Mobile Networking (I) CS 395T - Mobile Computing and Wireless Networks Department of Computer Sciences THE UNIVERSITY OF TEXAS AT AUSTIN CS 395T - Mobile Computing and Wireless Networks Mobile Networking (I) © 2002 Yongguang Zhang

Contents Mobility at the Network Layer IETF Mobile-IP Discussions Other Mobile-IP Discussions Architectural issues Common implementation issues Future Directions Spring 2002 © 2002 Yongguang Zhang

Mobility at the Network Layer Where can you manage mobility? Application Session Transport Network Data-link Physical Mobile-IP: an extension to current IP architecture To manage mobility at the IP layer To hide mobility from the upper layers Spring 2002 © 2002 Yongguang Zhang

Terminology Mobile Node (MN or MH) Correspondent Node (CN or CH) Home Network and Foreign Network Mobility Agent Home Agent (HA) and Foreign Agent (FA) Home Address (HoA) and Care-of Address (CoA) Binding and Binding Update Spring 2002 © 2002 Yongguang Zhang

IETF Mobile-IP: Basic Concept MN always uses its home address HoA When MN visits a foreign network, Registration with FA Discover mobile agents and CoA Registration with HA Binding update (HoA -> CoA) When CN communicates with MN, it uses HoA HA forwards packet from HoA to CoA Spring 2002 © 2002 Yongguang Zhang

Agent Discovery Through Agent Discovery Process Agent advertisement (beaconing): Mobile agent broadcast agent advertisement at regular intervals (“I am here”) Agent solicitation: MN can solicit advertisement (“anyone here?”) Mobile agent respond to agent solicitation Question: why agent solicitation? Spring 2002 © 2002 Yongguang Zhang

Functions of Agent Advertisement Allow for the detection of mobility agents Let the MN know whether the agent is a HA, or a FA List one or more available care-of addresses Inform the MN about special features provided by FA Example: Alternative encapsulation techniques Let MN determine the network number and status of their link to the Internet Spring 2002 © 2002 Yongguang Zhang

CoA Two types of CoA: Depends on foreign network configuration FA’s IP address MN’s temporary address Locally-assigned address in the foreign network E.g., DHCP address Depends on foreign network configuration Foreign network may or may not hand out addresses to visitors Spring 2002 © 2002 Yongguang Zhang

Implementing Agent Discovery Protocol details Built on top of an existing standard protocol: Router Advertisement (RFC 1256) Simply extends the fields of existing router advertisements Spring 2002 © 2002 Yongguang Zhang

Registering CoA HA must know a MH’s CoA (binding update) Binding: (HoA->CoA) Binding has a lifetime (can expire) Registration process MH sends a registration request with CoA information HA authenticate the request HA approves or disapproves the request HA adds the necessary information to its routing table HA sends a registration reply back to MH Spring 2002 © 2002 Yongguang Zhang

Registration Operations Spring 2002 © 2002 Yongguang Zhang

Authentication A malicious node could cause remote redirect Authentication and protection against replay attacks, and need for unique identification field Timestamp and Pseudorandom Number Spring 2002 © 2002 Yongguang Zhang

Automatic Home Agent Discovery Problem: what if MH never knew its HA? Example: MH reboots and losses all states Subnet-wise broadcast packet is sent to the home network Subnet-wise broadcast: cell-cast HA responds If more than one, other HAs on the home network send rejection notice Spring 2002 © 2002 Yongguang Zhang

Forwarding to CoA Encapsulation Default encapsulation mechanism: Sending the original packet (CH->MH) in another packet (HA->CoA) Default encapsulation mechanism: IP-within-IP (tunnel) Tunnel header: A new IP header inserted by the tunnel source (home agent) Destination IP: CoA Alternative encapsulation mechanism: Minimal encapsulation Spring 2002 © 2002 Yongguang Zhang

Tunneling Operations in Mobile IP Spring 2002 © 2002 Yongguang Zhang

The Triangle Routing Problem MH->CH: direct; CH->MH: CH->HA->MH Inefficient Solution: Route optimization in Mobile-IP Deliver binding updates directly to CH Spring 2002 © 2002 Yongguang Zhang

Discussion System issues Spring 2002 © 2002 Yongguang Zhang

Home Network Where Can We Put the Home Agent? At the router As a separate server? At the router What if there is multiple routers for the home network? As a separate server How can it pick up a packet [CHMH]? Spring 2002 © 2002 Yongguang Zhang

Foreign Network Where is FA? (Router or Separated Server?) How Can FA deliver MH the packet [CHMH] Normally, [CHMH] would go straight to a router (because MH is foreign) Is There Adequate Support at A Foreign Network What if there is no FA at the network you visit? Co-located FA What is the Minimum Requirement from the Foreign Network? Keep it as small as possible Spring 2002 © 2002 Yongguang Zhang

Security Issues Visitors Are Threats! How to provision your LAN to support nomadic users And to protect your LAN from nomadic users Foreign Network Firewall Traversal Can firewall allows inbound [HAFA] tunnel? Can [MHCH] pass through an egress filter? Bi-directional tunneling Mutual Authentication Can you trust MH? Can you trust FA? Spring 2002 © 2002 Yongguang Zhang

Mobile Computing Model What is the binding in IETF Mobile-IP? HoA -> CoA (one level of indirection) Where is the binding being managed? HA In the route optimization case: CH Scale of mobility? Internet-wide What is a cell in Mobile-IP? Subnet Spring 2002 © 2002 Yongguang Zhang

Further Discussions Variants of IETF Mobile-IP Mobility Scope Implementation issues Mobility Scope Macro-mobility: Mobile-IP Micro-mobility: Hierarchical Mobile-IP, Cellular-IP, HAWAII, TeleMIP, EMA, … Combining network-layer mobility with link-layer mobility Features: fast handoff, paging, etc. Mobility in a higher layer Transport layer, session layer Spring 2002 © 2002 Yongguang Zhang

Summary IETF Mobile-IP Other versions of Mobile-IP Other extensions to Mobile-IP Future Directions Spring 2002 © 2002 Yongguang Zhang