Table of Contents

Introduction

Introduction

This chapter contains an overall description of the BPX 8600 Series. For installation information, refer to the Cisco BPX 8600 Series Installation and Configuration publication. Also, refer to the Cisco WAN Switching Command Reference publications.

This chapter contains the following:

• General Description
  
• New with Release 9.1
  
• Continuing Features with Release 9.1
  
• BPX Switch Operation
  
• Traffic and Congestion Management
  
• Network Management
  
• Switch Availability
  

General Description

The Cisco BPX® 8600 Series wide-area switches are standards based high-capacity broadband ATM switches that provides backbone ATM switching and deliver a wide range of user services (see Figure 1-1). The BPX 8600 Series includes the BPX 8620 switch and the BPX 8650 tag switch.

BPX Capabilities

Fully integrated with the Cisco MGX™ 8220 edge concentrator, Cisco IPX® wide-area switch, and Cisco IGX™ 8400 series wide-area switch, the BPX switch is a scalable, standards-compliant unit. Using a multi-shelf architecture, the BPX switch supports both narrowband and broadband user services. The modular, multi-shelf architecture enables users to incrementally expand the capacity of the system as needed. The BPX switch consists of the BPX shelf with fifteen card slots which may be co-located with the MGX 8220 and Extended Services Processor (ESP), as required.

Three of the slots on the BPX switch shelf are reserved for common equipment cards. The other twelve are general purpose slots used for network interface cards or service interface cards. The cards are provided in sets, consisting of a front card and associated back card. The BPX shelf can be mounted in a rack enclosure which provides mounting for a co-located ESP and the MGX 8220 interface shelves.

Extended Services Processor

With a co-located Extended Services Processor (ESP), the BPX switch adds the capability to support ATM and frame relay switched virtual circuits (SVCs), and soft permanent virtual circuits (SPVCs).

New with Release 9.1

BPX Switch

• Tag Switching with the BXM
  
  
• BME Multicasting
  
  
• Release 9.1 adds traffic shaping for BXM for UBR, VBR, and CBR per VC scheduling policies. This was previously supported for ABR only.
  
  
• Extended Services Processor (ESP) Release 2.2
  
  
  • Support for SPVCs, including auto-grooming of SPVCs
    
    
  • Dynamic resource partitioning for migration of PVCs to SPVCs
    
    
  • Interworking with the LS1010 ATM switch to provide point-to-multipoint SVC connections.
    
    

  Continued ESP features that were available in Release 2.0 including:

• ATM switched virtual circuits (ATM SVCs)
  
  
• Frame Relay switched virtual circuits (Frame Relay SVCs)
  
  
• ESP redundancy
  
  
• Call billing and call detail records (for ATM, Frame Relay, and SVCs only)
  
  

MGX 8220

• MGX 8220, Rel. 4.1, supported
  
  

IGX Switch

• UXM adds native ATM trunks and ports (UNI)
  
  

Continuing Features with Release 9.1

The following is a list of previously provided features that are included in this release along with the new features previously listed:

Cisco StrataView Plus Network Management

• NMS enhancements including additional management and provisioning capabilities including support of IGX switch tiered network voice and data applications
  
  
• Support for 12 Cisco StrataView Plus workstations
  
  
• Multi-network Cisco StrataView Plus capability
  
  
• Frame relay connection and MGX 8220 equipment management by the Cisco StrataView Plus Connection Manager and Equipment Manager
  
  
• SNMP Enhancements for connection management and monitoring
  
  
• Support for Solaris 2.5.1
  
  

Network

• Support for IGX switch hubs and associated interface shelves in tiered network
  
  
• The number of nodes supported in a network is increased to over 1100, of which 223 can be routing nodes.
  
  
• Inverse Multiplexing ATM (IMA)
  
  
• Frame Relay to ATM Network Interworking (Supported by FRP on IPX switch, FRM on IGX switch, and FRSM on MGX 8220
  
  
• Frame Relay to ATM Service interworking (Supported by FRSM on MGX 8220)
  
  
• Tiered networks
  
  
• Automatic end-to-end routing of virtual connections (AutoRoute)
  
  
• Closed-loop, rate-based congestion management (using ForeSight for ABR)
  
  
• Effective management of quality of service (OptiClass)
  
  
• Per -VC queueing and per-VC scheduling (FairShare)
  
  

BPX Switch

• The BXM cards provide a range of trunk and service interfaces and support ATM Forum Standards UNI 3.1 and ATM Traffic Management 4.0 including ABR connections with VS/VD congestion control. The BXM cards are implemented with Stratm technology which uses a family of custom Application Specific Integrated Circuits (ASICs) to provide high-density, high-speed operation. The three types of BXM cards are:
  
  
  • The BXM T3/E3 is available as an eight or twelve port card that provides T3/E3 interfaces at 44.736 or 34.368 Mbps rates, respectively. The BXM-T3/E3 can be configured for either trunk or access applications.
    
    
  • The BXM 155 is available as a four or eight port card that provides OC-3/STM-1 interfaces at 155.52 Mbps rates. The BXM-155 can be configured for either trunk or access applications.
    
    
  • The BXM 622 is available as a one or two port card that provides OC-12/STM-4 interfaces at 622.08 Mbps rates. The BXM-622 can be configured for either trunk or access applications.
    
    
• Enhanced network scaling:
  
  
  • 50/64 trunks per BPX switch equipped with BCC-32 or BCC-64, respectively
    
    
  • 72/144 lines per node equipped with BCC-32 or BCC-64, respectively
    
    
  • 223 routing nodes (with BPX switch or IGX switch)
    
    
  • trunk based loading
    
    
  • BCC-3-64 supported on BPX switch
    
    
  • 7000 virtual connections (BCC-3-32)
    
    
  • 12000 virtual connections (BCC-3-64)
    
    
  • de-route delay timer
    
    
  • connection routing groups by cell loading
    
    
• ATM and Frame Relay SVCs, and Soft Permanent Virtual Circuits (SPVCs) with Extended Services Processor
  
  

  ESP is an adjunct processor that is co-located with a BPX switch shelf. The ESP provides the signaling and Private Network to Network Interface (PNNI) routing for ATM and Frame Relay SVCs via BXM cards in the BPX switch and AUSM and FRSM cards in the MGX 8220.

