Table of Contents

Specifying Channel Utilization
Specifying Class of Service
Managing Bandwidth
Summary of Commands
cnfchutl
cnfcos
cnfpref
dncon
dspload
dspospace
dsprts
dsptrkutl
prtrts
upcon

Optimizing Traffic Routing
and Bandwidth

To achieve peak network performance, the routing of traffic and use of available bandwidth is configurable. The information used in configuring traffic routing and bandwidth is gathered from historical network trends. The tasks required to optimize the network are: specifying channel utilization, specifying the class of service, and managing bandwidth. These tasks are discussed in the paragraphs that follow.

Specifying Channel Utilization

Use the cnfchutl command to specify the expected utilization of frame relay, data, or voice channel as a percentage of the channel's total capacity. The specified value can be in the range of 0% to 100%. 100% is the default for data and frame relay channels. The default for voice channels is 40%. To display the utilization of a particular trunk, use the dsptrkutl command. This command displays a details on the packets transmitted over the trunk. The user can specify the rate in seconds at which the screen is updated. Use the dspload command to display the load for a specified trunk at a node.

Specifying Class of Service

Use the cnfcos command to specify a class of service (COS) for a frame relay, data, or voice channel. The class of service is a number from 0 to 15 that determines the channel's priority for rerouting in the event of trunk failure. The lower the number, the higher the priority. For each COS number, there is delay of 1 second in rerouting the next COS number. Thus COS 2 channels are rerouted 2 seconds after COS 0 channels. By spreading out the COS numbers to increase the delay interval, one class of channels have a chance to reroute before the next class starts to reroute.

Managing Bandwidth

There are a number of commands that assist in managing bandwidth to achieve satisfactory traffic patterns.

Summary of Commands

Table 11-1 shows the full command name and starting page for each description.

cnfchutl

Informs the system software of the expected utilization rate of connections with traffic-dependent compression algorithms (voice connections with VAD, data connections with DFM, frame relay connections, FastPAD voice connections with ATC-8K, ATC-12K, ATC-16K, or CELP-8K compression). The software load model then takes the full rate for the connection (e.g. 381 packets/second for a voice connection) and modifies it using the specified percentage. The resulting rate is used in calculations for loading trunks. The load model uses these figures instead of estimates calculated from real traffic patterns.

On a FastPAD channel, the compression rate adapts to the congestion level within the network. The configured compression rate indicates the maximum rate for the channel. FastPAD channels detect FAX signals and adapt their rates for FAX transmittal. For the full benefits of the compression algorithms to be used, the default utilizations should be modified after traffic studies have been performed. Also, traffic studies of frame relay connections should be used to determine optimum utilization settings. When calculating loads in a network, the load allocated to a connection is:

  channel utilization x full load for the connection type

For example, with a channel utilization of 50% and a full load of 480 packets per second, the load allocated to a connection is:

  0.50 x 480 pps = 240 pps

For data connections with DFM turned off, for voice connections with VAD turned off, and for all FastPAD data connections, the bandwidth allocated is always the maximum bandwidth for the connection type. In other words, the utilization, although configurable, is ignored for a voice channel without VAD, a data channel without DFM and all FastPAD data channels.

If the cnfchutl command is used to increase the utilization of a connection, the system verifies that the additional bandwidth is available on the connection's current route. If the bandwidth is not available, the system attempts to reroute the connection. If no other route is found, the connection is failed. If the cnfchutl command is used to decrease the utilization of a connection, the system makes the bandwidth available to other connections that require a route. The screen displayed by the cnfchutl command depends upon whether a data channel, voice channel, or frame relay channel is specified. The screen displayed is the same as that for the dspchcnf command.

