipment is available. The standards dictate the configuration of the open interfaces and the function of each subsystem; however, the implementation is vendor or operator specific. This has led into much more modular network architecture than we find in today's GSM networks. NSN fully supports open interfaces. The network elements are designed to be modular and are built in the manner that the functions can mature and evolve from new developments. Each year, the UMTS specifications are upgraded to support continuing functionality in the network. The next version of the specifications is known as UMTS Release 4 followed UMTS Release 5, Release6 and further. UMTS Release 4 will focus among others on having a specified IP or ATM Telephony Core. The focus of Release 5 is to have IP Multimedia Subsystem.
TM51102EN03GLA0 1
©No kia Siemens Networks
Fig. 2 UMTS network architecture
6
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
2
User equip ment
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
7
UMTS Architecture and Element Functionalities
2.1
Architecture
The UE has a substructure. It consists of the Universal Integrated Circuit Card (UICC), which communicates with the Mobile Equipment (ME). The UICC is a smart card, like the SIM card in GSM, and contains subscriber-specific information. It is prepared and sold by the operator of a UMTS Network. The ME is an end system which is independent of the subscription. This clear division between subscriberspecific and subscriber-independent elements allows for the sale and purchase of end systems and subscriptions separately. Early mobile Telecommunication Networks did not make this distinction. It was introduced in GSM and is considered to be one of the factors contributing to its success. Traditionally, the UE is a single piece of equipment, i.e. a single ME containing a UICC; when 3GPP started work on UMTS, this was a tacit assumption. Increasingly, however, UEs can consist of several networked MEs, e.g. all of the mobile devices of a subscriber, sharing the same UICC. The ME is composed of the Terminal Equipment (TE) and the Mobile Termination (MT) which we will explain below.
8
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1 ©No kiaS iemensN etworks
Fig. 3 UE architecture form
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
9
UMTS Architecture and Element Functionalities
2.2
Termin al Equipment
The TE can be a specialized UMTS mobile phone. In principle, however, it can be any end system, e.g. a laptop. The TE manages the end system hardware such as display, camera, microphone, etc. It runs the applications, and performs session control by communicating with a peer TE at the other end of the communication session.
2.3
Mobi le Termin ation
The MT terminates the radio transmission, performs radio resource control, deals with security on the radio link and supports mobility and QoS for data received from the TE. It can be integrated with the TE in a mobile phone. However, it can also be a separate card that—together with the UICC—is included in a laptop to make it UMTS capable. In this case the MT contains a Terminal Adaptation Function (TAF) that allows it to interface with the TE. A MT can also support multiple TEs simultaneously, all on the basis of the same UICC, in other words on the basis of a single subscription. In this way Personal Area Networks (PANs) can be supported.
2.4
UICC
This section discusses the UICC, a core concept in 3G Networks, in more detail. The UICC is a smart card, typically of a size 25mm*15mm. It is bought together with the subscription and inserted into the end system, e.g. mobile phone. In fact, the UICC normally resembles the SIM card for GSM that most readers are likely to have come across. The UICC, however, is more general than a SIM card: the SIM card holds subscriber-specific data for precisely one technology, namely GSM. The UICC, by contrast, may hold subscriber-specific data—so called applications—for several technologies: it may hold a SIM application for GSM, a Universal Subscriber Identity Module (USIM) application for UMTS and an IP Multimedia Services Identity Module (ISIM) application for IMS usage, all on the same physical UICC. This way, the user may access GSM, and UMTS including IMS, all with one UE. A UICC application identifies a user, and, most importantly, identifies how to charge this user. Without it, only emergency calls are possible. AUICC application also contains the secret keys that allow for subscriber authentication. This information is also available on the network side. It is stored, of course, in the HLR. One important feature is that the UICC is inaccessible to the user. The identifier and secret keys can only be manipulated by the operator who is selling the UICC. The UICC thus creates a secure environment (for the operator) which is essential to many commercial applications. One could speculate that the UICC will prove to be one of the key assets for UMTS operators when it comes to 4G and in competition with other mobile Communication Networks.
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
Technically, UICC applications contain the following data: •
USIM [3GPP 31.102]: o Identifier
International Mobile Subscriber Identity (IMSI), this is a unique identifier of the subscription. The IMSI is a number which is only used within the UMTS Network. It is not used as an identifier with regard to the outside.
(Packet) Temporary Mobile Subscriber Identity (P-TMSI/TMSI), these are the temporary identifiers of a subscription. For security reasons, temporary identifiers are used instead of the IMSI after the UE is attached to the network. The P-TMSI is used for the PS Domain, the TMSI for the CS Domain.
Mobile Station International ISDN number (MSISDN). This is the phone number under which this subscription can be reached. At the same time, the MSISDN is the publicly known identifier – called public identifier - of a subscription…
The identifier information is mirrored in the HLR. o Secret keys. This information is mirrored in the HLR. o Current location—the UE thus replicates the information about location that is also kept in the network (SGSN, MSC and RNC). o Miscellaneous information such as preferred language, the list of preferred networks (e.g. the Home Network), etc. o SMS, MMS, etc. •
SIM information is the GSM equivalent to the USIM data above.
Additionally, the UICC contains an address book. The UICC includes a CPU that allows it to access and process the information above, e.g. to perform authentication on the basis of the secret keys.
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
11
UMTS Architecture and Element Functionalities
12
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
3
UTRAN
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
13
UMTS Architecture and Element Functionalities
3.1
Node B
One or more Node B’s are controlled and addressed by an RNC. A Node B is a physical unit for implementation of the UMTS radio interface. It is converting the physical transmission of the data from fixed network transmission (ATM based) to WCDMA transmission. As a central transmission and reception site, it serves on or more UMTS cells. It is serving one UMTS cell in case of an omni cell with 360º service or, for example, 2, 3, or 6 sector cells with 180º 120º and 60º service respectively. The Node B is connected: via Iub interface to its controlling RNC via Uu interface to the UEs.