• Cisco StrataView Plus NMS enhancements including additional management and provisioning capabilities.
  
  
• BCC-3-64
  
  
• BCC-4 supporting 19.2 Gbps switching with the BXM cards supporting egress at up to
  1600 Mbps and ingress at up to 800 Mbps.
  
  
• Hot Standby Redundancy
  
  
• MGX 8220 Release 4.1, which will include:
  
  
  • BNM-155 interface to BXM on BPX switch
    
    
  • FRSM support for both SVC and PVC frame relay connections with ESP
    
    
  • AUSM support for both SVC and PVC ATM connections with ESP
    
    
  • FRSM-8 with ELMI
    
    
  • IMATM-B
    
    
  • AUSM-8
    
    
  • CESM/4T1E1
    
    
  • FRSM-HS1 (HSSI and X.21 interfaces)
    
    
  • SRM 3T3
    
    
• Access Products
  
  
  • FastPAD MM and MP
    
    
  • Cisco 3810
    
    
• Virtual Trunking.
  
  
• Inverse Multiplexing ATM (IMA).
  
  
• Enhanced Ingress buffers for ASI-155 and BNI-155 to 8K cells for Release 8.1 and up.
  
  
• BPX switch OC3 network and service interfaces on the BNI and ASI cards.
  
  
• High-speed switching capacity.
  
  
• Powerful crosspoint switching architecture.
  
  
• 53-byte cell-based ATM transmission protocol.
  
  
• Twelve 800 Mbps switch ports for network or access interfaces with BNI and ASI cards.
  
  
• Three DS3 or E3 ATM network interface ports per card (BNI).
  
  
• Totally redundant common control and switch fabric.
  
  
• Up to 20 million point-to-point cell connections per second between slots.
  
  
• Switches individual connections rather than merely serving as a virtual path switch.
  
  
• Easy integration into existing IPX switch and IGX switch networks.
  
  
• Internal diagnostics and self-test routines on all cards and backplane, status indication on each card.
  
  
• Collection of many ATM and other network statistics and transfer of the data collected to Cisco StrataView Plus over high-speed Ethernet LAN interface.
  
  
• Integration with the Cisco StrataView Plus Network Management System to provide configuration, control, and maintenance.
  
  
• Conformation to recommendations from all current ATM standards bodies: ATM Forum, ITU, ETSI, and ANSI.
  
  
• Compliant with all applicable safety, emissions, and interface regulations. Meets requirements of NEBS for Central Office equipment.
  
  

MGX 8220

• Inverse Multiplexing ATM (IMA) support for the BPX switch with Rel. 3 MGX 8220
  
  
• CES T1/E1
  
  
• MGX 8220 T1/E1 frame relay and T1/E1 ATM service interfaces
  
  
• FUNI (Frame Based UNI over ATM)
  
  

IGX Switch

• The IGX switch is configurable as a tiered network routing hub supporting voice and data over IGX switch interface shelves.
  
  

Access Products

• Cisco 3810
  
  
• FastPAD MM and MP products
  
  

BPX Switch Operation

BPX Switch Operation

With the BCC-4, the BPX switch employs a redundant 19.2 Gbps non-blocking crosspoint switch matrix for cell switching. The switch matrix can establish up to 20 million point-to-point connections per second between ports. A single BPX switch provides twelve card slots, with each card capable of operating at 800 Mbps for ASI and BNI cards. The BXM cards support egress at up to 1600 Mbps and ingress at up to 800 Mbps. Access to and from the crosspoint switch is through multi-port network and user access cards. It is designed to easily meet current requirements with scalability to higher capacity for future growth.

A BPX switch shelf is a self-contained chassis which may be rack-mounted in a standard 19-inch rack or open enclosure. All control functions, switching matrix, backplane connections, and power supplies are redundant, and non-disruptive diagnostics continuously monitor system operation to detect any system or transmission failure. Hot-standby hardware and alternate routing capability combine to provide maximum system availability.

The BPX Switch with MGX 8220 Shelves

Many network locations have increasing bandwidth requirements due to emerging applications. To meet these requirements, users can overlay their existing narrowband networks with a backbone of BPX switches to utilize the high-speed connectivity of the BPX switch operating at 19.2 Gbps with its T3/E3/OC3/OC12 network and service interfaces. The BPX switch service interfaces include BXM and ASI ports on the BPX switch and service ports on MGX 8220 shelves. The MGX 8220 shelves may be co-located in the same cabinet as the BPX switch, providing economical port concentration for T1/E1 Frame Relay, T1/E1 ATM, CES, and FUNI connections.

Tag Switching

For multi-service networks, the BPX 8650 tag switch provides ATM, frame relay, and IP Internet service all on a single platform in a highly scalable way. Support of all these services on a common platform provides operational cost savings and simplifies provisioning for multi-service providers.

By integrating the switching and routing functions, tag switching combines the reachability information provided by the router function with the traffic engineering optimizing capabilities of the switch. The BPX 8650 tag switch combines a BPX switch with a separate router controller (Cisco Series 7200 or 7500 router).

The BPX Switch with Extended Services Processor

With a co-located ESP, the BPX Switch adds the capability to support ATM and Frame Relay switched virtual circuits (SVCs), and also soft permanent virtual circuits (SPVCs). Refer to the Cisco WAN Service Node Extended Services Processor Installation and Operation document for detailed information abut the ESP.

