The Internet is rapidly becoming an electronic agent for commerce, entertainment, communication, and information retrieval. New network-enabled intranet applications and powerful desktop computers are driving an exponential increase in network traffic. Service providers and enterprises are rapidly deploying packet-switching infrastructures to handle this tremendous growth in data traffic.
The Cisco 12000 series gigabit switch router (GSR) is the premier routing product family from Cisco designed and developed for the core of service provider and enterprise IP backbones. The Cisco 12000 GSR family includes three models: the Cisco 12008, 12012 and 12016.
The Cisco 12016 has 16 slots that can be used to support up to 180 DS3, 60 OC-3c/STM-1c, and 60 OC-12c/STM-4c or 15 OC-48c/STM16c interfaces, with support for 15 OC-192c/STM-64c interfaces in the future.
- High-density, high-speed interfaces from DS3 to OC-48c/STM-16c can be added as needed, with support for OC-192 in the future
- Dynamic Packet Transport (DPT) ring interfaces at 2 x 622 Mbps (OC-12c/STM-4c)
- Packet over Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) (PoS) interfaces at 155-Mbps (OC-3c/STM-1c), 622-Mbps (OC-12c/STM-4c), and 2.5 Gbps (OC-48c/STM-16c) data rates
- Asynchronous transfer mode (ATM) interfaces at 155-Mbps (OC-3c/STM-1c) and 622-Mbps (OC-12c/STM-4c) data rates
- LAN interfaces at 1-Gbps (Gigabit Ethernet) and 100-Mbps (Fast Ethernet)
- Frame-based interfaces (Point-to-Point Protocol [PPP], Frame Relay) at 45 Mbps (DS3), 155 Mbps (OC-3c/STM-1c), and 622 Mbps (OC-12c/STM-4c)
Figure 1 Cisco 12000 Series
- Innovative switch fabric design supports virtual output queues (VoQs) that eliminate head-of-line blocking (HOLB) and increase overall system efficiency, and it supports partial fulfillment for multicast traffic when replication of multicast traffic is performed by the switch fabric.
- Distributed architecture delivers scalable Layer 3 switching performance through intelligent line cards (LCs) that can be added incrementally.
- Microprogrammable application-specific integrated circuits (ASICs)-based queuing provides line rate forwarding for unicast and multicast traffic that fills SONET/SDH transmission facilities to capacity, ensuring best return on investment on expensive bandwidth.
- Industry-leading Cisco IOS® software
- State-of-the-art queuing and congestion management techniquesRandom Early Detection (RED), Weighted RED (WRED), and distributed round robin (DRR)that provide an enhanced Weighted Fair Queuing (WFQ) mechanism
- Multiprotocol Label Switching (MPLS) Tag Switching support to deliver scalable traffic engineering features
- Redundancy in all key system componentsprocessors, switch fabric, LCs, power, and coolingto minimize network disruption in the event of a failure.
- Hot-swap capability enables components to be added or removed without service disruption.
- Switch fabric redundancy provides fail-over to backup fabric with no data or user session loss.
- Automatic protection switching (APS)/multiplex section protection (MPS) enables SONET/SDH resiliency capabilities for providing interface redundancy.
The Cisco 12000 GSR is optimized for performing routing and packet-forwarding functions to transport IP datagrams across a network. The routing function is performed in the gigabit route processor (GRP) responsible for running the routing protocols and building the routing tables from the network topology. This information is then used to build the forwarding tables distributed to the LCs. In addition, the GRP is also responsible for the system control and administrative functions.
The packet-forwarding functions are performed by each of the LCs. A copy of the forwarding tables computed by the GRP is distributed to each of the LCs in the system. Each LC performs an independent lookup of a destination address for each datagram received on a local copy of the forwarding table, and the datagram is switched across a crossbar switch fabric to the destination LC.
All cards are installed from the front of the chassis and plugged into a passive backplane. This backplane contains serial lines that interconnect all the LCs to the switch-fabric cards as well as other connections for power and maintenance functions. Each slot in the GSR has up to four serial line connections (1.25 Gbps), one to each of the switch-fabric cards (see below) to provide a total capacity of 5 Gbps per slot (2.5 Gbps full-duplex).
