QoS in 3G Core Network

Quality of Service in 3G CoreNetworkDN01154225 Nokia Corporation 1 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service in 3G Core Network

The information in this documentation is subject to change without notice and describes onlythe product defined in the introduction of this documentation. This documentation is intended

for the use of Nokia's customers only for the purposes of the agreement under which thedocumentation is submitted, and no part of it may be reproduced or transmitted in any form ormeans without the prior written permission of Nokia. The documentation has been prepared tobe used by professional and properly trained personnel, and the customer assumes fullresponsibility when using it. Nokia welcomes customer comments as part of the process ofcontinuous development and improvement of the documentation.The information or statements given in this documentation concerning the suitability, capacity,or performance of the mentioned hardware or software products cannot be considered bindingbut shall be defined in the agreement made between Nokia and the customer. However, Nokiahas made all reasonable efforts to ensure that the instructions contained in the documentationare adequate and free of material errors and omissions. Nokia will, if necessary, explain issueswhich may not be covered by the documentation.Nokia's liability for any errors in the documentation is limited to the documentary correction oferrors. NOKIA WILL NOT BE RESPONSIBLE IN ANY EVENT FOR ERRORS IN THISDOCUMENTATION OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL(INCLUDING MONETARY LOSSES), that might arise from the use of this documentation orthe information in it.This documentation and the product it describes are considered protected by copyrightaccording to the applicable laws.NOKIA logo is a registered trademark of Nokia Corporation.Other product names mentioned in this documentation may be trademarks of their respectivecompanies, and they are mentioned for identification purposes only.

Copyright Nokia Corporation 2002. All rights reserved.2 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

ContentsContents 3

List of tables 5

List of figures 6

1 About this document 9

2 Quality of Service in Brief 11

3 Quality of Service Overview 173.1 QoS in GPRS/EDGE Networks and in WCDMA/UMTS Networks 173.2 QoS provides new means for service differentiation 18

4 IP Traffic in Mobile Networks 214.1 Protocol stacks in GPRS and UMTS 214.2 TCP slow start 244.3 Statistical multiplexing 264.4 Basic mechanisms for implementing QoS in IP Networks 274.5 Overview of Multiprotocol Label Switching 274.5.1 Using MPLS for traffic engineering 294.5.2 Using MPLS Virtual Private Networks for intersite connections 29

5 3GPP Quality of Service framework 335.1 Mapping of 3GPP Rel '97/'98 QoS attributes to Rel '99 attributes 375.2 Traffic Flow Template 385.3 Service quality related enhancements in 3GPP Rel 4 and Rel 5 395.4 Mapping Between 3GPP Traffic Classes and IETF Differentiated

Services 405.5 IETF DiffServ 425.5.1 Expedited Forwarding and Assured Forwarding PHBs 445.5.2 DiffServ over MPLS 45

6 Quality of Service Mechanisms in Nokia 3G Packet Core 476.1 QoS support in Nokia 3G SGSN and GGSN 476.2 QoS support in Nokia SGSN 546.3 HLR QoS profiles 566.4 Setting up a QoS aware PDP context 576.5 Examples on QoS profile usage 596.6 QoS information in Call Detail Records 616.7 Handovers 616.8 QoS in roaming cases 62

7 Quality of Service Mechanisms in Nokia 3G Circuit Core 637.1 Quality of Service in IP Trunk 637.2 QoS in MSC Server and Media Gateway 65

8 Quality of Service Interworking with Backbone 67DN01154225 Nokia Corporation 3 (86)Issue 2-1 en Nokia Proprietary and Confidential


8.1 QoS interworking mechanisms 688.2 Nokia QoS interworking with Pure IP backbone 68

8.3 Nokia IP QoS interworking with IPowerSDH MPLS WAN backbone 688.4 Nokia IP QoS interworking with operator existing ATM WAN

backbone 70

9 Quality of Service in Application Servers 71

10 Nokia NetAct Quality of Service Support 7310.1 Integrated Service and Network Quality Assurance 7410.2 Network development and optimisation 7510.3 IP backbone management 7610.4 NetAct Tracing 7610.5 Administration 7610.6 Future steps 77

Appendix A. UMTS bearer attributes and Radio Access bearer attributes 79

Appendix B. 3GPP Rel '97/'98 specified QoS parameters 81

Appendix C. Overview on ATM Forum Service Categories 82

Appendix D. Overview on ITU-T ATM QoS Classes 84

References 854 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

List of tablesTable 1. The most important IP-based applications 25Table 2. 3GPP UMTS QoS classes. 35Table 3. UMTS bearer attributes and Radio Access bearer attributes. 36Table 4. Mapping of Rel '97/'98 attributes to Rel '99 attributes. 38Table 5. Assured forwarding PHB Group Classes and Drop Precedence values:

Recommended Codepoints. 44Table 6. 3GPP Rel '99 attributes and the resulting Nokia SGSN behavior. 54Table 7. Examples of QoS profiles in the Nokia HLR. 56Table 8. Example QoS profiles for GPRS networks and terminals. 59Table 9. Example QoS profiles for 3G networks and terminals. 60Table 10. Recommended ATM QoS classes for MSC server traffic. 66Table 11. Overview on ITU-T ATM QoS Classes. 84DN01154225 Nokia Corporation 5 (86)Issue 2-1 en Nokia Proprietary and Confidential


List of figuresFigure 1. Factors that have an effect on the end-user service quality in a 3Gnetwork. 13

Figure 2. Document overview. 15Figure 3. GPRS/EDGE and WCDMA QoS capabilities. 18Figure 4. Protocol stacks for GPRS. 22Figure 5. Protocol stacks for 3G. 23Figure 6. Protocol layer alternatives in the backbone 24Figure 7. TCP slow start 25Figure 8. Statistical multiplexing benefit 26Figure 9. MPLS principle 28Figure 10. MPLS VPN for operator intersite connections. 30Figure 11. Comparison of OPEX between IPoverATM and MPLS VPNs when adding

one new node to the network 31Figure 12. 3GPP UMTS QoS Architecture. 33Figure 13. Real-time serving RNC relocation. 39Figure 14. Mapping between 3GPP traffic classes and IETF DiffServ codepoints. 41Figure 15. Differentiated Services Field marked in IPv4 packet. 42Figure 16. IETF Differentiated Services Architecture. 43Figure 17. DSCP mapping for DiffServ over MPLS. 45Figure 18. Bitrate limits for different traffic classes and admission control. 48Figure 19. QoS interworking in the Gi interface. 49Figure 20. 3G SGSN and GGSN QoS architecture. 50Figure 21. Effect of priority based QoS scheme with heavy traffic load. 52Figure 22. Traffic policing and traffic shaping in 3G SGSN and GGSN. 53Figure 23. Nokia SGSN internal QoS implementation. 56Figure 24. The PDP context QoS negotiation signaling flows. 58Figure 25. Roaming between QoS capable networks. 62Figure 26. IP Trunk for Circuit Core traffic. 64Figure 27. Nokia MSC Server (MSS) Concept. 65Figure 28. Operator site interconnection over a backbone network. 676 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

Figure 29. DiffServ interworking with MPLS WAN backbone. 69

Figure 30. Nokia IP QoS interworking with operator existing ATM WAN. 70Figure 31. Nokia NetAct Framework. 73Figure 32. Integrated service quality management. 74DN01154225 Nokia Corporation 7 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service in 3G Core Network8 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

About this document1 About this documentThe purpose of the document is to give an overview of the Quality of Servicesolutions in the Nokia 3G core mobile network. The Quality of Service (QoS) isdescribed as defined in the 3GPP Release '99 and Release 4.

This document concentrates on the network element hardware and softwareeffects and in particular on how the 3GPP QoS support is implemented in theNokia mobile packet core network. QoS mechanisms in the Nokia circuit coreVoice Over IP (VoIP) solutions are also discussed.DN01154225 Nokia Corporation 9 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service in Brief2 Quality of Service in BriefIn mobile IP networks the end-user experienced performance of different servicesand applications depends for example on the perceived quality of real-timeservices like voice and video and the response times for non-real-time services.For non-real-time services the end-user service quality can be measured in termsof effective transmission rates (kbit/s) and as the time required to downloadselected WAP or WEB pages.

Mobile services require high session set-up quality and high session quality sothat the end-user experiences high overall service quality. The following factorshave an effect on the session set-up quality:

Service accessibility (wide network coverage, minimum networkdowntime, minimum cell barring and no signaling failures)

service availability (no session blocking or congestion in the network) service access time (minimum network response delay and minimum

resource allocation delay)

Different applications have different requirements for quality in terms of packetloss, transmission delay and delay variation. Many real-time applications likevoice are relatively insensitive to packet loss but require very short transmissiondelays and minimum delay variation. On the other hand, many non-real-timeapplications like file download can tolerate delay but are very sensitive to packetloss. The following factors are required for high session quality:

optimised data loss, transmission delay and jitter (delay variation) duringservice time

usable throughput by end application (minimum protocol overhead anderror ratio)

continuity of service connection (wide service coverage and successfulhandovers)

For GPRS/EDGE phase1 non-real-time QoS can be applied already today. 3GPPRel '99/Rel 4 provides efficient and standardised tools real-time support QoS forWCDMA packet bearers in a controlled operator environment. The main tools toguarantee end-to-end QoS include:DN01154225 Nokia Corporation 11 (86)Issue 2-1 en Nokia Proprietary and Confidential


3GPP Rel '99/Rel 4 QoS model and PDP context QoS parameters

DiffServ/DiffServ over MPLS for packet prioritisation

MPLS or IPoverATM for traffic engineering

SLAs for inter-operator and service provider links

OSS-support for end-to-end QoS management

QoS does not create additional network resources, but allows the existing bufferand bandwidth resources to be managed to allow efficient transportation ofpackets through the network with predictable delay, delay variation and packetloss rates.

