Managing Virtual Channels

This chapter provides information to help you manage the virtual channels (VCs) in your ATM network.

Virtual Channels--Terminology

To work with VCs, you should have a basic understanding of the following terms:

• VC--Any logical connection in the ATM network. Uniquely identified by a virtual path identifier (VPI)/virtual channel identifier (VCI) value, a VC is the basic unit of switching in the ATM network. It is the channel on which ATM cells are transmitted by the switch for the virtual channel connection (VCC).

• Virtual path (VP)--A group of virtual paths defined by a unique VPI value. A VP contains a bundle of VCs.

• VCC--An end-to-end connection made up of VCs that are switched between switch hops. Each hop has a unique VCI associated with it. The two endpoints can use different VCIs for the same VCC. There could be several points within the network at which VCs are switched, and the VCI can change at those endpoints. Thus, a VCC is a concatenation of one or more VC links, with the VCI changing at the VC switch point.

VCCs provide user-to-user, user-to-network, or network-to-network information transfer.

• Virtual path connection (VPC)--An end-to-end connection of intermediate VPs. The connection can exist either between an endpoint and a VP switch point or between two VP switch points. When a VPC passes through one or more VP switch points, the VPI changes at each switch point. Thus, a VPC is a concatenation of one or more VP links.

• VCI--An integer value that identifies a particular VC link for a given VP.

• VPI--An integer value that identifies a particular VP link.

• Virtual path link (VPL)--A group of VP links, identified by a common value VPI, between a point where the VPI value is assigned and the point where that value is translated or terminated.

• Permanent virtual channel (PVC)--A VC that remains allocated for communication between two points. The VC is set up manually through the console or by the network management station (NMS) through SNMP. It can only be torn down on request from the console or NMS.

• Permanent virtual path (PVP)--A VP that remains allocated for communication between two points. The VP is set up manually through the console or by the network management station (NMS) through SNMP. It can only be torn down on request from the console or NMS.

• Switched virtual channel (SVC)--A VC that is set up on demand for communication between two points.

• Switched virtual path (SVP)--A VP that is set up on demand for communication between two points.

• Soft permanent virtual channel (SPVC)--A connection between two ATM end hosts. The connection consists of PVCs between the ATM end hosts and their respective switches and SVCs between the switches.

• Soft permanent virtual path (SPVP)--A connection between two ATM end hosts. The connection consists of PVPs between the ATM end hosts and their respective switches, and SVPs between the switches.

Virtual Channel Management--Overview

AtmDirector provides the following information to help you manage the PVCs and SVCs in your network:

• VC list

• VC selection

• Link utilization

• VC utilization

• Utilization plotting

• VC tracing

• VC display between devices

This information is available from the VC List window (Figure 7-1). Select a link from the topology map. From the AtmDirector main window (Figure 1-1), select Tools>VC List>All Connections, or Tools>VC List>By SVC Addresses.

Listing Virtual Channels

To display a list of VCs in an ATM network, follow these steps:

Step 1 From the fabric topology window (Figure 2-2), click the desired link in the topology map.

Step 2 Select Tools>VC List>All Connections, or select VC List from the toolbar.

The VC List window opens (Figure 7-1), listing all the selected VCs for the VCC.

Figure 7-1: VC List Window

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Note This option has a cascaded menu that provides a finer granularity for the selection of VCs on that link. This is useful when you have several VCs on the desired connections and would like to focus on particular types of VCs.

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Selecting Virtual Channels

You can display VCs based on the choices in the cascaded menu when you select VC List or Tools>VC List. The cascaded menu provides the following choices:

• All Connections--displays all the active connections on the selected link. This is the default selection.

• Between Devices--allows you to select two links and display a list of VCs between them. See "Displaying Virtual Channels Between Devices." This is valid only for SVCs and links connecting ATM hosts.

Checking Link Utilization

You can obtain the percentage of available bandwidth used by a particular link. The link utilization value is provided in the Utilization field, as shown in Figure 7-1.

Checking Virtual Channel Utilization

You can obtain the percentage of available bandwidth for the displayed VCs by clicking Utilization. The utilization values appear in the Transmit (Tx) column and in the Receive (Rx) column. These values represent the percentage of the available bandwidth that the source device (shown in the From Device field) used to transmit and receive data. For example, the connection for VPI 0 and VCI 37 in Figure 7-1 is using 30 percent of the available bandwidth to transmit data and 40 percent of the available bandwidth to receive data.

