Network Layer Mobile IP Slides adapted from Prof. Dr.-Ing. Jochen - PowerPoint PPT Presentation

Network Layer Mobile IP Slides adapted from Prof. Dr.-Ing. Jochen H. Schiller and W. Stallings 1

Mobile IP - Definition  “Mobile IP (MIP) is a modification to IP that allows nodes to continue to receive datagrams no matter where they happen to be attached to the Internet” 2

Mobile IP Concept  Mobile IP adds mobility support to the Internet network layer protocol IP.  The Internet started at a time when no-one had a concept of mobile computers. • The Internet of today lacks mechanisms for the support of users traveling through the world. – IP is the common base for thousands of applications and runs over dozens of different networks; this is the reason for supporting mobility at the IP layer.  Motivation for Mobile IP:  Routing • based on IP destination address, network prefix determines physical subnet • Change of physical subnet implies change of IP address to have a topological correct address (standard IP) or needs special entries in the routing tables 3

 Create specific routes to end-systems – mobile nodes? • change of all routing table entries to forward packets to the right destination • does not scale with the number of mobile hosts and frequent changes in the location  Changing the IP address? • adjust the host IP address depending on the current location • almost impossible to find a mobile host, DNS has not been built for frequent updates • TCP connection break 4

Mobile IP Requirements  Transparency • mobile end-systems keep their IP address • continuation of communication after interruption of link possible • point of connection to the fixed network can be changed  Compatibility • support of the same layer 2 protocols as IP does • no changes to current end-systems and routers required • Mobile end-systems can communicate with fixed systems  Security • authentication of all registration messages  Efficiency and scalability • only little additional messages to the mobile system required (connection typically via a low bandwidth radio link) • world-wide support of a large number of mobile systems in the whole Internet 5

Real-life Solution  Take up the analogy of you moving from one apartment to another. What do you do?  Leave a forwarding address with your old post-office  The old post-office forwards mail to your new post- office, which then delivers it to you 6

MIPv4: Overview  MIPv4 Nodes  MN (Mobile Node): Host  CN (Correspondent Node): Host  HA (Home Agent): Router  FA (Foreign Agent): Router  MIPv4 Address  HoA (Home Address): MN  CoA (Care-of-Address): FA CNP 7/50

MIPv4 Agents  Home Agent (HA) & Foreign Agent (FA) CNP 8/50

Home Address (HoA) and Care-of Address (CoA) CNP 9/50

Protocols Operation  Agent Discovery  Registration  Data Transfer CNP 10/50

MIPv4: Control Operations  Agent Discovery  MN  FA (CoA)  ICMP Agent Solicitation & Advertisement  Registration to HA (via FA)  MN  FA  HA  Over UDP (destination port 434)  Data Tunneling  CN => HA (HoA) => FA (CoA) => MN  IP-in-IP Tunneling, .. CNP 11/50

Mobile IP in detail MIPv4 MIPv6 MN FA HA MN FA HA CN CN -- CoA and HA Discovery -- -- CoA and HA Discovery -- 1 1 1. CoA Discovery 1. CoA Discovery 2 2 2. HA Discovery Request 2. HA Discovery Request 3 3 3. HA Discovery Reply 3. HA Discovery Reply -- Registration Procedure -- -- Registration Procedure -- 4. HA Registration BU 4. HA Registration through FA 4 4 5. HA Registration BU Ack. 5. HA Registration Ack. 5 5 -- MN is Registered with HA -- -- MN is Registered with HA -- -- CN starts communication with MN -- -- CN starts communication with MN -- 6. Data Packet 6 6 6. Data Packet 7. IP-in-IP Encapsulation 7 7. IP-in-IP Encapsulation 8. Tunneled Data 7 8 8 8a 8a Detunnelled Data 9 9 8. Tunneled Data 9. Binding Update 9 9 9. Binding Update 10. IP-in-IP tunneling 10 10a 10a. Detunnelled Data 10. Binding Ack 10 -- MN starts communication with CN -- -- MN starts communication with CN -- -- Discovery and Registration as above -- -- Discovery and Registration as above -- 6a 6a 6a 6a 6a. Data Packet 6a. Data Packet -- Signals 6-10a as above -- -- Signals 6-10 as above -- 12

Discovering the care-of address  Discovery process built on top of an existing standard protocol: router advertisements  Router advertisements extended to carry available care-of addresses called: agent advertisements  Foreign agents (and home agents) send agent advertisements periodically  A mobile host can choose not to wait for an advertisement, and issue a solicitation message 13

