In infrastructure-based networks devices often move from one attachment
point in the network or a sub-network thereof to another attachment
point. Communications sessions may be established between Mobile Hosts
attached to such nodes. Communications sessions between nodes established
using Session Initiation Protocol (SIP), Mobile Internet Protocol with
Location Registers (MIP-LR) or Mobile Internet Protocol version 6 (MIPv6)
may fail if there is simultaneous mobility of two Mobile Hosts in an
ongoing communication session. Stationary binding update proxies and
stationary location proxies are introduced into such communications
networks in order to provide a solution to the problem of simultaneous
mobility of Mobile Hosts. Specific implementation for SIP, MIP-LR and
MIPv6 are provided. IN SIP networks, the SIP server for the mobile hosts
acts as the stationary binding update proxy and the stationary location
proxy. In MIP-LR networks, the Home Location Register (HLR) functions as
the stationary binding update proxy and the intercepting is performed by
the Foreign Agent or Advertisement Agent. In MIPv6 networks, the home
agent of each the first and second mobile host functions as the
stationary location proxy and the stationary binding update proxy for
each mobile host respectively.