Frame Relay to ATM Interworking

Interworking allows users to retain their existing services, and as their needs expand, migrate to the higher bandwidth capabilities provided by BPX switch networks. Frame Relay to ATM Interworking enables frame relay traffic to be connected across high-speed ATM trunks using ATM standard Network and Service Interworking

Two types of Frame Relay to ATM interworking are supported, Network Interworking
(see Figure 1-2) and Service Interworking (see Figure 1-3). The Network Interworking function is performed by the AIT card on the IPX switch, the BTM card on the IGX switch, and the FRSM card on the MGX 8220. The FRSM card on the MGX 8220 and the UFM cards on the IGX switch also support Service Interworking.

The frame relay to ATM network and service interworking functions are available as follows:

Network Interworking

Part A of Figure 1-2 shows typical frame relay to network interworking. In this example, a frame relay connection is transported across an ATM network, and the interworking function is performed by both ends of the ATM network. The following are typical configurations:

• IGX switch or IPX switch frame relay (shelf/feeder) to IGX switch or IPX switch frame relay (either routing node or shelf/feeder)
  
  
• MGX 8220 frame relay to MGX 8220 frame relay
  
  
• MGX 8220 frame relay to IGX switch or IPX switch frame relay (either routing node or shelf/feeder)
  
  

Part B of Figure 1-2 shows a form of network interworking where the interworking function is performed by only one end of the ATM network, and the CPE connected to the other end of the network must itself perform the appropriate service specific convergence sublayer function. The following are example configurations:

• IGX switch or IPX switch frame relay (either routing node or shelf/feeder) to BPX switch or MGX 8220 ATM port.
  
  
• MGX 8220 frame relay to BPX switch or MGX 8220 ATM port.
  
  

Network Interworking is supported by the FRP on the IPX switch, the FRM, UFM-C, and UFM-U on the IGX switch, and the FRSM on the MGX 8220. The Frame Relay Service Specific Convergence Sublayer (FR-SSCS) of AAL5 is used to provide protocol conversion and mapping.

Service Interworking

Figure 1-3 shows a typical example of Service Interworking. Service Interworking is supported by the FRSM on the MGX 8220 and the UFM-C and UFM-U on the IGX switch. Translation between the Frame Relay and ATM protocols is performed in accordance with RFC 1490 and RFC 1483.

In Service Interworking, for example, for a connection between an ATM port and a frame relay port, unlike Network Interworking, the ATM device does not need to be aware that it is connected to an interworking function.

The frame relay service user does not implement any ATM specific procedures, and the ATM service user does not need to provide any frame relay specific functions. All translational (mapping functions) are performed by the intermediate IWF.

The following is a typical configuration for service interworking:

• MGX 8220 Frame Relay (FRSM card) to BPX switch or MGX 8220 ATM port.
  
  
• IGX switch Frame Relay (FRM-U or FRM-C) to BPX switch or MGX 8220 ATM port.
  
  

Additional Information

For additional information about interworking, refer to Chapter 12, Frame Relay to ATM Network and Service Interworking.

Tiered Networks

Networks may be configured as flat (all nodes perform routing and communicate fully with one another), or they may be configured as tiered. In a tiered network interface shelves are connected to routing hubs, where the interface shelves are configured as non-routing nodes.

By allowing CPE connections to connect to a non-routing node (interface shelf), a tiered network is able to grow in size beyond that which would be possible with only routing nodes comprising the network.

Starting with Release 8.5, in addition to BPX switch routing hubs, tiered networks now support IGX switch routing hubs. Voice and data connections originating and terminating on IGX switch interface shelves (feeders) are routed across the routing network via their associated IGX switch routing hubs. Intermediate routing nodes must be IGX switches, and IGX switch interface shelves are the only interface shelves that can be connected to an IGX switch routing hub. With this addition, a tiered network can now provide a multi-service capability (frame relay, circuit data, voice, and ATM).

Routing Hubs and Interface Shelves

In a tiered network, interface shelves at the access layer (edge) of the network are connected to routing nodes via feeder trunks (Figure 1-4). Those routing nodes with attached interface shelves are referred to as routing hubs. The interface shelves, sometimes referred to as feeders, are non-routing nodes. The routing hubs route the interface shelf connections across the core layer of the network.

The interface shelves do not need to maintain network topology nor connection routing information. This task is left to their routing hubs. This architecture provides an expanded network consisting of a number of non-routing nodes (interface shelves) at the edge of the network that are connected to the network by their routing hubs.

For detailed information about tiered networks, refer to Chapter 13, "Tiered Networks".

BPX Switch Routing Hubs

T1/E1 Frame Relay connections originating at IPX switch and IGX switch interface shelves and T1/E1 Frame Relay, T1/E1 ATM, CES, and FUNI connections originating at MGX 8220 interface shelves are routed across the routing network via their associated BPX switch routing hubs.

The following requirements apply to BPX switch routing hubs and their associated interface shelves:

• Only one feeder trunk is supported between a routing hub and interface shelf.
  
  
• No direct trunking between interface shelves is supported.
  
  
• No routing trunk is supported between the routing network and interface shelves.
  
  
• The feeder trunks between BPX switch hubs and IPX switch or IGX switch interface shelves are either T3 or E3.
  
  
• The feeder trunks between BPX switch hubs and MGX 8220 interface shelves are T3, E3, or OC3-c/STM-1.
  
  
• Frame Relay connection management to an IPX switch or IGX switch interface shelf is provided by Cisco StrataView Plus.
  
  
• Frame Relay and ATM connection management to an MGX 8220 interface shelf is provided by Cisco StrataView Plus.
  
  
• Telnet is supported to an interface shelf; the vt command is not.
  
  
• Frame Relay connections originating at IGX switch interfaces shelves connected to IGX switch routing hubs may also be routed across BPX switch intermediate nodes.
  
  
• Remote printing by the interface shelf via a print command from the routing network is not supported.
  
