Line Cards And Physical Layer Interface Modules; Switch Fabric Modules - Cisco CRS-1 - Carrier Routing System Router Getting Started Manual

Hardware Overview: Single-Chassis System

Line Cards and Physical Layer Interface Modules

Each Layer 3 MSC and its associated PLIM is installed as a two-card set to provide the physical
interfaces for incoming and outgoing IP traffic. The MSC provides the forwarding engine for Layer 3
routing of data, and the PLIM provides the physical interface connections.
The Layer 3 MSC and PLIM mate through the chassis midplane (see
card to be used with a variety of interface types. Only one type of MSC (L3 forwarding engine) exists,
but it can be associated with several different PLIMs, and can support different interfaces and
technologies. This configuration also allows the Layer 3 MSC to be removed from the chassis without
the need to disconnect the cables attached to the associated PLIM.
Figure 1-4

Switch Fabric Modules

IP packets are forwarded from one interface to another via a three-stage switching fabric contained in
the switch fabric module cards:
1.
2.
3.
Cisco CRS-1 Series Carrier Routing System Getting Started Guide
1-6
Layer 3 Line Card and PLIM Connected at the Chassis Midplane
Modular Services Card
(Layer 3 line card)
Slots 0–15
Stage 1 distributes incoming traffic evenly across all Stage 2 components within the same plane to
achieve load balancing.
Stage 2 routes the cells to the appropriate Stage 3 element to which the destination MSC is
connected. The routing is based on the destination address of the incoming cells.
Stage 3 routes the cells to the appropriate destination MSC.
Chapter 1
Midplane
PLIM card
Slots PL0–PL15
Getting Started on the Cisco CRS-1 Router
Figure 1-4), allowing the Layer 3
Physical
interface
"ports"