User:Bvenkat2/mycrs

Carrier Routing System or CRS is a modular and distributed core router developed by Cisco Systems Inc that enables service providers to deliver data, voice, and video services over a scalable IP Next-Generation Network (NGN) infrastructure. In a network topology, these routers are generally positioned in the core or edge of a service provider network. They are also used by Over-the-top content providers and large enterprises. It supports a wide range of interface speeds and types such as channelized OC3, OC12 to OC768 on Packet over SONET and from 1GE, 10GE all the way to 100GE on the Ethernet technologies. A standalone CRS-3 system can handle 2.2Tbit/s and a multi-chassis system could be designed to handle 322Tbits/s.

Architecture
A standalone Carrier Routing System is deployed with a Line card chassis(LCC). The three main functional units of this LCC are the the Line cards, Switching fabric and Route processor. The Line card comprises of the physical interface card and a modular services card. The physical connectivity could be using Fiber optic cables or using Twisted pair cables. The routing decisions are made by the route processor and the switching fabric takes care of the routing based on the Route processor input. The CRS runs IOS XR which is said to be designed for high-end carrier grade routers and was launched with CRS-1. In a multi-chassis deployment, the Line card chassis is used along with another variety of chassis called as the Fabric Card Chassis(FCC). The architecture enables scalability by increasing the number of Line Card Chassis and/or Fabric Card Chassis. In both single- and multi-chassis configurations, the CRS switch fabrics are based on a three-stage Beneš architecture. In a single-chassis system, the three switching stages—S1, S2, and S3—are all contained on one fabric card. In a multi-chassis system, the S2 stage is contained within the Fabric Card Chassis, with the S1 and S3 stages resident in the Line Card Chassis.

The CRS Line card chassis comes in three different flavors: 4-slot, 8-slot and 16-slot. The number of slots indicates the number of line cards that the chassis can accommodate. There is only one variety of Fabric card chassis.

Deployment
Internet service providers Mobile network operator Over-the-top content Wireline services, Service providers – P, PE, Peering Large Enterprises

CRS-3
The CRS-3 is the second and the latest generation of the CRS series launched in March, 2010. In CRS-3 each line card slot has a capacity of 140Gbits/s, which is more than three times the capacity of the previous CRS-1 generation. The architecture is retained as in the previous generation and hardware is compatible with the CRS-1 system. Apart from the single-chassis system and the multi-chassis system, CRS-3 supports back-to-back configuration as well. In this configuration, two Line Card Chassis are connected back-to-back and there is no Fabric Card Chassis involved as in the case of a multi-chassis configuration. This configuration works only for the 8-slot and 16-slot chassis models. CRS-3 also supports IPoDWDM. This solution reduces transport elements, while supporting multilayer features such as proactive protection and control plane interaction, reducing operating expenses and capital costs.

CRS-1
CRS-1 is the first generation of Carrier Routing System launched in 2004. This replaced the Cisco 12000 routers which were used as core routers. Each slot of CRS-1 has a capacity of 40Gbits/s. CRS-1 supports both standalone and multi-chassis configurations.