The QoS mechanisms both decrease operator costs and increase revenue. Theoperator does not need to overdimension the network nor overprovision capacityto guarantee user satisfaction for the services as the QoS schemes ensure that thehigh priority subscribers and applications will always have capacity available.The QoS mechanisms will ensure that the high priority subscribers will get theirsessions through when the network is heavily loaded. In case that congestionoccurs in the network nodes and packets have to be discarded because of bufferoverload, the QoS mechanisms ensure that only the low priority data is discardedwhile the high priority data is provided high throughput rates with low delay.

The figure below summarises the following issues that have an effect on theoverall service quality experienced by the end-user:

the terminal and network element hardware and software (a) network planning and dimensioning (b) application software (c)12 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

Quality of Service in Brief

a) support of 3GPP QoSFigure 1. Factors that have an effect on the end-user service quality in a 3Gnetwork.

The QoS schemes also allow differentiating the service profiles that enable theoperator to increase the revenue by applying higher tariffs for services with higherservice quality. On the other hand, lower priority applications can beimplemented with minimum extra investments to the network capacity meaningthat the operator is able to price the lower priority services attractively to increasethe amount of subscribers.

parameters and mechanisms in UE - UE support of different CH typesa) internal delays generated by UEa) UE memory (effects TCP kbit/s)c) used TCP window sizec) supported HTTP version (1.0/1.1)c) support of WAP optimisation

a) protocol processing, transmission delays, 3GPP QoS supportb) lu transmission resource

dimensioning, topology/distances

a) internal delays in WAP gateways, http-proxies, servers, etc.b) application server capacityb) geographical location (e.g. localised content caching vs. centralised servers)c) supported HTTP version (1.0/1.1)c) support of WAP optimisation

8.6.00

RNC3G SGSN

IP/MPLS/IPoATM backboneGGSN

ApplicationServers

(co-locatedor remote)

a) internal BTS delaysa) interleaving/propagation delaysb) site locationsb) antenna directions/height/qualityb) cable length/qualityb) BTS capacity

a) RNC internal delays, 3GPP QoS supportb) RNC capacityb) H0 thresholdsb) cell traffic load thresholdsb) interference/transmission power thresholdsb) used packet scheduling criteriab) used RLC buffer payload thresholds (TCP effect)b) used DCH bitrate allocation stepsb) allocation of dedicated NRT capacity (RAN2)b) usage of DSCHs for NRT traffic (RAN2)

a) internal processing/ queuing and L1 delaysa) memories/buffer sizes (TCP effect)b) transmission/router capacityb) geographical locations/ distance, number of hop

= terminal/NW element HW and SW effects= application software effects= network planning/dimensioning effects

a) internal processing/ queuing delaysa) 3GPP QoS supportb) packet core capacityb) configuration of RT traffic limitsb) configuration of interactive queue weightsb) used HLR QoS profilesDN01154225 Nokia Corporation 13 (86)Issue 2-1 en Nokia Proprietary and Confidential


By implementing appropriate QoS mechanisms in the network the operator isable to provide high quality services for premium users and critical applications

in a cost-efficient way. The premium subscribers will have priority in session-setup when the network is heavily loaded and their data will have priority overnormal and low-end users. The premium users will also pay higher tariffs for theirservices. The QoS mechanisms guarantee efficient network utilisation andtherefore implementing the low-end services will require minimum investment inthe network meaning that they can be priced very attractively to attract more usersto the network.

Note that the service quality is only as strong as the weakest link on thetransmission path. Therefore it is crucial that the service quality issues are takeninto account in the design of the whole network. The Nokia solutions providingGPRS (General Packet Radio Service) and UMTS (Universal MobileTelecommunications System) access implement state-of-the-art solutions toprovide high service quality immediately.

3GPP defines a Quality of Service architecture for GPRS and 3G radio and PacketCore networks. The Nokia GPRS Packet Core Release 2 and 3G Packet CoreRelease 1 support 3GPP Rel '99 QoS architecture. QoS parameter mapping to Rel'99 parameters is supported for 3GPP Rel '97/'98 terminals. According to the Rel'99 specification, the QoS attributes are mapped to Internet Engineering TaskForce (IETF) defined Differentiated Services (DiffServ) parameters. DiffServoffers a scaleable packet prioritization scheme to be applied in IP networks. Alsosolutions for QoS interworking with different layer 2 and 2.5 Wide Area Networktechnologies (IPoverSDH, ATM, MPLS etc.) can be applied.

The figure below presents the main issues covered in this document. The textboxes refer to chapters in this document.14 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

Quality of Service in BriefFigure 2. Document overview.

IPBackbone

MPLSBackbone

Existing ATMBackbone

2G SGSN

HLR

SIGTRAN

GGSN

3G SGSN

PacketCore

OperatorSite

Examples on QoSprofile usage

Nokia QoS interworkingwith pure IP backbone

Nokia IP QoS interworkingwith operator existingATM WAN backbone

RAN QoS

BSS QoS

8.6.00

QoS supportin Nokia SGSN

HLR QoSprofiles

Gb

lu

QoS interworking in G*

*

SS7

BS RNC

BS BSC

Nokia QoS interworkingwith IPowerSDH MPLSWAN backbone

QoS in ApplicationServers

QoS mechanismsin Nokia 3Gcircuit core

Examples on QoSprofile usage

QoS supportin Nokia SGSNand GGSN

Handovers

3G MSC/IP Trunk

OSR

SS7DN01154225 Nokia Corporation 15 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service Overview3 Quality of Service OverviewWhat is Quality of Service in Packet Core?

Technically Quality of Service (QoS) in 3G core can be defined as the packet corenetwork's ability to successfully transport IP (Internel Protocol) packets withinthe requirements of the application. From the end-user viewpoint QoS ismeasured in terms of transmission quality and transmission delay. High QoSmeans low error-rate, low delay and low delay variation in the transmission ofinformation.

From the operator viewpoint the QoS mechanisms provide cost-efficient meansto implement services that meet the end user expectations, meaning high end-userservice quality. QoS does not create additional network resources, but allows theexisting buffer and bandwidth resources to be managed in a way that allowsefficient transportation of packets through the network with predictable delay,delay variation and packet loss rates.

Delay-critical applications like IP telephony cannot be deployed in wide scalewithout ensuring a certain QoS level. Even though many traditional applicationslike file transfer work without any QoS functions implemented in the network onIP level, it is clear that all applications will benefit from the optimised networkresource utilisation that can be achieved with appropriate QoS mechanisms.

3.1 QoS in GPRS/EDGE Networks and inWCDMA/UMTS Networks

GPRS/EDGE networks can offer prioritisation mainly on subscription basis. Thistype of QoS support is applicable for example for Web/WAP browsing, databaseretrieval, server access, email downloading and SMS/Multimedia Messaging(MMS). The main QoS improvement in the WCDMA (Wideband Code DivisionMultiple Access) and UMTS networks compared to GPRS/EDGE (EnhancedData rates for Global Evolution) networks is the support for real-time sessions inthe radio interface. Voice calls and streaming video require guaranteed transportcapacity, meaning very short transport delay and minimum delay variation. Thefigure below gives an overview on the QoS capabilities in GPRS/EDGE andWCDMA networks.DN01154225 Nokia Corporation 17 (86)Issue 2-1 en Nokia Proprietary and Confidential


In the future real-time IP QoS support can be extended also to EDGE with theintroduction of GERAN (also known as EDGE phase 2).Figure 3. GPRS/EDGE and WCDMA QoS capabilities.

3.2 QoS provides new means for servicedifferentiation

Tariffing and radio coverage have initially been the main means for competitionfor the mobile network operators. The introduction of Wireless ApplicationProtocol (WAP) and mobile data has introduced service provisioning as a newcompetition area. Implementing QoS aware services provides the networkoperator new means for service differentiation. End-to-end QoS support allowsthe network operator to

differentiate service providers

differentiate end-users (gold, silver and bronze subscriptions, seeexample 2 below)

differentiate service offering relative to competitors

8.6.00

Gb

Iu-PS

HLR

ApplicationServers

QoS aware GRX

Non-Real-Time IP QoS

Non-Real-Time IP QoSand Real-Time IP QoS

GPRS packet core

3G packet core18 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

Quality of Service Overview

Example 1.One example of QoS-based service provider differentiation is providing Intranetaccess to a company's employees. In this scenario the corporate customers aretagged as "Corporate NN Employees" in the subscriber database. When theemployees are contacting the corporate intranet, they are assigned apredetermined QoS profile with high transmission capacity, low transmissiondelay and low packet loss ratio.

Example 2.

Another example of QoS-based service provider differentiation is QoS profiles.Different QoS profiles can be associated with end-user subscriptions. In thisscenario the subscription determines the QoS level that is offered to the end-user.The operator creates "gold", "silver" and "bronze" subscriptions for differentcustomer segments. A "gold" user automatically gets a higher bit rate for Internetbrowsing than a "bronze" user. Also, a "gold" user has prioritised access over thesilver and bronze users, when the network is heavily loaded. The tariffing schemereflects the QoS levels of different end-user categories.

