Routing Issues in Mobile IP

Sudarshan VasudevanChun Zhang

PART 1

Unicast Routing using Mobile IP

Terminology

Care-of-AddressTunnelingDHCP (Dynamic Host Configuration Protocol)HA - Home Agent FA - Foreign AgentMH - Mobile Host CH - Correspondent Host

1. Overview

Mobile IP Provide Host Migration Transparency small modifications to IP routing is sufficient

Involves 3 basic functions Advertisement Registration Tunneling

ProtocolWhen MH is in its home network

Normal IP Routing

When MH is away from it home network HA keeps track of MH’s care-of-address

either FA’s IP address or one obtained using DHCP

Care-of-Address represents the MH’s current location

When the MH migrates into another foreign network, MH notifies its new care-of-address to the HA

Example

Wired backbone network

HA

FA

C HMH

MH

Han

d-O

ff / R

oam

ing

Tunneling & Triangular Routing

Data Entry for HA

Data Entry for MH

HA

FA

C H

Normal IP datagram

Destined for MH

MH

ARP cache Entry of MH141.223.120.1 = FF:FF:FF:FF:FF:FF141.223.84.60 = 0F :0F :0F :0F :0F :0F

141.223.84.1

141.223.84.60

141.223.120.1

Tunneling Datagram

Tunn

el

Foreign MH entry141.223.84.60 = 0F:0F:0F:0F:0F:0F

Data Entry for HA

Remote MH entryIP address C are- of- Address141.223.84.60 141.223.120.1

ARP cache Entry of FA for MH141.223.84.60 = 00:00:00:00:00:00

Tunneling & Triangular Routing

HA

FA

C H

MH

141.223.84.1

141.223.84.60

141.223.120.1

Tunn

el

Encapsulation

Decapsulation

text

IP header

IP payload IP payload

new IP headerIP header

IP- within- IP Encapsulation

Triangular Route

Route Optimization

Triangular path is not optimal routeRoute Optimization

Supply binding update to CHs authentication and replay protection for binding

updates registration key between MH and FA for smooth

handoff

Route Optimization

HA

FA1

C H

MH

Binding Update

C ac he the current care- of- address of MH

HA

FA1

C H

MH

After B inding Update

Smooth Hand-Off

HA

FA1

C H

MH

FA2

MH

Hand-O ff

(1) Register with FA

(2) Register with HA

(2) B inding update to FA1

(3) B inding warning

(4) B inding Update

C ac he the current care- of- address of MH

C ontrol Packet Flow

Conclusion

Triangular Routing can be eliminated sending binding updates to CHs

Smooth handoffs very valuable counteract unwanted effects of dropped packets special tunnels can further reduce this effect

Main difficulty establishment of security associations between FA

and MH

Future Work

Mobility Security Association Management authentication of all messages that affect routing currently manual establishment of MSAs difficult to manage, no scalability efficient Key Distribution Protocols needed

Certification of Foreign Agents prevent malicious nodes pretending as FAs

Security issues introduced by Tunneling

References

Perkins, Charles E., ed. “Ipv4 Mobility Support” RFC 2002. October 1996b. Perkins, Charles E. “Minimal Encapsulation within IP”. RFC 2004.October 1996c. Perkins, Charles E. “IP Encapsulation within IP”. RFC 2003. October 1996a. Perkins, Charles E and Johnson, David B. “Mobility Support in IPv6.” In ACM Mobicomm96.

November 1996. Johnson, David B. “Scalable and Robust Internetwork Routing for Mobile Hosts” In Proceedings of

the 14th International Conference on Distributed Computing Systems. June 1994. Hanks Stan, Tony Li, Dino Farinacci, and Paul Traina,Generic Routing Encapsulation over IPv4

networks. RFC 1702. October 1994b. Deering, Stephen E., ed., “ICMP Router Discovery Messages.” RFC 1256. September 1991. Hellman, M.E., W.Diffie, and R.C. Merkle. “Cryptographic Apparatus and Method.” US Patent

4,200,770. April 1980. Rivest, Ronald L. “The MD5 Message-Digest Algorithm”. RFC 1321. April 1992. Maughan, Douglass, Mark Schetler, Mark Schneider, and Jeff Turner. Internet Security Association

and Key Management Protocol (ISAKMP). (Internet-draft) draft-ietf-ipsec-isakmp08.txt, .ps. July 1997.

