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Configuration, ATM Connections

Configuration, ATM Connections

This chapter describes how ATM connection services are established by adding ATM connections between ATM service interface ports in the network using ATM standard UNI 3.1 and Traffic Management 4.0. It describes BXM and ASI card operation and summarizes ATM connection parameter configuration

The chapter contains the following:

ATM Connection Services

ATM connection services are established by adding ATM connections between ATM service interface ports in the network. ATM connections can originate and terminate on the ASI (ATM Service Interface) cards, on BXM-T3/E3, BXM-155 (OC-3), and BXM-622 (OC-12) cards configured for port (service access) operation on the BPX switch, or on the MGX 8220 (using the AUSM card for the MGX 8220). Frame relay to ATM network interworking connections are supported between either BXM or ASI cards to the IPX, IGX, or MGX 8220. Frame relay to ATM service interworking connections are supported between either BXM or ASI cards to FRSM cards on the MGX 8220.

Figure 13-1 is a depiction of ATM connections over a BPX switch network. It shows ATM connections via BXM-T3/E3, BXM-155, BXM-622, ASI-1, and ASI-155 cards, as well as over MGX 8220 switches. It also shows Frame Relay to ATM interworking connections over the MGX 8220, IPX, and IGX shelves. For further information on the MGX 8220, refer to the Cisco MGX 8220 Reference document.


Figure 13-1: ATM Connections over a BPX Switch Network


SVCs

When an Extended Services Processor (ESP) is co-located with a BPX switch, ATM and Frame Relay Switched Virtual Circuits (SVCs) are supported in addition to Permanent Virtual Circuits (PVCs). For further information on ATM SVCs, refer to the Cisco WAN Service Node Extended Services Processor Installation and Operation document.

Traffic Management Overview

The ATM Forum Traffic Management 4.0 Specification defines five basic traffic classes:

Table 13-1 summarizes the major attributes of each of the traffic management classes:


Table 13-1: Standard ATM Traffic Classes
Attribute CBR rt-VBR nrt-VBR UBR ABR

Traffic Parameters

PCR & CDVT

x

x

x

x

x

SCR & MBS

x

x

MCR

x

QoS Parameters

Pk-to-Pk CDV

x

x

Max CTD

x

x

CLR

x

x

x

nw specific

Other Attributes

Congestion Control Feedback

x

Traffic parameters are defined as:

QoS (Quality of Service) parameters are defined as:

Congestion Control Feedback:

Standard ABR notes:

Standard ABR uses RM (Resource Management) cells to carry feedback information back to the connection's source from the connection's destination.

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.

VSVD Description

ABR sources and destinations are linked via bi-directional connections, and each connection termination point is both a source and a destination; a source for data that it is transmitting, and a destination for data that it is receiving. The forward direction is defined as from source to destination, and the backward direction is defined as from destination to source. Figure 13-2 shows the data cell flow in the forward direction from a source to its destination along with its associated control loop. The control loop consists of two RM cell flows, one in the forward direction (from source to destination) and the other in the backward direction (from destination to source).

The data cell flow in the backward direction from destination to source is not shown, nor are the associated RM cell flows. However, these flows are just the opposite of that shown in the diagram for forward data cell flows.

A source generates forward RM cells which are turned around by the destination and returned to the source as backward RM-cells. These backward RM-cells may carry feedback information from the network elements and/or the destination back to the source.

The parameter Nrm is defined as the maximum number of cells a source may send for each forward RM cell, i.e., one RM cell must be sent for every Nrm-1 data cells. Also, in the absence of Nrm-1 data cells, as an upper bound on the time between forward RM cells for an active source, an RM cell must be sent at least once every Trm msecs.

BXM Connections

The BXM-T3/E3, BXM-155, and BXM-622 cards support ATM Traffic Management 4.0. The BXM cards are designed to support all the following service classes: Constant Bit Rate (CBR), real time Variable Bit Rate (rt-VBR), non-real time Variable Bit Rate (nrt-VBR), Available Bit Rate (ABR with VSVD, ABR without VSVD, and ABR using ForeSight), and Unspecified Bit Rate (UBR). ABR with VSVD supports explicit rate marking and Congestion Indication (CI) control.


Figure 13-2: ABR VSVD Flow Control Diagram

ForeSight Congestion Control

ForeSight may be used for congestion control across BPX/IGX switches for connections that have one or both end points terminating on ASI-T3/E3 or BXM cards. The ForeSight feature is a proprietary 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. The BXM cards also support the VSVD congestion control mechanism as specified in the ATM Traffic Management 4.0 standards.

ATM Connection Requirements

There are two connection addressing modes supported. The user may enter a unique VPI/VCI address in which case the BPX switch functions as a virtual circuit switch. Or the user may enter only a VPI address in which case all circuits are switched to the same destination port and the BPX switch functions as a virtual path switch in this case. The full ATM address range for VPI and VCI is supported.Virtual Path Connections are identified by an * in the VCI field. Virtual Circuit Connections specify both the VPI and VCI fields.

The VPI and VCI fields have significance only to the local BPX switch, and are translated by tables in the BPX switch to route the connection. Connections are automatically routed by the AutoRoute feature once the connection endpoints are specified.

ATM connections can be added using either the Cisco WAN Manager Connection Manager or a node's command line interface (CLI). Typically, the Cisco WAN Manager Connection Manager is the preferred method as it has an easy to use GUI interface. The CLI may be the method of choice in some special cases or during initial node setup for local nodes.

When adding ATM connections, first the access port and access service lines connecting to the customer CPE need to be configured. Also, the trunks across the network need to configured appropriately for the type of connection. Following that the addcon command may be used to add a connection, first specifying the service type and then the appropriate parameters for the connection.

For example, when configuring a BXM for CPE connections, the BXM is configured for port mode, a line is upped with the upln command and configured with the cnfln command. Then the associated port is configured with the cnfport command and upped with the upport command. Following this, the ATM connections are added via the addcon command with the syntax.

Connection Routing

ATM connections for a BXM or ASI card are identified as follows:

The slot and port are related to the BPX switch hardware. Virtual path connections (VPCs) are identified by a "*" for the VCI field. Virtual circuit connections (VCCs) are identified by both a VPI and VCI field.

Connections added to the network are automatically routed once the end points are specified. This AutoRoute feature is standard with all BPX, IGX, and IPX switches. The network automatically detects trunk failures and routes connections around the failures.

addcon Command Syntax

The following parameters are entered for the BXM addcon command. Depending upon the connection type, the user is prompted for the appropriate parameters as shown in the following:

addcon local_addr node remote_addr traffic_type/class number....extended parameters EXAMPLES addcon 2.2.11.11 pubsbpx1 2.3.12.12 3 addcon 2.3.22.22 pubsbpx1 2.2.24.24 abrstd 50/50 100/100 50/50 25000/* e e e d 50/50 * 3 * 80/* 35/* 20/* 50/* * 100 128 16 32 0 *

Field Value Description

local/remote_addr

slot.port.vpi.vci

desired VCC or VPI connection identifier

node

slave end of connection

traffic_type/connection class

Type of traffic, chosen from service type (nrt/rt-VBR, CBR, UBR, ABRSTD, ABRFST, ATFR, ATFST, ATFT, ATFTFST, ATFX, ATFXFST) or connection class. For example, for rt-VBR, connection class 3 for a new node runing Rel. 9.2.20.

