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128.0.1.2 192.6.7.8
Mobile Node 128.0.1.2 192.9.5.4
128.0.1.2
Home
Agent




Home agent has multiple bindings and will
Foreign forward packets to foreign agents serving
Agent both cells

192.9.5.4

Figure 5.72 Mobile IP cell handover
260 IP APPLICATIONS FOR GPRS/UMTS


home agent to add the new binding but leave all existing bindings in place. The procedure
to achieve smooth handover will be as follows:

1. Contact the new foreign agent before the cell handover has taken place to obtain a
new care-of address.
2. Register the new care-of address with the home agent with the S bit set. Now the
home agent will deliver packets to both cells.
3. After a certain amount of time to allow the node to handover to the new cell, the
mobile node re-registers the new care-of address but this time with the S bit set to 0
to remove the old binding.


5.14.7 Mobile IP for CDMA2000
Mobile IP is supported in CDMA2000. The foreign agent functionality is sited at the
PDSN and supports the following functions:

• routing to mobile station from home agent;
• route reverse tunnelling back to home agent;
• hand off between PDSNs without involving home network;
• establishment of IPSec security association with home agent;
• sending agent advertisements to its served mobile stations;
• dynamic home address assignment;
• AAA service for visiting users.

Mobile IP provides similar functionality in CDMA2000 as the GTP within UMTS.
Both support the roaming of the user within the radio access network without having
to change IP address. The difference is that mobile IP allows the user to roam beyond
the cellular domain and still remain contactable. The GTP tunnel, on the other hand,
only exists within the operator™s network and therefore cannot be used to provide mobile
routing when the user attaches using a non-GPRS connection method.


5.14.8 Mobile IP for UMTS
TS23.923 is a feasibility study on the use of mobile IP within UMTS to provide tunnelling
and mobility management. It describes two architectures. The ¬rst is an overlay of mobile
IP on the current GPRS network to provide truly ubiquitous mobility, in which a user can
be reached whether they are connected via GPRS or other means. This is a conventional
mobile IP architecture and it is assumed that the foreign agent functionality is placed
within the GGSN. In this case the GGSN will send out a foreign agent advertisement on
receipt of a PDP context request. Since not all GGSN may support IP mobility the choice
of this service would be decided by the APN of the original request.
FURTHER READING 261


The second proposal is a wholesale replacement of GTP with mobile IP. In this the
SGSN and GGSN are combined into one unit called the Internet GPRS support node
(IGSN). The IGSN would act as a foreign agent and provide a tunnel to transfer packets
between itself and the user™s home agent. Note that TS 23.923 is only a feasibility study
and is not a mandatory requirement for UMTS.



5.15 SUMMARY
In this chapter the application of IP to 3GPP R99 UMTS networks is explored. The IP
suite of protocols is examined as well as their application to the UMTS environment,
in particular to the GPRS core network. The need for QoS is justi¬ed as well as a
number of mechanisms on how it can be implemented, including the contrasting DiffServ
and IntServ approaches. Also, security for IP is covered in two forms, session based
and connectionless, and in particular the TLS and IPSec protocols were described in
some detail. The use of PPP and CHAP to provide a con¬gured and authenticated IP
point-to-point service is examined, as is its application to CDMA2000. Finally, the AAA
protocols are examined, and their use within IP, paying particular attention to RADIUS
(for CDMA2000) and DIAMETER (for UMTS).



FURTHER READING
RFC 0114: File Transfer Protocol. A. K. Bhushan. Apr-10-1971.
RFC 0495: Telnet Protocol speci¬cations. A. M. McKenzie. May-01-1973.
RFC 0760: DoD standard Internet Protocol. J. Postel. Jan-01-1980.
RFC 0768: User Datagram Protocol. J. Postel. Aug-28-1980.
RFC 0791: Internet Protocol. J. Postel. Sep-01-1981.
RFC 0793: Transmission Control Protocol. J. Postel. Sep-01-1981.
RFC 0799: Internet name domains. D. L. Mills. Sep-01-1981.
RFC 0826: Ethernet Address Resolution Protocol: Or converting network protocol
addresses to 48.bit Ethernet address for transmission on Ethernet hardware. D. C.
Plummer. Nov-01-1982.
RFC 0903: Reverse Address Resolution Protocol. R. Finlayson, T. Mann, J. C. Mogul,
M. Theimer. Jun-01-1984.
RFC 1034: Domain names “ concepts and facilities. P. V. Mockapetris. Nov-01-1987.
RFC 1035: Domain names “ implementation and speci¬cation. P. V. Mockapetris. Nov-
01-1987.
RFC 1055: Nonstandard for transmission of IP datagrams over serial lines: SLIP. J. L.
Romkey. Jun-01-1988.
RFC 1058: Routing Information Protocol. C. L. Hedrick. Jun-01-1988.
RFC 1144: Compressing TCP/IP headers for low-speed serial links. V. Jacobson. Feb-
01-1990.
RFC 1320: The MD4 Message-Digest Algorithm. R. Rivest. April 1992.
262 IP APPLICATIONS FOR GPRS/UMTS