PART 2

Multicast Routing using Mobile IP

Multicast algorithms classification

Unicast dependent vs. Unicast independent

Source-Based vs. Shared Multicast Tree

[Directly impact on Mobile IP]

Sparse mode vs. Dense mode

Protocols: DVMRP, MOSPF, CBT, PIM(Dense/Sparse)

Unicast dependent vs. Unicast independent

Unicast

Multicast

Unicast

Multicast

Which one is better ?

• Use property of specific unicast routing algorithm

• Deploy limitation

• DVMRP(RIP) MOSPF(OSPF)

• Use general unicast function

• Extra Multicast related state

• Better interoperability

• Protocol Independent Multicast

Source-Based vs. Shared Multicast TreeSource-Based Tree (DVMRP,MOSPF,PIM_Dense)

Receiver 1

E

BA D F

Source1(128.119.240.5)

C

Receiver 2

Source2 (113.117.238.2)

? How to maintain LEAST UNICAST-COST PATH TREE• Multicast Open Shortest Path First• Distance Vector Multicast Routing Protocol

Source-Based vs. Shared Multicast Tree

Forwarding Packet with Source-Based Tree

Reverse Path Forwarding Algorithm

Transmit the packet on all of its outgoing links only if the packet arrived on the link that is on its own shortest path back to the source

Receiver 1

BA

C E

Source

Receiver 2

D

Receiver 3

Source-Based vs. Shared Multicast TreeShared Tree (Core Base Tree, PIM_Sparse)

Source 1

Receiver 1

B

E

A D (Shared Root) F

C

Receiver 2

Source 2

Sparse mode vs. Dense mode

Sparse mode Dense mode

Few receiver Few non-receiver

Join explicitlyJoin by default

Broadcastprune,graft

Source based treeShared/Source based tree

CBT, PIM_Sparse DVMRP, PIM_Dense

Pay Per View Radio Broadcast

Sparse Mode PIM Example

Receiver 1

B

E

A D

Source

C

Receiver 2

RP

Link

Data

Control

Sparse Mode PIM Example

Receiver 1

B

E

A D

Source Receiver 1 Joins Group GC Creates (*, G) State, Sends(*, G) Join to the RP

C

Receiver 2

RP

Join

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source RP Creates (*, G) State

C

Receiver 2

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source Source Sends DataA Sends Registers to the RP

C

Receiver 2

Register

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source RP de-encapsulates RegistersForwards Data Down the Shared TreeSends Joins Towards the Source

C

Receiver 2

Join Join

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source RP Sends Register-Stop OnceData Arrives Natively

C

Receiver 2

Register-Stop

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source C Sends (S, G) Joins to Join theShortest Path (SPT) Tree

C

Receiver 2

(S, G) Join

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source When C Receives Data Natively,It Sends Prunes Up the RP tree forthe Source. RP Deletes (S, G) OIF andSends Prune Towards the Source

C

Receiver 2

(S, G) RP Bit Prune

(S, G) Prune

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source New Receiver 2 JoinsE Creates State and Sends (*, G) Join

C

Receiver 2

(*, G) Join

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source C Adds Link Towards E to the OIFList of Both (*, G) and (S, G)Data from Source Arrives at E

C

Receiver 2

Sparse Mode PIM Example

Receiver 1

B

E

A RP D

Source New Source Starts SendingD Sends Registers, RP Sends JoinsRP Forwards Data to Receiversthrough Shared Tree