  

Inverse Multiplexing ATM

Where greater bandwidths are not needed, the Inverse Multiplexing ATM (IMA) feature provides a low cost trunk between two BPX switches. The IMA feature allows BPX switches to be connected to one another over any of the 8 T1 or E1 trunks provided by an AIMNM module on an MGX 8220 shelf. A BNI port on each BPX switch is directly connected to an AIMNM module in an MGX 8220 by a T3 or E3 trunk. The AIMNM modules are then linked together by any of the 8 T1 or E1 trunks. Refer to the Cisco MGX 8220 Reference and the Cisco WAN Switching Command Reference publications for further information.

Virtual Trunking

Virtual trunking provides the ability to define multiple trunks within a single physical trunk port interface. Virtual trunking benefits include the following:

• Reduced cost by configuring the virtual trunks supplied by the public carrier for as much bandwidth as needed instead of at full T3, E3, or OC3 bandwidths.
  
  
• Utilization of the full mesh capability of the public carrier to reduce the number of leased lines needed between nodes in the Cisco WAN switching networks.
  
  
• Choice of keeping existing leased lines between nodes, but using virtual trunks for backup.
  
  
• Ability to connect BNI trunk interfaces to a public network using standard ATM UNI cell format.
  
  
• Virtual trunking can be provisioned via either a Public ATM Cloud or a Cisco WAN switching ATM cloud.
  
  

A virtual trunk may be defined as a "trunk over a public ATM service". The trunk really doesn't exist as a physical line in the network. Rather, an additional level of reference, called a virtual trunk number, is used to differentiate the virtual trunks found within a physical trunk port. Figure 1-5 shows four Cisco WAN switching networks, each connected to a Public ATM Network via a physical line. The Public ATM Network is shown linking all four of these subnetworks to every other one with a full meshed network of virtual trunks. In this example, each physical line is configured with three virtual trunks.

Traffic and Congestion Management

The BPX switch provides ATM standard traffic and congestion management per ATM Forum TM 4.0 using BXM cards.

The Traffic Control functions include:

• Usage Parameter Control (UPC)
  
  
• Traffic Shaping
  
  
• Connection Management Control:
  
  
• Selective Cell Discarding
  
  
• Explicit Forward Congestion Indication (EFCI)
  
  

In addition to these standard functions, the BPX switch provides advanced traffic and congestion management features including:

• Support for the full range of ATM service types per ATM Forum TM 4.0 by the BXM-T3/E3, BXM-155, and BXM-622 cards on the BPX Service Node.
  
  
• FairShare, dedicated queue, and rate controlled servers for each VPC/VCC at the network ingress.
  
  
• OptiClass, guarantees QoS for individual connections by providing up to 16 queues with independent service algorithms for each trunk in the network.
  
  
• AutoRoute, end-to-end connection management that automatically selects the optimum connection path based upon the state of the network and assures fast automatic alternate routing in the event of intermediate trunk or node failures.
  
  
• PNNI, a standards based routing protocol for ATM and Frame Relay SVCs.
  
  
• Frame Based Traffic Control (FBTC) for AAL5 connections, including early and partial frame discard.
  
  
• ForeSight, an end-to-end closed loop rate based congestion control algorithm that dynamically adjusts the service rate of VC queues based on network congestion feedback.
  
  
• ABR Standard with VSVD congestion control using RM cells and supported by BXM cards on the BPX Switch.
  
  

FairShare(TM)

Fairshare provides per-VC queueing and per-VC scheduling. Fairshare provides fairness between connections and firewalls between connections. Firewalls prevent a single non-compliant connection from affecting the QoS of compliant connections. The non-compliant connection simply overflows its own buffer.

The cells received by a port are not automatically transmitted by that port out to the network trunks at the port access rate. Each VC is assigned its own ingress queue that buffers the connection at the entry to the network. With ABR with VSVD or with ForeSight, the service rate can be adjusted up and down depending on network congestion.

Network queues buffer the data at the trunk interfaces throughout the network according to the connections class of service. Service classes are defined by standards-based QoS. Classes can consist of the four broad service classes defined in the ATM standards as well as multiple sub-classes to each of the four general classes. Classes can range from constant bit rate services with minimal cell delay variation to variable bit rates with less stringent cell delay.

When cells are received from the network for transmission out a port, egress queues at that port provide additional buffering based on the service class of the connection.

OptiClass(TM)

OptiClass provides a simple but effective means of managing the quality of service defined for various types of traffic. It permits network operators to segregate traffic to provide more control over the way that network capacity is divided among users. This is especially important when there are multiple user services on one network.

Rather than limiting the user to the four broad classes of service initially defined by the ATM standards committees, OptiClass can provide up to 16 classes of service (service subclasses) that can be further defined by the user and assigned to connections. Some of the COS parameters that may be assigned include:

• Minimum bandwidth guarantee per subclass to assure that one type of traffic will not be preempted by another.
  
  
• Maximum bandwidth ceiling to limit the percentage of the total network bandwidth that any one class can utilize.
  
  
• Queue depths to limit the delay.
  
  
• Discard threshold per subclass.
  
  

These class of service parameters are based on the standards-based Quality of Service parameters and are software programmable by the user. The BPX switch provides separate queues for each traffic class.

AutoRoute

With AutoRoute, connections in Cisco WAN switching networks are added if there is sufficient bandwidth across the network and are automatically routed when they are added. The user only needs to enter the endpoints of the connection at one end of the connection and the IPX switch, IGX switch, and BPX switch software automatically set up a route based on a sophisticated routing algorithm. This feature is called AutoRoute. It is a standard feature on the IPX switch, IGX switch, BPX switch, and MGX 8220.

System software automatically sets up the most direct route after considering the network topology and status, the amount of spare bandwidth on each trunk, as well as any routing restrictions entered by the user (e.g. avoid satellite links). This avoids having to manually enter a routing table at each node in the network. AutoRoute simplifies adding connections, speeds rerouting around network failures, and provides higher connection reliability.

