Cisco Systems 8600 Series manual Detailed Description, Port UNI and Trunk Modes, DeMux/Mux

BXM Functional Description

Detailed Description, Port (UNI) and Trunk Modes

The following provides a summary of the principal functions performed by the major functional circuits of the BXM.

DRSIU

The DRSIU provides a total egress capacity from the BPX switch fabric of 1.6 Gbps.

SONET/SDH UNI (SUNI)

The SUNI ASIC implements the BXM physical processing for OC3 and OC12 interfaces. The SUNI provides SONET/SDH header processing, framing, ATM layer mapping and processing functions for OC12/STM-4 (622.08 Mbps) or OC3/STM1 (155.52 Mbps).

For ingress traffic, the BXM physical interface receives incoming SONET/SDH frames, extracts ATM cell payloads, and processes section, line, and path overhead. For egress traffic ATM cells are processed into SONET/SDH frames.

Alarms and statistics are collected at each level: section, line, and path.

DeMux/Mux

The Demux/Mux and associated circuits implement the BXM physical layer processing for T3/E3 interfaces, providing header processing, framing, ATM layer mapping, and processing functions for T3 at a 44.736 Mbps rate or E3 at a 34.368 rate.

RCMP

Usage Parameter Control (UPC) is provided by the RCMP. Each arriving ATM cell header is processed and identified on a per VC basis. The policing function utilizes a leaky bucket algorithm.

In addition to UPC and traffic policing, the RCMP provides route monitoring and also terminates OAM flows to provide performance monitoring on an end-to-end per VC/VP basis.

Traffic policing and UPC functionality is in accordance with the GCRA as specified by ATM Forum’s UNI 3.1 using dual leaky buckets.

•

•

Leaky Bucket 1 utilizes:

—Peak Cell Rate (PCR)

—Cell Delay Variation Tolerance: CDVT Leaky Bucket 2 utilizes:

—Sustainable Cell Rate (SCR)

—Maximum Burst Size (MBS)

In addition, two selective cell discard thresholds are supported for all queues for discard of CLP=1 cells should congestion occur.

6-22Cisco BPX 8600 Series Reference