Pros and Cons of Interconnection Between UMTS and WLAN Through MG

There are several advantages to employing proxy architecture for intertechnology
roaming. The proxy architecture is scaleable. There is the possibility
of further minimizing the encapsulation and routing inefficiencies with mobile IP. However, the real reduction in overhead may not be very significant
due to the need for additional control protocols. If the proxy is under
the control of the same organization that owns the mobile hosts/station, it is
possible to configure the proxy to support the peculiar needs of its population
of mobile hosts. An optimized protocol may be run between the mobile
and proxy depending on the link being employed. The proxy can manage
resource-poor connections more efficiently. For example, it can drop structured
data such as e-mail headers and frames in a Motion Picture Expert
Group (MPEG) stream selectively or drop unstructured data.
Proxies are already in place in many organizations as firewalls or Web
caching servers. These may be reused for mobility management and intertechnology
roaming. Proxies can be used for logging the characteristics of
connection, the details of which may be usefully employed in various applications
including accounting and management.
The main disadvantages of the proxy architecture are as follows. First,
the architecture is not standardized, and therefore it requires proprietary protocols
for intertech roaming. Second, the performance of a proxy is poor
because a significant latency is added to the client-server communication
path. Potentially, the end-to-end semantics of the transport protocol may
also be violated. If a single proxy is employed and it fails, it may result in the
failure of the entire network—there is a need to have some fault tolerance.
Third, there is the issue of developing protocols for mobility management
with the proxy architecture. There are some more issues that are open. The
placement and number of proxies to be employed may depend on the situation.
It is preferable to have the proxy connected to the last links of each services
that the MS may use so that it can gather information about the quality
of each of the last links. However, the ownership of such a proxy will be contentious.
The number of proxies that have to be placed for optimum performance
is also subject to network conditions.