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 4 Node B
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
15
UMTS Architecture and Element Functionalities
3.2
Radio Network Contr oller
The UMTS Terrestrial Radio Access Network (UTRAN) is sub-divided into Radio Network Subsystems RNS. The Radio Network Controller (RNC) is the central controlling unit of a RNS. It is controlling itself and all the Node Bs of the RNS. The RNC is connected via the following ATM based interfaces: •
Iub interface: to connected the Node Bs
•
Iur interface: to neighboring RNCs
•
Iu interface: to the Core Network CN
Due to different protocol stacks, the Iu interface can be sub-divided into an Iu –ps interface and an Iu-cs interface. The Iu-ps interface is used for data and signaling transmission to the PS domain of the CN, the Iu-cs interface is used for data exchange with the CS domain. The main task of the RNC is to perform Radio Resource Management RRM for all UEs in its service area. Therefore, it can be compared to the GSM BSC. Different to the GSM BSC, it is 100% autonomously responsible for all RRM decisions. RRM means to be that the RNC is responsible for signaling with the UEs via Radio Resource Control (RRC) protocol, it is deciding about the allocation of resources, Handover to other cells and release of resources. The RNC is holding the RRC connection to the UEs as long as data have to be transmitted. It is storing the UEs location information to transmit the data to the right location. The location information can be requested by the CN for Location Based Services. It is responsible for reliable transmission over the radio interface, performing Backward Error Correction in acknowledged mode. It is responsible for Ciphering/De- Ciphering and Integrity Check.
16
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 5 Radio Network Controller
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
17
UMTS Architecture and Element Functionalities
18
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
4
Core Networ k
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
19
UMTS Architecture and Element Functionalities
4.1
General A rchi tectu re fo r UMTS R.99
The UMTS networks are based on GSM Phase 2+ Core Networks. This approach safeguards the investments made by today's GSM network operators and reduces the 3G implementation risks. The UMTS Terrestrial Radio Access Network (UTRAN) is connected to the enhanced Phase 2+ Core Network (CN) via Iu interface. The GERAN and UTRAN can be connected to the same CN. The GSM Mobile Station (MS) is connected to the GERAN via GSM radio interface Um, the UMTS User Equipment (UE) to UTRAN via UMTS radio interface Uu. Important note: In order to allow a smooth evolution, some network elements are used in the 2G and 3G context, such as the MSC. In this material, it will be normally called MSC. If a specific reference to the second or third generation is required, it will be called 2GMSC and 3G-MSC, respectively. The same is true for the SGSN. CS Domain The CS Domain of the UMTS CN consists of the following functions: MSC: Mobile Services switching Center GMSC: Gateway MSC SMS-GMSC: Short Message Service Gateway MSC SMS-IWMSC: Short Message Service Interworking MSC VLR: Visitor Location Register TC/IWF: Transcoding & Interworking Function PS Domain The PS Domain of the UMTS CN consists of the following functions: GGSN: Gateway GPRS Support Node SGSN: Serving GPRS Support Node CGF: Charging Gateway Function BG: Border Gateway Function Entities common to the CS & PS Domain HLR: Home Location Register AUC: Authentication Center EIR: Equipment Identity Register
20
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 6 UMTS R.99 Core Network
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
21
UMTS Architecture and Element Functionalities
4.1.1 •
Common Elements
IN Service :
The term Intelligent Network (IN) stands for IN solutions with INAP protocol (only in home PLMN) as well as for the CAMEL solution for international roaming. The IN platform provides the operators the tools for creating completely new services as well as full access to modify existing one, even on a subscriber basis. The highly scalable intelligent network platform offers the possibility to efficiently introduce and operate value adding intelligent services. The best example for this is the prepaid service in Mobile Network. Not only prepaid services can be built based on Mobile Network, but also are Virtual Private Network (VPN), Freephone, premium rate, split charging, and many more.
•
Home Location Register :
The Home Location Register (HLR) is a database in charge of the management of the mobile subscribers. There may be one or more HLRs in GSM PLMN The HLR is always associated with an Authentication Center (AC). It participates in different procedures, for e.g.: o It sends all necessary data to the VLR. o
o
Itrouting supports the call setup case ofMSC Mobile Termination Call (MTC) by sending information to the in Gateway (Interrogation). It transmits the security parameters from AuC to VLR on request.
An HLR contains different semi-permanent mobile subscriber data, e.g.: o IMSI: International Mobile Subscriber Identity o MSISDN: Mobile Station International ISDN number o Packet Data Protocol (PDP) address(es), e.g. IP address o Services: Bearer Services (BS), Tele Services (TS), Supplementary Services(SS) o A list of all the group IDs a service subscriber is entitled to use to establish voice group or broadcast calls o CAMEL Subscriber Information(s) o Service Restrictions (e.g. roaming limitations) Additionally, the HLR contains different temporary information of the mobile subscriber, e.g.: o VLR and SGSN addresses o Mobile station Roaming Number o SMS flags The organization of the subscriber data is outlined in GSM 23.008
22
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
•
Authentication Center :
The Authentication Center (AuC) is responsible to store the secret Keys of the subscribers and the security algorithm, which are necessary for the generation of the GSM and UMTS security parameters. On request of the VLR respectively the SGSN the AuC generates the security parameters. They are delivered via HLR to VLR/SGSN to enable Authentication, Ciphering and Integrity Check. The AuC is connected only with the HLR via the non-standardized interface H. The HLR requests data for authentication and cipher setting from the AuC. The HLR can store this data, and makes it available to the VLR and SGSN on demand. The data delivered from the AuC is used for: o Mutual authentication of the SIM-card (via IMSI) and the serving PLMN o Delivering a key to check the communication integrity over the radio path between the user equipment and the VPLMN o Ciphering over the radio path between the user equipment and the RNC. The AuC is responsible to store the secret Keys of the subscribers and the security algorithm, which are necessary for the generation of the GSM and UMTS security parameters. On request of the VLR respectively the SGSN the AuC generates the security parameters. They are delivered via HLR to VLR/SGSN to enable Authentication, Ciphering and Integrity Check.