Note For a new node running 9.2.20 or later, the rt-VBR connection class number is 3. An upgraded node wil retain existing connection classes. Therefore, it won't have the rt-VBR connection class 3. However, the user can configure the connection classes to whatever service and parameters they want using the cnfcls/cnfatmcls command.

extended parameters

Additional traffic management and performance parameters associated with some of the ATM connection types, for example ABRSTD with VSVD enabled and default extended parameters disabled.

Note The range of VPIs and VCIs reserved for PVC traffic and SVC traffic is configurable using the cnfport command. While adding connections, the system checks the entered VPI/VPC against the range reserved for SVC traffic. If there is a conflict, the addcon command fails with the message "VPI/VCI on selected port is reserved at local/remote end".

addcon Example

The following example shows the initial steps in adding a connection with the addcon command, and the addcon prompt requesting the user to enter the ATM type of service.

pubsbpx1 TN silves BPX 8620 9.2.2G July 21 1999 21:32 PDT Local Remote Remote Route Channel NodeName Channel State Type Avoid COS O 2.2.1.4 pubsbpx1 2.3.5.7 Ok nrt-vbr 2.2.1.5 pubsbpx1 2.3.5.8 Ok rt-vbr 2.2.1.6 pubsbpx1 2.3.5.9 Ok rt-vbr 2.3.5.7 pubsbpx1 2.2.1.4 Ok nrt-vbr 2.3.5.8 pubsbpx1 2.2.1.5 Ok rt-vbr 2.3.5.9 pubsbpx1 2.2.1.6 Ok rt-vbr This Command: addcon 2.2.11.11 pubsbpx1 2.3.12.12 Enter (nrt/rt-VBR,CBR,UBR,ABRSTD,ABRFST,ATFR,ATFST,ATFT,ATFTFST,ATFX,ATFXFST) or class number:

Instead of entering a class of service, the user can instead enter a class number to select a pre-configured template, for example, class 4 for NTR-VBR, and class 3 for RT-VBR. The class of service templates can be modified as required using the cnfcls/cnfatmcls command and displayed using the dspcls/dspatmcls command.

Note For a new node running 9.2.20 or later, the rt-VBR connection class number is 3. An upgraded node will retain existing connection classes. Therefore, it won't have the rt-VBR connection class 3. However, the user can configure the connection classes to whatever service and parameters they want using the cnfcls/cnfatmcls command.

An example of a cnfcls/cnfatmcls command and response is shown in the following example:

pubsbpx1 TN silves:1 BPX 8620 9.2.2G July 16 1999 10:42 PDT ATM Connection Classes Class: 2 Type: nrt-VBR PCR(0+1) % Util CDVT(0+1) AAL5 FBTC SCR 1000/1000 100/100 10000/10000 n 1000/1000 MBS Policing 1000/1000 3 Description: "Default nrt-VBR 1000 " This Command: cnfcls atm 2 Enter class type (rt-VBR, nrt-VBR, CBR, UBR, ABRSTD, ABRFST, ATFR, ATFST, ATFT, ATFTFST, ATFX, ATFXFST):

ATM Connection Flow

ATM Connection Flow through the BPX

The BPX supports the standard ATM service types, CBR, rt-VBR, nrt-VBR, ABR, and UBR. When adding a connection, using the addcon command, these service types are selected by entering one of the CLI service type entries shown in Table 13-2 when prompted:


Table 13-2: Standard ATM Type and addcon
CLI Service Type Entries Connection Description

CBR

cell bit rate

rt-VBR

real time VBR

nrt-VBR

non real time VBR

UBR

unspecified bit rate

ABRSTD

ABR per forum standard, with option to enable VSVD congestion control.

ABRFST

ABR with Cisco ForeSight congestion control.

The BPX also supports ATM to Frame Relay Network Interworking and Service Interworking connections. When adding a connection using the addcon command, these service types are selected by entering one of the CLI service type entries shown in Table 13-3 when prompted:


Table 13-3: ATM to Frame Relay Network and Service Interworking
CLI Service Type Entries for addcon command Connection Description

ATFR

ATM to Frame Relay Network Interworking

ATFST

Same as ATFR with ForeSight

ATFT

ATM to Frame Relay Transparent Service Interworking

ATFTFST

Same as ATFT with ForeSight

ATFX

ATM to Frame Relay Translational Service Interworking

ATFXFST

Same as ATFX with ForeSight

Advanced CoS Management

Advanced CoS management provides per-VC queueing and per-VC scheduling. CoS management 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 Optimized Bandwidth Management (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 connection's class of service. Service classes are defined by standards-based QoS. Classes can consist of the five service classes defined in the ATM standards as well as multiple sub-classes to each of these 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.

CoS Management provides an 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 five broad classes of service defined by the ATM standards committees, CoS management 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:

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.

Connection Flow Example

The example shown in Figure 13-3 shows the general ATM connection flow through BXM cards in BPX switches. The cnfport, cnfportq, cnfln, cnftrk, and cnftrkparm commands are used to configure resources affecting the traffic flow of a connection. Examples are described in Traffic Shaping for CBR, rt-VBR, nrt-VBR, and UBR.

Note In this example, BXM cards are referenced. However, connection flow through BNI trunk and ASI service cards is similar, although they do not support all the features provided by BXM cards.

Ingress from CPE 1 to BXM 3

ATM cells from CPE 1 that are applied to BXM 3, Figure 13-3, are processed at the physical level, policed per individual VC based on ATM header payload type, and routed to the applicable one of 15 per card slot servers, each of which contains 16 CoS service queues, including ATM service types CBR, rt-VBR, nrt-VBR, ABR, and UBR.

ATM cells undergoing traffic shaping, e.g., ABR cells, are applied to traffic shaping queues before going to one of the 15 per card slot servers. ATM cells applied to the traffic shaping queues receive additional processing, including congestion control by means of VSVD or ForeSight and virtual connection queuing.

Cells are served out from the slot servers via the BPX backplane to the BCC crosspoint switch. The cells are served out on a fair basis with priority based on class of service, time in queue, bandwidth requirements, etc.

Note For a description of traffic shaping on CBR, rt-VBR, nrt-VBR, and UBR connections, refer to the section later in this chapter, Traffic Shaping for CBR, rt-VBR, nrt-VBR, and UBR.

Egress to Network via BXM 10

In this example, ATM cells destined for BPX 2 are applied via the BCC crosspoint switch and BPX backplane to BXM 10 and out to the network. The cells are served out to the network via the appropriate trunk qbin, CBR, rt-VBR, nrt-VBR, ABR, or UBR.

Ingress from Network via BXM 5

ATM cells from the network that are applied to BXM 5 in BPX 2 are processed at the physical level and routed to one of 15 per card slot servers, each of which contains 16 CoS service queues, including ATM service types CBR, rt-VBR, nrt-VBR, ABR, and UBR.

Cells are served out from the slot servers via the BPX backplane to the BCC crosspoint switch. The cells are served out on a fair basis with priority based on class of service, time in queue, bandwidth requirements, etc.

Egress from BXM 11 to CPE 2

In this example, ATM cells destined for CPE 2 are applied via the BCC crosspoint switch and BPX backplane to BXM 11 and out to CPE 2. The cells are served out to CPE 2 via the appropriate port qbin, CBR, rt-VBR, nrt-VBR, or ABR/UBR.

