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Circuit Pack Descriptions
Issue 3 June 2001
7-55
â– Alarms:
Local LAN port failures are detected by monitoring for the presence of
either MAC frames or Link Pulses per IEEE 802.3. From the SONET
direction, failures are detected by monitoring for VT1.5 (AIS, LOP), DS1
LOF, Loss of IMA frame, Loss of IMA Delay Synchronization (LODS), Loss
of Cell Delineation (LCD) and excessive AAL5 CRC errors. The alarm level
for a local LAN port failure is user provisionable (Major, Minor, Not
Alarmed).
LAN Interface (BBF10) 7
â– Electrical Specification:
The BBF10 LAN circuit pack provides a single 100BaseFX, IEEE 802.3
compliant interface. The LAN port performs protocol transparent filtering
and bridging of incoming MAC frames. MAC frames with a destination
address on the local bus are filtered by the BBF10 to prevent unnecessary
transmission of frames over the wide area network (WAN). The LAN
interface autonegotiates mode (full/half duplex) and speed (100 Mb/s)
when interfacing with other 802.3 compliant devices over fiber. The circuit
pack occupies two adjacent low-speed slots and converts an optical signal
to from one to 8 DS1 signals to provide native mode LAN transport through
aSONETWAN.
â– LAN port:
— 100BaseFX IEEE 802.3 compliant
— SC optical connector
— 1300 nm nominal center wavelength
— 62.5 micron multimode fiber
— Buffering .5 MByte for each direction
— See Table 10-2 for optical characteristics.
â– Format Specification:
The LAN interface converts incoming MAC frames to an ATM cell format
using ATM adaptation layer 5 (AAL5) encapsulation as specified in IETF
RFC-1483. ATM cells are distributed in round robin order on 1 to 8 ESF
formatted DS1 signals using the ATM forum IMA Specification Version 1.1
for inverse multiplexing. The DS1 signals are mapped into asynchronous
VT1.5 signals for transport through a SONET network. The circuit pack can
compensate for up to 50 ms of differential delay among the 8 DS1s and
uses a single IMA group with one ATM virtual channel (VC). The following
provisioning options are provided:
— AAL5 Protocol - VC multiplex or LLC encapsulation (Bridged)
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