Full Name

Configure channel utilization

Syntax

cnfchutl <channel(s)> <%_util>

Related Commands

dspchcnf

Attributes

Example 1

cnfchutl 5.1 40

Description

Set utilization on data channel 5.1 at 40%

System Response

Example 2

cnfchutl 14.1 55

Description

Set utilization on voice channel 14.1 at 55%

System Response

Example 3

cnfchutl 8.1.100 60

Description

Set utilization on frame relay channel 8.1.100 at 60%

System Response

cnfcos

Sets the priority for rerouting a connection. When connections have failed (normally due to trunk failures), they are rerouted according to priorities that are set primarily by the COS. The assigned class of service determines the order of rerouting for connections owned by a node. The routing algorithm waits 1 second between each COS increment. Thus, a connection with a COS of 0 is rerouted 2 seconds before a connection with a COS of 2.

If a network carries large volumes of traffic, use fewer COS increments. A larger increment means fewer increments. For example, an increment of 3 would mean COSs of 0, 3, 6, 9, 12, and so on. For a network with little traffic, assign COS values in increments of 2 (COSs of 0, 2, 4, and so on). This ensures that all connections of a given COS reroute before the connections with the next COS start to reroute.

Full Name

Configure class of service for connections

Syntax

cnfcos <group | channel(s)> <cos>

Related Commands

dspcons

Attributes

Example 1

cnfcos 5.1 0

Description

Set the COS for channel 5.1 to 0

System Response

cnfpref

Specifies the preferred route for a connection, connection group, or range of connections. Enter cnfpref only at a node that is an end point of the connection. This command applies only to connections that exist within a domain. Do not attempt to execute cnfpref on connections that exist between domains.

The preferred route for a connection is used when possible. If the preferred route is different from the existing route, the connection automatically moves to the preferred route whenever network conditions allow (for example, when trunks are out of alarm and sufficient bandwidth exists).

Full Name

Configure preferred route for connections

Syntax

cnfpref <channels> <route> [d]

Related Commands

dsprts

Attributes

Example 1

cnfpref 14.1 13/beta 15/gamma d

Description

Select the preferred route for channel 14.1 to be through beta trunk 13 to beta then to gamma trunk 15. For gamma, the "d" in the command specifies that the route is directed.

System Response

Example 2

cnfpref 6.4

Description

Remove the preferred route for channel 6.4

Example 3

cnfpref * +

Description

Designate the current routing of all locally owned connections to be the preferred routing. Using a "-" instead of a "+" in the command would remove the preferred routing designation of all locally owned connections.

System Response

dncon

Deactivates (downs) a connection, bundle of connections, a connection group or all connection in a COS or COS range. The dncon command temporarily removes a connection or connections from the network. This command is useful for temporarily removing voice connections when additional bandwidth is necessary for other types of connections.

Connections can be downed immediately or with courtesy. Even with immediate downing, a prompt appears that requests confirmation. With courtesy downing, the system waits until the connection is onhook before downing the connection. Courtesy downing is possible only if the onhook status has been configured with the cnfvchtp command. Courtesy downing is not available for FastPAD connections because the signalling information between the end points is not visible to the IPX or IGX. The upcon command reactivates the voice connections. The up/down status of the voice connections appears in the "State" column of the dspcons screen. The following describes each status.

Full Name

Down connections

Syntax

dncon {<group | local_chan(s)> | COS <cos_range>} {i | c}

Related Commands

upcon

Attributes

Example 1

dncon 14.1 c

Description

Down connection 14.1 with courtesy

Example 2

dncon 14.1 i

Description

Down connection 14.1 immediately

Example 3

dncon cos 4-8 c

Description

Courtesy down on-hook connections network-wide with COS 4 through 8. This command marks all connections that may be courtesy downed at one time and does not monitor new connections or those that later fit the COS.

Example 4

dncon 3.1.100 i

Description

Immediately down connection 3.1.100.

System Response

Example 5

dncon cos 4-8 i

Description

Immediately down all connections network-wide with COS 4 through 8. This command executes once, so if individual connections are subsequently upped or new connections added in this COS range, they remain up.