Cost-Based AutoRoute

Cost-based route selection can be selectively enabled by the user as the route selection per node. With this feature a trunk cost is assigned to each trunk (physical and virtual) in the network. The routing algorithm then chooses the lowest cost route to the destination node. The lowest cost routes are stored in a cache to reduce the computation time for on-demand routing.

Cost-based routing can be enabled or disabled at anytime, and there can be a mixture of cost-based and hop-based nodes in a network.

The section, Cost-Based Connection Routing, contains more detailed information about cost-based AutoRoute.

PNNI

The Private Network to Network Interface (PNNI) protocol provides a standards-based dynamic routing protocol for ATM and frame relay SVCs. PNNI is an ATM-Forum-defined interface and routing protocol which is responsive to changes in network resources, availability, and will scale to large networks. PNNI is available on the BPX switch when an ESP is installed. For further information about PNNI and the ESP, refer to the Cisco WAN Service Node Series Extended Services Processor Installation and Operation publication.

Congestion Management, VS/VD

The BPX/IGX/IPX switch networks provide a choice of two dynamic rate based congestion control methods, ABR with VS/VD and ForeSight. This section describes Standard ABR with VSVD.

When an ATM connection is configured between BXM cards for Standard ABR with VSVD per ATM Forum TM 4.0, Resource Management (RM) cells are used to carry congestion control feedback information back to the connection's source from the connection's destination.

The ABR sources periodically interleave RM cells into the data they are transmitting. These RM cells are called forward RM cells because they travel in the same direction as the data. At the destination these cells are turned around and sent back to the source as backward RM cells.

The RM cells contain fields to increase or decrease the rate (the CI and NI fields) or set it at a particular value (the explicit rate ER field). The intervening switches may adjust these fields according to network conditions. When the source receives an RM cell, it must adjust its rate in response to the setting of these fields.

When spare capacity exists with the network, ABR with VSVD permits the extra bandwidth to be allocated to active virtual circuits.

Congestion Management, ForeSight

The BPX/IGX/IPX switch networks provide a choice of two dynamic rate based congestion control methods, ABR with VS/VD and ForeSight. This section describes ForeSight.

ForeSight may be used for congestion control across BPX/IGX/IPX switches for connections that have one or both end points terminating on other than BXM cards, for example ASI cards. The ForeSight feature is a dynamic closed-loop, rate-based, congestion management feature that yields bandwidth savings compared to non-ForeSight equipped trunks when transmitting bursty data across cell-based networks.

ForeSight permits users to burst above their committed information rate for extended periods of time when there is unused network bandwidth available. This enables users to maximize the use of network bandwidth while offering superior congestion avoidance by actively monitoring the state of shared trunks carrying frame relay traffic within the network.

ForeSight monitors each path in the forward direction to detect any point where congestion may occur and returns the information back to the entry to the network. When spare capacity exists with the network, ForeSight permits the extra bandwidth to be allocated to active virtual circuits. Each PVC is treated fairly by allocating the extra bandwidth based on each PVC's committed bandwidth parameter.

If the network reaches full utilization, ForeSight detects this and quickly acts to reduce the extra bandwidth allocated to the active PVCs. ForeSight reacts quickly to network loading in order to prevent dropped packets. Periodically, each node automatically measures the delay experienced along a frame relay PVC. This delay factor is used in calculating the ForeSight algorithm.

With basic frame relay service, only a single rate parameter can be specified for each PVC. With ForeSight, the virtual circuit rate can be specified based on a minimum, maximum, and initial transmission rate for more flexibility in defining the frame relay circuits.

ForeSight provides effective congestion management for PVC's traversing broadband ATM as well. ForeSight operates at the cell-relay level that lies below the frame relay services provided by the IPX switch and IGX switch. With the queue sizes utilized in the BPX switch, the bandwidth savings is approximately the same as experienced with lower speed trunks. When the cost of these lines is considered, the savings offered by ForeSight can be significant.

Network Management

BPX switches provide one high-speed and two low-speed data interfaces for data collection and network management. The high-speed interface is an Ethernet 802.3 LAN interface port for communicating with a Cisco StrataView Plus NMS workstation. TCP/IP provides the transport and network layer, Logical Link Control 1 is the protocol across the Ethernet port.

The low-speed interfaces are two RS-232 ports, one for a network printer and the second for either a modem connection or a connection to an external control terminal. These low-speed interfaces are the same as provided by the IPX switch and IGX switch.

A Cisco StrataView Plus NMS workstation connects via the Ethernet to the LAN port on the BPX and provides network management via SNMP. Statistics are collected by Cisco StrataView Plus using the TFTP protocol. On IPX switch and IGX switch shelves, frame relay connections are managed via the Cisco StrataView Plus Connection Manager. On MGX 8220 shelves, the Cisco StrataView Plus Connection Manager manages frame relay and ATM connections, and the Connection Manager is used for MGX 8220 shelf configuration.

Each BPX switch can be configured to use optional low-speed modems for inward access by the Cisco Technical Response Team for network troubleshooting assistance or to autodial Customer Service to report alarms remotely. If desired, another option is remote monitoring or control of customer premise equipment through a window on the Cisco StrataView Plus workstation.

Network Interfaces

Network interfaces connect the BPX switch to other BPX, IGX, or IPX switches to form a wide-area network.

The BPX switch provides T3, E3, OC3/STM-1, and OC12/STM-4 trunk interfaces. The T3 physical interface utilizes DS3 C-bit parity and the 53-byte ATM physical layer cell relay transmission using the Physical Layer Convergence Protocol. The E3 physical interface uses G.804 for cell delineation and HDB3 line coding. The BNI-155 card supports single-mode fiber (SMF), single-mode fiber long reach (SMF-LR), and multi-mode fiber (MMF) physical interfaces. The BXM-155 cards support SMF, SMFLR, and MMF physical interfaces. The BXM-622 cards support SMF and SMFLR physical interfaces.

