120 Software Networks
terminal. The interfaces may be different access technologies and be
connected to different networks. Each interface obtains an IP address
assigned by its own network;
– several interfaces, with one or more IP addresses per interface.
This is the most commonplace situation. The terminal has several
physical interfaces, each of which can receive one or more IP
addresses, attributed by the attached networks.
There are two main approaches to multihoming: one using the
routing protocol BGP (Border Gateway Protocol), and one using the
Network Address Translation mechanism. These solutions are based
on network routing and address management techniques to achieve
high connection ability and improved performance.
The earliest multihoming protocols were at transport level, with
SCTP (Stream Control Transmission Protocol) and its extensions. At
network level, SHIM6 (Level 3 Multihoming Shim Protocol for IPv6)
and HIP (Host Identity Protocol) are the two protocols supporting
multihoming standardized by the IETF.
Another way of looking at multihoming protocols for a mobile
terminal is to develop the multipath transmission protocol on the basis
of the single-path transmission protocol. Such is the case with the
registration of multiple addresses in a mobility situation: addresses
known as the multiple Care-of-Address (mCoA) and MTCP
(Multipath TCP). The mCoA protocol is an evolution of Mobile IPv6,
which allows multiple temporary addresses (CoAs) to be registered on
the same mobile terminal. This solution defines a registration ID
whose purpose is to distinguish the CoAs of the same terminal.
MPTCP is a recent extension of TCP to take care of data transmission
along several paths simultaneously. An MPTCP connection is made
up of several TCP connections.
The objectives of a multihoming protocol for a multi-interface
mobile terminal are as follows:
– the available paths must be simultaneously used to increase the
bandwidth;
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