RFC 1321: The MD5 Message-Digest Algorithm. R. Rivest. April 1992.
RFC 1332: The PPP Internet Protocol Control Protocol (IPCP). G. McGregor. May 1992.
RFC 1518: An Architecture for IP Address Allocation with CIDR. Y. Rekhter, T. Li.
September 1993.
RFC 1519: Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggre-
gation Strategy. V. Fuller, T. Li, J. Yu, K. Varadhan, September.
RFC 1548: The Point-to-Point Protocol (PPP). W. Simpson. December 1993.
RFC 1633: Integrated Services in the Internet Architecture: an Overview. R. Braden,
D. Clark, S. Shenker. June 1994.
RFC 1752: The Recommendation for the IP Next Generation Protocol. S. Bradner,
A. Mankin. January 1995.
RFC 1771: A Border Gateway Protocol 4 (BGP-4). Y. Rekhter, T. Li. March
RFC 1809: Using the Flow Label Field in IPv6. C. Partridge. June 1995.
RFC 1881: IPv6 Address Allocation Management. IAB, IESG. December 1995.
RFC 1918: Address Allocation for Private Internets. Y. Rekhter, B. Moskowitz,
D. Karrenberg, G. J. de Groot, E. Lear. February 1996.
RFC 1933: Transition Mechanisms for IPv6 Hosts and Routers. R. Gilligan, E. Nordmark.
April 1996.
RFC 1939: Post Of¬ce Protocol “ Version 3. J. Myers, M. Rose. May 1996.
RFC 1999: Request for Comments Summary RFC Numbers 1900“1999. J. Elliott. Jan-
uary 1997.
RFC 2001: TCP Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery
Algorithms. W. Stevens. January 1997.
RFC 2002: IP Mobility Support. C. Perkins, Ed. October 1996.
RFC 2060: Internet Message Access Protocol “ Version 4rev1. M. Crispin. December
1996.
RFC 2131: Dynamic Host Con¬guration Protocol. R. Droms. March 1997.
RFC 2139: RADIUS Accounting. C. Rigney. April 1997.
RFC 2205: Resource ReSerVation Protocol (RSVP) “ Version 1 Functional Speci¬cation.
R. Braden, Ed., L. Zhang, S. Berson, S. Herzog, S. Jamin. September 1997.
RFC 2210: The Use of RSVP with IETF Integrated Services. J. Wroclawski. September
1997.
RFC 2211: Speci¬cation of the Controlled-Load Network Element Service. J. Wroclawski.
September 1997.
RFC 2212: Speci¬cation of Guaranteed Quality of Service. S. Shenker, C. Partridge,
R. Guerin. September 1997.
RFC 2246: The TLS Protocol Version 1.0. T. Dierks, C. Allen. January 1999.
RFC 2309: Recommendations on Queue Management and Congestion Avoidance in the
Internet. B. Braden, D. Clark, J. Crowcroft, B. Davie, S. Deering, D. Estrin, S. Floyd,
V. Jacobson, G. Minshall, C. Partridge, L. Peterson, K. Ramakrishnan, S. Shenker,
J. Wroclawski, L. Zhang. April 1998.
RFC 2328: OSPF Version 2. J. Moy. April 1998.
RFC 2338: Virtual Router Redundancy Protocol. S. Knight, D. Weaver, D. Whipple,
R. Hinden, D. Mitzel, P. Hunt, P. Higginson, M. Shand, A. Lindem. April 1998.
RFC 2401: Security Architecture for the Internet Protocol. S. Kent, R. Atkinson. Novem-
ber 1998.
FURTHER READING 263