The design of the BPX switch permits it to support network interfaces up to 622 Mbps in the current release while providing the architecture to support higher broadband network interfaces as the need arises.

Optional redundancy is on a one-to-one basis. The physical interface can operate either in a normal or looped clock mode. And as an option, the node synchronization can be obtained from the DS3 extracted clock for any selected network trunk.

Service Interfaces

Service interfaces connect ATM customer equipment to the BPX switch. ATM User-to-Network Interfaces (UNI) and ATM Network-to-Network Interfaces (NNI) terminate on the ATM Service Interface (ASI) cards and on BXM T3/E3, OC-3, and OC-12 cards configured for as service interfaces (UNI access mode). The ASI-1 card provides two T3 or E3 ports. The ASI-155 card OC3/STM-1 trunk interfaces are single-mode fiber (SMF), single-mode fiber long reach (SMF-LR), and multi-mode fiber (MMF) physical interfaces. The BXM T3/E3 card supports the standard T3/E3 interfaces. The BXM-155 cards support SMF, SMFLR, and MMF physical interfaces. The BXM-622 cards support SMF and SMFLR physical interfaces. The ASI and BXM cards support cell relay connections that are compliant with both the physical layer and ATM layer standards.

The MGX 8220 interfaces to a BNI or BXM card on the BPX, via a T3, E3, or OC3 interface. The MGX 8220 provides a concentrator for T1 or E1 frame relay and ATM connections to the BPX switch with the ability to apply ForeSight across a connection from end-to-end. The MGX 8220 also supports CES and FUNI (Frame Based UNI over ATM) connections.

Statistical Alarms and Network Statistics

The BPX Switch system manager can configure alarm thresholds for all statistical type error conditions. Thresholds are configurable for conditions such as frame errors, out of frame, bipolar errors, dropped cells, and cell header errors. When an alarm threshold is exceeded, the NMS screen displays an alarm message.

Graphical displays of collected statistics information, a feature of the Cisco StrataView Plus NMS, are a useful tool for monitoring network usage. Statistics collected on network operation fall into two general categories:

• Node statistics
  
  
• Network trunk statistics
  
  
• Network Service, line statistics
  
  
• Network Service, port statistics
  
  

These statistics are collected in real-time throughout the network and forwarded to the StrataView Plus workstation for logging and display. The link from the node to the Cisco StrataView Plus workstation uses a protocol to acknowledge receipt of each statistics data packet. Refer to the Cisco StrataView Plus Operations publication, for more details on statistics and statistical alarms.

Node Synchronization

A BPX Service switch network provides network-wide, intelligent clock synchronization. It uses a fault-tolerant network synchronization architecture recommended for Integrated Services Digital Network (ISDN). The BPX switch internal clock operates as a Stratum 3 clock per ANSI T1.101.

Since the BPX switch is designed to be part of a larger communications network, it is capable of synchronizing to higher-level network clocks as well as providing synchronization to lower-level devices. Any network access input can be configured to synchronize the node. Any external T1 or E1 input can also be configured to synchronize network timing. A clock output allows synchronizing an adjacent IPX or IGX switch or other network device to the BPX switch and the network. In nodes equipped with optional redundancy, the standby hardware is locked to the active hardware to minimize system disruption during system switchovers.

The BPX switch does not accept clock from an IPX switch. The BPX Service Node can be configured to select clock from the following sources:

• External (T1/E1)
  
  
• Line (DS3/E3)
  
  
• Internal
  
  

Switch Software Description

The Cisco WAN switching cell relay system software shares most core system software, as well as a library of applications, between platforms. System software provides basic management and control capabilities to each node.

IPX, IGX, and BPX node system software manages its own configuration, fault-isolation, failure recovery, and other resources. Since no remote resources are involved, this ensures rapid response to local problems. This distributed network control, rather than centralized control, provides increased reliability.

Software among multiple nodes cooperates to perform network-wide functions such as trunk and connection management. This multi-processor approach ensures rapid response with no single point of failure. System software applications provide advanced features that may be installed and configured as required by the user.

Some of the many software features are:

• Automatic routing of connections (AutoRoute feature).
  
• Various classes of service that may be assigned to each connection type (OptiClass feature).
  
• Bandwidth reservation on a time-of-day basis.
  
  
• Detection and control of network congestion with ABR with VSVD or ForeSight algorithms.
  
  
• Automatic self-testing of each component of the node.
  
  
• Automatic collecting and reporting of many network-wide statistics, such as trunk loading, connection usage, and trunk error rates, as specified by the user.
  
  

The system software, configuration database, and the firmware that controls the operation of each card type is resident in programmable memory and can be stored off-line in the Cisco StrataView Plus NMS for immediate backup if necessary. This software and firmware is easily updated remotely from a central site or from Customer Service, which reduces the likelihood of early obsolescence.

Connections and Connection Routing

The routing software supports the establishment, removal and rerouting of end-to-end channel connections. There are three modes:

• Automatic Routing—the system software computes the best route for a connection.
  
  
• Manual Routing—the user can specify the route for a connection.
  
  
• Alternate Routing—the system software automatically reroutes a failed connection.
  
  

The system software uses the following criteria when it establishes an automatic route for a connection:

• Selects the most direct route between two nodes.
  
  
• Selects unloaded lines that can handle the increased traffic of additional connections.
  
  
• Takes into consideration user-configured connection restrictions (for example whether or not the connection is restricted to terrestrial lines or can include satellite hops or routes configured for route diversity).
  