At the heart of the Cisco 12000 GSR is a multigigabit crossbar switch fabric that is optimized to provide high-capacity switching at gigabit rates. The crossbar switch enables high performance for two reasons: connections from the LCs to a centralized fabric are point-to-point links that can operate at very high speeds and multiple bus transactions can be supported simultaneously, increasing the aggregate bandwidth of the system. A GSR system can be configured as 40 Gbps for the Cisco 12008, 60 Gbps for the Cisco 120012, and 80 Gbps for the Cisco 12016.
The switch fabric includes two card types: switch-fabric cards (SFCs) and clock and scheduler cards (CSC). Each GSR must have at least one CSC in the chassis. The CSC handles requests from LCs, issues grants to access the fabric, and provides a reference clock to all the cards in the system to synchronize data transfer across the crossbar. The SFCs receive the scheduling information and clocking reference from the CSC cards and perform the switching functions.
- Gigabit speed interconnections between LCs (5 Gbps per slot)
- State-of-the-art scheduling algorithm combined with virtual output queues to eliminate head-of-line blocking, achieving 99-percent efficiency
- Hardware-based multicast
- High availability via redundancy (1:4 for SFC, 1:1 for CSC) with lossless fail-over and hot-swap capability
The GRP is a high-performance engine that provides the routing intelligence for the Cisco 12000 GSR family. It is dedicated to determining the network topology and calculating the best path across the network. The GRP has the following hardware characteristics:
- 200-MHz R5000 CPU
- Optionally up to 256-MB CPU DRAM (default 128 MB)
- 512-KB Layer 2 cache
- 512-KB configuration nonvolitile RAM (NVRAM)
- 8-MB boot Flash
- Two PCCard Type II software upgrades
- Ethernet (RJ-45 and MII connectors) for network management access
- Local console and modem ports (DB-25/EIA/TIA-232c)
- Processes interior gateway protocols (IGPs) such as Intermediate System-to-Intermediate System (IS-IS), Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF), and Enhanced IGRP (EIGRP) to determine the network topology
- Processes external gateway protocols (EGPs) such as Border Gateway Protocol (BGP)
- Creates and maintains the routing table (up to one million route entries)
- Distributes and updates Express Forwarding (EF) tables on the LCs and maintains copies of the tables of each LC for card initialization
- Handles general maintenance functions such as diagnostics, console support, and LC monitoring
- Processes in-band management through Simple Network Management Protocol (SNMP), Management Information Base (MIB), Telnet, BOOTP, and Trivial File Transfer Protocol (TFTP)
LCs connect the GSR to other devices via electrical or optical media. The LCs are designed for the transmission of IP packets over DPT, PPP, Frame Relay, or ATM interfaces. The features and functions of the LCs are interface specific.
DPT interfaces on the GSR enable connections to other Cisco 12000 GSRs or other Cisco routers such as the Cisco 7500, via dual counter-rotating optical rings. DPT rings can be provisioned over dark fiber, wave-division multiplexing (WDM), or SONET/SDH infrastructure. The GSR currently offers the following DPT interfaces:
Table 1 Key Features of the DPT Interfaces
|Interface Type||Density/LC||Physical Layer|
- Spatial Reuse Protocol (SRP) Media Access Control (MAC)
- SRP fairness algorithm
- Intelligent protection switching (IPS) with enhanced pass-through capabilities
- Multiple packet priority levels
- Ring bandwidth multiplication
- "Plug-and-play" provisioning and configuration
- MAC-level counters and MAC-based packet filtering
Packet over SONET (PoS) interfaces on the GSR enable connections to other Cisco 12000 GSR or other Cisco routers such as the Cisco 7500 or 7200, via optical interfaces. These interfaces can be circuit provisioned over a SONET/SDH infrastructure or dark fibers, connections, or wavelength WDM systems. The Cisco 12000 GSR offers the following PoS interfaces:
Table 2 Key Features of the PoS Interfaces
|Interface Type||Density/LC||Physical Layer||SONET/SDH Layer||Packet Layer|
Table 3 Key Features of the ATM Interfaces
|Interface Type||Density/LC||Physical Layer||SONET/SDH Layer||ATM Layer|
Gigabit Ethernet (GE) and Fast Ethernet (FE) interfaces on the GSR enable connections to other Cisco 12000 GSR or other Cisco routers such as Cisco 7500 or 7200. The Cisco 12000 GSR offers the following Ethernet interfaces:
Table 4 Key Features of the Ethernet Interfaces
|Interface Type||Density/LC||Physical Layer||Ethernet Layer||Packet Layer|
Table 5 Technical Specification
|Specification||Cisco 12008||Cisco 12012||Cisco 12016|
|System Level Specifications|