Internetworking. Mobile IP. Literature: Forouzan, TCP/IP Protocol Suite: Ch 24

Transcription

1 Internetworking Mobile IP Literature: Forouzan, TCP/IP Protocol Suite: Ch 24

2 Mobile use of Internet Mobility, Wireless and Portable are different terms Mobility: allows systems to move from one (network) location to another Degrees of mobility: Nomadic Get new IP-addresses by reconfiguring address/ DHCP Macro Mobility Hand-over between domains Two addresses: a home address and a foreign address (that changes) Home address static, foreign address changes Micro Mobility Seamless handover within a domain IP addresses and TP/UDP port numbers remain unchanged Applications continue uninterrupted

3 Mobility in an IP-setting IP designed for stationary environment Changing network is difficult. Two alternatives: 1. Change address 2. Keep address but distribute host-specific routes. But (1) is not mobile enough: We want to keep running applications up when moving We want to use one and the same IP address when moving! But (2) has drawbacks: Ruins route aggregation - routing tables would explode. Too much routing protocol traffic and converge too slowly if it at all Could one invent a way of achieving this with minimal changes to routing tables? Mobile IP RFC 3344 (1) on macro scale (between domains) (2) on micro scale (within a domain)

4 Mobile IP RFC 3344 Mobile IP is a compromise Other nodes see the same address Routing tables do not explode Destination applications need not change Unsuited for Micro mobility Fast movement/ small cells Seamless Handover Macro and Micro can be combined Use Macro for movement between domains Use Micro for movement within a domain

5 Mobile IP Architecture Mobile M Primary, Home address Secondary, Care of address Home Agent. M registers and obtains primary address with the home agent Foreign Agent (optional) M registers with foreign agent M destination M Mobile Internet Foreign Agent (opt ional) Traffic goes directly to destination Use home address as source Destination M via Home Agent Tunnels from Home Agent to Foreign Agent or Mobile Hom e Agent Dest inat ion Mobile s original hom e

6 Communication with co-located Mobile handles registration and forwarding itself Mobile has two addresses Applications use home address Communication software use care-of address Home agent tunnels packets to mobile s care-of-address Need special Mobile support in Mobile Works with existing infrastructure Foreign routers may be unaware! addressing IP-in-IP Tunnel M Mobile Internet Hom e Agent Dest inat ion Mobile s original hom e

7 Communication with foreign-agent addressing Mobile Mobile uses only home address Foreign agent handles forwarding Communicates with home agent Home agent tunnels packets to foreign agent. IP-in-IP Tunnel M Foreign Agent Foreign agent forwards packets to Mobile using home address on local network Mobile (almost) unmodified Foreign agent needs to support Mobility Internet Dest inat ion Hom e Agent Mobile s original hom e

8 Basic Capabilities of Mobile IP 1. Discovery: A mobile node uses a discovery procedure to identify home agents and foreign agents 2. Registration: A mobile node uses an authenticated registration procedure to inform its home agent of its care-of address 3. Data Transfer: Tunneling is used to forward IP-datagrams from a home address to a care-of address

9 1. Agent Discovery Mobile uses a discovery procedure to identify home agents and foreign agents. A hand-off takes place at the physical layer. Applications need not be aware the change Agents periodically send out ICMP router advertisements with mobile agent advertisement extensions Mobile nodes can use ICMP router solicitation to get agent information immediately M Mobile Agent Advert isem ent Internet

10 Mobility Agent Advertisement Extension Piggybacked on ICMP router advertisement LIFETIME How long agent accepts registrations requests CODE Agent Capabilities Care-of-addressing Home/Foreign IP-in-IP / GRE Encapsulation

11 2. Registration Registration involves four steps (foreign agent care-of address): The mobile node requests the forwarding service by sending a registration request to the foreign agent that the mobile node wants to use UDP port 434 The foreign agent relays the request to the mobile node s home agent The home agent either accepts or denies the request and sends a registration reply to the foreign agent The foreign agent relays the reply to the mobile node Co-located care-of address Mobile sends registration directly to Home Agent Registration involves authentication mobile nodes typically wireless subject to eavesdropping and active attacks

12 Registration relaying

13 Registration Message Format Type: request/reply Flags: encapsulation/care-of-address type/etc Lifetime: validity of registration Mobile and Home agent s Addresses Extensions: authentication

14 3. Data transfer Mobile uses home address as source address Replies come to Home agent Home agent must tunnel packet to Mobile / Foreign Agent IP-in-IP tunneling (RFC 2003) IP proto field 4 Minimal IP encapsulation (RFC 2004) IP proto field 55 GRE Generic Routing Encapsulation (RFC 1701) IP proto field 7 src: rem ote host dst: m obile hom e address Outer IP hdr Inner IP hdr Payload src: hom e agent dst: m obile foreign address

15 Tunneling architecture

16 Mobile IP Problems : Triangular delivery The triangular delivery High latency, high home agent server load

17 Mobile IP Problems : Double crossing Extreme variant of triangular delivery

18 Summary: Mobile IP Mobile IP adds macro mobility to IP Mobile IP may be combined with micro mobility eg host-specific routes within a domain Mobile host home address on home network home agent care-of address on foreign network foreign agent Protocol operation Agent discovery Registration Data transfer Triangular delivery/ two-crossing