Fig. 7 Home Location Register and Authentication Centre
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
23
UMTS Architecture and Element Functionalities
•
Equipment Identity Register :
Equipment Identity Register (EIR) optional database is used to verify the International Mobile Equipment Identity (IMEI) numbers. The EIR is organized in three lists: 1.
Black list
2.
Grey list
3.
White list
The black list holds IMEIs, which are forbidden in the PLMN. The grey list holds IMEIs under supervision by law enforcement agencies, and the white list holds IMEIs, which are allowed to access the PLMN. A mobile phone can be also classified as to be unknown in the EIR. The interface F connects the EIR with the VLR, while the Gf interface links it with the SGSN. The EIR is connected to: o The SGSN via Gf interface o The VLR via F interface
24
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 8 Identity Equipment Register
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
25
UMTS Architecture and Element Functionalities
4.1.2
Circui t Swit ched UMT S Netwo rk Eleme nt
MSC Server The MSC-Server is responsible for all call control tasks of the MSC and VLR. Its tasks include the: •
Call control of mobile srcinated and mobile terminated calls in the CS domain
•
The VLR functionality. For all subscribers in the MSC-Server supply area, it holds temporarily the subscriber profile, location information, identities, etc.
•
Interaction with the CS-MGW. The MSC-Server determines the QoS parameters required for the subscriber’s application. It is then the responsibility of the CSMGW to make the bearer available. The interaction between MSC-Server and CSMGW is done via an open interface, based on the ITU-T H.248 standard.
•
Termination of UE-network and network-network signaling. The UE-network signaling is done via the Iu-CS interface. For the network-network signaling, signaling protocols such as the BICC (Bearer Independent Call Control) protocol can be used.
•
CDR collection.
The MSC Server is connected to other network elements via the following interfaces: •
•
A-interface: to the GSM Base Station Controller BSC D-interface: to the HLR
•
F-interface: to the EIR
•
Gs-interface: to the SGSN
•
Iu CS-interface: to the RNC
•
Mc-interface: to the CS-MGW for separation between call control and bearer control. The ITU standard H.248 respectively its IETF standard equivalent Media Gateway Control (MEGACO) is used on Mc.
•
Nc-interface: to GMSC Server for Bearer-Independent Call Control (BICC)
GMSC Server The GMSC-Server adopts the call control tasks of the GMSC. Its tasks include: •
Interrogation of the HLR
•
Termination of network-network signaling
•
Interaction with the CS-MGW
CDR collection The GMSC Server is connected to other network elements almost the same as MSC-Server. •
26
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
Short Message Service Gateway MSC (SMS-GMSC) The SMS-GMSC acts as an interface between an external Short Message Service Center SMS-SC and the PLMN, to allow short message to be delivered to MS/UE from the Service Center. The choice of which MSCs can act as SMS Gateway MSCs is a network operator matter (e.g. all MSCs or some designated MSCs) Short Message Service Interworking MSC ( SMS-IWMSC) The SMS interworking MSC acts as an interface between the PLMN and a SMS-SC to allow short messages to be submitted from MS/UE to the SMS-SC. The choice of which MSCs can act as SMS Interworking MSCs is a network operator matter (e.g. all MSCs or some designated MSCs).
TM51102EN03GLA01 1
©N okiaS iemensN etworks
Fig. 9 SMS-GMSC & SMS-IWMSC
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
27
UMTS Architecture and Element Functionalities
Visitor Location Register The Visitor Location Register (VLR) is responsible to aid the MSC with information on the subscriber, which are temporarily in the MSC service area. Therefore, in praxis it is always associated with an MSC. The VLR request the subscriber profiles of subscriber with activated MS/UE it he MSC service area from the Home Location Register (HLR) and stores them temporarily.even Temporarily means as as the subscriber is not registered in a new MSC/VLR, if he deactivated thelong MS/UE. VLR stores temporary data, e.g. information on the subscriber's current location (the Location Area), the state of activation (Attached/Detached). Furthermore, the VLR is responsible for the initiation of security functions, e.g. the Authentication procedure, the start of ciphering and the TMSI re-allocation. Examples of subscriber data in the VLR:
28
•
MSISDN: Mobile Subscriber ISDN No.
•
IMSI: International Mobile Subscriber Identity
•
TMSI: Temporary Mobile Subscriber Identity
•
LMSI: Local Mobile Subscriber Identity
•
MSRN: Mobile Station Roaming Number
•
LAI: Location Area Identity
•
Authentication Parameter
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The identity of the SGSN where the MS has been registered
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©N okia Siemens Networks
Fig. 10 Visitor Location Register
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
29
UMTS Architecture and Element Functionalities
Transcoding Function TC The Transcoding TC function is used to perform conversion between standard ISDN 64 kbit/s speech transmission and the UMTS Adaptive Multi-Rate (AMR) speech codec (Specs: 26-series). The AMR speech coder is a single integrated speech codec with eight source rates from 4.75 kbit/s to 12.2 kbit/s, and a low rate background noise encoding mode. The speech coder is capable of switching its bit-rate every 20 ms speech frame upon command (TS 26.071). Different to GSM, in UMTS the Transcoding function is not part of the Radio Access Network RAN. It has been defined as part of the UMTS Core Network CN. Some optimization procedures allow it be passed through, without transcoding, in the case of UE to UE communication for example, when doubletranscoding would be performed for nothing. Interworking Function The “classical” Core Network CN interface (e.g. A-G) are all Time Division Multiplexed TDM based (E1/T1). Different to this, the Iu interface between UTRAN and the UMTS CN is ATM-based. An Interworking Function (IWF) is necessary for conversion between TDM-based and ATM-based interfaces. Remark: IWF and TC function can be stand-alone network elements or be integrated into the UMTS MSC, depending on the manufacturers / network operators decision / demands.