ATM cells undergoing traffic shaping, e.g., ABR cells, are applied to traffic shaping queues before going to one of the 15 per card slot servers. ATM cells applied to the traffic shaping queues receive additional processing, including congestion control by means of VSVD or ForeSight and virtual connection queuing.


Figure 13-3: ATM Connection Flow via BPX Switches


Traffic Shaping for CBR, rt-VBR, nrt-VBR, and UBR

With the introduction of traffic shaping for CBR, VBR, and UBR, the user has the option to provide traffic shaping for these connections types on the BXM. Previously, only ABR utilized traffic shaping. Traffic shaping involves passing CBR, VBR, or UBR traffic streams through VC queues for scheduled rate shaping.

Traffic shaping is performed on a per port basis. When traffic shaping is enabled, all traffic exiting the port (out to the network) is subject to VC scheduling based on the parameters configured by the user for the connection.

Figure 13-4 shows an example of traffic shaping. In this example, port 1 is configured to perform traffic shaping. Note that all the ATM cells regardless of class of service pass through the VC queues before leaving the card when traffic shaping is enabled. In the example, port 2 is not configured for traffic shaping, and only the ABR traffic with FCES (flow control external segment) passes through the VC queues.


Figure 13-4: Traffic Shaping Example


Traffic Shaping Rates

Traffic shaping rates are listed in Table 13-4.


Table 13-4: Traffic Shaping Rates
Service Type MCR PCR

CBR

PCR

PCR

rt-VBR and nrt-VBR

SCR * %Util

PCR

UBR

0

PCR

ABR

MCR * %Util

PCR

Configuration

Traffic shaping is disabled by default. The cnfport and cnfln command is used to enable and disable the function on a per port basis. The cnftrk command is used to enable traffic shaping on trunks.No connections should be enabled on the port prior to changing the port traffic shaping parameter. If there are existing connections when the port is toggled, then these connections will not be updated unless the card is reset, connections are rerouted, a switchcc occurs, or the user modifies the connection parameters. See the following examples of the cnfln, cnfport, and cnftrk commands:

Example of cnfln:

pubsbpx1 TN silves BPX 8620 9.2.2 Aug. 1 1999 14:41 PDT LN 2.2 Config OC3 [353208cps] BXM slot: 2 Loop clock: No Idle code: 7F hex Line framing: -- coding: -- CRC: -- recv impedance: -- E1 signalling: -- encoding: -- cable type: -- T1 signalling: -- length: -- HCS Masking: Yes Payload Scramble: Yes 56KBS Bit Pos: -- Frame Scramble: Yes pct fast modem: -- Cell Framing: STS-3C VC Shaping: No Last Command: cnfln 2.2 Next Command:

Example of cnfport:

pubsbpx1 TN silves BPX 8620 9.2.2 Aug. 1 1999 15:12 PDT Port: 2.2 [ACTIVE ] Interface: LM-BXM CAC Override: Enabled Type: UNI %Util Use: Disabled Shift: NO SHIFT (Virtual Trunk Operation) SIG Queue Depth: 640 Port Load: 28 % Protocol: NONE Protocol by Card: No Last Command: cnfport 2.2 Next Command:

Example of cnftrk:

pubsbpx1 TN silves BPX 8620 9.2.2G Aug. 1 1999 14:43 PDT TRK 2.4 Config OC3 [353207cps] BXM slot: 2 Transmit Rate: 353208 Line framing: STS-3C Protocol By The Card: No coding: -- VC Shaping: No CRC: -- Hdr Type NNI: Yes recv impedance: -- Statistical Reserve: 1000 cps cable type: -- Idle code: 7F hex length: -- Connection Channels: 256 Pass sync: No Traffic:V,TS,NTS,FR,FST,CBR,NRT-VBR,ABR, T-VBR clock: No SVC Vpi Min: 0 HCS Masking: Yes SVC Channels: 0 Payload Scramble: Yes SVC Bandwidth: 0 cps Frame Scramble: Yes Restrict CC traffic: No Virtual Trunk Type: -- Link type: Terrestrial Virtual Trunk VPI: -- Routing Cost: 10 Deroute delay time: 0 seconds This Command: cnftrk 2.4 Transmit Rate [ 1-353208 ]:

rt-VBR and nrt-VBR Connections

With Rel. 9.2.20 and later, rt-VBR and nrt-VBR connections are specified separately when adding a connection using the addcon command by entering either rt-vbr or nrt-vbr to select the rt-VBR or nrt-VBR connection class, respectively. Each connection is assigned the applicable associated default parameters for its type of service.

For rt-VBR an additional queue, referred to as the rt-VBR queue, is used at a BXM or ASI port. At BXM or BNI trunks, voice and rt-VBR traffic share a queue, referred to as the rt-VBR queue.

The rt-VBR and nrt-VBR service queues are configured differently from each other at both port ingress and port egress queues. The rt-VBR typically uses smaller queues for low delay, whereas the nrt-VBR queues are typically larger in size for more efficient bandwidth sharing with other non-real time service types.

The rt-VBR connections are configured per class 3 service parameters, and nrt-VBR connections are configured per class 2 service parameters. These class parameters can be changed using the cnfcls/cnfatmcls command, or the parameters can be entered individually for each connection by specifying `yes' to the extended parameters prompt of the addcon command.

Note For a new node running software release 9.2.20 or later, the rt-VBR connection class number is 3. An upgraded node wil retain existing connection classes. Therefore, it won't have the rt-VBR connection class 3. However, the user can configure the connection classes to whatever service and parameters they want using the cnfcls/cnfatmcls command. For nrt-VBR connections in a new node, running 9.2.20, a number of connection classes are pre-configured, including 2, 4, 5, and 6.

Examplef cnfcls 3, for rt-VBR

pubsbpx1 TN silves:1 BPX 8620 9.2.2G July 16 1999 10:42 PDT ATM Connection Classes Class: 3 Type: rt-VBR PCR(0+1) % Util CDVT(0+1) AAL5 FBTC SCR 4000/4000 100/100 10000/10000 n 4000/4000 MBS Policing 1000/1000 3 Description: "Default rt-VBR 4000 " This Command: cnfcls atm 3 Enter class type (rt-VBR, nrt-VBR, CBR, UBR, ABRSTD, ABRFST, ATFR, ATFST, ATFT, ATFTFST, ATFX, ATFXFST):

Example of cnfcls2, for NRT-VBR

pubsbpx1 TN silves:1 BPX 8620 9.2.2G July 16 1999 10:42 PDT ATM Connection Classes Class: 2 Type: nrt-VBR PCR(0+1) % Util CDVT(0+1) AAL5 FBTC SCR 1000/1000 100/100 10000/10000 n 1000/1000 MBS Policing 1000/1000 3 Description: "Default nrt-VBR 1000 " This Command: cnfcls atm 2 Enter class type (rt-VBR, nrt-VBR, CBR, UBR, ABRSTD, ABRFST, ATFR, ATFST, ATFT, ATFTFST, ATFX, ATFXFST):

Connection Criteria

Connection Management

The BPX Command Line Interface (CLI) and Cisco WAN Manager accept the same connection policing and bandwidth parameters as in previous releases for both rt-VBR and nrt-VBR service.

