How Mobile IP Works? Presenter: Ajoy Singh

Transcription

1 How Mobile IP Works? Presenter: Ajoy Singh

2 Agenda Required background What problems does Mobile IP solve? Mobile IP: protocol overview Scope Requirements Design goals Functional entities 5/2/2002 How Mobile IP Works? 2

3 Agenda (continued) The gory details Agent discovery Registration Packet delivery Case study: campus mobility Q & A 5/2/2002 How Mobile IP Works? 3

4 Required Background I am assuming you already know: the different layers of the OSI model, what IP and ICMP are, what ARP, proxy ARP and gratuitous ARP are, IP: Internet Protocol how IP routing works. IP: Internet Protocol ICMP: ICMP: Internet Internet Control Control Message Message Protocol Protocol ARP: ARP: Address Address Resolution Resolution Protocol Protocol 5/2/2002 How Mobile IP Works? 4

5 What Problems Does Mobile IP Solve? An IP address not only identifies a host but also a point-of-attachment. Host-specific routes approach suffers from serious scalability, robustness and security concerns if applied to the global Internet. Mobility Mobilityis is the the ability ability of of a node node to to change change its its point-of-attachment point-of-attachment while while maintaining maintaining all all existing existing communications communications and and using using the the same same IP IP address. address. 5/2/2002 How Mobile IP Works? 5

6 What Problems Does Mobile IP Solve? (continued) A host cannot change its IP address without terminating on-going sessions and restarting them after it acquires a new address. Other link layer mobility solutions exist but are not sufficient enough for the Nomadicity global Internet. Nomadicityallows allows a node node to to move move but but it it must must terminate terminate all all existing existing communications communications and and then then can can initiate initiate new new connections connections with with a new new address. address. 5/2/2002 How Mobile IP Works? 6

7 Mobile IP: Protocol Overview 5/2/2002 How Mobile IP Works? 7

8 Scope Mobile IP is a network layer solution for homogenous and heterogeneous mobility on the global Internet which is scalable, robust, secure and which allows nodes to maintain all ongoing communications while moving. 5/2/2002 How Mobile IP Works? 8

9 Requirements MN must be able to communicate with other nodes after changing its LL POA. MN must be able to communicate using only its home (permanent) IP address regardless of its current LL POA. MN: MN: mobile mobile node node LL: LL: link link layer layer POA: POA: point-of-attachment point-of-attachment 5/2/2002 How Mobile IP Works? 9

10 Requirements (continued) MN must be able to communicate with other nodes that do not implement Mobile IP mobility functions. MN must not be exposed to any new security threats over and above those which any fixed node on the Internet is exposed to. 5/2/2002 How Mobile IP Works? 10

11 Design Goals Mobile IP was designed to make the size and the frequency of required routing updates as small as possible. It was designed to make it simple to implement mobile node software. It was designed to avoid solutions that require mobile nodes to use multiple addresses. 5/2/2002 How Mobile IP Works? 11

12 Functional Entities Mobile Node (MN): a node which can change its POA while maintaining any ongoing communications and using only its home (permanent) IP address. Home Agent (HA): a router with at least one interface on the MN s home link which: MN keeps informed of its current location, i.e., its care-of-address (COA), intercepts packets destined to the MN s home address and tunnels them to the MN s current location (or COA). 5/2/2002 How Mobile IP Works? 12

13 Functional Entities (continued) Foreign Agent (FA): a router on a foreign link which: assists the MN in informing its HA of its current COA, sometimes, provides a COA and de-tunnels packets for the MN, acts as the default router for packets generated by the MN while connected to this foreign link. 5/2/2002 How Mobile IP Works? 13

14 Correspondent Node Router 3 Home Agent Internet Router 1 Foreign Agent Router 2 Mobile Node 5/2/2002 How Mobile IP Works? 14

15 Common Scenario (1) CN HA Router Router 1 Home Link FA 2 MN Internet 5 1 Foreign Link Router 2 5/2/2002 How Mobile IP Works? 15

16 Common Scenario (2) CN 1 HA 3 6 Router 3 Router 1 2 Home Link FA 4 MN Internet 5 Foreign Link Router 2 5/2/2002 How Mobile IP Works? 16

17 Agenda Progress Required background What problems does Mobile IP solve? Mobile IP: protocol overview The gory details Agent discovery Registration Packet delivery Case study: campus mobility Q & A 5/2/2002 How Mobile IP Works? 17

18 The Gory Details 5/2/2002 How Mobile IP Works? 18

19 Agent Discovery Agent discovery allows the MN to: determine whether it home or not, detect whether it has moved, obtain a COA when away from home. Agent discovery consists of 2 messages: Agent Advertisement Agent Solicitation MN determines it has moved in 2 ways: move detection using advertisement lifetimes move detection using network prefixes 5/2/2002 How Mobile IP Works? 19

20 Registration Mobile IP registration allows the MN to: request routing services from a FA, inform its HA of its current COA, renew a registration which is about to expire, deregister when it returns home, have multiple simultaneous COA s registered with its HA, deregister a particular COA while retaining others, dynamically discover the address of a potential HA. 5/2/2002 How Mobile IP Works? 20

21 Registration (continued) Registration consists of 2 messages: registration request registration reply 5/2/2002 How Mobile IP Works? 21

22 Q & A Any Questions? 5/2/2002 How Mobile IP Works? 22

23 Agent Solicitation Message IP Header Fields IP header Type = 10 Code = 0 reserved Checksum ICMP Router Solicitation 5/2/2002 How Mobile IP Works? 23

24 Agent Advertisement Message Type = 9 Num Addrs Type = 16 Type = 19 Code Addr Entry Size Length Max Registration Lifetime Length IP Header Fields Router Address [1] Preference Level [1] B H F M Care-of-address [1] R G Prefix-Length[1] Checksum Advertisement Lifetime Sequence Number V reserved Prefix-Length[2] IP Header ICMP Router Advertisement Mobility Agent Advertisement Extension Prefix-Length Extension (Optional) 5/2/2002 How Mobile IP Works? 24

25 Registration Request Message Type = 1 Type = 32 S Index (SPI) B D M G Length IP Header Fields UDP Header Fields V rsv MN s Home Address HA Address COA Address Identification (64 bits) Optional Extensions Lifetime (requested) Security Parameter Authenticator (Default equals Keyed MD5) IP Header UDP Header Fixed-Length Portion of Registration Request Mobile-Home Authentication Extension More Optional Extensions 5/2/2002 How Mobile IP Works? 25

26 Registration Reply Message (Fixed Portion Only) Type = 3 Code Lifetime (granted) MN s Home Address HA Address Identification Fixed- Length Portion of Registrati on Reply 5/2/2002 How Mobile IP Works? 26