RFC 2402: IP Authentication Header. S. Kent, R. Atkinson. November 1998.
RFC 2409: The Internet Key Exchange (IKE). D. Harkins, D. Carrel. November 1998.
RFC 2412: The OAKLEY Key Determination Protocol. H. Orman. November 1998.
RFC 2474: De¬nition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6
Headers. K. Nichols, S. Blake, F. Baker, D. Black. December 1998.
RFC 2475: An Architecture for Differentiated Service. S. Blake, D. Black, M. Carlson,
E. Davies, Z. Wang, W. Weiss. December 1998.
RFC 2507: IP Header Compression. M. Degermark, B. Nordgren, S. Pink. February 1999.
RFC 2510: Internet X.509 Public Key Infrastructure Certi¬cate Management Protocols.
C. Adams, S. Farrell. March 1999.
RFC 2511: Internet X.509 Certi¬cate Request Message Format. M. Myers, C. Adams,
D. Solo, D. Kemp. March 1999.
RFC 2581: TCP Congestion Control. M. Allman, V. Paxson, W. Stevens. April 1999.
RFC 2582: The NewReno Modi¬cation to TCP™s Fast Recovery Algorithm. S. Floyd,
T. Henderson. April 1999.
RFC 2597: Assured Forwarding PHB Group. J. Heinanen, F. Baker, W. Weiss,
J. Wroclawski. June 1999.
RFC 2598: An Expedited Forwarding PHB. V. Jacobson, K. Nichols, K. Poduri. June
1999.
RFC 2616: Hypertext Transfer Protocol “ HTTP/1.1. R. Fielding, J. Gettys, J. Mogul,
H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee. June 1999.
RFC 2821: Simple Mail Transfer Protocol. J. Klensin, Ed. April 2001.
RFC 2865: Remote Authentication Dial In User Service (RADIUS). C. Rigney, S. Willens,
A. Rubens, W. Simpson. June 2000.
RFC 2866: RADIUS Accounting. C. Rigney. June 2000.
RFC 3022: Traditional IP Network Address Translator (Traditional NAT). P. Srisuresh,
K. Egevang. January 2001.
RFC 3024: Reverse Tunneling for Mobile IP, revised. G. Montenegro, Ed. January 2001.
RFC 3095: RObust Header Compression (ROHC): Framework and four pro¬les:
RTP, UDP, ESP, and uncompressed. C. Bormann, C. Burmeister, M. Degermark,
H. Fukushima, H. Hannu, L.-E. Jonsson, R. Hakenberg, T. Koren, K. Le, Z. Liu,
A. Martensson, A. Miyazaki, K. Svanbro, T. Wiebke, T. Yoshimura, H. Zheng. July
2001.
RFC 3096: Requirements for robust IP/UDP/RTP header compression. M. Degermark,
Ed. July 2001.
RFC 3135: Performance Enhancing Proxies Intended to Mitigate Link-Related Degrada-
tions. J. Border, M. Kojo, J. Griner, G. Montenegro, Z. Shelby. June 2001.
3GPP TS23.002: Network Architecture.
3GPP TS23.101: General UMTS Architecture.
3GPP TS23.107: Quality of Service (QoS) concept and architecture.
3GPP TS23.207: End to end quality of service concept and architecture.
3GPP TS23.922: Architecture for an All IP network.
3GPP TS23.923: Combined GSM and Mobile IP mobility handling in UMTS IP CN.
3GPP TS24.008: Mobile radio interface Layer 3 speci¬cation; Core network protocols;
Stage 3.
3GPP TS25.323: Packet Data Convergence Protocol (PDCP) speci¬cation.
264 IP APPLICATIONS FOR GPRS/UMTS


3GPP TS29.060: General Packet Radio Service (GPRS); GPRS Tunnelling Protocol (GTP)
across the Gn and Gp interface.
draft-ietf-aaa-diameter-09.txt: Diameter Base Protocol, P. Calhoun, j. Arkko, 03/04/2002.
draft-ietf-mobileip-optim-11.txt: Route Optimization in Mobile IP, C. Perkins, D. Johnson,
09/06/2001.
draft-ietf-mobileip-ipv6-15.txt: Mobility Support in IPv6, C. Perkins, D. Johnson,
11/21/2001.
S. Floyd, V. Jacobson (1993) ˜Random early detection gateways for congestion avoid-
ance™, IEEE/ACM Transactions on Networking, 1(4), 397“413.
A list of the current versions of the speci¬cations can be found at http://www.3gpp.org/
specs/web-table specs-with-titles-and-latest-versions.htm, and the 3GPP ftp site for the
individual speci¬cation documents is http://www.3gpp.org/ftp/Specs/latest/
6
Universal Mobile
Telecommunications System


6.1 UMTS NETWORK ARCHITECTURE

Development is now well on the road towards third generation (3G), where the network
will support all traf¬c types“voice, video and data“and we should see an eventual explo-
sion in the services available on the mobile device. The driving technology for this is
the Internet protocol (IP). Many cellular operators are now at a position referred to as
2.5G, with the deployment of the general packet radio service (GPRS), which introduces
an IP backbone into the mobile core network. Figure 6.1 shows an overview of the key
components in a GPRS network, and how it ¬ts into the existing global system for mobile
communications (GSM) infrastructure.
The interface between the serving GPRS support node (SGSN) and the gateway GPRS
support node (GGSN) is known as the Gn interface and uses the GPRS tunnelling pro-
tocol (GTP, as discussed in Chapter 4). The primary reason for the introduction of this
infrastructure is to offer connections to external packet networks, such as the Internet or
a corporate intranet.
This brings the IP protocol into the network as a transport between the SGSN and
GGSN. This allows data services such as email or web browsing on the mobile device,
with users being charged based on volume of data rather than time connected.
The ¬rst deployment of the universal mobile telecommunications system (UMTS) is
the release 99 (R99) architecture, shown in Figure 6.2.
In this network, the major change is in the radio access network (RAN) with the
introduction of code division multiple access (CDMA) technology for the air interface,
referred to as wideband CDMA (WCDMA), and asynchronous transfer mode (ATM) as
a transport in the transmission part. These changes have been introduced principally to
support the transport of voice, video and data services on the same network. The core

Convergence Technologies for 3G Networks: IP, UMTS, EGPRS and ATM J. Bannister, P. Mather and S. Coope
™ 2004 John Wiley & Sons, Ltd ISBN: 0-470-86091-X
266 UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM


NSS



HLR AuC EIR
BSS
PSTN

MSC/VLR GMSC

GPRS IP Backbone
Mobile BSC
BTS
Station

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