The displayed addcon parameter prompts for both rt-VBR and nrt-VBR connections are the same. These prompts are: PCR, %util, CDVT, FBTC flag, SCR, MBS, and Policing Type.

There is no change in CDVT usage and the previous policing system.

When using the addcon command without the extended parameters, rt-VBR connections, automatically use the parameters provided by connection class 3 which contains pre-determined values. Similarly, nrt-VBR connections use connection class 2. The values of a connection class can be modified by using the cnfcls/cnfatmcl command. These values are displayed by the dspcls/dspatmcls commands.

Configuring Resources

Qbin values on both ports and trunks used by rt-VBR connections and nrt-VBR connections can be configured separately.

Trunk Queues for rt-VBR and nrt-VBR

A rt-VBR connection uses the rt-VBR queue on a trunk. It shares this queue with voice traffic. The rt-VBR and voice traffic shares the default or user configured parameters for the rt-VBR queue. These parameters are queue depth, queue CLP high and CLP low thresholds, EFCI threshold, and queue priority.

A nrt-VBR connection uses the nrt-VBR queue on a trunk. The configurable parameters are queue depth, queue CLP high and CLP low thresholds, EFCI threshold, and queue priority.

The following example shows the cnftrkparm screen and the parameters that can be configured for the various service type queues:

pubsbpx1 TN silves:1 BPX 8620 9.2.2G July 16 1999 10:50 PDT TRK 2.4 Parameters 1 Q Depth - rt-VBR [ 885] (Dec) 15 Q Depth - CBR [ 600] (Dec) 2 Q Depth - Non-TS [ 1324] (Dec) 16 Q Depth - nrt-VBR [ 5000] (Dec) 3 Q Depth - TS [ 1000] (Dec) 17 Q Depth - ABR [20000] (Dec) 4 Q Depth - BData A [10000] (Dec) 18 Low CLP - CBR [ 60] (%) 5 Q Depth - BData B [10000] (Dec) 19 High CLP - CBR [ 80] (%) 6 Q Depth - High Pri [ 1000] (Dec) 20 Low CLP - nrt-VBR [ 60] (%) 7 Max Age - rt-VBR [ 20] (Dec) 21 High CLP - nrt-VBR [ 80] (%) 8 Red Alm - I/O (Dec) [ 2500 / 10000]22 Low CLP/EPD-ABR [ 60] (%) 9 Yel Alm - I/O (Dec) [ 2500 / 10000]23 High CLP - ABR [ 80] (%) 10 Low CLP - BData A [ 100] (%) 24 EFCN - ABR [ 20] (%) 11 High CLP - BData A [ 100] (%) 25 SVC Queue Pool Size [ 0] (Dec) 12 Low CLP - BData B [ 25] (%) 13 High CLP - BData B [ 75] (%) 14 EFCN - BData B [ 30] (Dec) This Command: cnftrkparm 2.4

Port Queues for rt-VBR and nrt-VBR

The rt-VBR and nrt-VBR connections use different queues on a port, these are the rt-VBR and nrt-VBR queues, respectively. A user can configure these separately, using the cnfportq command.

The following example shows he configuration parameters available for a port queue.

Port Queue Parameters, cnfportq

pubsbpx1 TN silves:1 BPX 8620 9.2.2G July 16 1999 10:47 PDT Port: 2.2 [ACTIVE ] Interface: LM-BXM Type: UNI Speed: 353208 (cps) SVC Queue Pool Size: 0 CBR Queue Depth: 600 rt-VBR Queue Depth: 0 CBR Queue CLP High Threshold: 80% rt-VBR Queue CLP High Threshold: 80% CBR Queue CLP Low Threshold: 60% rt-VBR Queue CLP Low/EPD Threshold: 60% CBR Queue EFCI Threshold: 60% rt-VBR Queue EFCI Threshold: 80% nrt-VBR Queue Depth: 5000 UBR/ABR Queue Depth: 20000 nrt-VBR Queue CLP High Threshold: 80% UBR/ABR Queue CLP High Threshold: 80% nrt-VBR Queue CLP Low Threshold: 60% UBR/ABR Queue CLP Low/EPD Threshold:60% nrt-VBR Queue EFCI Threshold: 60% UBR/ABR Queue EFCI Threshold: 20% This Command: cnfportq 2.2

Related Switch Software Commands

The following commands are related to the process of adding and monitoring ATM connections

addcon, dspload, cnfcls, cnfatmcls, cnfcls, cnfcon, cnftrkparms, dsptrkcnf, dspatmcls, dspcls, dsconcls, dspconcnf, dspcon, dspcons, dlcon, dcct, dvcparms, dvc, cnfpre, dsptrkcnf, dspload, chklm, dsplm, updates, upport, dspportq, cnfportq, dspblkfuncs, dspchstats, dspportstats, dsptrkstats, dsptrkerrs.

Related Documentation

For additional information on CLI command usage, refer to the Release 9.2, Cisco WAN Switching Command Reference and Super User manuals.

ATM Connection Configuration

The following figures and tables describe the parameters used to configure ATM connections:

The following figures list the connection parameters in the same sequence as they are entered when a connection is added:

The following figure shows the VSVD network segment and external segment options available when ABR Standard or ABR ForeSight is selected. ForeSight congestion control is useful when both ends of a connection do not terminate on BXM cards. At present, FCES (Flow Control External Segment) as shown in Figure 13-8 is not available for ABR with ForeSight.

The following figures list the connection parameters in the same sequence as they are entered when a connection is added:

Note With DAX connections, the trunk cell routing restriction prompt is not displayed since there is no trunking involved.

Table 13-5: Traffic Policing Definitions
Connection Type ATM Forum TM spec. 4.0 conformance definition PCR Flow (1st leaky bucket) CLP tagging (for PCR flow) SCR Flow (2nd leaky bucket) CLP tagging (for SCR flow)

CBR

CBR.1

when policing set to 4 (PCR policing only)

CLP(0+1)

no

off

n/a

CBR

when policing set to 5 (off)

off

n/a

off

n/a

UBR

UBR.1

when CLP setting = no

CLP(0+1)

no

off

n/a

UBR

UBR.2

when CLP setting = yes

CLP(0+1)

no

CLP(0)

yes

rt/nrt-VBR, ABR, ATFR, ATFST

VBR.1

when policing set to 1

CLP(0+1)

no

CLP(0+1)

no

rt/nrt-VBR, ABR, ATFR, ATFST

VBR.2

when policing set to 2

CLP(0+1)

no

CLP(0)

no

rt/nrt-VBR, ABR, ATFR, ATFST

VBR.3

when policing set to 3

CLP(0+1)

no

CLP(0)

yes

rt/nrt-VBR, ABR, ATFR, ATFST

when policing set to 4

CLP(0+1)

no

off

n/a

rt/nrt-VBR, ABR, ATFR, ATFST

when policing set to 5 (off)

off

n/a

off

n/a

Note 1: - For UBR.2, SCR = 0

Note 2:


Table 13-6: Connection Parameters with Default Settings and Ranges
PARAMETER WITH [DEFAULT SETTING] BXM T3/E3, OC3 & OC12 RANGE ASI T3/E3 RANGE ASI-155 RANGE

PCR(0+1)[50/50]

50- T3/E3 cells/sec

50 - OC3

50 - OC12

T3: MCR - 96000

E3: MCR - 80000

Limited to MCR -
5333 cells/sec for ATFR connections.