Note that packet delay, delay variation and packet loss result form heavy load andcongestion in the network. The network elements are not intentionally delayingor dropping lower-level QoS packets that are conforming to the agreed trafficprofile. Therefore the difference between different QoS levels is most obviousduring busy hours when the traffic prioritisation schemes come into effect.DN01154225 Nokia Corporation 19 (86)Issue 2-1 en Nokia Proprietary and Confidential

IP Traffic in Mobile Networks4 IP Traffic in Mobile NetworksThis chapter covers some mobile IP traffic characteristics and traffic managementmechanisms that have an effect on how the end-user experiences service quality.

4.1 Protocol stacks in GPRS and UMTS

QoS is implemented with different mechanisms on protocol layers 1- 3 indifferent parts of the network. In the example illustrations presented in the twofigures below the application level IP packets carry Wireless ApplicationProtocol (WAP) over User Datagram Protocol (UDP).

In the GPRS radio network QoS is implemented on GPRS layers 1 and 2. TheGPRS Tunneling Protocol (GTP) tunnel extends from the SGSN (Serving GPRSSupport Node) over the IP backbone to the GGSN (Gateway GPRS SupportNode). The GGSN and the application servers are also connected over an IPbackbone. This is illustrated in the figure below.DN01154225 Nokia Corporation 21 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service in 3G Core NetworkFigure 4. Protocol stacks for GPRS.

In the UMTS radio network QoS is implemented on WCDMA layers 1 and 2. TheGTP tunnels extend from the RNC (Radio Network Controller) to the 3G SGSNand from the 3G SGSN over the IP backbone to the GGSN. The GGSN and theapplication servers are also connected over an IP backbone. This is illustrated inthe figure below.

WAP

UDP

IP

WAP

UDP

IP

GPRSL1+L2

WAP

UDP

IP

GTP

UDP

IP

L2

L1

WAP

UDP

IP

L2

L1

WAP

UDP

IP

GTP Tunnel

8.6.00

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IP backbone Server22 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

IP Traffic in Mobile NetworksFigure 5. Protocol stacks for 3G.

The figure below illustrates the alternative protocol layers in the IP backbone partof the network. If Ethernet, Gigabit Ethernet or IPoverSDH (Internet Protocolover Synchronous Digital Hierarchy) and Point to Point Protocol (PPP) is used onlevel 2, the QoS support is based on IETF (Internet Engineering Task Force)Differentiated Services (DiffServ, or DS). Multiprotocol Label Switching(MPLS) can be used for traffic engineering and/or Virtual Private Networks(VPN) in IP networks. In the case that a so-called frame-based MPLS (that isMPLS and IPoverSDH) is used, the DiffServ QoS information in IP packetheaders is mapped to MPLS packet headers to implement DiffServ over MPLS.In the case that ATM or MPLS over ATM (so-called cell-based MPLS) is usedon layer 2, the ATM service categories are applied to implement QoS. The IPpackets are segmented into ATM cells and carried in ATM Permanent VirtualCircuits with the appropriate QoS category.

In 3GPP Rel '99 specifications the usage of ATM as the layer 2 technology ismandated in the Iu-PS interface from the RNC to the 3G SGSN. However, in thesubsequent 3GPP releases the choise of the layer 2 technology is left to the vendorand/or operator.

WAP

UDP

IP

WAP

UDP

IP

WCDMAL1+L2

WAP

UDP

IP

GTP

UDP

IP

L2

L1

WAP

UDP

IP

L2

L1

WAP

UDP

IP

GTP Tunnel

8.6.00

3G SGSN IP backboneGGSN

IP backbone ServerRNC

MobileTerminal

GTP TunnelDN01154225 Nokia Corporation 23 (86)Issue 2-1 en Nokia Proprietary and Confidential


DiffServ over MPLSFigure 6. Protocol layer alternatives in the backbone

4.2 TCP slow start

The Transmission Control Protocol (TCP) offers reliable transmission of IPpackets. The basic principle is that the destination sends acknowledgements(ACK) to the source to inform that it has received the data. If the source does notreceive an acknowledgement, it will retransmit the data.

The TCP slow start algorithm has been introduced to force the sender to controlthe amount of outstanding (non-acknowledged) data being sent into the network.Congestion window is a parameter that defines the maximum amount ofunacknowledged data that the source can send to the network at a particular pointof time. For each ACK the source increases the "congestion window" by 1segment. This results in an exponential growth of the congestion window until thereceiver's advertised window size is reached as illustrated in the figure below.

Ethernet orGigabit Ethernet

Physical cables/Fiber

PPPMPLS

PPPATM

MPLS

ATM

Fiber + SDH/DWDM

IPLayer 3

Layer 2

Layer 1

IETF DiffServ ATM Service Categories24 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

IP Traffic in Mobile NetworksFigure 7. TCP slow start

The impact of slow start is highly dependent on the Round Trip Time (RTT).Short RTT allows a rapid growth of the congestion window and therefore resultsin the source sending large bursts of data to the network. In the case of packet loss,the congestion window size is decreased and thus the TCP speed is dropped toavoid congestion.

For example, the Hypertext Transfer Protocol (HTTP), the File Transfer Protocol(FTP) and the Simple Mail Transfer Protocol (SMTP) use TCP connections fortransmission. Instead of TCP, some applications use the User Datagram Protocol(UDP) for transport. UDP is an unreliable protocol where the data is notacknowledged. Thus the TCP slow start does not affect these applications. Thetable below illustrates the most important IP-based applications that use TCP andUDP.

Receiver Sender

dataack

1* Maximum Segment Size (MSS)

2* MSS

3*MSS4*MSS

5*MSS6*MSS7*MSS8*MSS

Table 1. The most important IP-based applications

HTTP 1.0,HTTP 1.1, FTP, SMTP WML,xHTML, RTP

TCP: Sessions UDP: Single messages

IP: packet routing

Data Link Layer: GPRS bearer, PPP, Ethernet, ATM, etc.DN01154225 Nokia Corporation 25 (86)Issue 2-1 en Nokia Proprietary and Confidential


4.3 Statistical multiplexingIP traffic is bursty in nature, which means that packets are not sent at a constantrate but in bursts consisting of several packets. The bursts are adjoined byvariable-length silent periods. Statistical multiplexing can be utilised in order touse the available bandwidth more efficiently. It relies on the fact that differenttraffic sources' active and passive periods are not simultaneous. Thereforemultiplexing different IP traffic flows on the same link results in more efficientresource utilisation. The capacity that needs to be reserved for aggregated trafficflows is less than the sum of capacities reserved for individual traffic flows. Theidea of statistical multiplexing is illustrated in the figure below:

Figure 8. Statistical multiplexing benefit

In traditional IP networks no traffic management schemes are applied to ensureQoS on IP level. This means that the traffic flows are offered the so-called BestEffort (BE) service. Packets arriving from the IP network nodes are forwarded inthe same order as they arrive. In order to prevent packet loss in case of high load,buffers are implemented in the IP network nodes. Buffering causes delays anddelay variation in packet forwarding. Both dropped packets and severely delayedpackets trigger retransmissions by the higher level protocols (meaning the TCP orthe application protocol) which in turn further increases the load in the network.

Traditional IP networks give no guarantees for the transmitted packets in terms ofloss or delay. Sufficient transmission quality has been ensured by over-engineering, that is by increasing the transmission capacity of the network nodesand increasing the buffer sizes.

Fixed resource allocation:no statistical multiplexing(traditional TDM traffic) Statistical multiplexing

Time

Amou

nt o

f tra

ffic

Wasted capacity Free capacity26 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

IP Traffic in Mobile Networks

Traditional IP applications have been mainly used for file transfer and have notset strict restrictions on transmission delay. Packet losses have been handled by

retransmission requested by higher level protocols. When introducing time-critical applications like voice and video calls to IP networks, the support for QoSmechanisms becomes essential. The operator also has requirements on optimalnetwork capacity dimensioning and resource utilisation. These targets can be metby implementing appropriate QoS mechanisms.

4.4 Basic mechanisms for implementing QoS in IPNetworks

The basic mechanisms that can be applied to enforce QoS in IP networks include:

admission control

policing and shaping

prioritisation of traffic flows

Admission control (access control) means controlling the amount andcharacteristics of the traffic flows that are allowed to be transmitted in thenetwork. Admission control maintains information about allocated and availableresources (meaning transmission capacity and buffer space) in an IP networknode. The admission control function may allow or refuse a requested service tobe provided according to the current load level and administrative aspects (that isif the user has the rights to access the requested service).

Policing and shaping are applied to change the characteristics of a traffic flow toenforce the traffic contract negotiated between the user and the network. Withpolicing and shaping algorithms the maximum bitrate can be restricted to theagreed level. Policing can result in discarding packets that are not conforming tothe traffic contract. Shaping means delaying packets within a traffic flow to causeit to conform to the traffic profile.

Prioritisation of traffic flows means allocating different buffers to traffic flowsbelonging to different priority classes. Packets in the higher priority buffers areforwarded before the packets in the lower priority buffers. Different serviceschemes have been developed to ensure appropriate service level for differentpriority classes.

4.5 Overview of Multiprotocol Label Switching

Multiprotocol Label Switching (MPLS) is a fully IP compatible way of providingATM like functionality such as traffic engineering virtual private networking ina cost-effective way.DN01154225 Nokia Corporation 27 (86)Issue 2-1 en Nokia Proprietary and Confidential


In IP networks each node makes independent routing decisions based on the IPaddress of an incoming packet. MPLS Architecture, defined in the specification

IETF RFC 3031, provides means to partition the incoming packets to a set ofForwarding Equivalence Classes (FECs) when they enter the network. The FECto which the packet is assigned is encoded in the packet header as an MPLS label.