30
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kia Siemens N etworks
Fig, 11 Transcoding and Interworkng Function
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
31
UMTS Architecture and Element Functionalities
4.1.3
Packet Swit ched Network Eleme nt
Serving GPRS Support Node The Serving GPRS Support Node (SGSN) constitutes an interface between the radio access network and the core network. It is responsible to perform all necessary functions to handle packet switched services to and from the mobile phone. SGSN performs following task: • Network Access Control Authentication is one aspect of network access control. Hereby, the network is checking the validity of the subscriber’s USIM and the USIM is checking the validity of the network (SGSN). Only if both sides determine a successful authentication, network services can be used. Then the subscriber is requesting a service, the Authorization process makes sure, that the subscriber is allowed to use the requested service. The services, the subscriber is authorized to use may depend on his location. Other important tasks of network access control are the collection of Charging Data Records (CDR) and Operator Determined Barring. •
Mobility Management
Similar to the MSC, the SGSN is responsible for the mobility management, which includes procedures like routing area update and paging. Packet Routing and Transfer Its tasks include the classical packet switching aspects, such as relaying, routing, address translation, encapsulation, and tunneling. In contrast to the 2G-SGSN, a 3GSGSN is not responsible for ciphering and user data compression. Gateway GPRS Support Node The Gateway GPRS Support Node (GGSN) constitutes the interface between the PLNM and external packet data networks (PDN). Similar to the SGSN, it is responsible for the PS service provisioning. GGSN performs following task: •
Network Access Control
Two main network access control tasks are performed with a GGSN: It is responsible for screening, i.e. the operator can determine, which type of packets is allowed to be transmitted via a GGSN. Some manufacturers have outsourced this function into a separate firewall. The GGSN is also responsible for charging data generation. •
Mobility Management
The mobility management tasks include HLR inquiries in case of a mobile terminated call.
32
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
•
Packet Routing and Transfer
Packets have to be routed. The GGSN is responsible to relay them from one link to another, determine the next route with the help of routing tables. The GTP protocol is used between the GGSN and SGSN/RNC. The user data is encapsulated to be transparently transmitted between the GGSN and RNC. This is called tunneling. Border Gateway Function Roaming is possible for packet switched services. Hereby, user data and signaling information is transmitted between the two PLMN via the interface Gp. The data has to pass Border Gateways (BG) in each PLMN. The BG interfaces the PLMN and external, inter-PLMN backbone networks. Based on the roaming agreement between two operators, border gateways can perform mutual authentication of each other before a secure connection is established between them and data flows pass via them. Charging gateway Function Both SGSN and GGSN generate Charging Data Records (CDR). The CDRs routed via the CGF to the billing system. The interface Ga is used between SGSN/GGSN and Charging Gateway Function (CGF). CGF is responsible to: •
•
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Manage reliable CDRs Act as intermediate storage for CDRs Pre-processing of CDRs before forwarding them to the billing centre.
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
33
UMTS Architecture and Element Functionalities
4.2
UMTS R.4 Arc hit ectur e
UMTS networks are designed to offer a wide range of multimedia services. A consequence of more variable services is that the core network must offer more efficient and flexible transport options than the Release 99 network does. Therefore the UMTS Core Network CS domain is a central aspect of Release 4 modification (TS 23.002). The intention of these modifications is a separation of the call control from the transport the user data. A wide range of bearers must be made available in the core and radio access network to make these new services available for the subscriber. Today’s exchanges and MSCs are optimized for voice transport. An MSC is responsible for: •
Bearer control and bearer management
•
Call control
•
Service provisioning
With so many different tasks combined in one network element, any modification is costly and time consuming. With a traditional MSC it is very hard for operators to react fast to changing demand in the market. More flexible solutions are required. Beginning with UMTS Release 4, call control and bearer control and management are separated. The separation of planes is done in the UMTS Release 4 circuit switched domain. The UMTS Release 99 network elements MSC/VLR, and GMSC are substituted by the network entities MSC-Server, GMSC-Server and CS-MGW (Circuit Switched – Media Gateway).
34
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kia Siemens Networks
Fig. 12 UMTS Core Network R.4 CS domain
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
35
UMTS Architecture and Element Functionalities
The CS-MGW is responsible for bearer control. Its functions include: •
Bearer control: The requirements for the bearer control are set in the (G)-MSCServer. The CS-MGW gets this information via an open interface. The CS-MGW must determine, whether it can make bearers available in accordance to the QoS parameters set.
•
Bearer channel termination: The different transmission technologies may be in use, e.g. ATM and IP over Ethernet. The ATM bearer then ends in the MGW and
•
the IP bearer begins at the MGW for user data transport. Media conversion and payload processing: If the CS-MGW is interfacing UTRAN, voice information must be processed. E.g. voice may be transmitted with 64 kbps in the core network, but for the radio interface, 12.2 kbps speech is required. The UMTS specific voice codec is found in the MGW. The same is true for conference bridges, echo cancellers, etc.
Mobile specific functions: A CS-MGW must support mobility specific functions, such as SRNC relocation and handover procedures. The CS MGW can also be connected to other networks such as PSTN and PLMN using the following interfaces: •
36
•
A-interface: to the GSM Base Station Controller BSC
•
Iu-CS interface: to the RNC
•
Nb-interface: to other MGW. Different options are possible on Nb for user data transfer and bearer control signaling (e.g. ATM, IP).
