connectionmigration 818l network centric computing spring 2002 ishan banerjee
Post on 18-Dec-2015
214 views
TRANSCRIPT
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
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
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
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.