Specifications

Sample Scenarios 63
4.1 Review of IBM 2212 Frame Relay Basics
This section explains the basics of frame relay. In order to understand the sample
scenarios in this chapter, you should have some knowledge of frame relay basics.
You can skip to the next section if you are familiar with IBM 2212 frame relay
basics.
4.1.1 DLCI (Data Link Connection Identifier)
A frame relay (FR) network consists of FR switches, which in the case of a FR
public network are provided by the service provider. The routers act as the FR
connection device. The router encapsulates traffic in FR frames, the format of
which will be reviewed later, and routes them to the FR network based on the
Data Link Connection Identifier (DLCI). The DLCI is the address the identifies
either the permanent virtual connection (PVC - statically defined in advanced) or
switched virtual circuit (SVC - setup as needed) between the router and the FR
destination device. As no standard exists for carrying voice over SVCs, no further
discussion of SVCs will be included in this book.
DLCIs can have either local or global significance throughout the FR network. To
the router, the DLCI is usually only of local significance, so DLCIs can be
duplicated within the network. Within the router, each interface can support
multiple DLCIs but clearly the DLCI must be unique on the interface. The same
DLCI can be used on different interfaces.
2212A BRS [i 3] [dlci 200]>
CREATE-SUPER-CLASS
This circuit is currently using circuit defaults...
Are you sure you want to override the defaults ?(Yes or [No]):
y
Class name [DEFAULT]?
VOICE
2212A BRS [i 3] [dlci 200]>
ASSIGN
Protocol or filter name [IP]?
vofr
Class name [DEFAULT]?
VOICE
Priority <URGENT/HIGH/NORMAL/LOW> [NORMAL]?
u
Frame Relay Discard Eligible <NO/YES> [NO]?