OC3 (STM1): 0 - 353200

%Util [100/100]

for UBR [1/1]

0 - 100%

1 - 100%

1 - 100%

MCR[50/50]

cells/sec

6 - T3/E3OC3/0C12

T3: 0 - 96000 cells/sec

E3: 0 - 80000 cells/sec

N/A

FBTC (AAL5 Frame Base Traffic Control):

for rt/nrt-VBR [disable]

for ABR/UBR [enable]

for Path connection [disable]

enable/disable

Note With the BXM, FBTC means packet discard on queueing only.

enable/disable

Note With the ASI, FBTC means packet discard on both policing and queueing.

enable/disable

Note With the ASI, FBTC means packet discard on both policing and queueing.

CDVT(0+1):

for CBR [10000/10000],

others [250000/250000]

0 - 5,000,000 usec

T3/E3 1 - 250,000 usecs.

OC3/STM1: 0 - 10000 usecs.

VSVD[disable]

enable/disable

enable/disable

Select disable, as only ABR w/o VSVD is supported.

FCES (Flow Control External Segment) [disable]

enable/disable

enable/disable

N/A

Default Extended Parameters[enable]

enable/disable

enable/disable

N/A

CLP Setting[enable]

enable/disable

enable/disable

enable/disable

SCR [50/50]

cells/sec

50 - T3/E3OC3/OC12

T3: MCR - 96000:T3

E3: MCR - 80000: E3

Limited to MCR - 5333 cells/sec for ATFR connections.

OC3/STM1: 0 - 353200

MBS [1000/1000]

1 - 5,000,000cells

T3/E3: 10 - 24000 cells

OC3 (STM1): 10 - 1000 cells

Policing[3]

For CBR: [4]

1 - VBR.1

2 - VBR.2

3 - VBR.3

4 - PCR policing only

5 - off

1 - VBR.1

2 - VBR.2

3 - VBR.3

4 - PCR policing only

5 - off

1 - VBR.1

2 - VBR.2

3 - VBR.3

4 - PCR policing only

5 - off

ICR:

max[MCR, PCR/10]

MCR - PCR cells/sec

MCR - PCR cells/sec

N/A

ADTF[1000]

62 - 8000 msec

1000 - 255000 msecs.

N/A

Trm[100]

ABRSTD: 1 - 100 msec

ABRFST: 3 - 255 msec

20 - 250 msecs.

N/A

VC QDepth [16000/16000]

For ATFR/ATFST [1366/1366]

0 - 61440 cells

Applies to T3/E3 only
ABR: 1 - 64000 cells
ATFR: 1 - 1366 cells

ATFR: 1 - 1366 cells

CLP Hi [80/80]

1 - 100%

1 - 100%

N/A

CLP Lo/EPD [35/35]

1 - 100%

1 - 100%

N/A

EFCI [30/30]

For ATFR/ATFST [100/100]

1 - 100%

1 - 100%

0 - 100%

RIF:

For ForeSight:

max[PCR/128, 10]

For ABR STD[128]

If ForeSight, then in absolute (0 - PCR)

If ABR then 2n

(1 - 32768)

If ForeSight, then in absolute (0 - PCR)

If ABR, then 2n

(1 - 32768)

N/A

RDF:

For ForeSight [93]

For ABR STD [16]

If ForeSight, then %

(0% - 100%)

If ABR then 2n

(1 - 32768)

If ForeSight, then %

(0% - 100%)

If ABR, then 2n

(1 - 32768)

N/A

Nrm[32], BXM only

2 - 256 cells

N/A

N/A

FRTT[0], BXM only

0 - 16700 msec

N/A

N/A

TBE[1,048,320], BXM only

0 - 1,048,320 cells

(different max range from TM spec. but limited by firmware for CRM(4095 only) where CRM=TBE/Nrm

N/A

N/A

IBS[1/1]

0 - 24000 cells

T3/E3 ABR: 0 - 24000 cells

ATFR: 1 - 107 cells

0 - 999 cells

Trunk cell routing restrict (Y/N) [Y]

Y/N

Y/N

Y/N


Table 13-7: Connection Parameter Descriptions
Parameter Description

PCR

Peak cell rate:

The cell rate which the source may never exceed

%Util

% Utilization; bandwidth allocation for: rt/nrt-VBR, CBR, UBR it's PCR*%Util, for ABR it's MCR*%Util

MCR

Minimum Cell Rate:

A minimum cell rate committed for delivery by network

CDVT

Cell Delay Variation Tolerance:

Controls time scale over which the PCR is policed

FBTC (AAL5 Frame Basic Traffic Control)

To enable the possibility of discarding the whole frame, not just one non-compliant cell. This is used to set the Early Packet Discard bit at every node along a connection.

Note With the ASI, FBTC means packet discard on both policing and queueing. With the BXM, FBTC means packet discard on queueing only.

VSVD

Virtual Source Virtual Destination:

(see Meaning of VSVD and Flow Control External Segments, Figure 13-8)

FCES (Flow Control External Segments)

(see Meaning of VSVD and Flow Control External Segments, Figure 13-8)

SCR

Sustainable Cell Rate:

Long term limit on the rate a connection can sustain

MBS

Maximum Burst Size:

Maximum number of cells which may burst at the PCR but still be compliant. Used to determine the Burst Tolerance (BT) which controls the time scale over which the SCR is policed

Policing

(see definitions of Traffic Policing, Table 13-5)

VC QDepth

VC Queue Depth

CLP Hi

Cell Loss Priority Hi threshold (% of VC QMax)

CLP Lo/EPD

Cell Loss Priority Low threshold (% of VC QMax)/Early Packet Discard. If AAL5 FBTC = yes, then for the BXM card this is the EPD threshold setting. For ASI cards, regardless of the FBTC setting, this is the CLP Lo setting.

EFCI

Explicit Forward Congestion Indication threshold (% of VC QMax)

ICR

Initial Cell Rate:

The rate at which a source should send initially and after an idle period

ADTF (ATM Forum TM 4.0 term)

The Allowed-Cell-Rate Decrease Factor:

Time permitted between sending RM-cells before the rate is decreased to ICR

Trm (ATM Forum TM 4.0 term)

An upper bound on the time between forward RM-cells for an active source, i.e., RM cell must be sent at least every Trm msec

RIF (ATM Forum TM 4.0 term)

Rate Increase Factor:

Controls the amount by which the cell transmission rate may increase upon receipt of an RM cell

RDF (ATM Forum TM 4.0 term)

Rate Decrease Factor:

Controls the amount by which the cell transmission rate may decrease upon receipt of an RM cell

Nrm (ATM Forum TM 4.0 term), BXM only.

Nrm

Maximum number of cells a source may send for each forward RM cell, i.e. an RM cell must be sent for every Nrm-1 data cells

FRTT (ATM Forum TM 4.0 term),

BXM only.

Fixed Round Trip Time: the sum of the fixed and propagation delays from the source to a destination and back

TBE (ATM Forum TM 4.0 term), BXM only.

Transient Buffer Exposure:

The negotiated number of cells that the network would like to limit the source to sending during start-up periods, before the first RM-cell returns.

IBS

Initial Burst Size

Trunk cell routing restriction (Y/N) [Y]

The default (Y) restricts ATM connection routes to include only ATM trunks. Selecting (N) allows the network to route these connections over non-ATM trunks (e.g., Fastpacket trunks).

