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Configuration Guide
Contivity Secure IP Services Gateway
Frame Relay on Contivity Secure IP Services Gateway
Address resolution for PVCs
Address resolution for PVCs maps a remote network address such as an IP address to a local DLCI number. IP uses the Address Resolution Protocol (ARP). ARP dynamically generates an ARP table of addresses and DLCI numbers by sending messages back and forth to each network node to gather address information. This process increases broadcast traffic across the network.
Committed information rate
The committed information rate (CIR) is the rate at which the network supports data transfer under normal operations. Its name is descriptive: you have a contract with your carrier, who has committed to providing a given throughput, here called the committed information rate. The CIR is measured in bits per second. You configure this value that the carrier provides per virtual circuit.
When configuring the CIR, consider the following:
CIR of 0
You can contract with a carrier for a CIR of 0, which yields
Maximum CIR
The maximum CIR should not be greater than the speed of the access line on the slower end of a virtual circuit. In a big pipe/little pipe topology likely CIRs at the remote sites would be 32 Kb/s, 56 Kb/s, or 64 Kb/s. If you configure CIRs for these virtual circuits at the central site, you can use CIR enforcement (described in the next section) to prevent the big pipe from sending traffic that exceeds the PVC CIRs.
Committed burst rate and excess burst rate
The committed burst rate (Bc) defines the number of bits that the CES can transmit over a specified time interval (Tc) when congestion is occurring. The excess burst (Be) defines the number of extra bits that the CES attempts to send over the Tc when there is no congestion. Both the Bc and the Be are values that you configure.
The sum of the Bc and the Be is the maximum amount of traffic that can travel across the network per Tc when there is no congestion. If you set the Be to a value greater than zero, the CES can send traffic exceeding the CIR. To enforce the CIR, that is, to limit traffic that the CES can send to the amount of the CIR, set the Be to 0.
CG030601 | 2.00 | July 2003 | Page: 3 of 14 |