The packets are not routed. They are switched along a label switched path (LSP).The MPLS labels represent the destination of the packet but they can also be usedfor VPN and traffic engineering purposes. There are several mechanisms forassigning and distributing MPLS labels. Label Distribution Protocol (LDP) is themost commonly used protocol. MPLS can also be used for providing existing cellbased networks an IP compatible control plane. The figure below illustrates theMPLS principle:

Figure 9. MPLS principle

In the subsequent hops the label is used to determine the next hop and a new label.The old label is replaced with the new label and the packet is forwarded to its nexthop. The MPLS architecture allows the routing decisions to be based on all theinformation available on the packet when the packet enters the network (forexample the port the packet enters from) without any impact on the routers thatmerely forward labelled packets.

Packet switching along the path

Routing based ondestination IP addresson IP packet header

Packet forwardingbased on MPLS labels

Routing based ondestination IP addresson IP packet header

IP domainIP domain MPLS domain28 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


4.5.1 Using MPLS for traffic engineeringTraditional routing protocols like Open Shortest Path First (OSPF), RoutingInformation Protocol (RIP) v2 and IS-IS can not take into account for examplethe available physical link bandwidth (E1 / STM-1 / STM-4 etc.) and the linkloading level when making the next-hop routing decision. As a result, trafficengineering is sometimes needed to force the IP packets to be routed against theserouting protocols. MPLS traffic engineering provides tools for control of linkloading and automatic recovery features. MPLS traffic engineering is also fullyinteroperable with the Differentiated Services QoS scheme.

MPLS is emerging as the standard mechanism for traffic engineering in routerbased IP backbones. It can provide more efficient use of network resources andimproved QoS because of optimal routing.

4.5.2 Using MPLS Virtual Private Networks for intersite connections

In addition to traffic engineering the second major MPLS application is VirtualPrivate Network (VPN). With MPLS the network operator can provide IP VPNservices in a cost-effective way. At an operator site a Virtual LAN (VLAN) canbe used to connect the network nodes at that site. A VLAN is a switched networkthat can be logically segmented to separate different types of traffic, for exampletraffic on different network interfaces, network management, signalling,charging, content distribution, legal interception. One-to-one mapping of theintrasite VLANs to MPLS VPNs can be used for connecting to remote operatorsites. The figure below illustrates the MPLS VPN solution for operator intersiteconnections.DN01154225 Nokia Corporation 29 (86)Issue 2-1 en Nokia Proprietary and Confidential


Gn interfaceFigure 10. MPLS VPN for operator intersite connections.

The main benefit of the MPLS VPN approach compared to an ATM or tunneledIP VPN is minimised Operational Expenditure (OPEX) when adding new nodesto the network. In a tunnelled VPN or ATM environment the number ofconnections that need to be configured to interconnect all the VPN members isgrowing fast with increased VPN size (N x (N-1)/2 connections with N VPNmembers). When MPLS VPNs are used, no connections between the VPNmembers need to be configured. Connectivity is provided by routing protocols.The network configuration and OPEX comparison is illustrated in the figurebelow:

Virtual LAN at operator's site

HLR

GGSN

3G SGSN

Operator IPWAN

MGW

MPLSVPN

Gi interfaceNb interfaceManagement

OSR,MPLSedgeRoaming,peering etc.

Servers30 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


New node New nodeFigure 11. Comparison of OPEX between IPoverATM and MPLS VPNs whenadding one new node to the network

0

200

400

600

800

1000

Overlay VPN (IPoverATM)

Cost

to a

dd o

ne n

ode

0

200

400

600

800

1000

IP/MPLS-based VPN with Routing

VPN size(numberof nodes)

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3GPP Quality of Service framework5 3GPP Quality of Service framework3GPP Rel '99 defines a layered UMTS bearer service architecture. Thisspecification provides the framework for implementing QoS aware end-to-endservices for UMTS networks. Note that only the QoS attributes and architectureare provided whereas the implementation of the actual QoS mechanisms andservice schemes is left as the vendors' and the operators' choice. The 3GPP UMTSQoS architecture is illustrated in the figure below.

Figure 12. 3GPP UMTS QoS Architecture.

8.6.00

End-to-End Service

TE MT UTRAN CN Iuedgenode

UMTS Bearer Service

TECNGateway

CNBearerService

Radio AccessBearer Service

RadioBearerService

BackboneBearerService

IuBearerService

UTRAFDD/TDDService

PhysicalBearerService

BS RNC3G

SGSN

GGSN

ApplicationServer

ExternalBearerService

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The End-to-End Service is the service that the operator offers to the end-users.The UMTS bearer service contains mechanisms to implement QoS over the

UMTS network consisting of UTRAN and Core Network (CN). It is furtherdivided into Radio Access Bearer Service and Core Network Bearer Service. TheRadio Access Bearer Service is based on the characteristics of the radio interfaceand is maintained for a moving user equipment. The Core Network BearerService controls and utilises the backbone network to provide the contractedUMTS bearer service. The role of the radio bearer service is to cover all theaspects of the radio interface transport. The Iu-Bearer Service together with thePhysical Bearer Service provides the transport between UTRAN and the corenetwork. The Backbone Bearer Service covers the Layer 1/ Layer2 functionalityand its selection is left as operators' choice in order to fulfill the QoS requirementsof the Core Network Bearer Service.

QoS management functions are defined for the UMTS bearer service in thecontrol plane and in the user plane. The implementation of the functions is notspecified, rather it is stated that they are responsible for enforcing the QoScommitments negotiated for the UMTS bearer service.

3GPP Rel '99 defines four different UMTS QoS classes or traffic classes:

Conversational class

Streaming class

Interactive class

Background class

The main differentiating factor between the QoS classes is the sensitivity towardsdelay and packet loss. Conversational and streaming classes are mainly intendedto carry real-time traffic flows whereas interactive and background classes aremainly meant for traditional Internet applications like WWW, email, Telnet, FileTransfer Protocol (FTP) and mobile internet specific non-real-time applicationslike WAP and Multimedia Messaging Service (MMS). Due to less strict delayrequirements compared to conversational and streaming classes, both providebetter error rate by means of channel coding and retransmission. The table belowsummarises the features of each class.34 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

3GPP Quality of Service framework3GPP Rel '99 defines also QoS attributes to describe the service provided to theuser of the UMTS bearer service. These attributes form a QoS profile. A QoSprofile can be used in the ways listed below:

The user equipment (UE) capabilities form a QoS profile that may limit theprovided service.

The UE or the terminal equipment in the network (for example contentserver) may request a QoS profile when an UMTS bearer service isestablished or modified.

A QoS profile is associated with each PDP context. A QoS profile can be included in the subscription data in the Home

Location Register (HLR). The operator may configure default QoS profiles for the UMTS bearer

services provided by the network.

A network-specific QoS profile may for example indicate the currentresource availability or other network capabilities.

Table 2. 3GPP UMTS QoS classes.

Traffic class Characteristics Example application

Conversational class Preserve time relation(variation between informationentities of the stream.

Conversational pattern:stringent and low delay

Real-time traffic

Voice call

Streaming class Preserve time relationbetween information entities ofthe stream.

Real-time traffic

Streaming video

Interactive class Request response pattern Preserve payload content Best effort traffic (non-real-

time)

Web/WAP browsing, databaseretrieval, server access

Background class Destination is not expectingthe data within a certain time.

Preserve payload content Best effor traffic (non-real-

time)

Background download of e-mails,SMS/MMSDN01154225 Nokia Corporation 35 (86)Issue 2-1 en Nokia Proprietary and Confidential


The UMTS bearer attributes and Radio Access bearer attributes defined for eachtraffic class are summarised in the table below. Note that the traffic class is also

an attribute itself. 3GPP Rel '99 defines the value ranges of each attributereflecting the network capabilities.

Table 3. UMTS bearer attributes and Radio Access bearer attributes.

Traffic Class Conversational Streaming Interactive Background

Maximum bitrate(kbps)

3GPP Quality of Service framework

Table 3. UMTS bearer attributes and Radio Access bearer attributes.For the parameter explanations, see Appendix A.

The application may request certain QoS attribute values at Packet Data Protocol(PDP) context setup. The requested values are compared to the user's QoS profilestored in the Home Location Register (HLR). In the case that the requested valuesare higher than the HLR QoS profile allows, the profile overrides the requestedvalues, meaning that the QoS is downgraded to the maximum allowed level. Anexample is that the application may request a higher bitrate than allowed by theuser's QoS profile. The allotted bitrate will then be set as the maximum allowedby the profile.

5.1 Mapping of 3GPP Rel '97/'98 QoS attributes to Rel'99 attributes

The 3GPP Rel '97/'98 specifies the following QoS parameters:

Reliability Class

Delay Class

Precedence Class

Peak Throughput Class

Mean Throughput Class

For the parameters explanations, see Appendix B.

Note that 3GPP Rel '97/'98 does not specify how these parameters should beapplied to implement QoS especially in the radio network, as the 3GPP Rel '99specification does. For this reason, 3GPP Rel '99 defines the mapping of Rel'97/'98 attributes to Rel '99 attributes as presented in the table below. The 3GPPRel '99 specification defines the exact parameter values to be used in themappings (see Table UMTS bearer attributes and Radio Access bearerattributes). For more information on the exact mappings with the parametervalues, see the 3GPP Rel '99 TS 23.107 specification.

