Addressing: when mobile is moving around. Mobile Registration. Principles of Mobile Routing. Mobility via Indirect Routing

Transcription

1 Wireless Networks Wireless Networks Kai Shen Advantages of wireless links: Mobility, easy setup Wireless s: Infrastructured wireless s Ad hoc wireless s Often, but sometimes fixed location /8/009 CSC 57/57 - Fall 009 /8/009 CSC 57/57 - Fall 009 Infrastructured Network Model Wireless host communicates with a base station or access point (AP). Basic Service Set (BSS) contains: a base station; wireless hosts reachable from the base station. Base stations are connected to each other and wide-area through wired links. /8/009 CSC 57/57 - Fall Addressing: when is at : permanent of e.g., 8.9.0/ permanent address: address in, can always be used to reach e.g., agent: entity that will perform mobility functions on behalf of, when is remote : wants to communicate with /8/009 CSC 57/57 - Fall 009 CSC 57/57 - Fall 009

2 Addressing: when is moving around Permanent address: remains constant (e.g., ) visited : in which currently resides (e.g., /) Mobile Registration visited Care-of-address: address in visited. (e.g., 79,9.3.) : entity in visited that performs mobility functions on behalf of. contacts agent : this is resident in my End result: Foreign agent knows about Home agent knows location of contacts on entering visited /8/009 CSC 57/57 - Fall /8/009 CSC 57/57 - Fall Principles of Mobile Routing Indirect routing communication from to goes through agent, then forwarded to remote Direct routing gets foreign address of, sends directly to Mobility via Indirect Routing addresses packets using address of agent intercepts packets, forwards to receives packets, forwards to 3 visited ii replies directly to /8/009 CSC 57/57 - Fall /8/009 CSC 57/57 - Fall CSC 57/57 - Fall 009

3 Forwarding Packets to Remote Mobile: Encapsulation Indirect Routing: Discussions foreign-agent-to- packet packet sent by agent to foreign dest: agent: a packet within a packet dest: dest: Permanent address: dest: packet sent by Care-of address: Mobile uses two addresses: permanent address: used by care-of-address: used by agent to forward packets to triangle routing: corres.--- suppose user moves to another registers with new new registers with agent agent updates care-of-address for packets continue to be forwarded to (but with new care-of-address) Mobility, changing foreign s transparent /8/009 CSC 57/57 - Fall /8/009 CSC 57/57 - Fall Mobility via Direct Routing requests, receives foreign address of forwards to receives packets, forwards to 3 5 replies directly to visited ii Indirect Routing vs. Direct Routing Efficiency Indirect routing is inefficient, especially when, are near but is far Transparency Indirect routing is transparent to, smoother handoff when moving between s /8/009 CSC 57/57 - Fall 009 /8/009 CSC 57/57 - Fall 009 CSC 57/57 - Fall 009 3

4 Mobile IP Ad Hoc Network Model Network-layer mobility protocol interoperable with IP [C. Perkins, 00] Has many features we ve seen: agents, s, foreign-agent registration, care-of-addresses, encapsulation (packet-within-apacket) use indirect routing No base stations or access points Wireless hosts communicate with each other directly to get packet from wireless host A to B may need to route through wireless hosts X, Y, Z Compared with based station model more flexible require complex support Applications: laptop p meeting in conference room, car interconnection of personal devices battlefield /8/009 CSC 57/57 - Fall /8/009 CSC 57/57 - Fall 009 Addressing in Ad Hoc Networks Routing in Ad Hoc Networks Requirements for addressing in ad hoc s? Hierarchical Unique Any ideas? DSR [Johnson 99] Broadcast-style path discovery Source maintains whole path, each packet carries whole path AODV [Perkins and Royer 999] Every node maintains a routing table, routing hop by hop Source routing vs. hop-by-hop routing? /8/009 CSC 57/57 - Fall /8/009 CSC 57/57 - Fall CSC 57/57 - Fall 009

5 Geographic Location-based Routing Disclaimer [Li et al. 000] Each device is identified d by its geographic location (e.g., longitude and latitude) At each routing step, the packet is directed to the current node s neighbor with shortest Cartesian distance to dest. Advantage: Simple scheme, low routing overhead Problem? Routing loops or dead ends Work best for dense s Parts of the lecture slides contain original work of James Kurose, Larry Peterson, and Keith Ross. The slides are intended for the sole purpose of instruction of computer s at the University of Rochester. All copyrighted materials belong to their original owner(s). /8/009 CSC 57/57 - Fall /8/009 CSC 57/57 - Fall CSC 57/57 - Fall 009 5