Applications in Use

Network designers are concerned with two specific characteristics of the traffic when selecting a
WAN protocol. The first consideration relates to the upper layer protocol that will be used. For
example, it’s not possible to use SLIP with any other upper layer protocol except IP. To use a different
protocol, the administrator would have to select another lower level protocol (PPP, for
example) to transport native Internetwork Packet Exchange (IPX) packets. The second consideration
has to do with the acceptability of delay on the part of the upper layer protocol. Systems Network
Architecture (SNA), a mainframe protocol, traditionally cannot accept a high level of delay.
Fortunately, most applications can use many transport protocols and most operate using IP.
This enables the remote access solution to focus on supporting a single protocol in most cases,
and it enables the use of a protocol that does not suffer significantly from the delay present in
low-bandwidth and on-demand connections. Because of this, many vendors and designers will
opt to use PPP as a transport protocol.