Allocation/Retention priority

1, 2, 3 1, 2, 3 1, 2, 3 1, 2, 3

Source statisticdescriptor*

Speech / unknown Speech / unknown

* Only a Radio Access bearer service attribute** For further study

Traffic Class Conversational Streaming Interactive BackgroundDN01154225 Nokia Corporation 37 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service in 3G Core Network5.2 Traffic Flow Template

3GPP Rel '97/'98 allows only one PDP context to be established per one terminalIP address. Rel '99 specifies a Traffic Flow Template (TFT) that allows theestablishing of several simultaneous PDP contexts with different QoScharacteristics using one IP address of the terminal. A TFT is assigned to thesePDP contexts to direct the incoming downlink traffic to the right PDP context inthe GGSN. The TFT assignment is based on different combinations of thefollowing attributes:

Source Address and Subnet Mask

Protocol Number (IPv4) / Next Header (IPv6) Destination Port Range

Source Port Range

IPSec Security Parameter Index (SPI) Type of Service (TOS) (IPv4) / Traffic class (IPv6) and Mask Flow Label (IPv6)

Table 4. Mapping of Rel '97/'98 attributes to Rel '99 attributes.

Rel '97/'98 attribute Rel '99 attribute

Delay class Traffic classTraffic handling priority

Reliability class SDU error ratioResidual bit error ratioDelivery of erroneous SDUs

Peak throughput class Maximum bitrate (kbps)Precedence class Allocation/retention priority

Reordering Required (Information in the SGSN andGGSN PDP contexts)

Delivery order38 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


5.3 Service quality related enhancements in 3GPP Rel

4 and Rel 5

The main service quality related enhancement introduced in 3GPP Rel 4 specifiesEnhanced Real Time Serving RNC Relocation. The feature is applied to providesuccessful (meaning that no packets are lost) transmission of real-time servicedata (for example voice services) for moving end-users.

The figure below illustrates a Serving RNC Relocation together with a SGSNrelocation. The end-user is moving from a source RNC coverage area to a targetRNC coverage area. In a Rel '99based implementation the packets that havebeen sent from the GGSN towards the SGSN and the source RNC but have notreached the user equipment are lost.

In a Rel 4 based implementation the source RNC starts to duplicate the downlinkGTP Protocol Data Units (GTP-PDUs) when a relocation is likely to happen. Onecopy is sent to the local Base Station and the other copy is forwarded to the targetRNC. The source RNC continues processing and sending downlink data normallytowards the UE. The target RNC discards all forwarded GTP-PDUs until it startsto operate as the serving RNC. When the target RNC takes over the serving RNCrole, it starts to process the arriving downlink GTP-PDUs and sends the downlinkdata to the UE.

Figure 13. Real-time serving RNC relocation.

8.6.00

Moving MT

BS Source RNC

3G SGSN

GGSN

3G SGSN

Target RNC

lu-PS

lur

lu-PSDN01154225 Nokia Corporation 39 (86)Issue 2-1 en Nokia Proprietary and Confidential


In the case that both the source RNC and the target RNC are connected to thesame SGSN, the inter-SGSN handover is not needed as the handover takes place

only between the RNCs.

3GPP Rel 5 introduces a Session Initiation Protocol (SIP) based IP MultimediaSystem (IMS). This introduces SIP/IMS-specific QoS additions, for example aso-called Go interface between GGSN and Policy Control Function (PCF). PCFis a new logical network functionality used to apply policy to the bearer usage inthe GGSN with an IP Multimedia Subsystem (IMS) session. In Rel 5 the PCF isco-located with the Proxy Call State Control Function (P-CSCF) and the interfacebetween the PCF and the P-CSCF is not standardised. The PCF interfaces withthe GGSN via the standardised Go interface.

5.4 Mapping Between 3GPP Traffic Classes and IETFDifferentiated Services

According to the 3GPP specifications, Differentiated Services defined by IETF isused to select the traffic class and appropriate traffic attribute values for IP-basedIu bearer services and for IP-based Core Network. As presented in figure 3GPPUMTS QoS Architecture, DiffServ is used for the Iu Bearer Service and the CNbearer Service. The figure below illustrates the mapping between 3GPP trafficclasses and IETF DiffServ Codepoints (DSCP). The UMTS bearer service equalsto the PDP context.40 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


8.6.003GFigure 14. Mapping between 3GPP traffic classes and IETF DiffServcodepoints.

The mapping from UMTS QoS classes to DiffServ Codepoints will be controlledby the operator. The mapping depends on bandwidth and provisioning ofresources among the different DiffServ classes that the operator controls to satisfythe cost and performance requirements. Interoperability between operators willbe based on the use of DiffServ Service Level Specifications (SLS).

End-to-End Service

TE MT UTRAN CN Iuedgenode

UMTS Bearer Service

TECNGateway

CNBearerService

Radio AccessBearer Service

RadioBearerService

BackboneBearerService

IuBearerService

UTRAFDD/TDDService

PhysicalBearerService

3GPP defined UMTSBearer Service andRadio Access BearerService attributes

Mapping of3GPP attributesto IETF Diffserv

IETF Diffserv used forIP-based Iu and CNbearer services.

BS RNC SGSN

GGSN

ApplicationServer

ExternalBearerService

TE/MT LocalBearerServiceDN01154225 Nokia Corporation 41 (86)Issue 2-1 en Nokia Proprietary and Confidential


5.5 IETF DiffServThe DiffServ architecture is defined by Internet Engineering Task Force (IETF).It aims at providing scalable service differentiation for IP-based packet networks.The architecture defines an IP packet classification scheme where the packets aremarked at IP level: the Type of Service bits in the IPv4 packet header or the TrafficClass octet in the IPv6 packet header is used to mark the DiffServ Codepoint(DSCP). For more information, see the specifications IETF RFC 2475 and IETFRFC 2474.

Figure 15. Differentiated Services Field marked in IPv4 packet.

A DiffServ domain consists of DiffServ capable boundary nodes and interiornodes. The boundary nodes classify the incoming packets and mark them with aDSCP codepoint value. The classification can be based on the value of acombination of one or more header fields such as source/destination address,DSCP, protocol ID, source and destination port numbers and other informationsuch as GPRS/UMTS QoS class and the incoming interface.

Each node in the DiffServ domain implements Per-Hop-Behaviors (PHB) to offerdifferentiated forwarding treatment for packets having different DSCP values.PHBs may be specified in terms of their resource allocation (for example bufferor bandwidth) relative to other PHBs or in terms of their relative observabletraffic characteristics. Per-Hop-Behaviors are implemented in the DiffServ nodesby means of buffer management and packet scheduling mechanisms.

0 1 2 3 4 5 6 7

differentiated services codepoint currentlyunused

IPv4 type of service bits

data

options (if any)32-bit destination IP address

32-bit source IP address

8-bit time-to-live (TTL) 16-bit header checksum

16-bit total length (in bytes)13-bit fragment offset16-bit identification

8-bit protocol

4-bitversion

4-bitheaderlength 3-bit

flags

8-bit type ofservice (TOS)42 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


Service Level Agreement Service Level AgreementDiffServ DomainFigure 16. IETF Differentiated Services Architecture.

The DiffServ (DS) boundary and interior nodes examine the DSCP value of theincoming packets. All packets having the same DSCP value are experiencing thesame externally observable forwarding behavior (that is packet loss, delay, jitter)in a particular DS node.

Note that the forwarding behavior is a general concept. The accurate value of forexample packet delay will depend on the traffic load on that particular link. Thisis because the Behavior Aggregate (BA) determines the relative priority of thebehavior aggregates rather than giving exact guarantees on how different BAs aretreated in the DiffServ nodes.

Traffic conditioning may be performed at the DiffServ domain boundary nodes.Traffic conditioning performs metering, shaping, policing and remarking.Shaping means that out-of-profile packets may be queued until they are in-profile.Policing means discarding the out-of profile packets. Remarking is markingpackets with a new DSCP value.

A Service Level Specification (SLS) needs to be established between a DiffServdomain and connecting network domains. The SLS specifies packet classificationand remarking rules and may also specify traffic profiles (bitrate, burst size) andactions to traffic streams that are in-profile or out-of-profile.

The Traffic Conditioning Specification (TCS) between the domains is derived(explicitly or implicitly) from the SLS. The TCS specifies how transit traffic fromone DiffServ domain to another is conditioned at the boundary between the twoDiffServ domains. A DiffServ ingress node is responsible for ensuring that thetraffic entering the DiffServ domain conforms to any TCS between it and theconnecting domain.

Per-Hop-Behavioursimplemented in each node

DS boundary node

DS interior node

Other DiffServ or non-DiffServ capable domain

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5.5.1 Expedited Forwarding and Assured Forwarding PHBsTwo Per-Hop-Behavior groups are currently defined by IETF: the ExpeditedForwarding PHB and Assured Forwarding PHB. For more information, see thespecifications IETF RFC 2598 and IETF RFC 2597.

The Expedited Forwarding PHB (EF PHB) can be used to build low packet loss,low latency, low jitter, guaranteed bandwidth end-to-end service throughDiffServ domains. The service appears to the customer as a point-to-pointconnection or a "virtual leased line". Packets belonging to the EF PHB behavioraggregate are guaranteed a minimum forwarding bitrate in all the DiffServ nodesindependently of the traffic load level in these nodes. This minimum bitrate is aconfigurable parameter. DiffServ Codepoint value 101110 is recommended forthe EF PHB.