Example 6

dncon cos 14.1.3

Description

Down FastPAD voice connection 14.1.3

Example 7

dncon cos 14.1.1.5

Description

Down FastPAD data connection 14.1.1.5

dspload

Displays both the used and available bandwidth for the transmit and receive directions for a trunk. The "transmit" direction is FROM the node specified TO the node at the other end of the trunk. Disabled trunks have their trunk number displayed in dim, reverse video on the screen.

The dspload display reflects the static load model stored by the node. You can use it to determine the available bandwidth for new connections and reroutes. The display does not represent the variations caused by dynamic utilization of the trunks.

Some types of connections suppress packet generation. Examples of connections that suppress packet generation are voice connections using adaptive voice and data connections using DFM. In contrast, frame relay connections may generate additional packets when bandwidth permits.

When you execute dspload at a local node in a structured network, the information reflects any node on the intra-domain lines belonging to the same domain. When you execute dspload at a junction node, the information reflects all inter-domain lines between all junction nodes. To calculate the trunk load, switch software uses the calculated load of the terminating and through-routed connections. The connection type (v, c, a, or d) or baud rate (9.6 Kbps, 56 56 Kbps, and so on) and other factors determine the basic load. The calculated trunk load is also modified by the cnfchutl command for connections that use VAD, DFM, or frame relay.

By using cnftrk, you can reserve a potion of bandwidth on a trunk. Statistical reserve is available for only high priority packets (PCC traffic, for example). The node cannot route connections using this bandwidth. The reserved bandwidth is the sum of the statistical reserve and the SVC bandwidth. The following loading, in packets per second, is calculated for each trunk in each direction:

dspospace

Displays the open space for a connection route.

Full Name

Display open space for a route

Syntax

dspospace <connection | group>

Related Commands

Attributes

Example 1

dspospace 4.1.1

Description

Display the open space for the ATM-farme relay connection 4.1.1. The line interface card is a UFM-8C.

System Response

dsprts

Displays the routes used by all connections at a node. The display shows the trunk numbers and names of all nodes in the path. For FastPAD connections, the displayed connection routes terminate at the IPX or IGX nodes. A blinking trunk indicates a failed line. A tilde trunk (~) indicates a satellite line.

Full Name

Display connection routing

Syntax

dsprts [start group | chan] [nodename]

Related Commands

cnfpref

Attributes

Example 1

dsprts

Description

Display the connection routes.

System Response

dsptrkutl

Displays dynamic utilization information for a specified trunk. The trunk must be upped and added to use this command. Table 11-12 lists the trunk utilization and terminated connection parameters included in the display. The parameter values are updated according to the specified or default interval and the screen remains displayed until the DEL key is depressed. The numbers of disabled trunks appear in dim, reverse video on the screen.

prtrts

Prints the connection routes for channels on the IPX or IGX node. It uses the same syntax and prints the same information as the dsprts command. See the dsprts description for output information.

Full Name

Print connection routes

Syntax

prtrts [start_channel] [dest_nodename]

Related Commands

dsprts

Attributes

Example 1

prtrts

Description

Print connection routes.

System Response

None available as command produces hardcopy.

upcon

Ups (activates) a connection, bundle of connections, group of connections, or all connections with a COS or COS range. When a connection is upped, the system tries to route. If the connection cannot immediately be routed, the connection is failed and generates a major alarm. The State display column in an upcon or dspcons screen has the following meaning:

Full Name

Up a connection

Syntax

upcon {<group | local_chan(s)> | COS <cos_range>}

Related Commands

dncon, dspcon, dspcons

Attributes

Example 1

upcon 5.1

Description

Activate connections 5.1

System Response

Example 2

upcon 9.1-4

Activate a range of connections 9.1-4

Example 3

upcon alpha

Activate a Frame Relay group connection

Example 4

upcon 9

Activate all downed connections with a COS of 9

Example 5

upcon cos 9-12

Activate all downed connections with a COS of 9-12

Posted: Thu Jan 18 13:05:49 PST 2001
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