Chapter 6. Configuration56 ISU 2x64 Dual Port ISDN Service Unit User Manual 61200051L1-1DClear ChannelClear channel provides the entire bearer channel to the DTE with-out regard to data format or protocol. This provides a rate adap-tation at or near the ISDN circuit rate. The primary usage forClear Channel in dial line mode is 56 kbps and 64 kbps synchro-nous. It is useful when the DTE performs its own internal syn-chronous protocol/rate adaptation or the ISU 2x64 is calling a 4-wire Switched 56 DSU. In the leased line mode, clear channel canprovide synchronous bit rates of 56 kbps, 64 kbps, 112 kbps, and128 kbps.BONDING mode 1The BONDING mode 1 protocol allows the ISU 2x64 to commu-nicate at bit rates in excess of 64 kbps to a maximum of 128 kbps.BONDING provides high-speed communication between ISU2x64s, ISDN TE/TAs, and inverse multiplexing equipment sup-porting the BONDING protocol. The protocol allows for the useof both synchronous and asynchronous bit rates. When the ISU2x64 uses the BONDING mode 1 protocol, it must make two sep-arate ISDN phone calls to seize control of both ISDN bearer chan-nels. The protocol corrects any delays existing between the twobearer channels and presents a single high-speed data channel tothe DTE. For successful high-speed operation, both the near- andfar-end DCE need to be configured to use BONDING mode 1protocol. BONDING mode 1 protocol negotiation phase hasnumerous timers to allow for transmission delays due to satellitehops, international calls, etc. The timers may be adjusted if neces-sary by entering into BONDING mode 1 submenu. See Figure 6-22 for the menu tree.
