We've reached the last week of the quarter!!! Tuesday lecture: support for host mobility!" Focus: IP mobility!" FYI (if time): cellular mobility!! Thursday lecture: review!" Your suggestions are most welcome here!!# Please email me what you would like to see covered!! Office hours this week:!" Thursday 6/2: 3:00-4:00PM!" Friday 6/3: 4:00-6:00PM!! Final exam: Sat 6/4 3:00-6:00PM !" Location to be announced later!CS118!1!Mobility: Vocabulary (I)!CS118!2!home network: permanent “home” of mobile (e.g., 128.119.40.0/24) Permanent address: mobile's address in home network, can always be used to reach mobile (e.g., 128.119.40.186) wide area network home agent: entity that will perform mobility functions on behalf of mobile when mobile is away from home correspondent Correspondent: a computer that wants to communicate with mobile wide area network Vocabulary (II): when away from home!CS118!3!visited network: network in which mobile currently resides (e.g., 79.129.13.0/24) Permanent address: remains constant (e.g., 128.119.40.186) foreign agent: an entity in visited network that provides mobility function on behalf of mobile Care-of-address: mobile’s address obtained from the visited network (e.g. 79.129.13.2) 79.129.13.0/24 Home network Home agent How do you contact a mobile friend?!! search all phone books?!! expect her to let you know where she is?!! call her parents?!CS118! 4!I wonder where Alice moved to? Consider a friend who frequently changes addresses, how do you find her?!Mobility: approaches!! Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange.!" routing tables indicate where each mobile located!" no changes to end-systems!! Let end-systems handle it:!" Mobile keeps home agent updated on its whereabouts !" indirect routing: correspondent sends packets to mobile’s home agent, which forwards to mobile!" direct routing: correspondent gets mobile’s foreign address, sends directly to mobile!CS118!5!Cannot scale to millions of mobiles Mobility: registration!End result:!! Foreign agent knows about mobile!! Home agent knows location of mobile!CS118!6!wide area network home network visited network 1 mobile contacts foreign agent on entering visited network 2 foreign agent contacts home agent home: “this mobile is resident in my network” Supporting Mobility via Indirect Routing!CS118!7!wide area network home network visited network 3 2 4 1 correspondent addresses packets using home address of mobile home agent intercepts packets, forwards to foreign agent through tunneling foreign agent receives packets, forwards to mobile mobile replies directly to correspondent Q: Which address will mobile use as source address?!Mobile IP: indirect routing!CS118!8!Permanent address: 128.119.40.186 Care-of address: 79.129.13.2 dest: 128.119.40.186 packet sent by correspondent dest: 79.129.13.2 dest: 128.119.40.186 home agent tunnels the packet to foreign agent: IP encapsulation dest: 128.119.40.186 foreign-agent-to-mobile packetIndirect Routing: handling further movement!CS118!9!wide area network home!network!visited!network!2 3 1 4 Q: Will the correspondence be aware of mobile's move? !5 Indirect Routing: moving between networks!! When mobile moves to another network!" registers with new foreign agent!" new foreign agent registers with home agent!" home agent update care-of-address for mobile!" Home agent continue to forward packets to mobile through IP-in-IP tunnel (to the new care-of-address)!! Mobility is transparent to correspondent!! mobility is transparent to TCP (or any other transport protocol)!" TCP connection uses mobile’s home address, ongoing connections can be maintained while mobile moves!CS118!10!Summary of Indirect Routing!! Mobile uses two addresses:!" permanent address: used by correspondent to send packet to mobile!" care-of-address: used by home agent to forward packet to mobile!! Mobile can perform foreign agent function itself!" Just get a care-of address from foreign DHCP server!! Mobility is transparent to correspondent!! May result in triangle routing: correspondent$home-network$mobile!" Inefficient, especially when!correspondent & mobile are !close but home agent is far away!CS118!11!Mobility via Direct Routing!CS118!12!wide area network home network visited network 4 2 5 1 correspondent requests, receives foreign address of mobile correspondent sends packet to foreign agent foreign agent receives packets, forwards to mobile mobile replies directly to correspondent 3Mobility via Direct Routing: comments!! Good: Eliminate triangle routing problem!! bad:!" Correspondent must be aware of mobility support!" what if mobile moves from network to network?!CS118!13!Accommodating mobility with direct routing!! anchor foreign agent: FA in the first visited network!! data always routed first to anchor FA!! when mobile moves: new FA notifies the old FA to have data forwarded from old FA (chaining)!CS118!14!wide area network 1 anchor foreign agent foreign net visited at session start 2 4 new foreign agent 3 5 correspondent new foreign network IP mobility: summary!! A mobile has!" a home-agent, and!" a permanent home IP address!! When a mobile moves to a new location,!" Obtain a new care-of address!" Informing its home agent of its new IP address!! Indirect routing: A correspondent sends data to a mobile’s home address, the home-agent forward data to the mobile’s care-of address!! Direct routing: correspondent obtains mobile’s care-of address, sends packet to mobile directly!CS118!15!Mobility via indirect routing!! correspondent sends data to the mobile’s home agent!" Source = CD; destination = P (mobile's permanent address)!! Home agent tunnels data to mobile!" Outer IP header: Source = P; destination = CA!" Inner IP header: source = CD; destination = P!! Mobile tunnels data to correspondent!" Outer header: Source = CA; destination = CD!" Inner header: source = P; destination = CD!! Supports mobile movement transparently!" No change to transport protocols!" Cost: triangle routing!CS118!16!CD CA P P = mobile’s Permanent home address CA = Care-of Address CD = CorresponDent addressComponents of cellular network architecture!CS118!Mobile Switching Center Public telephone network, and Internet
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