Internet Mobility 4x4. Stuart Cheshire and Mary Baker

Transcription

1 Internet Mobility 4x4 Stuart Cheshire and Mary Baker

2 Basic Mobile IP - from mobile hosts Mobile host uses its home IP address as source address Lower latency Still transparent to correspondent host No obvious need to encapsulate packet to This is called a triangle route Home Network HA Foreign Network FA MH

3 Problems with Foreign Agents Assumption of support from foreign networks Do foreign agents exist in all networks? Is the foreign agent robust and up and running? Is the foreign agent trustworthy? Correctness in security-conscious networks We ll see that triangle route has problems MH under its own control can eliminate this problem Other undesirable features Some performance improvements are harder with FAs We want end-to-end solution that allows flexibility

4 Solution Mobile host is responsible for itself Mobile host decapsulates packets Mobile host sends its own packets Co-located FA on MH MH must acquire its own IP address in foreign network Home Network HA Foreign Network MH

5 Obtaining a foreign IP address Can we expect to obtain an IP address? DHCP is common Your friend can reserve an IP address for you Various other tricks More support for dynamic IP address binding in IPv6 This assumes less than getting others to run a FA

6 Design implications New issues: the mobile host now has two roles: Home role Local role - More complex mobile host - Loss of in-flight packets? (This can happen anyway.) + Can visit networks without a foreign agent + Can join local multicast groups, etc. + More control over packet routing = more flexibility

7 Optimization Goals Ensure Deliverability Minimize latency Minimize Size Constraints No special support from routers Permissiveness of the network Level of mobility awareness of

8 Problem: Ingress Filtering Mobile host uses its home IP address as source address Security-conscious routers will drop packet Some networks don t allow transit traffic Home Network HA Foreign Network MH

9 Solution: Bi-directional Tunnel Provide choice of safe route through home agent both ways This is the slowest but most conservative option At the other extreme Home Network HA Foreign Network MH

10 Problem: performance Example: short-lived communication When accessing a web server, why pay for mobility? Do without location-transparency Unlikely to move during transfer; can reload page Works when keeps no state about MH

11 Solution: More Flexibility Use current care-of address and send packet directly This is regular IP! More generally: MH should have flexibility to adapt to circumstances A range of options: from slow-but-safe to regular IP Should be an end-to-end packet delivery decision (no FA) Home Network HA Foreign Network MH

12 Problem: Size Encapsulation or tunneling Adds overhead to packets which in turn makes fragmentation more likely

13 Routing options Allow MH to choose from among all routing options Options Encapsulate packet or not? Use home address or care-of address as source address? Tunnel packet through home agent or send directly? Choice determined by Performance Desire for transparent mobility Mobile-awareness of correspondent host Security concerns of networks traversed Equivalent choices for sending packets to MH

14 Achieving Optimizations Influence path taken by packets by changing source and destination address in IP header Using the best according to the situation Avoid encapsulation if possible

15 Packets Unencapsulated

16 Out-IE: Indirect Conservative Supported by all nodes Motivation Required for basic mobility Privacy Pro No router problems need not be MobileIP Aware Con Indirect delivery Encapsulation overhead Packet IPIP MH Source COA Haddr Dest HAgent HA

17 Out-DE: Direct Decaspulation capable Motivation Communicating with a that can handle encapsulated packets Routers check source address Pro No router problems Direct delivery Con Encapsulation overhead must be able to tunnel Packet IPIP MH Source COA haddr Dest HA

18 Out-DH: Direct Home No source address filtering Motivation Communicating with a that can handle encapsulated packets Routers do not check source address Pro Direct delivery No encapsulation overhead need not be MobileIP Aware Con Possible router problems Packet IPIP MH Source Haddr Dest HA

19 Out-DT: Direct Temporary No MobileIP Motivation Transparent mobility not required Short lived connections Pro Direct delivery No encapsulation overhead need not be MobileIP Aware No router problems Con No mobility! Packet IPIP MH Source COA Dest HA

20 Packets Unencapsulated

21 In-IE: Indirect Conservative Supported by all nodes Motivation Required for basic mobility Pro No router problems need not be MobileIP Aware Con Indirect delivery Encapsulation overhead Packet Packet IPIP MH Source To HA To MH HAgent HA Dest HAddr COA Haddr

22 In-DE: Direct Mobile-aware Motivation Communicating with a mobile-aware knows current COA Pro No router problems Direct delivery Con Encapsulation overhead must be able to tunnel Packet IPIP MH Source Dest COA HAddr HA

23 In-DH: Direct Home Same physical network segment Motivation Communicating with a on same segment MH far from home Pro Direct delivery No encapsulation overhead need not be MobileIP Aware Con and MH must be on same network segment Packet IPIP MH Source Dest HAddr HA

24 In-DT: Direct Temporary No MobileIP Motivation Short lived connections Pro Direct delivery No encapsulation overhead need not be MobileIP Aware No router problems Con No mobility! Packet IPIP MH Source Dest COA HA

25 Mobility 4x4 Indirect, Direct, Direct, Home Direct, Temp. Conventional Indirect, Most reliable, least efficient Requires decapsulation on No securityconscious routers on path Mobile-Aware Direct, Not needed Requires fully mobile-aware No securityconscious routers on path Both Hosts on Same Network Direct, Home Not needed Not needed Requires both hosts to be on same net. seg. No Mobility Support Direct, Temp. Most efficient, no mobility support

26 Mobility 4x4 Communication with Conventional Indirect, Direct, Direct, Home Direct, Temp. Conventional Indirect, Most reliable, least efficient Requires decapsulation on No securityconscious routers on path Mobile-Aware Direct, Not needed Requires fully mobile-aware No securityconscious routers on path Both Hosts on Same Network Direct, Home Not needed Not needed Requires both hosts to be on same net. seg. No Mobility Support Direct, Temp. Most efficient, no mobility support

27 Mobility 4x4 Communication with Mobile-aware Indirect, Direct, Direct, Home Direct, Temp. Conventional Indirect, Most reliable, least efficient Requires decapsulation on No securityconscious routers on path Mobile-Aware Direct, Not needed Requires fully mobile-aware No securityconscious routers on path Both Hosts on Same Network Direct, Home Not needed Not needed Requires both hosts to be on same net. seg. No Mobility Support Direct, Temp. Most efficient, no mobility support

28 Mobility 4x4 Communication with on same network Indirect, Direct, Direct, Home Direct, Temp. Conventional Indirect, Most reliable, least efficient Requires decapsulation on No securityconscious routers on path Mobile-Aware Direct, Not needed Requires fully mobile-aware No securityconscious routers on path Both Hosts on Same Network Direct, Home Not needed Not needed Requires both hosts to be on same net. seg. No Mobility Support Direct, Temp. Most efficient, no mobility support

29 Mobility 4x4 Communication directly with Indirect, Direct, Direct, Home Direct, Temp. Conventional Indirect, Most reliable, least efficient Requires decapsulation on No securityconscious routers on path Mobile-Aware Direct, Not needed Requires fully mobile-aware No securityconscious routers on path Both Hosts on Same Network Direct, Home Not needed Not needed Requires both hosts to be on same net. seg. No Mobility Support Direct, Temp. Most efficient, no mobility support