TSIN02 - Internetworking

Transcription

1 Literature: Forouzan ch.27 Lecture 9: Mobile IP Article: Mobile IP by Charles E. Perkins, IEEE Communications Magazine,Vol. 40, Issue: 5, May 2002, Pages:66-82 Lecture 9: Mobile IP Goals: Article: IP multimedia services: analysis of mobile IP and SIP interactions in 3G networks by Faccin, S.M.; Lalwaney, P.; Patil, B. Communications Magazine, IEEE,Volume: 42, Issue: 1, Jan. 2004, Pages: Image Coding Group, Linköpings Universitet 2 Lecture 9: Mobile IP Mobile IP - Introduction Outline: Mobile IP - Introduction Addressing Agents Three Phases Agent discovery Registration Data transfer Inefficiency Wireless connections to the Internet are now common. 802.x series Bluetooth GPRS 3G Mobility is sometimes a desired feature. This means that sessions are transferred between network access points on- the- fly. 3 4

2 Addressing Addressing cont. The IP addresses are designed to work with stationary hosts because part of the address defines the network to which the host is attached. Possible solutions: Keep IP- address and update routing tables. Not realistic to update all routers every time a host moves to a new network. Get a new IP- address. This requires that configuration files are changed, the computer must be rebooted, DNS tables need to be revised and any ongoing transmission will be interrupted. Two addresses: Home address Care- of address 5 6 Host address and Care- of Address Agents The change of address should be transparent to the rest of the Internet. This is achieved through the use of agents: A home agent acts on behalf of the mobile host. A foreign agent handles the connection between the mobile host and its home agent. Sometimes the mobile host can act as a foreign agent (co- located care- of address) Mobile IP has two addresses for a mobile host: one home address and one care- of address. The home address is permanent; the care- of address changes as the mobile host moves from one network to another. 7 8

3 Home Agent and Foreign Agent Three Phases These three phases describes how to communicate with a remote host: 1) Agent discovery the mobile host needs to discover the addresses of both home and foreign agent. 2) Registration update information stored by home and foreign agents 3) Data transfer 9 10 Agent Advertisement Agent Advertisement cont. Description of the fields: Type (8 bits) - set to 16 Length (8 bits) total length of extention message Sequence number Lifetime (16 bits) the number of seconds that the agent accepts requests 11 Code (8 bits) List of care- of addresses Bit Meaning 0 Registration required 1 Agent busy 2 Agent acts as home agent 3 Agent acts as foreign agent 4 Agent uses minimal encapsulation 5 Agent uses generic routing encapsulation 6 Agent supports header compression 7 Unused 12

4 Router Advertisement Message Registration There are four aspects of registration. The mobile agent must: Register with the foreign agent Register with the home agent Renew registration if expired Cancel registration when returning home Registration Request and Reply Registration Request Format Sent using UDP port

5 Registration reply format Data Transfer Sent using UDP port Data Transfer cont. Double Crossing 1) From remote host to home agent 2) From home agent to foreign agent 3) From foreign agent to mobile host 4) From mobile host to remote host Not very efficient! 19 20

6 Triangle Routing Mobile IP v6 There is no need for foreign agents in MIPv6 since there are plenty addresses available. MIPv6 supports route optimization Both care- of address and home address are sent along with the message so that the remote host can use the care- of address for direct transmission. Message overhead have been reduced Mobile IP in 3G Networks SIP and Mobile IP There are two dominating 3G networks: GPRS/UMTS (Specified by 3GPP) The mobile host gets IP connectivity through a GGSN which provides the care- of address. MIP is not explicitly supported, but can be used to support mobility in multi- access networks. CDMA2000 (Specified by 3GPP2) Here a PDSN (Packet Data Switching Node) provides the link between the radio network and the Internet. MIPv4 is deployed, MIPv6 is only partly supported. The Session Initiation Protocol (SIP) has been chosen for the support of IP multimedia services (IMS) in both 3GPP and 3GPP2. In 3GPP IPv6 is used for IMS. Both IPv4 and IPv6 are allowed for IMS in 3GPP2 networks. SIP also supports mobility

7 SIP and MIPv4 SIP and MIPv6 When a mobile host connects to an IPv4 network, NATs are needed to connect to a IPv6 SIP infrastructure. With SIP, the packet payload also needs modification by the NAT. This requires an ALG, since NATs normally does not modlfy the payload. There are some routing issues that makes IMS services over MIPv4 complex and inefficient. At SIP registration an IP address is provided. When Mobile IP is used, there are two addresses available, home address and care- of address The home address should be used for SIP communication to make the changes in IP addresses transparent to applications. The care- of address should be used for SIP signaling to avoid tunneling Closing remarks MIPv4 has been a standard for some years MIPv6 is not yet a standard The interworking of SIP and MIP has not yet been standardized. 27