CBR Connections

The CBR (constant bit rate) category is a fixed bandwidth class. CBR traffic is more time dependent, less tolerant of delay, and generally more deterministic in bandwidth requirements. CBR is used by connections that require a specific amount of bandwidth to be available continuously throughout the duration of a connection. Voice, circuit emulation, and high-resolution video are typical examples of traffic utilizing this type of connection. A CBR connection is allowed to transmit cells at the peak rate, below the peak rate, or not at all. CBR is characterized by peak cell rate (PCR).

The parameters for a CBR connection are shown in Figure 13-5 in the sequence in which they occur during the execution of the addcon command. The CBR policing definitions are summarized in Table 13-8.


Figure 13-5: CBR Connection Prompt Sequence



Table 13-8:
Connection Type ATM Forum TM spec. 4.0 conformance definition PCR Flow (1st leaky bucket) CLP tagging (for PCR flow) SCR Flow (2nd leaky bucket) CLP tagging (for SCR flow)

CBR

CBR.1

when policing set to 4 (PCR Policing only)

CLP(0+1)

no

off

n/a

CBR

When policing set to 5 (off)

off

n/a

off

n/a

CBR Policing Definitions

rt-VBR and nrt-VBR Connections

VBR (variable bit rate) connections may be classified as rt-VBR or nrt-VBR connections.

The rt-VBR (real-time variable bit rate) category is used for connections that transmit at a rate varying with time and that can be described as bursty, often requiring large amounts of bandwidth when active. The rt-VBR class is intended for applications that require tightly constrained delay and delay variation such as compressed voice video conferencing. For example, video conferencing which requires real-time data transfer with bandwidth requirements that can vary in proportion to the dynamics of the video image at any given time. The rt-VBR category is characterized in terms of PCR, SCR (sustained cell rate), and MBS (maximum burst size).

The nrt-VBR (non-real time variable bit rate) category is used for connections that are bursty but are not constrained by delay and delay variation boundaries. For those cells in compliance with the traffic contract, a low cell loss is expected. Non-time critical data file transfers are an example of an nrt-VBR connection. A nrt-VBR connection is characterized by PCR, SCR, and MBS.

Configuring VBR connections. The characteristics of rt-VBR or nrt-VBR are supported by appropriately configuring the parameters of the VBR connection.

Note When configuring a rt-VBR connection, the trunk cell routing restriction prompt does not occur, as rt-VBR connection routing is automatically restricted to ATM trunks.

The parameters for a VBR connection are shown in Figure 13-6 in the sequence in which they occur during the execution of the addcon command. The VBR policing definitions are summarized in Table 13-9.


Figure 13-6: rt-VBR and nrt-VBR Connection Prompt Sequence



Table 13-9:
Connection Type ATM Forum TM spec. 4.0 conformance definition PCR Flow (1st leaky bucket) CLP tagging (for PCR flow) SCR Flow (2nd leaky bucket) CLP tagging (for SCR flow)

rt/nrt-VBR, ABR, ATFR, ATFST, ATFT, ATFTST, ATFX, ATFXFST

VBR.1

when policing set to 1

CLP(0+1)

no

CLP(0+1)

no

rt/nrt-VBR, ABR, ATFR, ATFST, ATFT, ATFTST, ATFX, ATFXFST

VBR.2

when policing set to 2

CLP(0+1)

no

CLP(0)

no

rt/nrt-VBR, ABR, ATFR, ATFST, ATFT, ATFTST, ATFX, ATFXFST

VBR.3

when policing set to 3

CLP(0+1)

no

CLP(0)

yes

rt/nrt-VBR, ABR, ATFR, ATFST, ATFT, ATFTST, ATFX, ATFXFST

when policing set to 4

CLP(0+1)

no

off

n/a

rt/nrt-VBR, ABR, ATFR, ATFS, ATFT, ATFTST, ATFX, ATFXFST

when policing set to 5 for off

off

n/a

off

n/a

VBR Policing Definitions

ABR Notes

The term ABR is used to specify one of the following:

ABR Connections

The ABR (available bit rate) category utilizes a congestion flow control mechanism to control congestion during busy periods and to take advantage of available bandwidth during less busy periods. The congestion flow control mechanism provides feedback to control the connections flow rate through the network in response to network bandwidth availability. The ABR service is not restricted by bounding delay or delay variation and is not intended to support real-time connections. ABR is characterized by: PCR and MCR.

Policing for ABR connections is the same as for VBR connections which are summarized in Table 13-9.

The ABR connections are configured as either ABR Standard (ABRSTD) connections or as ABR ForeSight (ABRFST) connections.

The parameters for an ABRSTD connection are shown in Figure 13-7 in the sequence in which they occur during the execution of the addcon command.

The ABRSTD connection supports all the features of ATM Standards Traffic Management 4.0 including VSVD congestion flow control.

VSVD and flow control with external segments are shown in Figure 13-8.

ABRSTD Connections

The ABRSTD connection uses VSVD congestion control.

The parameters for an ABRSTD connection are shown in Figure 13-9 in the sequence in which they occur during the execution of the addcon command


Figure 13-7: ABR Standard Connection Prompt Sequence



Figure 13-8: Meaning of VSVD and Flow Control External Segments

ABRFST Connections

The ABRFST connection uses the propriety ForeSight congestion control and is useful when configuring connections on which both ends do not terminate on BXM cards.

The parameters for an ABRFST connection are shown in Figure 13-9 in the sequence in which they occur during the execution of the addcon command.


Figure 13-9: ABR ForeSight Connection Prompt Sequence


UBR Connections

The unspecified bit rate (UBR) connection service is similar to the ABR connection service for bursty data. However, UBR traffic is delivered only when there is spare bandwidth in the network. This is enforced by setting the CLP bit on UBR traffic when it enters a port.

Therefore, traffic is served out to the network only when no other traffic is waiting to be served first. The UBR traffic does not affect the trunk loading calculations performed by the switch software.

The parameters for a UBR connection are shown in Figure 13-10 in the sequence in which they occur during the execution of the addcon command.

The UBR policing definitions are summarized in Table 13-10.


Figure 13-10: UBR Connection Prompt Sequence



Table 13-10:
Connection Type ATM Forum TM spec. 4.0 conformance definition PCR Flow (1st leaky bucket) CLP tagging (for PCR flow) SCR Flow (2nd leaky bucket) CLP tagging (for SCR flow)

UBR

UBR.1

when CLP setting = no

CLP(0+1)

no

off

n/a

UBR

UBR.2

when CLP setting = yes

CLP(0+1)

no

CLP(0)

yes

UBR Policing Definitions

Network and Service Interworking Notes

Frame Relay to ATM Interworking enables Frame Relay traffic to be connected across high-speed ATM trunks using ATM standard Network and Service Interworking (see Figure 13-11 and Figure 13-12).

Two types of Frame Relay to ATM interworking are supported, Network Interworking and Service Interworking. The Network Interworking function is performed by the BTM card on the IGX switch. The FRSM card on the MGX 8220 supports both Network and Service Interworking.


Figure 13-11: Frame Relay to ATM Network Interworking
Figure 13-12: Frame Relay to ATM Service Interworking

ATFR Network Interworking Connections

An ATFR (ATM to Frame Relay) connection is a Frame Relay to ATM connection and is configured as a VBR connection, with a number of the ATM and Frame Relay connection parameters being mapped between each side of the connection.

