
140 Part Two • IPv6 Protocols
to a single IP address even as they are moved from one subnet to another?
This problem is distinguishable from that of cellular mobile nodes, which
must be capable of maintaining a virtual circuit as the nodes move from
one cell to another, in several important ways. First, the mobile IP node
must be able to support a more formal definition of a virtual circuit, capa-
ble of transmitting data with error detection. Also, the mobile IP node is
not expected to be quite as continuously or rapidly mobile as a mobile
telephone, for example.
The problem of mobility for IPv4 was first addressed in a standards track
specification,