6 Mobility Management

Transcription

1 Politecnico di Milano Facoltà di Ingegneria dell Informazione 6 Mobility Management Reti Mobili Distribuite Prof. Antonio Capone

2 Introduction Mobility management allows a terminal to change its point of access to the network : Without changing its address/identifier Keeping sessions active (at application level) This is not always necessary Application clients do not need to be reached with the same address/identifier They can change address/identifier whenever they need and issue requests to servers as long as session continuity is not a problem A. Capone: Wireless s 2

3 Client mobility Change IP address Start new sessions A. Capone: Wireless s 3

4 Mobility Management (MM) If you must be reached by other hosts with your address/identifier: Server applications And/or you want your sessions remain active Real time applications Then you need some mobility management support by the network Application layer Transport layer application layer Identifiers IP Layer Link layer Physical layer routing layer Adresses A. Capone: Wireless s 4

5 Application Layer Change address and keep the same application layer identifier Manage sessions changing their description when address change Examples: Dynamic DNS SIP A. Capone: Wireless s 5

6 Application Layer Dynamic DNS Name: myname.com Address: My_IP Dynamic DNS Server DNS query Dynamic DNS Client DNS reply No session continuity Mainly devised for static servers with dynamic IP addresses A. Capone: Wireless s 6

7 Application Layer SIP mobility sip.polimi.it sip.ucla.edu Home domain capone@polimi.it Foreign domain capone%40polimi.it@ucla.edu Both pre-call and mid-call mobility can be provided with session continuity A. Capone: Wireless s 7

8 routing layer: Link Layer We already analyzed the MM at layer 2 for WiFi: R Bridging tables updated AP1 Broadcast Message (Gratuitous ARP reply) AP2 AP3 A A A. Capone: Wireless s 8

9 routing layer: Link Layer Let s take a closer look: Bridging tables have an entry for each MAC address When terminal changes its access point we just need to update the corresponding entries in all bridging tables of the network This approach is suitable for LANs It does not scale up to big networks A. Capone: Wireless s 9

10 routing layer: IP Layer How to manage mobility at IP layer? IP routing is based on the network address (prefix matching) Routing Table: /24 NH_b address /24 Routing Table: /0 NH_a Routing Table: /16 NH_b /24 IF: local_if Host address /24 A. Capone: Wireless s 10

11 routing layer: IP Layer How to manage mobility at IP layer? Corresponding Host (CH) address /24 Internet address /24 Home? Foreign Mobile Host (MH) /24 Mobile Host (MH) /24 A. Capone: Wireless s 11

12 routing layer: IP Layer How to manage mobility at IP layer? Can we use the same approach for link layer mobility per host routes? Routing Table: /24 NH_c /32 NH_c address /24 Routing Table: /16 NH_b /32 NH_b Routing Table: /0 NH_a /24 IF: local_if /32 IF: local_if MH /32 A. Capone: Wireless s 12

13 routing layer: IP Layer Per host routes Large routing tables: potentially one entry per mobile host Frequent routing updates that need to be distributed on the whole network Even for a relatively small number of mobile hosts, managing mobility with per host routes would not be easy A. Capone: Wireless s 13

14 MOBILE IP A. Capone: Wireless s 14

15 Mobile IP Mobile IP was developed as a means for transparently dealing with problems of mobile users Enables hosts to stay connected to the Internet regardless of their location Enables hosts to be tracked without needing to change their IP address Requires no changes to software of non-mobile hosts/routers Requires addition of some infrastructure Has no geographical limitations Requires no modifications to IP addresses or IP address format Supports security A. Capone: Wireless s 15

16 Mobile IP Mobile IP is an Internet Engineering Task Force (IETF) standard communications protocol Mobile IP for IPv4 (MIPv4) is described in IETF RFC 3344 and in RFC 4721 A. Capone: Wireless s 16

17 Basics Mobile IP allows a mobile host to move about without changing its permanent IP address (PIP) Each mobile host has a home agent (HA) on its home network (HN) Mobile host establishes a care-of address (COA) when it's away from home A. Capone: Wireless s 17

18 Basics Correspondent host is a host that wants to send packets to the mobile host Correspondent host sends packets to the mobile host s IP permanent address These packets are routed to the mobile host s home network Home agent forwards IP packets for mobile host to current care-of address Mobile host sends packets directly to correspondent, using permanent home IP as source IP A. Capone: Wireless s 18

19 Basics Corresponding Host (CH) address /24 Internet address /24 Home Agent Home Foreign Mobile Host (MH) /24 A. Capone: Wireless s 19

