For wide area networks, particularly those networks which desire to restrict the
number of transport protocols, encapsulation can be used. Encapsulation will be
performed at an end node, the de-encapsulation at a gateway which physically
connects the two networks. MPTN can similarly be used in a single gateway
configuration, with one end node being the access node. Multi-protocol servers
and a Remote API server can provide the physical connectivity as well as the
One might also wish to consider where the data is physically located in the
network in deciding among these solutions. For instance, a multi-protocol server
allows the data to be stored in one central facility that all users can access. For
distributed data, remote APIs, encapsulation, and MPTN might be appropriate.
Considerations to be kept in mind as these technologies are evaluated include
Are the LANs located in close enough proximity for a local bridge to
Is there too much unnecessary traffic to require filtering?
Will this encapsulating software be placed in the end nodes? Or will it
be placed in a separate node, requiring additional hardware?
How is the encapsulation actually performed? Are Data Link Control
protocols properly terminated and emulated? Are the transport-level
protocols properly emulated? Is filtering of unnecessary packets
What are the performance characteristics of this encapsulation software?
Is this acceptable?
How are the different network addresses handled? What directory
How expandable is this approach if the network grows and more nodes
Are all needed protocols handled by the router?
Are there any Data Link Control-level concerns? Does the router
properly handle these protocols?
What happens in congestion situations? Are all protocols equal? Can
the traffic be prioritized?
How much filtering is available for each protocol?
Do MPTN implementations exist for the necessary protocols?
If MPTN implementations exist for these protocols, do they exist on the
required operating system platforms in the end nodes? If not, do they
exist for operating system platforms, which could be used as a gateway?
What APIs are supported over which protocols? Does the correct
Does this “skinny client” provide enough functionality to satisfy the
Chapter 3. Typical Customer Situations