Agent advertisements  Foreign agents send advertisements to advertise available care-of addresses  Home agents send advertisements to make themselves known  Mobile hosts can issue agent solicitations to actively seek information  If mobile host has not heard from a foreign agent its current care-of address belongs to, it seeks for another care-of address 14

Agent advertisement  MIP does not use a new packet type for agent advertisement;  it uses the router advertisement packet of ICMP, and  appends an agent advertisement message. CNP 15/50

Registering the Care-of Address  Once mobile host receives care-of address, it registers it with the home agent  A registration request is first sent to the home agent (through the foreign agent)  Home agent then approves the request and sends a registration reply back to the mobile host  Security? 16

Registration Illustration 17

Home agent discovery  If the mobile host is unable to communicate with the home agent, a home agent discovery message is used  The message is sent as a broadcast to the home agents in the home network 18

Tunneling to the Care-of address  When home agent receives packets addressed to mobile host, it forwards packets to the care-of address  How does it forward it? - encapsulation  The default encapsulation mechanism that must be supported by all mobility agents using mobile IP is IP- within-IP  Using IP-within-IP, home agent inserts a new IP header in front of the IP header of any datagram 19

Tunneling (contd.)  Destination address set to the care-of address  Source address set to the home agent’s address  After stripping out the first header, IP processes the packet again 20

Tunneling Illustration 21

Encapsulation original IP header original data new IP header new data outer header inner header original data

Encapsulation I  Encapsulation of one packet into another as payload  e.g. IPv6 in IPv4 (6Bone), Multicast in Unicast (Mbone)  here: e.g. IP-in-IP-encapsulation, minimal encapsulation or GRE (Generic Record Encapsulation)  IP-in-IP-encapsulation (mandatory, RFC 2003)  tunnel between HA and COA ver. IHL DS (TOS) length IP identification flags fragment offset TTL IP-in-IP IP checksum IP address of HA Care-of address COA ver. IHL DS (TOS) length IP identification flags fragment offset TTL lay. 4 prot. IP checksum IP address of CN IP address of MN TCP/UDP/ ... payload

Encapsulation II  Minimal encapsulation (optional)  avoids repetition of identical fields  e.g. TTL, IHL, version, DS (RFC 2474, old: TOS)  only applicable for non fragmented packets, no space left for fragment identification ver. IHL DS (TOS) length IP identification flags fragment offset TTL min. encap. IP checksum IP address of HA care-of address COA lay. 4 protoc. S reserved IP checksum IP address of MN original sender IP address (if S=1) TCP/UDP/ ... payload

Mobile IPv6 (MIPv6)  MIPv6 = MIPv4 + IPv6  Major Differences from MIPv4  FA in MN • No FA for MIPv6  CoA: IP address of MN • By DHCPv6 or IPv6 Stateless Auto-Configuration  Route Optimization • To solve the “Triangular Routing” Problem • Provided by default • MN  CN CNP 25/50

MIP: Triangular Routing Problem CNP 26/50

MIPv6: Route Optimization 27/50 CNP

MIPv6: Binding Update  Binding Update to HA  Using IPSEC: MN and HA have a security association • AH (Authentication Header) • ESP (Encapsulating Security Payload)  Binding Update to CN  Return Routability (RR) procedure • For Security  Binding Update (BU) procedure • Route Optimization CNP 28/50

MIPv6: Binding Update 29/50 CNP

MIPv6: RR (Return Routability) CNP 30/50

MIPv6: Changes to IPv6  New IPv6 Protocol (Header)  Mobility Header: a new IPv6 extension header • To carry MIPv6 Binding Update messages • How is in the MIPv4 ?  New Option in Destination Option Header • Home Address Option  New Type in Routing Header • Type 2 Routing Header  New ICMP Messages  ICMP HA Address Discovery Request/Reply  ICMP Mobile Prefix Solicitation/ Advertisement CNP 31/50

MIPv6: IPv6 Header 32/50 CNP

MIPv6: Mobility Header  A New Extension Header of IPv6  Messages for Return Routability • Home Test Init Message • Care-of Test Init Message • Home Test Message • Care-of Test Message  Messages for Binding Update • Binding Update Message • Binding Acknowledgement Message • Binding Error Message • Binding Refresh Request Message CNP 33/50