20 Care-of address MHs has two options for the care-of address: Foreign agent care-of address: care-of address can be the address of a foreign agent on the remote network home agent tunnels packets to the home agent foreign agent delivers packets forwarded from home agent to mobile host Co-located care-of address: care-of can be a temporary, foreign IP address obtained through DHCP home agent tunnels packets directly to the temporary IP address In any case, care-of address must be registered with home agent A. Capone: Wireless s 20

21 Foreign agent care-of address Corresponding Host (CH) address /24 Internet address /24 Home Agent Home To: COA Foreign Agent Foreign Mobile Host (MH) /24 A. Capone: Wireless s 21

22 Co-located care-of address Corresponding Host (CH) address /24 Internet address /24 Home Agent Home Foreign Mobile Host (MH) /24 A. Capone: Wireless s 22

23 Tunneling Packet is encapsulated in another IP packet Source: CH Destination: PIP Payload Header Source: HA Destination: COA Payload Header A. Capone: Wireless s 23

24 Tables Mobility Binding Table Maintained on HA Maps MH s home address with its current COA Visitor List Maintained on FA serving an MN Maps MN s home address to its MAC address and HA address Home address Care-Of Address Home address Home Agent Address Lifetime (s) Lifetime (s) A. Capone: Wireless s 24

25 MIPv4 main functions Agent discovery HA and FA advertize service availability MHs can send solicitations to discover if an agent is present Registration MHs registers their COA at the HA either directly or through the FA Registrations are stored in the tables Tunneling Has tunnel datagrams to the COA through the IP-in-IP encapsulation A. Capone: Wireless s 25

26 MIPv4 (RFC 3344) Leaves Internet routing fabric unchanged Does not assume access points ( base stations ) exist everywhere Simple CHs don t need to know about mobility Works both for changing domains and network interfaces A. Capone: Wireless s 26

27 MIPv4 Operation (RFC 3344) HAs and FAs advertise their availability using agent-advertisement messages MHs receive advertisement messages and decide if it is a HA or a FA If it is its HA and MH is returning to home network, it deregisters previous COA on the HA If it a new FA, MH requests a COA (either FA COA, or a co-located COA) MH registers the COA at the HA possibly via the FA A. Capone: Wireless s 27

28 MIPv4 Operation (RFC 3344) HA intercepts packets sent to the MH HA tunnels packets to the COA Packets from the MH are sent directly to the CH A. Capone: Wireless s 28

29 Home Agent Operation HA MH ARP reply ARP request HA HA Gratuitous ARP reply Proxy ARP ARP request ARP reply A. Capone: Wireless s 29

30 Home Agent location A. Capone: Wireless s 30

31 Routing Optimization Suboptimal triangle routing Packets are sent to HA first and then tunneled to the MH Possible Solution: Home agent sends current care-of address to correspondent host Correspondent host caches care-of address Future packets tunneled directly to care-of address A. Capone: Wireless s 31

32 Routing Optimization FIRST PACKET Binding cache CH COA CH address /24 Internet address /24 HA Home Foreign MH /24 A. Capone: Wireless s 32

33 Routing Optimization SUBSEQUENT PACKETS Binding cache CH CH COA address /24 Internet address /24 HA Home Foreign MH /24 A. Capone: Wireless s 33

34 Problems with MIP "Ingress" filtering Routers which see packets coming from a direction from which they would not have routed the source address are dropped CH ERROR: Topologically incorrect address /24 Internet address /24 HA Home Foreign MH /24 A. Capone: Wireless s 34

35 Problems with MIP Security issues: Malicious host sends fake registration messages to home agent "on behalf" of the mobile host Packets could be forwarded to malicious host or to the bit bucket Solution: use secure authentication for registration request/reply Several other security issues A. Capone: Wireless s 35

36 Mobility in IPv6 Route Optimization is a fundamental part of Mobile IPv6 Mobile IPv4 it is an optional set of extensions that may not be supported by all nodes Foreign Agents are not needed in Mobile IPv6 MNs can function in any location without the services of any special router in that location Security Nodes are expected to employ strong authentication and encryption A. Capone: Wireless s 36

37 Hierarchy in MM Registration needed every time MH moves Registration adds delay when HA is far away Registration Request Foreign B Internet Registration Reply HA Home Registration Request Registration Reply Foreign A MH A. Capone: Wireless s 37

38 Hierarchy in MM Hierarchy of FAs or Mobility Routers Hierarchical MIP, Cellular IP, etc. FA5 Foreign C FA4 FA2 Foreign B Internet FA3 FA1 HA Home Registration Request Registration Reply Foreign A MH A. Capone: Wireless s 38