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
4.2.2
Mobile Switch ing Center Server
Mobile Switching Centre Server (MSC server) concept offers common core network for the GSM and the UMTS subscribers. Release 99 introduces the UTRAN network. NSN's 3G-MSC offers connections both towards the GSM Base Station Subsystem (BSS) and towards the WCDMA-based UMTS Terrestrial Radio Access Network (UTRAN). When the network architecture based on UMTS Release 4 is introduced, the user and control planes are separated in the network. This means that the 3G-MSC evolves to the direction where the MSC's switching functions are brought to the Media Gateway (MGW) product and the MSC evolves to an MSS-like product. The MSS product provides call control logic for terminals that use circuit switched logic. MSS mainly comprises the call control and mobility control parts of a GSM/UMTS MSC. The MSS is responsible for the control of mobile srcinated and mobile terminated circuit switched calls. It terminates the user-network signaling and translates it into the relevant network – network signaling. The MSS also contains a VLR to hold the mobile subscribers' service data and CAMEL related data. MSS controls the parts of the call state that pertain to connection control for media channels in a MGW. The MSC server connects to the Media Gateway using the H.248 protocol (MEGACO). The physical connection between the MSC server and Media Gateway (MGW) is Ethernet. The interface between two MGWs performs bearer control and transport through the ATM backbone by using several ATM Adaptation Layer protocols (AAL1, AAL2, and AAL5) or the IP backbone. The functionality of the MSC server can be divided into two roles: Visited MSS (VMSS) and Gateway MSS. •
VMSS contains VLR and controls the MGW that is connected towards the (BSS and UTRAN) radio networks.
•
Gateway MSS functionality is to control the MGW that is performing interworking between packet core network and the external PSTN/ISDN network.
The NSN product that performs the Gateway MSS functionality is called Gateway Control Server (GCS).
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
37
UMTS Architecture and Element Functionalities
4.2.3
Camel Service Environment CSE
For the introduction of CAMEL services, some network elements have to be enhanced and new functional entities have to be introduced (TS 23.078):
38
•
GSM Service Control Function (gsmSCF): functional entity that contains the CAMEL service logic to implement Operator-Specific Services OSS. It interfaces e.g. with the gsmSSF, the gprsSSF and the HLR.
•
GSM Service Switching Function (gsmSSF): functional entity that interfaces the MSC/GMSC to the gsmSCF. The concept of the gsmSSF is derived from the IN SSF, but uses different triggering mechanisms because of the nature of the mobile network.
•
GPRS Service Switching Function (gprsSSF): functional entity that interfaces the SGSN to the gsmSCF.
•
Home Location Register HLR: for subscribers requiring CAMEL support, the HLR stores different types of CAMEL Subscriber Information CSI (e.g. O-CSI for Mobile Originating Calls, T-CSI for Mobile Terminating Calls). The O-CSI is sent to VLR at Location Update, on data restoration of if the O-CSI is updated by administrative action. The O/T-CSI is sent to the GMSC when the HLR responds to a request for routing information.
•
MSC/VLR or SGSN: VLR or SGSN store the different CSI information as part of the subscriber data for subscribers roaming in the MSC/VLR or SGSN area. MSC or SGSN monitor the call states and communicate (internally) with gsmSSF for further proceeding.
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kia Siemens N etworks
Fig. 13 CAMEL Services
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
39
UMTS Architecture and Element Functionalities
40
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
5
Transport technologies
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
41
UMTS Architecture and Element Functionalities
5.1
ATM
The basic functioning of Asynchronous Transfer Mode (ATM) can be compared to an inner city street with separate lanes for different traffic types. For example there can be one or more lanes for normal traffic, maybe reserved lanes for bus traffic and finally bicycle lanes all with different properties and resource needs. ATM, also known as cell relay, is a fast packet switching and multiplexing technology. ATM was developed as part of the work on broadband ISDN to support a universe of services (for example, voice, data and video over public network). ATM is a connection-oriented, error-detecting protocol. ATM does not offer error correction. Error correction is the responsibility of end user nodes. Minimizing error correction in intermediate nodes provides the advantages of increased speed of switching and elimination of associated delay. ATM provides efficient support for transmission of bursty wideband services and offers an integrated solution to voice (circuit mode as well as packet voice), data, and video. ATM provides quality of service (QoS) guarantee and reliability even when resources are shared and thus ATM provides the benefit of sharing network resources and predictable network behavior based on packet switching technology. ATM utilizes statistical multiplexing to take advantage of the inherently bursty nature of applications. For a group of bursty connections, less bandwidth can be reserved than if bandwidth reservation would be based on the peak rate of the connections. Achieved transmissions cost savings are considerable. The fundamental strategy behind ATM is to split the information into small fixed-size units, called 'cells', that are easy to handle. The fixed size of the cell allows efficient switching. ATM networks allow statistical multiplexing (that is, multiplexing of many connections with variable rate characteristics), which altogether reduces the overall bandwidth requirements.
42
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 14 Asynchronous Transfer Mode
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TM51102EN03GLA2 © 2010 Nokia Siemens Networks
43
UMTS Architecture and Element Functionalities
5.1.1
ATM cell
The user traffic is split and delivered in fixed length packets called ATM cells. The size of the cell is 53 bytes, which is divided into a 5-byte header and a 48-byte payload field. The ATM cell is relayed based on a label in the header: Virtual Channel Identifier (VCI) and Virtual Path Identifier (VPI).
53 byte
H eade r 5 by t es
s
Payload 48 byte
s
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 15 ATM cell structure
44
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
There are two formats of an ATM cell (depending on the type of the interface): •
ATM UNI (User-Network Interface) cell that is used for communication between ATM endpoints and ATM switches.
•
ATM NNI (Network-Node Interface) cell that is used for communication between ATM switches.