  

When a node reroutes a connection, it uses these criteria and also looks at the priority that has been assigned and any user-configured routing restrictions. The node analyzes trunk loading to determine the number of cells or packets the network can successfully deliver. Within these loading limits, the node can calculate the maximum combination allowed on a network trunk of each type of connection: synchronous data, ATM traffic, frame relay data, multi-media data, voice, and compressed voice.

Network-wide T3, E3, OC3, or OC12 connections are supported between BPX switches terminating ATM user devices on the BPX switch UNI ports. These connections are routed using the virtual path and/or virtual circuit addressing fields in the ATM cell header.

Narrowband connections can be routed over high-speed ATM backbone networks built on BPX broadband switches. FastPacket addresses are translated into ATM cell addresses that are then used to route the connections between BPX switches, and to ATM networks with mixed vendor ATM switches. Routing algorithms select broadband links only, avoiding narrowband nodes that could create a choke point.

Connection Routing Groups

The re-routing mechanism is enhanced so that connections are presorted in order of cell loading when they are added. Re-routing takes place by rerouting the group containing the connections with the largest cell loadings first on down to the last group which contains the connections with the smallest cell loadings. These groups are referred to as routing groups. Each routing group contains connections with loading in a particular range,

  There are three configurable parameters for configuring the rerouting groups,

• total number of rerouting groups
  
  
• starting load size of first group
  
  
• load size range of each group
  
  

The three routing group parameters are configured with the cnfcmparm command.

  For example, there might be 10 groups, with the starting load size of the first group at 50, and the incremental load size of each succeeding group being 10 cells. Then group 0 would contain all connections requiring 0-59 cell load units, group 1 would contain all connections requiring from 60-69 cell load units, on up through group 9 which would contain all connections requiring 140 or more cell load units.

Cost-Based Connection Routing

Release 9.1 includes a cost-based route selection method to Cisco StrataCom's standard AutoRoute. This feature is referred to as cost-based AutoRoute. In standard AutoRoute, the path with the fewest number of hops to the destination node is chosen as the best route. The new cost-based route selection uses an administrative trunk cost routing metric. The path with the lowest total trunk cost is chosen as the best route. Cost-based route selection is based on Dijkstra's Shortest Path Algorithm, which is widely used in network routing environments. You can use cost-based route selection (that is, cost-based AutoRoute) to give preference to slower privately owned trunks over faster public trunks which charge based on usage time. This gives network operators more control over the usability of their network trunks, while providing a more standard algorithm for route selection.

Major Features of Cost-Based AutoRoute

The following list gives a short description of the major functional elements of Cost-Based Route Selection.

• Enabling Cost-Based Route Selection-cost-based route selection is selectively enabled by the user as the route selection algorithm per node. The feature is not a chargeable feature and does not require special password access. The default algorithm is the hop-based algorithm. cost-based route selection can be enabled or disabled at any time.
  
  
• Configuring Trunk Cost-A trunk cost is assigned by the user to each trunk (physical and virtual) in the network. One cost is assigned per trunk - no separate costs are used for different connection or service types. The valid range of trunk costs is 1 (lowest cost) to 50 (highest cost). A trunk has a default cost of 10 upon activation. The cost of a trunk can be changed before or after the trunk has been added to the network topology.
  
  

  The cost can also be changed after connections have been routed over the trunk. Such a change does not initiate automatic connection rerouting, nor does it cause any outage to the routed connections. If the new trunk cost causes the allowable route cost for any connections to be exceeded, the connections must be manually rerouted to avoid the trunk. This avoids large-scale simultaneous network-wide rerouting and gives the user control over the connection reroute outage.

• Cache vs. On-Demand Routing-In previous releases Hop-Based Route Selection always requires on-demand routing. On-demand routing initiates an end-to-end route search for every connection. Due to the computation time required for Dijkstra's algorithm in cost-based route selection, a route cache is used to reduce the need for on-demand routing.
  
  

  This cache contains lowest cost routes as they are selected. Subsequent routing cycles use these existing routes if the routing criteria are met. Otherwise on-demand routing is initiated. This caching greatly benefits environments where routing criteria is very similar among connections.

  Enabling cost-based route selection automatically enables cache usage. Enabling Hop-Based Route Selection automatically disables cache usage. Cache usage can also be independently enabled or disabled for both types of route selection.

• On-Demand Lowest Cost Route Determination-On-demand routing chooses the current lowest cost route to the destination node. This lowest cost route is bounded by the maximum route length of 10 hops. If more than one route of similar cost and distance is available, the route with most available resources is chosen. No route grooming occurs after the initial routing. A connection does not automatically reroute if its route cost changes over time. A connection also does not automatically reroute if a lower cost route becomes available after the initial routing. However, a forced reroute or a preferred route can be used to move the connection to a lower cost route.
  
  
• Delay Sensitive Routes-Delay sensitive IPX/IGX connection types (Voice and Non-Timestamped Data) may be configured to use the worst case queueing delay per trunk, rather than the configured trunk cost, in the lowest-cost route determination. The trunk delay acts as the cost attribute in the Dijkstra algorithm. The default mode for the delay sensitive connections is to use the trunk cost. All other connection types always use the trunk cost in the route determination.
  
  

  AutoRoute currently does not use the worst case end-to-end queueing delay in route selection for delay sensitive BPX connection types (ATM CBR). cost-based route selection does not change this.

• Cost Cap-A maximum allowable cost value (cost cap) is used during route determination to prevent selection of a route which exceeds an acceptable cost. For routing based on delay, the cost cap is the acceptable end-to-end delay for the connection type. This cap is configured network-wide per delay sensitive connection type.
  
  

  For routing based on trunk cost, the cost cap is the acceptable end-to-end cost. This cap is configured per connection. The default cost cap is 100, which is derived from the maximum hops per route (10) and default cost per trunk (10). The cost cap can be changed at any time. If the cost cap is decreased below the current route cost, the connection is not automatically rerouted. A manual reroute is required to route the connection to fit under the new cost cap. This gives the user more control over the connection reroute outage.

