Telindus 1031, User And Reference Manual

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Telindus 1031 Router Chapter 6
User manual Configuring the WAN encapsulation protocols
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6.3.1 Introducing Frame Relay
What is Frame Relay?
Frame Relay is a networking protocol that works at the bottom two levels of the OSI reference model:
the physical and data link layers. It is an example of packet-switching technology, which enables end
stations to dynamically share network resources.
Frame Relay devices fall into the following two general categories:
• Data Terminal Equipment (DTEs), which include terminals, personal computers, routers, and
bridges.
• Data Circuit-terminating Equipment (DCEs), which transmit the data through the network and are
often carrier-owned devices.
What is DLCI?
Frame Relay networks transfer data using one of the following connection types:
• Switched Virtual Circuits (SVCs), which are temporary connections that are created for each data
transfer and then are terminated when the data transfer is complete (not a widely used connection).
• Permanent Virtual Circuits (PVCs), which are permanent connections.
The Telindus 1031 Router makes use of Permanent Virtual Circuits. The Data Link Connection Identifier
(DLCI) is a value assigned to each virtual circuit and DTE device connection point in the Frame Relay
WAN. Two different connections can be assigned the same value within the same Frame Relay WAN,
one on each side of the virtual connection.
What is LMI?
A set of Frame Relay enhancements exists, called the Local Management Interface (LMI). The LMI
enhancements offer a number of features (referred to as extensions) for managing complex networks,
including:
• global addressing,
• virtual circuit status messages,
• multicasting.
What is CIR?
The Committed Information Rate (CIR) is the specified amount of guaranteed bandwidth (measured in
bits per second) on a Frame Relay service. Typically, when purchasing a Frame Relay service the cus-
tomer can specify the CIR level he wishes. The Frame Relay network provider guarantees that traffic not
exceeding this level will be delivered.
What is EIR?
The Excess Information Rate (EIR) is the specified amount of unguaranteed bandwidth (measured in
bits per second) on a Frame Relay service. It is the traffic in excess of the CIR. This traffic may also be
delivered, but this is not guaranteed. Obviously, the maximum possible EIR is the physical speed of the
customer's access circuit into the Frame Relay service provider.