Plotting Utilization

To plot VC utilization graphically, follow these steps:

Step 1 From the fabric topology window (Figure 2-2), select a link and display the list of VCs on that link.

Step 2 From the VC List window, select a VC.

Step 3 Click Plot Utilization.

The Utilization window opens with the utilization plotted graphically in the form of a trend graph. The Y-axis represents the percentage of utilization, and the X-axis represents the number of samples over time. The utilization graph is updated after each polling interval. The utilization polling interval is configured by selecting Preferences>Options>Polling.

Tracing Virtual Channels

VC tracing provides a topological span of the VC. It also displays the devices and ports involved in the routing of the VC. Once you identify all devices and ports for a VC, you can check them for performance and errors.

Displaying Trace Report in Tabular Form

A trace report for a selected VPI/VCI shows the starting device and port, the ending device and port, and the distance of the link segment to and from the root. The report includes the devices used to connect the two selected devices. Point-to-multipoint connections have an entry in the table for each connection.

You can use this information to identify the route of a particular VC by tracing the VC from one device to another.

To display the VC trace report in ASCII form, follow these steps:

Step 1 Display the desired VCs in your ATM network, as explained in "Listing Virtual Channels."

Step 2 From the VC List window, select a VC.

Step 3 Click Trace Report.

The VC Trace Report window opens (Figure 7-2), showing the selected link and the trace report in tabular form.

Figure 7-2: Trace Report Window

Step 4 Click Close to close the trace report, or Print to print the trace report.

Displaying Trace Report Graphically

To display the VC report graphically, follow these steps:

Step 1 Display the desired VCs in your ATM network, as explained in "Listing Virtual Channels."

Step 2 From the VC List window, select a VC.

Step 3 Click Trace Report.

The VC Trace Report window opens.

Step 4 Click Display.

The trace display is shown on the fabric topology map by highlighting the nodes and links. The VPI and VCI values for the link are also displayed on the highlighted links on the map.

A point-to-point trace is depicted with the trace from the root to the termination. In a point-to-multipoint tracing, the tracing is more involved because at each level the point-to-multipoint branches are explored and recursively exhausted until a termination point is reached. It can also be fairly compute intensive because each participating device needs to be queried for all possible paths.

Clearing the Trace Report

To clear the trace report from the fabric topology map, follow these steps:

Step 1 Select the highlighted trace display on the fabric topology map.

Step 2 Select Admin>Clear Trace.

Displaying Virtual Channels Between Devices

You can display the VCs between any two devices on the topology map. To do so, follow these steps:

Step 1 From the fabric topology window (Figure 2-2), select the source and destination links in the topology map.

Step 2 Select Tools>VC List>Between Devices.

The VC List window opens (Figure 7-1) with a list of the VCs between the two devices.

OAM--Definition

Operation Administration and Maintenance (OAM) services provide capability for fault and performance management at the ATM M-Plane layer. Current OAM implementation in LightStream 1010 includes connectivity verification and alarm surveillance.

Triggering OAM Pings

You can check the connectivity of a VC by triggering an OAM ping. To do so, follow these steps:

Step 1 Start AtmDirector.

The AtmDirector main window opens (Figure 1-1).

Step 2 Hold down the shift key to select both a LightStream 1010 switch and the adjacent link on which the OAM ping needs to be sent.

Step 3 Select Tools>OAM Ping or select OAM Ping from the toolbar.

The OAM Ping window opens (Figure 7-3).

Figure 7-3: OAM Ping Window

The IP address of the LightStream 1010 switch appears in the IP Address field, and the port number appears in the Port field. The list of all active VPIs and VCIs appears in the VPI and VCI fields, respectively.

Step 4 Select the VPI/VCI of the virtual channel on which you want to send the OAM ping from the VPI/VCI pull-down list.

Step 5 Enter, in seconds, in the Timeout field, the amount of time the LightStream 1010 switch must wait before determining that the OAM ping has failed. The default is five seconds.

Step 6 Enter, in seconds, in the Delay field, the amount of time the LightStream 1010 switch must wait before sending the next OAM ping. The default is five seconds.

Step 7 Select either Segment or End-End for the Ping Type.

Step 8 If you selected End-End as the ping type, do the following:

• Select either IP, NSAP Prefix, or None for the Destination Type.

• Enter one of the following in the Destination Address field, depending upon your selection in the Destination Type field:

IP address--a 32-bit IP address.