For ATM interfaces in 3G networks, User-Network Interface (UNI) refers to the interface between terminal equipment and a network termination where access protocols apply. The interface between a RNC and a WCDMA BTS is seen as an UNI interface. Network-Node Interface (NNI) is the interface between two network nodes like a RNC and an MGW. The figure shows the specified ATM interfaces between network elements in a 3G network.
ATM is employed Iub
Uu
RNC
BS
UE
Iu-CS NNI
UNI
A MG W
B PSTN
M SC
Iur NNI
NNI
UNI BS
Iu-PS
RNC UNI
Gn
Gi
BS SGSN
GGSN
IP network
TM51102EN03GLA01 1
©No kiaSiemensN etworks
Fig. 16 ATM interface in 3G network
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
45
UMTS Architecture and Element Functionalities
There is a slight difference between the first byte of the UNI and NNI header. The NNI header does not include the Generic Flow Control (GFC) field. Instead the NNI header has a Virtual Path Identifier (VPI) field that occupies the first 12 bits, allowing larger trunks between public ATM switches.
8
7
6
5
4
GFC
2
1
8
6
VCI
3
2
1
VCI VCI
PT
VCI
C LP
Us er N et wo rk I nt er f ac e ( UNI )
PT
C LP
HEC
P a y lo a d
Ge neric F low Co ntrol Vi rtua l Pa th Ide nt ifier Vi rt ua l Ch an ne l Id en ti fi er
4
VPI
HEC
Payload (48 bytes)
5 VPI
VCI VCI
GF C VP I VCI
7
VPI
V PI
Header (5 bytes)
3
P a y lo a d
Ne t wo rk N od e I nt er f ac e ( NNI ) PT CL P HE C
Pa y loa d T y pe Ce ll Lo ss Priority He ade r Er ror Co nt rol
TM51102EN03GLA01 1
©No kia Siemens N etworks
Fig. 17 Basic ATM cell format
46
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
Generic Flow Control (GFC) Provides local functions, such as identifying multiple stations that share a single ATM interface. This field is typically not used and is set to its default value. Virtual Path Identifier (VPI) In conjunction with the VCI, identifies the next destination of a cell as it passes through a series of ATM switches on the way to its destination. Virtual Channel Identifier (VCI) In conjunction with the VPI, identifies the next destination of a cell as it passes through a series of ATM switches on the way to its destination. Payload Type (PT) Indicates in the first bit whether the cell contains user data or control data. If the cell contains user data, the second bit indicates congestion, and the third bit indicates whether the cell is the last in a series of cells that represent a single AAL5 frame. Cell Loss Priority (CLP) Indicates whether the cell should be discarded if there is congestion in the network. If the CLP bit equals 1, the cell should be discarded in preference to cells with the CLP bit equal to zero. Header Error Control (HEC) Calculates the checksum only on the header itself. The network instantly discards any cell that fails the header error check.
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
47
UMTS Architecture and Element Functionalities
5.1.2
ATM connection
ATM is a connection-oriented technique. The end-to-end route is defined through the network at the beginning of the connection setup and the route remains the same throughout the connection. ATM cells are routed on the same route to both directions. This guarantees that the cells arrive in the receiving end in the same order they were sent. Furthermore, cell delay variation is also minimized and since routes are known it is possible to predict link behavior. •
ATM virtual connexion
Virtual connections (VC) are used for providing connectivity between communicating endpoints. There are two types of ATM connections: •
Virtual Channel Connection (VCC)
•
Virtual Path Connection (VPC).
Each ATM cell contains a label in its header to explicitly identify the VC, to which the cell belongs. This label consists of two parts: Virtual Channel Identifier (VCI) and Virtual Path Identifier (VPI). Virtual Channel Connection (VCC) is a logical connection in ATM. Virtual Channel Identifier (VCI) identifies a particular VC link under a given VPC. A specific value of a VCI is assigned each time a VC is switched in the network. Hence, it has only local meaning. Virtual Path Connection (VPC) is a logical grouping of VCCs having the same endpoints. Thus, all the cells flowing in a single VPC are switched together. Virtual paths are used for bundling a number of virtual channels into a higher bandwidth stream routed through ATM switches. That is, cross-connection and switching can be done on a higher level and not on individual VCC level. Virtual Path Identifier (VPI) identifies a group of VC links at a given reference point that share the same VPC. A specific value of a VPI is assigned each time a VP is switched in the network. Transmission path is a bundle of VPs. The following figure shows the relation among VCs, VPs and a transmission path.
48
TM51102EN03GLA2 © 2010 Nokia Siemens Networks
UMTS Architecture and Element Functionalities
VC
VP Transmission path
VC
VP
TM51102EN03GLA01 1
©No kiaS iemensN etworks
Fig. 18 Relation between transmission path
Virtual paths help to reduce the control cost by grouping connections that share common paths through the network into a single unit. Network management actions can then be applied to a small number of groups of connections instead of a large number of individual VCC connections. Virtual Path Connections (VPCs) have many advantages: Simplified network architecture Network transport functions can be separated into those related to individual logical connections (VCC) and those related to a group of logical connections (VPC). Increased network performance and reliability The network deals with fewer, aggregated entities. Segregation of traffic A form of priority control can be implemented by segregating traffic types requiring different quality of service (QoS).
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UMTS Architecture and Element Functionalities
Reduced processing and short connection setup time Much of the work is done when the VPC is set up. By reserving capacity on a VPC in anticipation of later call arrivals, new VCCs can be established by executing simple control functions at the end points of the VPC; no call processing is required at transit nodes. Thus, the addition of new VCCs to an existing VPC involves minimal processing which decreases the connection setup delay. Enhanced network services The VPC is used internally in the network but is also visible to the end user. Thus, the user may define closed user groups or closed networks of VC bundles. •
Network elements involved in transport
•
The following are the definitions of the network elements involved in the transport of user plane information (from ITU-T I.311):
•
VP cross-connect is a network element, which connects VP links. It translates VPI (not VCI) values and is directed by management plane functions not by control plane functions. −
•
•
VC cross-connect is a network element, which connects VC links. It terminates VPCs and translates VCI values and is directed by management plane functions not by control plane functions.