The parameters for an ATFR connection are shown in Figure 13-13 in the sequence in which they occur during the execution of the addcon command.


Figure 13-13: ATFR Connection Prompt Sequence


ATFST Network Interworking Connection

An ATFST connection is a Frame Relay to ATM connection that is configured as an ABR connection with ForeSight. ForeSight congestion control is automatically enabled when connection type ATFST is selected. A number of the ATM and Frame Relay connection parameters are mapped between each side of the connection.

The parameters for an ATFST connection are shown in Figure 13-14 in the sequence in which they occur during the execution of the addcon command.


Figure 13-14: ATFST Connection Prompt Sequence


ATFT Transparent Service Interworking Connections

An ATFT connection is a Frame Relay to ATM transparent Service Interworking connection and is configured as a VBR connection, with a number of the ATM and Frame Relay connection parameters being mapped between each side of the connection..

The parameters for an ATFT connection are shown in Figure 13-15 in the sequence in which they occur during the execution of the addcon command.


Figure 13-15: ATFT Connection Prompt Sequence


ATFTFST Transparent Service Interworking Connections

An ATFTFST connection is a Frame Relay to ATM transparent Service Interworking connection that is configured as an ABR connection with ForeSight. ForeSight congestion control is automatically enabled when connection type ATFTFST is selected. A number of the ATM and Frame Relay connection parameters are mapped between each side of the connection.

The parameters for an ATFTFST connection are shown in Figure 13-16 in the sequence in which they occur during the execution of the addcon command.


Figure 13-16: ATFTFST Connection Prompt Sequence


ATFX Translational Service Interworking Connections

An ATFX connection is a Frame Relay to ATM translational Service Interworking connection and is configured as a VBR connection, with a number of the ATM and Frame Relay connection parameters being mapped between each side of the connection..

The parameters for an ATFX connection are shown in Figure 13-17 in the sequence in which they occur during the execution of the addcon command.


Figure 13-17: ATFX Connection Prompt Sequence


ATFXFST Translational Service Interworking Connections

An ATFXFST connection is a Frame Relay to ATM translational Service Interworking connection that is configured as an ABR connection with ForeSight. ForeSight congestion control is automatically enabled when connection type ATFXFST is selected. A number of the ATM and Frame Relay connection parameters are mapped between each side of the connection.

The parameters for an ATFXFST connection are shown in Figure 13-18 in the sequence in which they occur during the execution of the addcon command.


Figure 13-18: ATFXFST Connection Prompt Sequence


Traffic Policing Examples

Traffic Policing, also known as Usage Parameter Control (UPC), is implemented using either an ATM Forum single or dual-leaky bucket algorithm. The buckets represent a GCRA (Generic Cell Rate Algorithm) defined by two parameters:

If the cells are clumped too closely together, they are non-compliant and are tagged or discarded as applicable. If other cells arrive on time or after their expected arrival time, they are compliant, but three is no accrued credit.

Dual-Leaky Bucket (An Analogy)

A GCRA viewpoint is as follows:

CBR Traffic Policing Examples

CBR traffic is expected to be at a constant bit rate, have low jitter, and is configured for a constant rate equal to Peak Cell Rate (PCR). The connection is expected to be always at peak rate.

When a connection is added, a VPI.VCI address is assigned, and the UPC parameters are configured for the connection. For each cell in an ATM stream seeking admission to the network, the VPI.VCI addresses are verified and each cell is checked for compliance with the UPC parameters. The CBR cells are not enqueued, but are processed by the policing function and then sent to the network unless discarded.

For CBR, traffic policing is based on:

The CBR connection may be configured with policing selected as either 4 or 5. With policing set to 5, there is no policing. With policing set to 4, there is single leaky bucket PCR policing as shown in Figure 13-19. The single leaky bucket polices the PCR compliance of all cells seeking admission to the network, both those with CLP = 0 and those with CLP =1. Cells seeking admission to the network with CLP set equal to 1 may have either encountered congestion along the user's network or may have lower importance to the user and have been designated as eligible for discard in the case congestion is encountered. If the bucket depth CDVT (0+1) limit is exceeded, it discards all cells seeking admission. It does not tag cells. If leaky bucket 1 is not full, all cells (CLP =0 and CLP=1) are admitted to the network.


Figure 13-19: CBR Connection, UPC Overview


Figure 13-20 shows a CBR.1 connection policing example, with policing set to 4, where the CDVT depth of the single leaky bucket is not exceeded, and all cells, CLP(0) and CLP(1) are admitted to the network.


Figure 13-20: CBR.1 Connection with Bucket Compliant


Figure 13-21 shows a CBR connection policing example, with policing =4, where the CDVT(0+1) of the single leaky bucket is exceeded and non-compliant cells are discarded. The leaky bucket only discards cells; it does not tag them


Figure 13-21: CBR.1 Connection, with Bucket Discarding non-Compliant Cells


VBR Dual-Leaky Bucket Policing Examples

The contract for a variable bit rate connection is set up based on an agreed upon sustained cell rate (SCR) with allowance for occasional data bursts at a Peak Cell Rate (PCR) as specified by maximum burst size MBS.

When a connection is added, a VPI.VCI address is assigned, and UPC parameters are configured for the connection. For each cell in an ATM stream, the VPI.VCI addresses are verified and each cell is checked for compliance with the UPC parameters as shown in Figure 13-22.

The VBR cells are not enqueued, but are processed by the policing function and then sent to the network unless discarded.

For VBR, traffic policing, depending on selected policing option, is based on:

The policing options, selected by entering 1-5 in response to the policing choice prompt, are as follows for VBR connections:

VBR.1

VBR with policing set to 1.

CLP(0+1) cells compliant with leaky bucket 1 are passed to leaky bucket 2; non-compliant cells are discarded. CLP(0+1) cells compliant with leaky bucket 2 are admitted to the network; non-compliant cells are discarded.

VBR.2

VBR with policing set to 2.

CLP(1) cells compliant with leaky bucket 1 are admitted to the network; non-compliant CLP(0+1) cells are dropped. CLP(0) cells compliant with leaky bucket 1 are applied to leaky bucket 2; non-compliant cells are dropped. CLP(0) cells compliant with leaky bucket 2 are admitted to the network; non-compliant cells are dropped.

VBR.3

VBR with policing set to 3.

CLP(1) cells compliant with leaky bucket 1 are admitted to the network; non-compliant CLP(0+1) cells are dropped. CLP(0) cells compliant with leaky bucket 1 are applied to leaky bucket 2; non-compliant cells are dropped. CLP(0) cells compliant with leaky bucket 2 are admitted to the network; non-compliant cells are tagged and admitted to the network.

VBR with policing set to 4.

CLP(0+1) cells compliant with leaky bucket 1 are admitted to the network; non-compliant cells are dropped. Leaky bucket 2 is not active.

VBR with policing set to 5.

Policing is off, so there is no policing of cells on ingress.