The Assured Forwarding PHB (AF PHB) can be used to provide different levelsof forwarding assurances in terms of packet loss, delay and jitter. The AF PHBdefines four AF classes with three different drop precedence values in each class.Each DiffServ node allocates a certain buffer space and bandwidth for each AFclass. In the case of congestion, the drop precedence of a packet determines therelative importance of the packet relative to the packets in the same AF class.

The table below lists the recommended codepoints for AF PHB group classes anddrop presedence values.

The IETF specifications allow any combination or subset of the 13 specified AFand EF codepoints to be used. It is required that the bandwidth and buffer spaceallocated to EF and AF classes are operator configurable in any vendor's DiffServcompliant routers. The IETF specifications do not define the relationship(priority) between EF class traffic and AF class traffic. This is operatorconfigurable. However, EF is commonly regarded as the traffic class for real-timetraffic.

Table 5. Assured forwarding PHB Group Classes and Drop Precedencevalues: Recommended Codepoints.

Class 1 Class 2 Class 3 Class 4

Low drop precedence 001010 010010 011010 100010

Medium drop precedence 001100 010100 011100 100100

High drop precedence 001110 010110 011110 10011044 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


5.5.2 DiffServ over MPLSMPLS support for DiffServ allows the MPLS network administrator to select howDiffServ Behavior Aggregates are optimally mapped onto the MPLS LabelSwitched Paths (LSP). The mapping of the DiffServ information to MPLS headerat the MPLS-edge is illustrated in the figure below.

Figure 17. DSCP mapping for DiffServ over MPLS.

The illustrated mapping applies to the so-called frame-based MPLS where theMPLS capable IPoverSDH router interfaces are used.

IPv4 Packet MPLSLabel IPv4 Packet

IP Domain MPLS Domain IP DomainMPLS-edge router

DSCP: xyz Mapping of DiffServ information DSCP: xyz

MPLS-edge routerDN01154225 Nokia Corporation 45 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service Mechanisms in Nokia 3G Packet Core6 Quality of Service Mechanisms in Nokia3G Packet Core

Nokia SGSN supports the 3GPP Interactive and Background classes that cancurrently be supported in a GPRS/EDGE radio network. The 3G SGSN supportsalso Conversational and Streaming traffic classes as they are supported byWCDMA capable radio networks.

6.1 QoS support in Nokia 3G SGSN and GGSNIn the Nokia 3G Packet Core release 1 the 3G SGSN and GGSN performadmission control by performing the PDP context activation and PDP contextQoS capability negotiation with the user equipment. For this purpose the 3GSGSN and the GGSN have operator-specified limits for Real-time class,Conversational class and Streaming class PDP contexts. In practice this meansthat when the sum of the bitrates of, for example, the Conversational Class PDPcontexts reaches the configured limit value, the admission control algorithm willrefuse all new Conversational Class PDP context setup requests until a sufficientamount of the existing context have been released and the load level in theparticular GSN has decreased. The admission control scheme is illustrated in thefigure below.DN01154225 Nokia Corporation 47 (86)Issue 2-1 en Nokia Proprietary and Confidential


AdmissionFigure 18. Bitrate limits for different traffic classes and admission control.

3G SGSN and GGSN use the following the PDP context QoS parameters fromthe 3GPP specified bearer attributes (see also Table UMTS bearer attributes andRadio Access bearer attributes):

Traffic Class

Maximum bitrate

Guaranteed bitrate

Traffic handling priority

Allocation/retention priority

Based on the negotiated traffic class and traffic handling priority (applicable onlyto the Interactive class PDP contexts), 3G SGSN and GGSN mark all the GTPtransport plane IP packets in Gp/Gn interface and application level IP packets inthe Gi interface with DiffServ Codepoints. In the Nokia GPRS Packet Corerelease 3 and in the Nokia 3G Packet Core release 2 the traffic class mappings areoperator configurable.

Maximum capacities allowed forConversational and Streaming PDP contexts.

Interactive andBackgroundonly

Streaming

Conversational

Total linkbandwidth

Control

Statistical multiplexingallows Background andInteractive traffic to usethe free capacity.

A new ConversationalClass context refusedas bandwidth limit wouldbe exceeded.48 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

Quality of Service Mechanisms in Nokia 3G Packet Core

QoS interworking between the GGSN and an external packet data network in Giinterface is illustrated in the figure below.Figure 19. QoS interworking in the Gi interface.

3G SGSN and GGSN internal QoS architecture is illustrated in the figure below.

Application

TCP/UDP

PDCP

RLC-U

MAC

RadioL1

IPv4/IPv6

L2

L1

Phy

RadioL1

MAC

UDPRLC-U

PDCP GTP-U

IP

L2

L1

Phy

LinkLayer

UDPUDP

GTP-U GTP

Phy

IPIP

Phy

LinkLayer

UDP

GTP

Phy

L1

L2

IP

DiffServ codepoint based onthe PDP context information

DiffServ codepoint can be mapped to theapplication layer IP packet header in the GGSN

Application

TCP/UDP

IPv4/IPv6

Phy Phy

L1 L1

L2 L2

IPv4/IPv6

DiffServ codepointbased on the PDPcontext information

8.6.00

UE/TE/MT GGSN3G SGSNBS

RNC

U Iu Gn Gi

ApplicationServerDN01154225 Nokia Corporation 49 (86)Issue 2-1 en Nokia Proprietary and Confidential


Network InterfaceFigure 20. 3G SGSN and GGSN QoS architecture.

In GGSN the packet classification in the downlink direction (from network) isbased on the Traffic Flow Template (TFT) and the IP source address. Packetclassification in the uplink direction (from user equipment) is based on the TunnelEnd-point ID (TEID). The packet classification in the 3G SGSN is based on TEIDboth in the uplink and downlink directions.

Policing forces the traffic of the PDP contexts to adjust to the reserved resources.If downlink traffic for a single PDP context exceeds the agreed maximum bitrate,user IP packets are discarded to maintain the traffic within its allowed limits. Thenon-real-time packets go to traffic shaping. For the real-time traffic, policing alsotakes care that the guaranteed bitrate is not exceeded. If it is exceeded, the packetis forwarded if there are resources available in the 3G SGSN.

Conv. Str. Int 1 Int 2 Int 3 Bgr

Strict Priority Scheduler

AF

Network Interface

Weighted FairQueuing

Policing and Shaping

Classification

RED RED RED RED

DiffServ Codepoint Marking50 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


Traffic shaping is done for the non-real-time traffic classes (Background andInteractive 1,2,3) exceeding the agreed maximum bitrate in the downlink

direction. The idea of traffic shaping is to smooth the traffic pattern of thecontexts and decrease the burstiness of the traffic. Traffic shaping makes thetraffic patterns more predictable, as packets are discarded if a burst is too big ortoo long.

The marking function marks the packets with the appropriate DSCP codepointvalue if they are not yet marked. The marking function may also change thepacket's DSCP marking if needed.

Separate queues are provided for EF, AF and for Best Effort DiffServ codepointtraffic. The queuing priorities between the three AF queues are operatorconfigurable. For the AF and Best Effort queue the IETF defined Random EarlyDetection (RED) algorithm is used for active buffer management. The REDalgorithm drops arriving packets probabistically. The probability of dropping anarriving packet increases as the average queue size grows. The RED responds toa time-averaged queue length, not to an instantaneous one.

The RED algorithm reduces the steady-state queue size and provides means tointentionally drop packets to decrease the congestion windows of the TCP trafficsources. This allows the accommodation of the arriving traffic bursts moreefficiently to decrease traffic load in the case of imminent congestion.

There is a strict priority scheduler in the output interfaces of the 3G SGSN andthe GGSN, which always gives priority to EF traffic, followed by AF traffic. Theamount of EF traffic can be limited with operator configurable limits.

The figure below illustrates the effect of the buffering and scheduling schemeapplied in 3G SGSN and GGSN compared to a Best Effort scheme.DN01154225 Nokia Corporation 51 (86)Issue 2-1 en Nokia Proprietary and Confidential


Best Effort Priority-based QoSFigure 21. Effect of priority based QoS scheme with heavy traffic load.

The same traffic pattern is considered in both cases. In the Best Effort scheme allpackets have the same priority and are served by the same buffer. The bufferdimensioning has to be done according to the most delay-sensitive traffic thatlimits the buffer size. In the case of congestion packets are discarded due to bufferoverflow and all packets experience longer transmission delays. If QoS schemesare not applied, the only way to prevent packet loss is over-dimensioning thenetwork to accommodate even very large traffic bursts.

When priority-based QoS is applied, very low delays can be offered to ExpeditedForwarding (Conversational) traffic. Assured Forwarding (Streaming andInteractive) traffic may experience some delays. The Best Effort (Background)traffic experiences the most delay. The buffers offered to the different prioritiescan be dimensioned taking into account the delay and delay variationrequirements of the particular applications using those priorities. Thereforeespecially the Best Effort buffer can be relatively large which in turn reducesconsiderably the amount of dropped packets in the case of congestion.

