Allied Telesis AT-WA7500 - Manual (Page 137)

AT-WA7500 User’s Guide
137
Comparing IP Tunnels to Mobile IP
The AT-WA7500 access point supports IP tunneling, which allows end
devices to roam across different subnets (routers) without having to
change IP addresses. IP tunneling supports IETF RFC 1701 using GRE and
the same encapsulation technique as mobile IP. IP tunnels technology is
designed primarily to operate in local environments, where handheld or
vehicle-mounted devices may move rapidly between access point
coverage areas on a subnet (although it is possible to attach a
geographically remote subnet through an IP tunnel).
The Internet Engineering Task Force developed RFC 2002, IP Mobility
Support, commonly referred to as mobile IP, to provide mobility for IP
hosts. Mobile IP is designed primarily to address the needs of wireless
end devices that may move between geographically separated
locations.
The two technologies are complimentary and may coexist. Both
protocols use similar encapsulation to forward frames to or from end
devices that have roamed away from a root IP subnet. The root access
point functions much like a mobile IP home agent; an access point
attached to the remote end of an IP tunnel functions much like a mobile
IP foreign agent.
Table 20 IP Tunnels and Mobile IP Comparison
Issue IP Tunneling Mobile IP
Software compatibility No changes are required to
existing IP software stacks in end
devices. Requires a mobile IP client
software stack in end devices.
Addressing limitations
for IP end devices Requires that end device IP
addresses belong to the root IP
subnet. None
Security Guest addresses are not used.
Data link security. Mobile IP authentication is
required for guest access to
foreign subnets.
Roaming detection Data link indications facilitate fast
roaming with no added broadcast
traffic. Foreign agent advertisements.
Roaming restrictions Currently, roaming is limited to a
single network that may include
multiple IP subnets. None