Applicability Statement for IP Mobility Support
Extracted elements (18)
Agent discovery (ICMP Router Discovery extension) is left unauthenticated because no Internet key management protocol was available at the time, making mandatory authentication impractical.
Mobile IP is designed to solve 'macro' mobility (movement across IP subnets) rather than 'micro' mobility (e.g., handoff among wireless transceivers covering small areas), where link-layer mechanisms may offer faster convergence and less overhead.
Mobile IP makes no attempt to solve local or global IP address renumbering; mobile nodes are assigned home addresses by the authority who owns them, in the same manner as stationary hosts.
Without route optimization, the home agent is a potential load point when serving many mobile nodes. The protocol addresses this by allowing additional home agents to be added and dynamically discovered by mobile nodes.
Interoperability of at least two independent implementations was demonstrated for all major Mobile IP features at an October 1995 interim meeting hosted by FTP Software, including agent advertisement, registration, tunneling (IP-in-IP and Minimal Encapsulation), and authentication failure handling.
Mobile IP is equally suitable for mobility across homogeneous media (e.g., Ethernet to Ethernet) and heterogeneous media (e.g., Ethernet to wireless LAN), as the subnet-level abstraction is media-independent.
TCP connections were demonstrated to remain open with data flowing while a mobile node moved from its home network to a foreign network and back, confirming transport-layer transparency of the mobility mechanism.
All Mobile IP implementations are required to support, at a minimum, keyed MD5 authentication with manual key distribution. Other authentication and key distribution algorithms may additionally be supported.
Implementations requiring privacy and/or authentication of data packets sent to and from a mobile node should use the IP security protocols described in RFCs 1827 and 1826.
Mobile IP mandates the use of cryptographically strong authentication for all registration messages exchanged between a mobile node and its home agent.
Replay protection for registration messages is required and realized via one of two possible mechanisms: timestamps or nonces.
Strong authentication between foreign agents and mobile nodes or home agents is optional; it is not mandated in the baseline protocol.
Mobile IP defines an authenticated registration procedure by which a mobile node informs its home agent(s) of its care-of address(es), enabling packet forwarding to the mobile node's current location.
Mobile IP extends ICMP Router Discovery (RFC 1256) to allow mobile nodes to discover prospective home agents and foreign agents on the attached network.
Mobile IP routing delivers packets destined to a mobile node to its home network, where the home agent tunnels them to the mobile node's most recently reported care-of address. In the reverse direction, packets from mobile nodes are routed directly using standard IP routing mechanisms.
Mobile IP specifies one mandatory tunneling mechanism (IP-in-IP encapsulation, RFC 2003) and two optional tunneling mechanisms: Minimal Encapsulation (RFC 2004) and GRE (RFC 1701).
Agent discovery messages are not required to be authenticated due to the unavailability of an Internet key management protocol at the time of publication.
Mobile IP defines security mechanisms only for the registration protocol. Data packet confidentiality and authentication are explicitly out of scope and delegated to IPsec (RFCs 1826, 1827).