ConnectionConnectionMigrationMigration

818L Network Centric Computing818L Network Centric ComputingSpring 2002Spring 2002

Ishan BanerjeeIshan Banerjee

Connection MigrationConnection Migration

Hosts MobilityNetwork A Network B

Wireless Network

A mobile device is attached to a different network

A mobile device migrates to another cell

Connection MigrationConnection Migration

Service Availability

Client may or may not be aware of redundant servers

I-TCPI-TCPHost MobilityHost Mobility

Rutgers DCS

TCP – Mobile HostsTCP – Mobile HostsTraditional fixed hosts TCP was developed keeping in mind the fixed nature of hosts. Physical link assumed was wired network

Mobile Hosts- Weak wireless link- Cell crossover causes dropped TCP segments and longer restoration time

I-TCP – Mobile HostsI-TCP – Mobile Hosts

MH

MH

MSR-2

MSR-1

FH

Handoff

Architecture

Split transport layer

I-TCP – Mobile HostsI-TCP – Mobile HostsIssues+ Concept is simple and direct+ Fixed TCP backbone unchanged + No new transport protocol is required Implemented over Mobile IP? Fixed host is unaware of mobility? Application is unaware of mobility? End-to-end semantics violated? Split transport layer

MigrateMigrateHost MobilityHost Mobility

MIT LCS

Internet Mobility – IssuesInternet Mobility – Issues Disconnected state is a fundamental property of any network connection End points must not have static addressing Application must be aware of network disconnection and treat it as natural, not an error Application must handle disconnection and resume upon network reconnection Upper layers should not depend on lower layer naming system

Reconsidering Internet mobility – Snoeren, Balakrishnan, Kaashoek – MIT LCS

Mobile IP – Host MobilityMobile IP – Host Mobility

Mobile Host

Home Agent

Care of address / foreign agent

Fixed Host

Architecture

Issues Pure network layer solution. Upper layers unchanged Triangle routing consumes more resources

Mobile IP – Host MobilityMobile IP – Host Mobility

Migrate – Host MobilityMigrate – Host Mobility

Addressing Mobile host location Connection migration

DNS UpdatesIP

TCP Modification

Migrate – Host MobilityMigrate – Host Mobility

AddressingIP address is used to identify the host. The policy of obtaining a new IP in a foreign domain is separated from the location mechanism.

+ Implies no change to the network layer infrastructure

Migrate – Host MobilityMigrate – Host Mobility

Mobile host location Uses DNS updates to broadcast new location Mobile Clients – require no DNS updates Mobile Servers – update DNS DNS entry for mobile hosts made non cacheable

? Are there any dropped packets? How scalable is DNS update

Migrate – Host MobilityMigrate – Host Mobility

Connection migration Traditional TCP connection - <source IP, source port, dest IP, dest port> Modification - <source IP, source port, token> Mobile host can re-establish a connection using the connection token

- Implies modifying the TCP stack

Issues Applications are unaware of mobility of hosts- TCP stack needs modification

Migrate – Host MobilityMigrate – Host Mobility

MigrateMigrateService AvailabilityService Availability

MIT LCS

Migrate – Migrate – Service AvailabilityService Availability

Health monitoring Server selection Connection migration

External

Application Independent

Migrate – Migrate – Service AvailabilityService AvailabilityConnection migration

Support group Client

Information advertised Application dependent Transport layer

IP, Port, Seq #

URL

Migrate – Migrate – Service AvailabilityService Availability

Issues What about transaction servers Transport state migrated Application-unaware

X Specific application (HTTP) aware Transport module

CommentsCommentsInternet has changed from a collection of fixed nodes to a combination of fixed and mobile nodesProvide temporary patchesSearch for permanent solutionsContent/ service naming- consider mobilityShould give up trying to protect one layer or the other from disconnection or mobility transparency. Accept the fact that short/ long disconnections are natural. Each layer should be prepared.