−
VP-VC cross-connect is a network element that acts both as a VP cross-connect and as a VC cross-connect. It is directed by management plane functions not by control plane functions. −
50
•
VP switch is a network element that connects VP links. It translates VPI (not VCI) values and is directed by control plane functions.
•
VC switch is a network element that connects VC links. It terminates VPCs and translates VCI values and is directed by control plane functions.
•
VP-VC switch is a network element that acts both as a VP switch and as a VC switch. It is directed by control plane functions.
•
Routing functions of virtual channels are done at a VC switch/cross-connect. This routing involves translation of the VCI values of the incoming VC links into the VCI values of the outgoing VC links.
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UMTS Architecture and Element Functionalities
Fig. 19 VC and VP switch
Fig. 20 VP switching
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UMTS Architecture and Element Functionalities
5.2
IP
Nowadays, engineers are aiming for the convergence of the whole network (from Radio Access to Core) by trying to make what we call “all IP” network. IP is becoming an important transport technology in telecommunication networks as it has too many advantages. Because of its widespread use and relatively easy implementation, the usage of TCP/IP protocols is, in practice, supported by every WAN and LAN technology used today. Today TCP/IP protocols are developed and standardized by the Internet Engineering Task Force (www.ietf.org). IETF membership is free and there is no subscription fee for documents. Although TCP/IP can be mapped and explained with the classical layered OSIprotocol model, there are some differences. There are, for example, no session or presentation layers defined, but the functionality of these is built directly into application layer protocols. Most data communication uses the client - server model. In this model, a client sends a request to a server that maybe located on another network somewhere on the Internet. The server processes the client’s request and sends a reply to the client. In order for the requests and replies to be understood, the client and the server must speak the same language.
Communication Network
r S Seerrve r
Cllieent
Fig. 21 Client/Server mode
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5.2.1
IP network s
Internet Protocol (IP) is a layer-3 protocol that is used to carry data over different types of network. IP works in connectionless packet mode; that is, data is transported to the destination without the establishment of a connection between the source and the destination similar to a postal system. Each packet will have an address for both sender and receiver, which is referred to as an IP address. There are two types of IP address:unique privateinIPthat addresses and public IP addresses. IP unique addresses are globally all IP packets in a public network Public will have IP sender and receiver addresses.
House 1
House 2
New Street
House 1
House 3
Crossing A
Old St reet
Router A Net work1
Host1
Host2
Net work2
Host 1
Host2
Host3
Fig. 22 Addressing in IP network
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UMTS Architecture and Element Functionalities
IP is used as the interconnection protocol in the Internet. The use of unique addresses means that every machine connected to the Internet can send packets to any other machine connected to the Internet, assuming this has not been denied for security reasons. Each packet will have an address for the sender and the receiver. Large deliveries may be divided or fragmented into several smaller packets to help transportation. The network does not guarantee when and how the packets will arrive. It is referred to as a best effort network.
IP Network B Router 1
IP Network C
IP Network A Router 2
Router 3
Internet
Fig. 23 IP network example
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UMTS Architecture and Element Functionalities
5.2.2
IP routing
Any IP device that can forward IP packets (which have a destination address other than its own) to other IP devices is called a router. The process of selecting the best data link and next hop on the route to the right destination network is called routing.
Application
Router Routing is the process of selecting the next destination using a routing table.
TCP/ UDP
IP
Relay
IP
L2
L2
L1
L1
• Layer 3 „swit ch“ • decides were to trans mit t he IP packet next aft er analysis of t he IP header information depending on data l ink and physical link layer, segment ati on or reassembly may necessary
IP L2‘ L1‘
Router
TM51102EN03GLA01 1
©No kia Siemens N etworks
Fig. 24 Router and its tasks
Routing can be either static or dynamic. In static routing the router will have a fixed routing table, which includes the destination IP networks and corresponding next hops. In dynamic routing, the routers exchange information on the destination IP networks and corresponding next hops. This dynamic information is exchanged via routing protocols like the OSPF (Open Shortest Path First), the RIP (Routing Information Protocol), the IGRP (Interior Gateway Routing Protocol) and the BGP (Border Gateway Protocol).
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5.2.3
Components in IP networks
Domain name server The Domain Name System (DNS) is an application layer protocol, which is used to convert difficult-to-remember 32-bit IP addresses to more easily remembered symbolic names, and vice versa. An example of a DNS is gprs.ntc.nsn.com which maps to the IP address 192.168.0.1. The conversion from the symbolic name to the IP address is done in DNS servers. A DNS server is a database containing IP addresses and corresponding symbolic names. A single DNS cannot store the information on all address-name pair.
Fig. 25 Operation in DNS
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UMTS Architecture and Element Functionalities
As shown in the figure, the host has to translate the IP address for gprs.ntc.nsn.com. For this, the following steps are performed: 1. The host sends a DNS query to its local DNS server, asking for the IP address of gprs.ntc.nsn.com. 2. The local DNS server does not know the answer, because it only has a database of the local users. It forwards the query to a predefined root level DNS server. The root level DNS server replies with a list of IP addresses to .com -level DNS servers. 3. The local DNS server sends the query to the .com DNS servers. The .com DNS server replies with a list of IP addresses of the nsn.com -level DNS servers. 4. The local DNS server sends the query to one of the nsn.com DNS servers, which replies with a list of the addresses of ntc.nsn.com -level DNS servers. 5. The local DNS server then forwards the query to one of the ntc.nsn.com DNS servers. The ntc.nsn.com - level DNS server replies with an IP address corresponding to the gprs.ntc.nsn.com DNS name. 6. The local DNS server forwards the reply to the srcinal host.