Buffering scheme: one buffer for all traffic

Packets discarded due to bufferoverflow, longer transmission delays

No traffic prioritisation applied

Linkcapacity

Time

Amou

nt o

f tra

ffic

Best Effort EF AF1 AF2 AF3 AF4 BE

Buffering scheme: priority buffers

Best EffortAssured Forwarding

Expedited Forwarding

EF and AF traffic do not experience anycongestion (delay, loss). BE buffer smoothstraffic, minimum packet loss.52 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


Policing and shaping are based on maximum and guaranteed bitrate parametersnegotiated for the PDP context. In the 3G SGSN policing is applied to the

downlink traffic coming from other operators' GGSNs. The uplink traffic does notneed to be policed since the air-interface efficiently limits the bandwidth. Policingis applied in the GGSN to traffic coming from external networks (for example theInternet). The figure below illustrates the traffic policing and shaping in 3GSGSN and GGSN.

Figure 22. Traffic policing and traffic shaping in 3G SGSN and GGSN.

For the support of Allocation/Retention attribute, 3G SGSN and GGSN haveinternal limits. These limits define the maximum capacity for real-time PDPcontexts (Conversational and Streaming class) and non-real-time (Interactive andBackground classes) queue loading level after which 3G SGSN or GGSN acceptonly PDP contexts from allocation retention priority 1 and 2 users or only priority1 users. The scheme guarantees that high priority users will have a highprobability of successful PDP context activation even when the network is highlyloaded.

Enforcing the SLSwith traffic policingand possible shaping

8.6.00

= EF PHB (DSCP = 101110)for voice packets generatese.g. MAX 1.5 ms delay +0.001% packet loss per hop.

Traffic policingand possible shapingaccording to PDPcontext parameters

Operator A DiffServ domain

MTBS RNC

Traffic policingand possible shapingaccording to PDPcontext parameters

End of GTP => DSCPmapped to applicationIP-packet headers

IP backbone

Backbone router

Packet Core3G SGSN

GGSN

Mobile ISP

Corporate

Operator B DiffServcapable or non-DiffServ capable domain

No policing needed as the radionetwork limits the capacity.GTP tunnel (+ IP-transport)starts => DSCP marking.

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The SGSN and the GGSN insert both requested UMTS QoS parameter values andnegotiated UMTS QoS parameter values to the CDRs. For statistical information

the 3G SGSN and GGSN both provide the following counters per Conversational,Streaming, Interactive 1,2,3 and Background traffic classes PDP contexts:

Uplink kilobytes counters

Downlink kilobytes

Dropped kilobytes

Active PDP contexts

Declined PDP contexts

The operator can use this statistical information to monitor the network load level,deployed network resources and to appropriately adjust for example themaximum bandwidth allowed for Conversational and Streaming class PDPcontexts.

6.2 QoS support in Nokia SGSNIn the Nokia GPRS Packet Core release 2 the SGSN supports 3GPP Interactiveand background traffic classes. The table below summarises the 3GPP Rel '99attributes and their resulting SGSN downlink behavior.

Table 6. 3GPP Rel '99 attributes and the resulting Nokia SGSN behavior.

3GPP Rel '99 Attributes Resulting SGSN downlink behavior

Conversational Traffic Class Downgraded to Interactive traffic class, Traffic handlingPriority = 2

Streaming As above.

Interactive Traffic Class, Traffic HandlingPriority = 1

Buffer for Interactive Traffic Class, Traffic Handling Priority =1





Background Buffer for Background traffic

Maximum Bitrate No effect (only mapping)Allocation/Retention Priority No effect in 2G SGSN. The SGSN delivers the ARP

parameter to the BSS and the GGSN.54 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


Table 6. 3GPP Rel '99 attributes and the resulting Nokia SGSN behavior.Note that the SGSN QoS mechanisms are applied only to downlink packets.Prioritisation of uplink packets from the UE is done by the BSC. Reliability class3 and 4 packets are handled in the same way in the Nokia SGSN but they arehandled differently in the Nokia BSS.

The figure below illustrates the SGSN internal QoS implementation. TheReliability Class parameter effects the probability that a packet will be discardedby the Random Early Detection (RED) algorithm. Packet discarding algorithmsare not applied to signaling and short messages.

Delivery Order in -sequence SDU delivery is provided if SDU Error Ratio


WFQFigure 23. Nokia SGSN internal QoS implementation.

6.3 HLR QoS profilesNokia HLR Release M11 supports 3GPP Rel '99 QoS attributes. Up to 250 QoSprofiles can be defined in the Nokia HLR. Each QoS profile has a different set of3GPP QoS parameter values. A total of 750 different QoS subscription profilescan be defined with the 3 priority levels defined in the Allocation/RetentionPriority parameter. The two tables below give a simplified example on QoSprofiles and subscription profiles in the Nokia HLR.

.

.

.

NS Buffer BSSGP Buffer

ToFrameRelay

LLC Buffer GTP Buffer

RED

FromGn

NS-VCn

WFQ

NS-VC1 Buffer for Interactive

Traffic Class, THP=1

Buffer for InteractiveTraffic Class, THP=2

Buffer for InteractiveTraffic Class, THP=3

Buffer for BestEffort Traffic Class

RED

RED

RED

RED

Buffer for SM andGMM messages SM, GMM messages

Reliability Class 3 to5 data packets, SM,

GMM and SMSmessages

Reliability Class 2data packets

Table 7. Examples of QoS profiles in the Nokia HLR.

Profilenumber Traffic class

Guaranteedbitrate (kbit/s)

Maximum bitrate(kbit/s) THP ...

1 Conversational 100 100 n/a

2 Conversational 10 20 n/a

3 Streaming 200 250 n/a

4 Streaming 100 150 n/a

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Table 7. Examples of QoS profiles in the Nokia HLR. (Continued)A subscriber can have a maximum of 10 simultaneous PDP contexts. Each ofthese PDP contexts can be linked to a different QoS profile. Each PDP contextcan have its own Access Point Name (APN). As an example, the user can have anIP voice session using the operators IP Telephony service and a VPN connectionto the office LAN at the same time and with different QoS levels.

The Nokia HLR QoS profiles conform to 3GPP Rel '99 standards. The supportedQoS profile parameters are listed below:

Traffic Class

Maximum Bit rate for Uplink/Downlink

Delivery Order

Maximum SDU size

SDU Error Ratio

Residual Bit Error Rate (BER) Delivery of Erroneous SDUs

Transfer Delay

Guaranteed Bit rate for Uplink/Downlink

Traffic Handling priority

The Allocation/Retention Priority parameter value is set on subscription basis.For more information, see Chapter QoS support in Nokia 3G SGSN and GGSN.

6.4 Setting up a QoS aware PDP contextIn this example the PDP context activation request comes from the userequipment. The PDP context activation request contains information on therequested QoS level. This signaling chain is illustrated in the figure below.

6 Interactive n/a 200 3

...

250 Background n/a 300 n/a

Profilenumber Traffic class

Guaranteedbitrate (kbit/s)

Maximum bitrate(kbit/s) THP ...DN01154225 Nokia Corporation 57 (86)Issue 2-1 en Nokia Proprietary and Confidential


SGSN checks available capacity for conversationalclass GGSN checks available capacity forFigure 24. The PDP context QoS negotiation signaling flows.

The 3G SGSN receives the request form the terminal application. It compares therequest against its own resource reservation level and the subscriber's QoS profilefrom the HLR associated with the requested access point name. The HLRconverts the internal database information to the 3GPP-defined format and sendsthe information over the standard MAP interface to the 3G SGSN.

Both of the above mentioned variables may serve as criteria for the 3G SGSN tosuggest the terminal a lower QoS than requested as a part of the PDP contextactivation.

Provided that the QoS request conforms with the subscriber's QoS profile and thatthe 3G SGSN has capacity available, the 3G SGSN continues the PDP contextset-up by sending the RNC a request for radio access bearer set-up with therequested PDP context QoS parameters. The 3G SGSN uses Radio AccessNetwork Application Protocol (RANAP) for this signaling.

The RNC either acknowledges a successful set-up of a radio bearer or rejects therequested bearer. After that the 3G SGSN signals with GPRS Tunneling ProtocolControl Plane (GTP-C) protocol to GGSN the request for PDP context activationwith the requested QoS parameters. The GGSN returns the activation request tothe SGSN. The returned information is either an acknowledgement on thesuccessfully set up radio bearer or a proposal for a lower QoS than requested.

RNC

8.6.00

For example DiffServor DiffServ over MPLScapable routers

GGSN

RANAP

ApplicationServers

Radio resource reservation forconversational class PDP context

QoS-aware radio bearer

GPRS resource reservation forconversational class PDP context

QoS-aware connection

3G SGSN

SGSN - RNC RABsetup negotiation

ok

PDP contexts and the subscriber's QoSprofile from HLR.

ok ok

conversational class PDP contexts.58 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en


In the case when the 3G SGSN, the RNC or the GGSN has requested a lower QoSthan requested by the terminal, the 3G SGSN sends the QoS degradation request

to the terminal. In the case that the 3G SGSN, the RNC and the GGSN have allaccepted the PDP context with requested QoS parameters, the 3G SGSNcompletes the PDP context set-up negotiation with the terminal.

6.5 Examples on QoS profile usage

Example 3. Using Rel '97/'98 GPRS terminals and Nokia GPRS network

This example applies to GPRS (Nokia SGSN) networks and 3GPP Rel '97/'98terminals that typically request the default QoS profile. In this case the defaultQoS attribute values provided in the HLR are used. The subscriber's QoS profiledefines the parameter values to be used for each access point. The QoS profile isdefined in Rel '99 attributes that can be mapped to Rel '97/'98 attributes that aresupported in the Nokia SGSN.

The table below illustrates a simple example with four different QoS profilesapplied in the GPRS networks.

