Cellular Concept of Mobility Users have a home system but can register at visited systems to make and receive calls – Single Number Service Users can roam among systems during a call and the call is handed-off without being dropped.
Functional Elements Home SystemVisited System HLRAC VLR Authentication Center – Authenticates users Visitor Location Register- Maintains temporary information on Visiting users. Home Location Register – Maintains current customer Location and service profile
GSM Registration HLR/AC VLR Old VLR Visited System 2) VLR queries previous VLR for user’s (actually the user’s smart card) permanent ID. Handset 1) Visited system detects handset, handset transmits temporary ID assigned by previous system. 3) The VLR sends a registration message to the HLR.
Name, Address, Routing Name: is a location independent identifier of a host Address: indicates where a given host is located. Route: tells how to get to a destination
Mobility Problem: The Internet Viewpoint Internet addresses are assigned in a topologically significant manner. –A mobile host must be assigned a new address when it moves. Change host address connection breaks. Retain host address routing fails. Host address must be preserved regardless of its location.
Constraints Inter-operability with TCP/IP protocol suite. Existing networking apps should run unmodified on mobile hosts. System should provide Internet-wide mobility. No modification on existing routing infrastructure should be required. Solution should be independent of wireless hardware technology. Solution should have good scaling properties.
IP’s subnet model vs. Mobility Terminals move from one IP subnet to another, but have the wrong “subnet prefix” for the destination subnet. Solution: two-tier IP addressing –The mobile keeps its static IP address, but borrows the service of a “care-of-address” on whatever IP subnet it happens to be visiting. –A “care-of-address”, offered by a mobility agent, can be shared by visiting mobiles.
Basic Mobile IP How does it work? –Agent discovery: advertisement/solicitation –MH registration –Use of Care-of-Address (COA) –Proxy ARP (Address Resolution Protocol) –Packet tunneling –Triangle routing
Key components HN R1R3 FN R2 HA MH CH FA Mobile Host: a host or router capable of changing its point of attachment to the Internet Foreign Network: a network, other than MA’s home network, that MH is currently attached to. Corresponding Host: a host or router communicationg with a mobile node. Home Network: the network identified with a mobile node Home Address: MH’s permanent IP address, network ID of this address identifies the mobile’s home network. Home Agent: a router attached to the MH’s home network maintains current location information for the MH is responsible for forwarding packets destined for the MH when MH is away from home. Foreign Agent (FA) a router in the foreign network that the MH is visiting provides routing services to the MH while registred de-tunnels datagram to MH may serve as default router for outgoing packet from MH Route Optimization
Provides a means for nodes to –cache the bindings of a mobile node –tunnel their own datagrams directly to the care-of- address –bypass mobile node’s home agent during datagram delivery Allow datagrams sent based on an out-of- data cached binding, to be forwarded directly to the mobile node’s new care-of-address.
Terminology Binding cache –a cache of mobility bindings of mobile nodes –maintained by CH for use in tunneling datagrams to those mobile nodes. Binding update –a message indicating a mobile node’s current mobility binding and its care-of-address. Registration lifetime –the time duration for which a binding is valid.
Binding Cache Creation/Update At CH, if no binding cache exists –datagrams will be routed to MH via basic mobile IP routing –home agent should then send a Binding Update message to the original source node –CH will then create a binding cache for the MH At an FA, if MH has moved to a new FA and the old FA still receives tunneled datagrams –old FA send Binding Warning message to HA to advise the change.
Foreign Agent Smooth Handoff As part of registration procedure, the mobile node may request its new FA to notify its previous FA on its behalf –a Previous Foreign Agent Notification extension is included in the Registration Request message The new FA builds a Binding Update message and transmits it to the mobile node’s previous FA as part of registration, requesting an ACK from the previous FA Security association between old FA and MH are used for authentication of the binding update message.
Mobile IP Refer to: http://computer.org/internet/ v2n1/perkins.htM http://www.ietf.org/html. charters/mobileip-charter.html http://wwwtgs.ctit.utwente.nl/Docs/ education/advanced/mobile/Tutorials/ MobileIPv6.pdf Slides on Mobile IP at: http://ing.ctit.utwente.nl/WU4/Documents/47 http://computer.org/internet/ http://www.ietf.org/html http://wwwtgs.ctit.utwente.nl/Docs/
Mobile ATM: System Model “M” UNI/NNI protocol extensions provide integrated & efficient support for mobility within ATM access network Functions include: location mgmt, handoff control, mobile QoS/routing ATM Network Mobile ATM Access Network Rerouted Connection After handoff Crossover switch Terminal Movement Connection Before Handoff Connect (ATM Addr A) Initial Location AL1 Next Location AL2 Location Mgmt provides mapping of A-> AL1, AL2 Handoff supports Dynamic rerouting Of active connections User Addr A (permanent) HO (BS1->BS2) BS1 BS2 User Addr A
Mobile ATM: Location Mgmt Location management can be integrated into existing ATM connection procedures.... (external servers can also be used) simple extensions to current CONNECT, RELEASE IE’s, etc. no need for a-priori partitioning of mobile & static address space ATM Host move setup (home_addr) release (foreign_addr) setup (foreign_addr, home_addr) update Home switch Current Foreign switch (1) (2) (3) (4)
Mobile ATM: Handoff Handoff can be implemented via modest extensions to existing ATM UNI/NNI signaling... new signaling messages/IE’s for handoff initiation, COS select, etc. provides high-performance, scalable solution (compared with external MSC, BSC, etc.) move handoff request (1) COS select ATM Host Crossover Switch (COS) add subpath tear down subpath handoff confirm
GSM Network Mobile ATM Access Network Terminal Movement GSM GSM/ATM gateway GSM Proxy M UNI GSM radio link M NNI M UNI M NNI GSM Handoff & loc mgmt within mobile ATM cloud provided By “M” UNI/NNI GSM radio link HLR/VLR GSM radio air interface Proxy migration M NNI GSM radio link GSM Proxy M UNI GSM radio link Mobile ATM: Use with Cellular For mobile ATM infrastructure, a “proxy M-UNI” can be used at the AP for interworking with a non-WATM radio protocol... GSM (or other cellular access protocol) converted to M-UNI at AP Mobile ATM provides handoff and location mgmt to GSM user GSM
25 Homework - Read tutorial papers on mobile IP & ATM - Download and browse Mobile IP RFC