High Performance OC12c ATM for Aggregating High Speed Connections from Enterprise to Service Provider ATM Backbones
Cisco 7600 Series 2-Port ATM Optical Services Module
The rapid growth of Internet-enabled user applications has led to a dramatic growth in the bandwidth provisioned through service provider networks. In order to accommodate this growth, service providers are consolidating their various existing network architectures that deliver traditional Layer-2 WAN transport, such as Frame Relay and ATM, with those that deliver Layer-3 WAN services, such as high speed Internet access and Layer-3 VPNs. The consolidation of these network architectures optimizes the service providers capital investments, so that all such expenditures simultaneously benefits all network services.
Achieving the convergence of these network architectures is particularly challenging at the network aggregation points that must deliver a variety of services. The devices at these network aggregation points must be capable of providing an efficient transfer of network traffic from the customer access nodes to the core network and back. Therefore, these aggregation devices must provide scalable bandwidth and interface density between the access and core networks, while simultaneously supporting a wide range of network protocols, as well as quality of service (QoS), security, and accounting features.
The Cisco 7600 is designed to provide the performance, density, and features that are needed for network aggregation devices in such consolidated network architectures. The Cisco 7600 is a high performance aggregation router, which integrates high speed LAN and WAN modules, and is specifically intended for service provider networks.
The two port OC12c/STM-4c ATM Optical Services Module expands the connectivity options for the Cisco 7600 Series Routers and Cisco Catalyst 6500 Series Switches. The cards are ideal for aggregating large enterprise virtual channels and connecting them to an existing ATM infrastructure.
The ATM OSM cards are standards based and completely compatible with the full-line of Cisco high-performance ATM switches and routers.
The Cisco 7600 Series ATM OSMs enable the integration of legacy ATM networks with next-generation IP backbones in several ways. The following applications provide two examples.
With the use of the Cisco 7600 Series ATM line cards, service providers can now offer connectivity to customers via an ATM network. (See Figure 2.)
Application 1: ATM WAN Connectivity
Using the Cisco 7600 Series ATM line cards, service providers can interconnect their points of presence (POPs) via a core ATM network. (See Figure 3.)
Application 2: Inter-POP Connectivity
In addition to the two OC12 ATM ports, each card comes with four switched Gigabit Ethernet interfaces that enable Ethernet connectivity in service provider networks. These line cards facilitate network growth with a variety of high-performance IP services.
TWO PORT OC12 ATM OSM FEATURE SUMMARY
• Parallel Express Forwarding (PXF) IP Services Processor on the line card. The PXF IP Services Processor consists of a 4 x 4 array of microprocessing units, each equipped with local memory, to deliver a pipelined, parallelized processing array. Each PXF IP Services Processor can apply IP services to 16 different packets simultaneously-all with high levels of performance. The OC12 ATM line cards are populated with one PXF IP Services processor.
• High-Performance forwarding of distributed IP service.
• Programmable software feature sets for "evergreen" IP service delivery. Unlike traditional ASICs, which have feature sets hardcoded in silicon, each PXF engine can be enhanced in the field via an easy software upgrade.
• Deep packet buffering to maximize TCP throughput, with advanced traffic management and prioritization schemes to ensure deterministic packet delivery.
• Four additional ports of Gigabit Ethernet provides connectivity to other routers or servers without burning up "customer-facing" line card slots.
• Unspecified Bit Rate (UBR)
• Variable Bit Rate-non real-time (VBR-nRT)
• Max VCs (1000 per card, 500 per port1)
• Max simultaneous segmentation and reassembly: 1000 (1000 Max active VCs)
• VPI Range 0-255 (up to 16 configured simultaneously)
Traffic shaping is typically provided on ATM edge devices to ensure that bursty traffic conforms to a predetermined "contract." The ATM OSM supports traffic shaping in hardware, on a per-VC basis or per-VP basis. Depending on the selected ATM service class, the ATM OSM supports configurable parameters such as: peak cell rate (PCR), sustainable cell rate (SCR), and maximum burst size (MBS). These parameters can be defined based on the specific bandwidth requirements of an individual VC, as needed for a specific application. To provide further flexibility, the ATM OSM allows each of these parameters to be set over a wide range of small increments:
• Peak and Sustainable Cell Rate (PCR, SCR): 37k to 299,520k with 1k increments
• Maximum Burst Size (MBS): 1-255 cells
The ATM OSM is based on an advanced dual-SAR architecture. Each OC12 port has one SAR processor dedicated for transmission and one for reception. Each SAR supports AAL5 ATM adaptation for high-performance data applications. The ATM OSM also includes a large amount of buffer memory. Head of Line (HOL) blocking is avoided through a TX credit check mechanism that runs on the PXFcode. This design ensures that bursty traffic from one VC does not prevent another VC from being serviced.
ATM Layer Connection Management
Operations and management (OAM) cells are used for ATM layer end-to-end link management messages. This ensures that the remote end of the connection is online. Support is provided for both OAM F4 and F5 flows. During segmentation, the OAM cells have the highest priority, and are transmitted ahead of other queued data.
ENHANCED TWO PORT OC12 ATM OSM FEATURES
The Enhanced two port OC12 OSM cards will support all of the same features as the Original 7600 OSMs, and will take the Cisco 7600 platform to a higher level of functionality. Some of the major feature differences between the enhanced and the original OSMs include:
• Support for enhanced QoS features, such as WRED
• Support for future software enhancements to deliver either Layer-2 or Layer-3 network aggregation services deployed over a network architecture based on either IP or MPLS protocols. The Cisco 7600 IR will then be capable of supporting Layer-2 services while simultaneously supporting Layer-3 services, such as Internet Access or IETF RFC 2547 VPNs.
Table 1. Enhanced 2-Port OC12 ATM OSM Ordering Information