M mode configuration requirements 23
The RSP2 determines the information the fabric needs to carry the packet to the correct egress point and determines the physical egress port. As part of the lookup process, the RSP2 may also determine and record the egress queue ID and pass it to the egress RSP2.
Encapsulation is the most significant operation that the egress RSP2 performs. To specify the egress queue, the queuing and traffic shaping functions use:
•encapsulation information from the egress RSP2
•MAC and IP packet headers
•Quality of Service (QoS) bits
The F2E egress ASIC supports the FFE QoS, including the functions of random early drop, queuing and selection, traffic shaping, and communicating to other similar R modules. Similarly, the F2I ingress ASIC provides packet policing and marking.
Each DPM also consists of the following:
•One Fast TAPmux (FTAP) interface to the Metro Ethernet Routing Switch 8600 Switch Fabric Modules
•One Feedback Output Queue Manager (FOQ)
The FTAP ASIC connects each DPM to the CPU/Switch Fabric modules through the Metro Ethernet Routing Switch 8600 switching backplane.
The FOQ Management system collects information about the state of queues, packet storage elements, and the fabric. This information is available to the F2I at the point at which packets are segmented for entry to the fabric. When congestion exists, Metro Ethernet Routing Switch 8600 modules with a BFM
The FOQ mechanism also provides information about the state of each of the egress queues and on the fullness of the F2E reassembly function buffers and queues. The F2E reports this information to the FOQ Manager FPGA on each module. The constellation of these FOQ FPGAs (one per DPM) drives a shared backplane bus that each FPGA senses. Therefore, each R module has pertinent information about the state of all other R modules in the system.
M mode configuration requirements
M mode supports the Metro Ethernet Routing Switch 8600 M module feature set. Full support of M mode requires the following configuration conditions:
•The chassis must include at least one 8691omSF CPU module.
Nortel Metro Ethernet Routing Switch 8600
Installation — Modules
4.27 July 2008