Dynamic Host Configuration Protocol The Dynamic Host Configuration Protocol (DHCP) is used to provide automatic network configuration information from the DHCP server to the DHCP client. From the IP point of view, the important configuration parameters that a client needs to know are the IP address, netmask, and the default gateway. This means that IP addresses are not assigned permanently to any client, but instead they are allocated from a pool of addresses assigned to a DHCP server. In order to avoid ‘ghost’ users using IP addresses they no longer need, the given IP addresses and the other parameters are associated with a lease time. This lease time can be configured to be from few to several days. Before the lease expires, the client has to try to renew the lease. The client must stop using the IP address if the lease expires.
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Fig. 26 Operations in DHCP
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UMTS Architecture and Element Functionalities
Virtual Private Network A Virtual Private Network (VPN) is a method of securely communicating between a VPN client, such as a user, and the user’s organization's network over a public nonsecure network such as the Internet. The VPN concept has been around for some time. The concept of VPN was initially used in telephone networks. Only recently have they become popular due to the prevalence of the Internet and advances in security technologies. Nowadays many companies use Internet-based VPNs because it is more cost effective than using private networks. Companies use the Internet as a virtual backbone for creating a secure virtual link between their corporate offices and remote offices. VPN uses a variety of encryption and security mechanisms to make the virtual link secure and to prevent hackers or eavesdroppers from accessing or modifying the data without being detected. VPNs use a technique known as tunneling to transport encrypted data over the Internet. Tunneling involves encapsulating one protocol such as IPX, AppleTalk, or IP, encrypting it, and then encapsulating it into IP datagrams. Tunneling offers the advantage of obscuring the srcinal network layer protocol.
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Fig. 27 Architecture of VPN
As shown in the figure, the following steps are performed to create a VPN connection: 1. A VPN client dials up to the NAS –Network Access Server, located at the ISP using a Point-to-Point Protocol (PPP) through a PSTN or wireless connection. 2. The NAS communicates with the security server to identify the VPN client. 3. The NAS initiates a communication link using a tunneling protocol over the Internet to the VPN client's organization gateway. 4. The organization’s gateway decides either to accept or reject the established tunnel from the ISP's NAS. 5. The organization gateway queries the organization security server to confirm the tunnel. 6. Once the tunnel is accepted by the organization gateway, the ISP's NAS logs the acceptance/ traffic. 7. The organization gateway exchanges information such as PPP with the VPN client and assigns the client an IP address. is created between the VPN client and the organization gateway to tunnel the data.
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UMTS Architecture and Element Functionalities
Firewalls A firewall is a system that controls access to and from an insecure external network to the local network of an organization. Firewalls are often implemented at a point where the local network of an organization connects to an external network such as the Internet. This is often the weakest point since it is vulnerable to an attack.
TM51102EN03GLA01 1
©No kia Siemens Networks
Fig. 28 Placement of the firewall
A firewall at this point will allow all the packets leaving and entering the local network to be examined thoroughly. The examination of packets is defined by the control access policy defined in the security policy of the network. Any packets observed by the firewall to come from an insecure source are discarded. As a result, the risk of an attack on the network is reduced.
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6
Exercises
Exercise 1 What is the first technology that was newly implemented in the UMTS network? FDMA WCDMA FDD TDD Exercise 2 What is the NE that makes the ATM/TDM adaption to the MSC interfaces in the R.99? TC IWF MSC RNC Exercise 3 Which of these information is not kept in the USIM? IMSI MSISDN TMSI Subscriber services Exercise 4 Where the Ciphering/Deciphering task is handled in the UMTS Network? Node B RNC MGW MSC
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Exercise 5 The Iur interface is used between 2 RNCs. What is the purpose of this interface? There is no use for this interface It is used for soft handovers It is used to transfer software files It is used for redundancy Exercise 6 Which information is stored in the EIR? IMSI MSISDIN IMEI K
Exercise 7 Which NEs are responsible for Mobility Management? RNC Node B MSS SGSN Exercise 8 Which NE is newly implemented in the UMTS R.4? GGSN RNC MGW HSS Exercise 9 What are the tasks of the MSS? Switching the CS traffic Call setup and release Generating charging data Control the MGWs
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Exercise 10 What is the smallest entity used in ATM networks? Cell Packet Time slot Frame Exercise 11 Which NE in IP network that provide IP addresses to hosts? DNS Router DHCP Server Firewall
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7
Solution
Exercise 1 What is the first technology that was newly implemented in the UMTS network? FDMA WCDMA FDD TDD Exercise 2 What is the NE that makes the ATM/TDM adaption to the MSC interfaces in the R.99? TC IWF MSC RNC Exercise 3 Which of these information is not kept in the USIM? IMSI MSISDN TMSI Subscriber services Exercise 4 Where the Ciphering/Deciphering task is handled in the UMTS Network? Node B RNC MGW MSC
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UMTS Architecture and Element Functionalities
Exercise 5 The Iur interface is used between 2 RNCs. What is the purpose of this interface? There is no use for this interface It is used for soft handovers It is used to transfer software files It is used for redundancy Exercise 6 Which information is stored in the EIR? IMSI MSISDIN IMEI K
Exercise 7 Which NEs are responsible for Mobility Management? RNC Node B MSS SGSN Exercise 8 Which NE is newly implemented in the UMTS R.4? GGSN RNC MGW HSS Exercise 9 What are the tasks of the MSS? Switching the CS traffic Call setup and release Generating charging data Control the MGWs
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UMTS Architecture and Element Functionalities
Exercise 10 What is the smallest entity used in ATM networks? Cell Packet Time slot Frame Exercise 11 Which NE in IP network that provide IP addresses to hosts? DNS Router DHCP Server Firewall
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