C

Receiver 2

Source 2

Register

Dense Mode PIM ExampleSource

Receiver 2Receiver 1

DD FF

II

BB

CC

AA

EE

GG

HH

Link

Data

Control

Dense Mode PIM Example

Initial Flood of Dataand Creation of State

Source

Receiver 2Receiver 1

DD FF

II

BB

CC

AA

EE

GG

HH

Dense Mode PIM Example

Prune to Non-RPF Neighbor

Source

Prune

Receiver 2Receiver 1

DD FF

II

BB

CC

AA

EE

GG

HH

Dense Mode PIM Example

C and D Assert to DetermineForwarder for the LAN, C Wins

Source

Asserts

Receiver 2Receiver 1

DD FF

II

BB

CC

AA

EE

GG

HH

Dense Mode PIM Example

I Gets PrunedE’s Prune is IgnoredG’s Prune is Overridden

Source

Prune

Receiver 2Receiver 1

Join Override

Prune

DD FF

II

BB

CC

AA

EE

GG

HH

Dense Mode PIM ExampleSource

Graft

Receiver 2Receiver 3

Receiver 1

New Receiver, I Sends Graft

DD FF

II

BB

CC

AA

EE

GG

HH

Dense Mode PIM ExampleSource

Receiver 2Receiver 3

Receiver 1

DD FF

II

BB

CC

AA

EE

GG

HH

Multicast + Mobile IP

Mobile Host as Sender Using Home Address as packet source address Using Care-of Address as packet source address

Mobile Host as Receiver Home Subscription

Join multicast group using Home Address Remote Subscription

Join multicast group using Care-of Address

Home Address as packet source address

Option 1: Packet directly sent out from foreign network For Source-Based Tree

(routing related to packet source address) Packet might not be delivered

For Central Based Tree

(routing uncorrelated to packet source address)Packet will be delivered correctly

Option 2: Packet tunneled to Home Agent, then sent outPacket will be delivered correctly

Care-of Address as packet source address

Packet directly sent out from foreign network

Packet will be delivered correctly

Problem:

How the misdelivered response reach the

roaming sender ?

Home Subscription

Packet first received at Home Agent, then

forward to the mobile host.Problem: Tunnel Convergence problem

Home Agent (A) Home Agent (B)

Source

Foreign Agent

Mobile Host (A) Mobile Host (B)

Home Subscription

Packet first received at Home Agent, then

forward to the mobile host.Problem: Tunnel Convergence problem

Home Agent (A)DesignatedMulticast Service Provider

Home Agent (B)

Source

Foreign Agent

Mobile Host (A) Mobile Host (B)

Remote Subscription

It works fine since multicast packet is

delivered based on multicast group address

Foreign network router should support multicast

Conclusion

Mobile Host as Sender Using Home Address as packet source address

Core Based Tree/ Tunneled packet sent out from Home Agent Using Care-of Address as packet source address

Hardly to use

Mobile Host as Receiver Home Subscription

Tunnel convergence problem Remote Subscription

Foreign network support multicast

References

Mobile Multicast(MoM) Protocol: Multicast Support for Mobile Hosts. Tim G. Harrison, Carey L. Williason, Wayne L. Mackrell, Richard B. Bunt. U. of Saskatchewan, Saskatoon, Canadan.Proceedings of the third annual ACM/IEEE international conference on Mobile computing and networking. September 26 - 30, 1997, Budapest Hungary

RelM: Reliable Multicast for Mobile Networks.Journal of Computer Communications, 1997.Kevin Brown, Suresh Singh

Supporting IP Multicast for Mobile Hosts, for review.Yu Wang, Weidong Chen.Southern Methodist University

Flexible Network Support for Mobile Hosts. X. Zhao, C. Castelluccia, M. Baker. Proc. MOBICOM '98, Dallas, Texas, 1998, pp. 145--156

IP Multicast Extensions for Mobile Internetworking. In Proceedings of IEEE Infocom'96, March 1996

IP Multicasting for wireless mobile hosts. George Xylomenos and George C. Polyzos. Proceedings of the IEEE MILCOM, 10 1996