* The Nokia SGSN provides the Allocation/Retention Priority (ARP) parametervalue to the Nokia Base Station Controller (BSC). The BSC Packet Control Unitsimplement a queue for each timeslot. The Nokia BSS Release 10.5 uses the ARPparameter value for prioritising the scheduling of the Temporary Block Flows(TBF) in each timeslot queue. For more information, see Nokia BSSdocumentation.

Table 8. Example QoS profiles for GPRS networks and terminals.

QoSparameters

Qos profiles

Executive Regular Economic Best Effort

Allocation/Retentionpriority (1,2,3)(Applied in BSS*)

1 2 3 3

Traffic class Interactive Interactive Interactive Background

Traffic handlingpriority (1,2,3) forinteractive traffic

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Example 4. Using Rel '99 UMTS/GPRS Terminals and Nokia 3G PacketCore NetworkThis example applies to GPRS and UMTS networks. The 3GPP Rel '99 terminalsare expected to request a more detailed QoS profile. If the terminals and/orterminal applications are able to request a QoS profile, it is possible to provideservices that require different QoS via the same Access Point. In this case theHLR QoS profile gives only the maximum QoS attribute values that are allowedfor the specific subscription.

The most visible QoS additions provided in the WCDMA / 3G networkscompared to the GPRS/EDGE networks are the introduction of Conversationaland Streaming traffic classes and the possibility to offer guaranteed bit rates forthese classes.

The table below illustrates example QoS profiles for Rel '99 GPRS/UMTSterminals.

Table 9. Example QoS profiles for 3G networks and terminals.

QoS parameters QoS profiles

Executive Regular Economic(high, medium,low)

Best Effort

Allocation/Retentionpriority (1,2,3)

1 2 3 3

Traffic Class Conversational Streaming Interactive Background

Traffic Handlingpriority (1,2,3) forinteractive traffic

n/a n/a Eco/high=1Eco/medium=2Eco/low=3

n/a

Guaranteed bitrate Exec 64 = 64kbit/sExec 128 =128 kbit/sExec 256 =256 kbit/s

Regular 20 =20 kbit/sRegular 200 =200 kbit/sRegular 400 =400 kbit/s

n/a n/a

Maximum bitrate Exec 64 =64kbit/sExec 128 =128 kbit/sExec 256 =256 kbit/s

Regular 20 =40 kbit/sRegular 200 =300 kbit/sRegular 400 =600 kbit/s

Economic 50 = 50 kbit/sEconomic 200 =200 kbit/sEconomic 500 =500 kbit/s

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6.6 QoS information in Call Detail Records

In the 3G SGSN and the GGSN the requested and negotiated QoS classes of thePDP context are marked in the Call Detail Records (CDRs). The user equipmentor the network may renegotiate the PDP context QoS during the connection. Thisleads to closing of a CDR with the QOS_CHANGE cause value in both 3G SGSNand GGSN. The next CDRs are written using the new QoS class. A Charging IDis used to combine the CDRs of the same PDP context in the Nokia ChargingGateway.

In case that a network element cannot provide the negotiated QoS, this can bemarked in the Service Degradation field in the charging record.

6.7 Handovers

Handover and QoS have been subject to a lot of discussion in 3GPPstandardisation. In Rel '99 new QoS Profiles have been defined for both GSM andUMTS to enhance the level of service that operators can offer to their customers.

Handover from WCDMA to GPRS/EDGE

If the Conversational and Streaming traffic classes introduced in Rel '99 are used,the service will be degraded when moving to a GPRS/EDGE SGSN. If the SGSNis not able to support the negotiated QoS level, it can downgrade the QoS level.In practice, if the UE moves from an UMTS network to a GSM/GPRS network,the SGSN downgrades all Conversational and Streaming class PDP contexts toInteractive class. The UE may then disconnect these contexts if the renegotiatedQoS level does not meet the application needs.Handover from Rel '99 to Rel '97/'98

If several PDP contexts are activated for the same IP address, the network willrelease all but one. The exact mechanisms are described in the 3GPPspecifications.

Handover from GPRS/EDGE to UMTS or form Rel '97/'98 network to Rel '99network

All services will be maintained in handovers from a GPRS/EDGE network to aWCDMA network or from a Rel '97/'98 network to Rel '99 network.DN01154225 Nokia Corporation 61 (86)Issue 2-1 en Nokia Proprietary and Confidential


6.8 QoS in roaming cases

QoS for roaming users is basically implemented in the same way as for the usersin the home network. The exception is that the interconnection agreements withthe other operators or GPRS Roaming Exchanges (GRX) connected over the Gpinterface need to include information on the service level agreements and on theusage of DiffServ Codepoints in the case when DiffServ is supported by the GRXof the visited operator. DiffServ codepoint translation can be performed in theborder gateway if needed. The figure below illustrates roaming between QoScapable networks.

Figure 25. Roaming between QoS capable networks.

RAN country A

3rd pty carrier

Different QoS schemes, e.g. UMTS, DiffServ over MPLS, IPoATM ...

SLAs and QoS mappingsfor inter-operator connections

country B

ATM Service Classes

RAN

Operator 1QoS

budget

Operator 2QoS

budget

Operator 3QoS

budget

E2EQoS

budgetbudget

delay

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Quality of Service Mechanisms in Nokia 3G Circuit Core7 Quality of Service Mechanisms in Nokia3G Circuit Core

7.1 Quality of Service in IP TrunkThe Nokia IP Trunk provides IP-based transmission for Circuit Core traffic overNokia 3GPP Rel '99 packet core network. For this purpose IP Exchange Terminal(IPET) cards are provided on top of the Nokia MSCi M11 release.

Voice and signaling traffic can be carried over IP while Time DivisionMultiplexing (TDM) connections are provided for data/fax, handover andemergency calls. A common IP backbone can be used to carry both Packet Coreand Circuit Core traffic and also possible IP traffic originating from fixed IPnetworks. QoS mechanisms are needed to ensure low-delay, successfultransmission for the Circuit Core traffic.DN01154225 Nokia Corporation 63 (86)Issue 2-1 en Nokia Proprietary and Confidential

Quality of Service in 3G Core NetworkFigure 26. IP Trunk for Circuit Core traffic.

Nokia IP Trunk can mark packets with DiffServ Codepoints. The operator canconfigure the codepoint used for the Circuit Core traffic. By using DiffServcapable routers the IP Trunk traffic can be given priority. This together withproper dimensioning of the transmission links guarantees QoS.

If dedicated IP routers are used for the IP Trunk, QoS can be guaranteed withproper router dimensioning and dedicated SDH (Synchronous Digital Hierarchy)transmission resources.

Circuit Core

MSC

IPET

Other IPnetworks

IPETIPET PSTNGMSC

3G SGSN

Circuit Core

SDH ring

IP backboneBackbone router

Packet Core

GGSN

GGSN

MSC64 (86) Nokia Corporation DN01154225Nokia Proprietary and Confidential Issue 2-1en

Quality of Service Mechanisms in Nokia 3G Circuit Core

7.2 QoS in MSC Server and Media Gateway

In 3GPP Release 4 MSC functionality is split into two distinct logical entities: theMSC Server is responsible for the call control and the control of the MediaGateways (MGW) and the MGW handles the user plane traffic. The Nokia MSCServer (MSS) is a product that includes the functionality of the MSC Server andthe Gateway MSC Server as defined in 3GPP Release 4. In addition, the MSS alsoincludes Media Gateway Control Function (MGCF) that is used to control theMGWs in IP Multimedia Subsystem (IMS). MSC Server concept makes use of apacket based transport network for circuit switched traffic as illustrated in thefigure below. As in the IP trunk solution, the PCM speech frames are convertedinto IP packets and forwarded to the IP network.

Figure 27. Nokia MSC Server (MSS) Concept.

The Nokia MGW Release 4 implements DiffServ codepoint mapping for the IPtraffic flows that are to be transmitted over the IP backbone. The operator canmodify the DiffServ codepoint (DSCP) mapping of MSC Server Conceptnetwork elements and the settings of the backbone products. In the MSC Serverthe operator can define the DSCP used for signaling traffic. If needed, DiffServcodepoint handling can be implemented in the Cisco OSR for O&M and chargingtraffic. In MGW the operator can define the DSCP used for IP user traffic andsignaling traffic.

If the operator backbone is based on ATM, preprovisioned QoS for PermanentVirtual Circuits (PVC) are applied to carry the MGW and MSS traffic. The tablebelow presents the recommended ATM QoS classes for the MSC server traffic.The ATM Forum service categories are shortly described in Appendix C. Thetable below also presents the recommended ITU-T ATM QoS class mappings andATM Forum service category mappings for MSC server and MGW traffic.

GSM

GSM

GSM

WCDMA

WCDMA

operatorIP/MPLS, IP orATM backbone

WCDMA

Standalone MSSIntegrated MSS

MGW MGWuser plane

A

A

Iu-CS Iu-CS

A

H.248MEGACO

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Quality of Service in 3G Core NetworkTable 10. Recommended ATM QoS classes for MSC server traffic.

Traffic class ortype

ATM QoS Class(ITU-T)

Service category(ATM Forum)

MGW rel U2 Added in MGWrel U2.1

MGW rel U2 Added in MGW relU2.1

Conversational (userlayer, voice)

Class 1 Class 2 CBR rt-VBR

Background (userlayer)

Unspecified UBR

3GPP controlprotocol

Class 1 Class 2 CBR rt-V

Documents

QoS in 3G Core Network