Chapter 7. Protocol Options
61202.029L2-1 ISU 128 User Manual 53
DSU 57.6 ASYNC
The DSU 57.6 ASYNC or DSTOP protocol allows the ISU 128 to communicate
asynchronously at 57.6 kbps with ADTRAN 2- and 4-wire Switched 56 DSU
products. In addition, the ISU 128 will communicate with other ISUs over dial
and leased connections using this protocol. Figure 7-1 illustrates the menu
path for setting the DSU 57.6 ASYNC protocol.
T-Link
The T-Link protocol allows the ISU 128 to communicate with 2-wire Switched
56 DataPath Data Units (DUs) such as the ADTRAN DSU III 52W. The T-Link
protocol performs two functions:
• The T-link protocol adapts DTE data subrates of 64 kbps to the 64 kbps
bandwidth of the ISDN bearer channel.
• For asynchronous and synchronous DTE rates up to 19.2 kbps, T-Link
transmits the status of the DCE-DTE EIA leads to facilitate flow control
and maintenance.
In addition to 2-wire Switched 56 DataPath DUs, the ISU 128 can communicate
with any other device that uses the T-Link protocol. Figure 7-1 shows the
menu path for selecting T-Link.
Simple ADTRAN Protocol (SAP)
Simple ADTRAN Protocol (SAP) is a rate adaption method providing DTE
service between ISU 128 units at a sub 64 kbps ISDN bearer channel rate. Se-
lecting this menu item causes the ISU 128 to use SAP protocol.
The primary usage for SAP is general purpose asynchronous rate adaption in
a dial-up or leased environment. SAP only operates on a 64 kbps data link.
See Figure 7-2 for the menu path to select SAP.