NSAP Prefix--first 13 bytes of the ATM address.

None--do not enter anything for the destination address.

Step 9 Click Apply.

NSAP--Definition

NSAP is a 20-byte ATM address that consists of 13 bytes of prefix, 6 bytes of End Station Identifier (ESI), and one selector bit.

Displaying OAM Ping Report

To view the results of an OAM ping, trigger an OAM ping. The Ping Report section of the OAM Ping window automatically opens and displays the results. Optionally, you can select the down arrow for Ping Report.

While the Ping Report section of the window is open, the OAM results are dynamically polled and refreshed. You can also delete a ping by selecting that row and clicking Delete. This is useful if you do not want to send out any more cells.

Setting Up Soft Permanent Virtual Channels or Paths

You can set up SPVCs or SPVPs between two end stations in an ATM network. To do so, follow these steps:

Step 1 From the AtmDirector main window, select the source link where the SPVC or SPVP will originate.

Step 2 Select the destination link where the SPVC/SPVP will terminate.

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Note The order of the source and destination selection is important because the configuration information is sent to the source switch. Also, the ATM address of the destination port is displayed based on the destination selection.

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Step 3 Select Tools>SPVC/SPVP Setup, or SPVC/SPVP Setup from the toolbar.

The SPVC/SPVP Setup window opens (Figure 7-4).

Figure 7-4: SPVC/SPVP Setup Window

Step 4 Select either SPVC or SPVP.

The ATM address is automatically filled in, depending on the destination link selected.

Step 5 Select either VCI (for SPVC) or VPI (for SPVP) from the VCI/VPI pull-down list, or enter that value in the VCI/VPI field.

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Note If there are no existing PVCs between the LightStream 1010 switch and the end hosts for both source and destination, enter new values for the VCI or the VPI in the VCI/VPI field. These new values should then be used to set up PVCs from the end hosts to the LightStream 1010 switches.

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Step 6 Enter the interval between connection retries for setting up SPVC/SPVP in the switch in the Slow Retry Interval field.

Step 7 Click Advanced, if you want to specify traffic parameters for the SPVC or SPVP.

The advanced parameters options open (Figure 7-5).

Figure 7-5: SPVC/SPVP Window with the Advanced Parameters Options

Step 8 If you clicked Advanced, do the following:

(a) Set up Usage Parameter Control (UPC) values as follows:

• Select either Pass, Tag, or Drop action. The default is Pass.

• Turn Packet Discard ON or OFF. The default is ON.

  (b) Click Select to specify the transmit traffic parameters. The Traffic Descriptor Table window opens displaying all the currently available traffic descriptors (Figure 7-6).

Figure 7-6: Traffic Descriptor Table Window

(c) Select one of the traffic parameter rows. When you select a row, the values from that row are filled in the fields below, thereby explaining the meaning of each parameter. Refer to Table 7-1 for an explanation of the traffic parameter fields.

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Note If you wish to modify the fields, enter the new values and click Add. A new row of parameters is added to the Traffic Descriptor Table. Click Commit to send the newly created row to the agent. You can now select the newly created row.

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(d) Click Apply. The values are filled in the Traffic Parameter fields in the SPVC/SPVP window.

(e) In the SPVC/SPVP window, select the Rx. Traffic Parameters field to specify the receive traffic parameters.

(f) Repeat Steps 8(c) and 8(d).

(g) Click Close. This closes the Traffic Descriptor Table window.

Step 9 Click Apply in the SPVC/SPVP window.

The configuration request is sent to the source switch. Error messages are displayed in a popup window.

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Note The SPVC or SPVP process starts on the originating LightStream 1010 switch. The SPVC/SPVP Setup window remains open until a successful SNMP-set message is received from the LightStream 1010 switch.

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Table  7-1: Traffic Parameter Fields

Field	Explanation
QoS	Quality of service.
PCR (0+1)	Peak cell rate, in cells per second, for cells with cell loss priority 0 or 1.
PCR (0)	Peak cell rate, in cells per second, for cells with cell loss priority 0.
SCR (0+1)	Sustained cell rate, in cells per second, for cells with cell loss priority 0 or 1.
SCR (0)	Sustained cell rate, in cells per second, for cells with cell loss priority 0.
CDVT	Cell delay variation tolerance in cell-times.
MBS	Maximum burst size in cells.
MCR	Minimum cell rate in cells per second.