Rate Adaption
Chapter 9
Rate Adaption
To allow greater flexibility for your DTE, three rate adaption protocols are available for use on the B-channel: T-Link, V.120, and Bonding (see Chapter 10 for a description of Bonding). These protocols allow your DTE to operate both synchronously and asynchronously, and at a different speed than the B-channel.
RATE ADAPTION
When a data call is placed, the TA tries to establish physical data connection on the ISDN B-channel. The B-channel is a digital channel that can transfer data at 56 or 64 kbps, depending on the path the network chooses when routing the call.
A rate adaption protocol is necessary if the user’s DTE rate is other than 56 or 64 kbps. The protocol adapts the lower speed of the DTE to the higher speed of the ISDN B-channel. The LCD menu or the AT%A2 command can be used to select a rate adaption protocol.
This chapter discusses two rate adaption protocols: TLink and
V.120.
•T-Linkdoes not guarantee error free data; it only adapts the lower DTE speed to the higher ISDN speed to a maximum of 19.2 kbps asynchronous and 64 kbps synchronous.
•V.120 is an error-controlling protocol that guarantees error free data transfer at speeds up to 128 kbps. (Throughput is limited by the B-Channel to about 70 kbps.)
T-LINK
T-Link is a Northern Telecom proprietary rate adaption protocol. It supports synchronous and asynchronous rate adaption at a variety of speeds.
To select T-Link with the LCD, scroll through the menu and select:
•CONFIGURATION OPTIONS?
•PORT CONFIG OPTIONS?
•PROTOCOL OPTIONS?
•PROTOCOL = T-LINK
To select T-Link with the AT%A2 command, enter
AT%A2=1.