• Software Upgrades-A software upgrade to Release 9.0 sets AutoRoute to use Hop-Based Route Selection. The cost of all trunks is set to the default cost (10). The cost cap of all connections is set to the maximum allowable cost (100). All other new cost-based routing parameters are set to regular default values.
  
  
• AutoRoute Interoperability-Since AutoRoute is source-based, nodes can interoperate using different route selection algorithms. The originating node computes the full end-to-end route based on its own knowledge of the network topology. The route is then passed to the subsequent nodes on the route. This source routing allows a mix of Cost-Based and Hop-Based Route Selection to run in a network.
  
  

Cost-Based AutoRoute Commands

The following switched software Command Line Interface (CLI) commands are used for cost-based route selection:

• cnfcmparm - enables cost-based route selection. This is a super-user command used to configure all AutoRoute parameters. By default cost-based route selection is disabled. Enabling or disabling cost-based route selection can be done at any time. Each connection routing cycle uses whichever algorithm is enabled when the cycle begins. The configuration is node-based, not network-based, which allows each node to have its own route selection algorithm.
  
  

  Enabling cost-based route selection automatically enables cache usage. Disabling cost-based route selection automatically disables cache usage. Cache usage may also be independently enabled or disabled.

• cnftrk - configures the administrative cost for a trunk. Both physical and virtual trunks have the cost attribute. Each trunk has a cost ranging from 1 (lowest) to 50 (highest). The default cost is 10 upon trunk activation.
  
  

  The cost can be configured from either end of the trunk. The cost can be changed before or after the trunk has been added to the network. The cost can also be changed after connections have been routed over the trunk. Any cost change is updated network-wide. Every node in the network stores the cost of every trunk in the network. This knowledge is required for successful source-based routing.

• cnfrtcost - new command which configures the cost cap for a connection. This command is valid only at the node where the connection is added.
  
  
• cnfsysparm - configures the delay cost cap for all delay sensitive connections in the network. This command was not modified in Release 9.0.
  
  
• dspcon - displays the maximum and current costs for a connection route
  
  
• dspload - displays the administrative cost and queue delay for a network trunk
  
  
• dsprts - displays the current costs for all connection routes
  
  
• dsptrkcnf - displays the configured cost of a trunk
  
  

The Cisco WAN Switching Command Reference contains detailed information about the use of BPX switch commands.

Network Synchronization

Cisco WAN switching cell relay networks use a fault-tolerant network synchronization method of the type recommended for Integrated Services Digital Network (ISDN). Any circuit line, trunk, or an external clock input can be selected to provide a primary network clock. Any line can be configured as a secondary clock source in the event that the primary clock source fails.

All nodes are equipped with a redundant, high-stability internal oscillator that meets Stratum 3 (BPX) or Stratum 4 requirements. Each node keeps a map of the network's clocking hierarchy. The network clock source is automatically switched in the event of failure of a clock source.

There is less likelihood of a loss of customer data resulting from re-frames that occur during a clock switchover or other momentary disruption of network clocking with cell-based networks than there is with traditional TDM networks. Data is held in buffers and packets are not sent until a trunk has regained frame synchronism to prevent loss of data.

Switch Availability

Hardware and software components are designed to provide a switch availability in excess of 99.99%. Network availability will be impacted by link failure, which has a higher probability of occurrence, than equipment failure.

Because of this, Cisco WAN network switches are designed so that connections are automatically rerouted around network trunk failures often before users detect a problem. System faults are detected and corrective action taken often before they become service affecting. The following paragraphs describe some of the features that contribute to network availability.

Node Redundancy

System availability is a primary requirement with the BPX switch. The designed availability factor of a BPX switch is (99.99%) based on a node equipped with optional redundancy and a network designed with alternate routing available. The system software, as well as firmware for each individual system module, incorporates various diagnostic and self-test routines to monitor the node for proper operation and availability of backup hardware.

For protection against hardware failure, a BPX switch shelf can be equipped with the following redundancy options:

• Redundant common control modules
  
  
• Redundant crosspoint switch matrixes
  
  
• Redundant high-speed data and control lines
  
  
• Redundant power supplies
  
  
• Redundant high-speed network interface cards
  
  
• Redundant service interface cards
  
  

If redundancy is provided for a BPX switch, when a hardware failure occurs, a hot-standby module is automatically switched into service, replacing the failed module. All cards are hot-pluggable, so replacing a failed card in a redundant system can be performed without disrupting service.

Since the power supplies share the power load, redundant supplies are not idle. All power supplies are active; if one fails, then the others pick up its load. The power supply subsystem is sized so that if any one supply fails, the node will continue to be supplied with adequate power to maintain normal operation of the node. The node monitors each power supply voltage output and measures cabinet temperature to be displayed on the NMS terminal or other system terminal.

Node Alarms

Each BPX switch shelf within the network runs continuous background diagnostics to verify the proper operation of all active and standby cards, backplane control, data, and clock lines, cabinet temperature, and power supplies. These background tests are transparent to normal network operation.

Each card in the node has front-panel LEDs to indicate active, failed, or standby status. Each power supply has green LEDs to indicate proper voltage input and output. An Alarm, Status, and Monitor card collects all the node hardware status conditions and reports it using front panel LED indicators and alarm closures. Indicators are provided for major alarm, minor alarm, ACO, power supply status, and alarm history. Alarm relay contact closures for major and minor alarms are available from each node through a 15-pin D-type connector for forwarding to a site alarm system.

BPX switches are completely compatible with the network status and alarm display provided by the Cisco StrataView Plus NMS workstation. In addition to providing network management capabilities, it displays major and minor alarm status on its topology screen for all nodes in a network. The Cisco StrataView Plus NMS also provides a maintenance log capability with configurable filtering of the maintenance log output by node name, start time, end time, alarm type, and user specified search string.