the router command prompt, type ttcp. This is a hidden command; you cannot view this
command using the question mark.
a method that allows you to decide which packets will get discarded within the Frame Relay
network when there is congestion. If you mark some packets as DE, the carrier will discard
those first rather than randomly guessing which packets to discard.
IP and IPX as DE to help make sure the SNA gets through. This would, of course, depend on
your network and how you purchased Frame Relay.
speed (56/64 for 56/64 K and 64 to 1.544 MB for T1 in increments of 64), and CIR.
512 Kbps. The packets above 128 Kbps are randomly marked as DE. If some congestion arises
on the carrier network, they are dropped. The DE list gives you a way to decide which packets
will get dropped.
TCP/IP doesn't get an acknowledgment. It closes the window and goes into slow start or restart.
The source can then drop back on the speed of retransmission, and hopefully the congestion will
clear up. If a server at the central site is pumping out bits faster than the Frame Relay cloud can
handle, the only way to relieve the congestion is to have the original sender slow down.
basis. Obviously, the higher the CIR on the PVC, the more impact it will have on the individual
interface's ability to handle the traffic. A T1 at the central site in Figure 10-16 could certainly
be expected to handle 24 64 K PVCs with little problem. A T1 with 24 64 k PVCs equals about
1536 K of bandwidth. But if there is a lot of broadcast traffic, it could affect performance,
because each broadcast would have to be replicated 24 times on the same interface at the central
site. And if you try to put more than 24 64 K DLCIs into a T1 interface, the possibility of
problems increases. This is known as oversubscription and is discussed later in this chapter.
encounter congestion.