Cisco BPX 8650, Installation And Configuration Manual

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32-2
Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 32 AT3-6ME (T3 to T2) Interface Adapter
General Description
General Description
The AT3-6ME Interface Adapter is a bidirectional device that provides a conversion between
transmission systems of the following different transmission rates:
•
North American T3 (44.736 Mbps)
• Japanese 6M (T2).
The AT3-6ME Interface Adapter is used only in ATM networks. The adapter is transparent to both users
and the network.
The T3 interface operates at 44.736 Mbps with the B-ISDN Physical Layer Convergence Protocol
(PLCP) and meets the ATM Forum standards. The T2 interface operates at 6 Mbps according to the
Japanese Nippon Telephone & Telegraph (NTT) User-Network Interface (UNI) specifications.
ATM cells from one interface are mapped to the other interface enabling users with ATM node
equipment with North American T3 ATM ports to operate in a T2 network. The ATM cell throughput on
a T2 digital trunk using this adapter is limited to 14,490 cells per second.
The cell transfer rate for T2 is greatly reduced from the T3 cell rate from a BPX port. It is very important
to restrict the cell rate from the node when using a T2 trunk. Cell rate adaptation is done via software
trunk configuration at the T3 ATM interface, where the non null cell throughput is limited to the T2
capacity. In the T2 to the T3 direction, the T3 ATM interface has more than enough capacity to
accommodate the T2 cell rate.
The Interface Adapter can buffer a 70-cell burst at the T3 rate before the T2 interface will begin to drop
cells. Cells will continue to be dropped until the T3 interface returns to a rate that complies with the
bandwidth of the T2 interface.
All alarms and line errors are passed through the Interface Adapter unchanged. Any existing network
management system has an instant view of the actual network transmission system. Errors at the ATM
layer propagate through from one interface to the other, thus you have complete knowledge and
statistical information regarding the network status at all times. Therefore a special network
management interface is not required.
Because the T3 interface is asynchronous and the T2 is synchronous, you can configure the AT3-6ME
to carry the synchronization information through from one interface to the other. The synchronization is
carried through the T3 interface using the PLCP-embedded 8 KHz. The T2 interface clock may be
generated locally or it may be slaved to the public network.
Equipment Description
The AT3-6ME is fully contained in a metallic housing designed to be mounted in a 19" equipment rack.
It occupies only one rack mounting space and is powered from normal AC line powering. The power
supply accommodates an input voltage over the range 90 to 240 VAC, 50 or 60 Hz.
Interface Connectors
The interface connectors are located on the rear panel (see Table 32-1 and Figure 32-2). The following
are the connectors:
•
Two T3 BNC connectors, XMT and RCV
• Two 6M BNC connectors, XMT and RCV