Figure 13-22: VBR Connection, UPC Overview


Leaky Bucket 1

Leaky bucket 1 polices for the PCR compliance of all cells seeking admission to the network, both those with CLP = 0 and those with CLP =1. For example, cells seeking admission to the network with CLP set equal to 1 may have either encountered congestion along the user's network or may have lower importance to the user and have been designated as eligible for discard in the case congestion is encountered. If the bucket depth in the first bucket exceeds CDVT (0+1), it discards all cells seeking admission. It does not tag cells.

With policing set to 1 (VBR.1), all cells (CLP=0 and CLP=1) that are compliant with leaky bucket 1, are sent to leaky bucket 2. With policing set to 2 (VBR.2) or to 3 (VBR.3), all CLP=1 cells compliant with leaky bucket 1 are admitted directly to the network, and all CLP=0 cells compliant with leaky bucket 1 are sent to leaky bucket 2.

Leaky Bucket 2

For VBR connections, the purpose of leaky bucket 2 is to police the cells passed from leaky bucket 1 for conformance with maximum burst size MBS as specified by BT and for compliance with the SCR sustained cell rate. The types of cells passed to leaky bucket 2 depend on how policing is set:

Examples

Figure 13-23 shows a VBR connection policing example, with policing set to 4, leaky bucket 1 compliant, and all cells being admitted to the network.


Figure 13-23: VBR Connection, Policing = 4, Leaky Bucket 1 Compliant

.

Figure 13-24 shows a VBR connection policing example, with the policing set to 4, and leaky bucket 1 non-compliant which indicates that the connection has exceeded the PCR for a long enough interval to exceed the CDVT (0+1) limit. Non-compliant cells with respect to leaky bucket 1 are discarded.


Figure 13-24: VBR Connection, Policing = 4, Leaky Bucket 1 Non-Compliant


Figure 13-25 shows a VBR.2 connection policing example, with policing = 2, and both buckets compliant. Leaky bucket two is policing the CLP(0) cell stream for conformance with maximum burst size MBS (as specified by BT), and for compliance with the SCR sustained cell rate.


Figure 13-25: VBR.2 Connection, Policing = 2, with Buckets 1 and 2 Compliant


Figure 13-26 shows a VBR.2 connection policing example, with policing set to 2, and leaky bucket 2 non-compliant. Leaky bucket 2 is shown policing the CLP(0) cell stream for conformance with maximum burst size MBS (as specified by BT), and for compliance with SCR (sustained cell rate). In this example (policing set to 2), CLP tagging is not enabled, so the cells that have exceeded the BT + CDVT limit are discarded. In the example, either the sustained cell rate could have been exceeded for an excessive interval, or a data burst could have exceeded the maximum allowed burst size.


Figure 13-26: VBR.2 Connection, Leaky Bucket 2 Discarding CLP (0) Cells


Figure 13-27 shows a VBR.1 connection policing example, with policing set to 1, and both buckets compliant. Leaky bucket 1 is policing the CLP (0+1) cell stream for conformance with the PCR limit. Leaky bucket 2 is policing the CLP (0+1) cell stream for conformance with CDVT plus maximum burst size MBS (as specified by BT), and for compliance with SCR sustained cell rate.


Figure 13-27: VBR.1 Connection, Policing = 1, with Buckets 1 and 2 Compliant


Figure 13-28 shows a VBR.3 connection policing example, with policing set to 3, and Leaky bucket 2 shown as non-compliant. Leaky bucket 2 is shown policing the CLP(0) cell stream for conformance with maximum burst size MBS (as specified by BT), and for compliance with SCR sustained cell rate. For the policing = 3 selection, CLP tagging is enabled, so the cells that have exceeded the BT + CDVT(0+1) limit are tagged as CLP=1 cells and admitted to the network. In this example, either the sustained cell rate could have been exceeded for an excessive interval, or a data burst could have exceeded the maximum burst size allowed.


Figure 13-28: VBR.3 Connection, Policing = 3, with Bucket 2 non-compliant


ABR Connection Policing

Available Bit Rate (ABR) connections are policed the same as the VBR connections, but in addition use either the ABR Standard with VSVD congestion flow control method or the ForeSight option to take advantage of unused bandwidth when it is available.

UBR Connection Policing

The contract for a unspecified bit rate connection is similar to the ABR connection service for bursty data. However, UBR traffic is delivered only when there is spare bandwidth in the network.

When a connection is added, a VPI.VCI address is assigned, and UPC parameters are configured for the connection. For each cell in an ATM stream, the VPI.VCI addresses are verified and each cell is checked for compliance with the UPC parameters as shown in Figure 13-29.

Leaky Bucket 1

Leaky bucket 1 polices the UBR connection for PCR compliance. When CLP=No (UBR.1), all cells that are compliant with leaky bucket 1 are applied to the network. However, these cells are treated with low priority in the network with % utilization default of 1%.

Leaky Bucket 2

When CLP=Yes (UBR.2), CLP(0) cells that are compliant with leaky bucket 1 are sent to leaky bucket 2. Since SCR=0 for leaky bucket 2, the bucket is essentially always full, and all the CLP(0) cells sent to leaky bucket 2 are therefore tagged with CLP being set to 1. This allows the network to recognize these UBR cells as lower priority cells and available for discard in the event of network congestion.


Figure 13-29: UBR Connection, UPC Overview


LMI and ILMI Parameters

The following is a listing of the LMI and ILMI parameters for the ASI and BXM:

For ILMI information, refer to Table 13-11


Table 13-11: ILMI Parameters
Parameter Description

VPI.VCI

VCCI for ILMI signaling channel equal 0.16

Polling Enabled

Keep-alive polling

Trap Enabled

VCC change of state traps

Polling Interval

Time between GetRequest polls

Error Threshold

Number of failed entries before ILMI link failure is declared.

Event Threshold

Number of successful polls before ILMI link failure is cancelled.

Addr Reg Enab

SVC Address Registration procedures enabled.

.

For the LMI information, refer to Table 13-11.

LMI Parameters

Parameter Description

VPI.VCI

VCCI for LMI signaling channel equal 0.31

Polling Enable

Keep-alive polling

T393

Status Enquiry timeout value

T394

Update Status timeout value

T396

Status Enquiry polling timer

N394

Status Enquiry retry count

N395

Update Status retry count

LMI and ILMI Enhancements on BXM

LMI and ILMI functions for the BXM card are moved to the card from the BCC to localize these functions. These functions support virtual UNIs and trunk ports - a total of 256 sessions on different interfaces (ports, trunks, virtual UNIs) per BXM.

Early Abit Notification with Configurable Timer on ILMI/LMI Interface

The time to reroute connections varies depending on different parameters, such as the number of connections to reroute, reroute bundle size, etc. It is important to notify the CPE if a connection is derouted and fails to transport user data after a specified time interval. However, it is also desirable not to send out Abit = 0, then Abit =1 when a connection is derouted and rerouted quickly. Such notifictions may prematurely trigger the CPE backup facilities causing instabilities in an otherwise stable system.

The early Abit Notification with configurable timer feature provides a way to send Abit = 0 status changes over the LMI interface or to send ILMI traps over the ILMI interface after connections are derouted a certain amount of time. The time period is configurable. The configurable time allows the user the flexibility to synchronize the operation of the primary network and backup utilities, such as dialed backup over the ISDN or PSTN network. The feature can be turned on using the cnfnodeparm command. For further information, refer to the Rel. 9.2.20 Cisco WAN Switching Command Reference.


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Posted: Thu Jul 26 18:03:23 PDT 2001
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