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This chapter provides information about provisioning ATM services.
ATM is a transfer mode in which the information is organized into cells. It is asynchronous in that the recurrence of cells containing information from an individual user is not necessarily periodic.
ATM is a connection-oriented service in that it requires that a virtual connection be established between the source and destination endpoints before traffic can be transmitted. The virtual connection is established as a path of links between intermediate nodes in the network. This path can be established through permanent connections (PVCs) or signalled connections (SPVCs and SVCs).
Permanent connections are logical connections between two or more endpoints. They are typically used for virtual connections that are permanent or used for a long time (for example, PVCs).
Signalled connections (SPVCs and SVCs) use signaling to set up and take down connections. The network sets up a virtual connection each time a remote location is addressed. It is a temporary connection that only requires network resources while in use. CPC supports SPVCs.
When you create an ATM service you convey the bandwidth and performance requirements through a traffic contract which includes the following components:
However, you can not specify values for all of these attributes. Once you have selected a service class you specify the remaining attributes as needed. Table 12-1 lists the options that you must specify for each service class.
There are five service classes for ATM traffic:
The constant bit rate service category is designed to support real-time applications like video and audio. CBR is used by connections that require a fixed amount of bandwidth, characterized by a PCR value that is continuously available during the connection lifetime. CBR has strict delay requirements and requires low cell loss.
The variable bit rate service class is designed to support bursty traffic (either video or frame relay traffic). It is characterized by sustained cell rate (SCR) and peak cell rate (PCR). SCR is measured over a defined period and represents the average transmission rate. PCR represents the minimum spacing of cells which represent the peak bandwidth required.
Real-time variable bit rate is intended for time-sensitive applications. Sources are expected to transmit at a rate that varies with time. rt-VBR has strict end-to-end delay requirements.
Non real-time variable bit rate is intended for applications that have bursty traffic characteristics and do not have tight constraints on delay and delay variation. nrt-VBR can be buffered because it does not guarantee any delay bounds.
The available bit rate service class is intended for sources that have the ability to reduce or increase their information rate if the network requires them to do so. This enables them to exploit the changes in the ATM layer traffic characteristics (for example, bandwidth availability) subsequent to connection establishment. ABR guarantees only a minimum amount of bandwidth and may be limited to a specified peak emission rate.
The unspecified bit rate service class is a "best effort" service intended for non-critical applications, which do not require tightly constrained delay and delay variation or a specified quality of service. UBR sources are expected to transmit non-continuous bursts of cells. UBR shares the remaining bandwidth without any specific feedback mechanisms. UBR service does not specify traffic related service guarantees. Nor does it include the notion of a per-connection negotiated bandwidth.
You have the option of not selecting a QoS when creating a service and instead indicating that it is profiled in the Service element profile. This allows you to use multiple networks with different QoS. For example, if you can create an ATM service that is travelling through Network A (which supports CBR) to Network B (which supports rt-VBR). To create this service with hybrid QoS, set the QoS field to SE-PROFILED and select one of the Service element profile names (for example, Gold ATM Service). This will allow the appropriate QoS values to be taken from the appropriate Service element profiles. At the network level, Network A's Gold ATM Service may be mapped to CBR with a PCR of 100 while Network B's Gold ATM Service may be mapped to rt-VBR with an SCR of 50.
There are three quality of service parameters used to measure the performance of the network for a given connection. These can be negotiated between end-systems and networks as part of the traffic contract. They are:
These can be negotiated between end-systems and networks as part of the traffic contract.
Cell loss ratio (CLR) is calculated as loss that occurs due to an overrun of the buffering resources. This happens when bursts arrive simultaneously from different connections.
The cell loss ratio QoS parameter is defined on a per connection basis as the number of lost cells divided by the total number of transmitted cells. The number of lost cells includes cells not reaching their destination, cells that are received with invalid headers, and cells for which the content has been corrupted by errors. The total number of transmitted cells is the total number of conforming cells transmitted over a given time period.
Cell transfer delay is the time elapsed between departure time of a cell from the generating endsystem and the arrival time of the cell at the destination. A maximum CTD is set and cells with delays that exceed this maximum are assumed lost or unusable.
Cell delay variation (CDV) represents the difference between the maximum CTD and the minimum CTD. This metric allows the evaluation of the maximum possible delay between two consecutive cells that were deterministically spaced. It also allows the estimation of worst possible amount of clumping due to queueing.
Traffic descriptors attempt to capture the cell inter-arrival pattern for resource allocation. Source traffic descriptors for an ATM connection include one or more of the following:
Each connection has two sets of traffic descriptors--one set for the a-z direction and another for the z-a direction. Traffic descriptors are conveyed at connection setup but may vary depending on the connection's service class.
Source traffic descriptors can only be specified for cells with a CLP=0 or CLP=0+1.
The Connection Traffic Descriptor is equal to the source traffic descriptor plus the CDVT which verifies the conformance of the traffic to the source traffic descriptors.
Peak cell rate is expressed in cells per second. Except for the ABR service class, PCR is always defined for the CLP=0+1 cell flow. With ABR, PCR is defined only on CLP=0 cell flow.
Sustained cell rate is the upper bound on the average transmission rate of the conforming cells of an ATM connection over time scales that are long relative to those for which a PCR is defined. Only connections using the VBR service class can specify a SCR.
SCR is always specified with a corresponding MBS. MBS represents the burstiness factor of the connection. It indicates the maximum number of cells that can be transmitted by the source at PCR while still complying with the negotiated SCR. SCR is defined for a CLP=0+1 or CLP=0 cell flow.
Minimum cell rate is the minimum allocated bandwidth for a connection. It does not describe the behavior of traffic. The connection can send traffic at a higher rate than MCR. It is used for bandwidth on demand services (like ABR) to ensure that a connection does not starve when there is not more available bandwidth.
The service categories are further defined by network traffic parameters. When creating, modifying, or deleting an ATM service you should select the traffic descriptor type from those specified for each QoS.
| QoS Class | Traffic Descriptor Type | Traffic Descriptor | Description |
|---|---|---|---|
CBR | CBR.1 | PCR CLP=0 PCR CLP=0+1 Tagging | Traffic conformance is based on the PCR of both the CLP=0 and CLP=0+1 cell streams with Tagging enabled. |
CBR.2 | PCR CLP=0 PCR CLP=0+1 No tagging | Traffic conformance is based on the PCR of both the CLP=0 and CLP=0+1 cell streams with no tagging. | |
CBR.3 | PCR CLP=0+1 | Traffic conformance is based only on the PCR of the CLP=0+1 aggregate cell stream with no best effort. | |
UBR | UBR.1 | PCR CLP=0+1 | Traffic conformance is based only on the PCR of the CLP=0+1 aggregate cell stream with no best effort. |
UBR.2 | Best effort | No traffic conformance is applies to this cell stream. A "best effort" attempt is made to deliver all traffic, but there is no guarantee the switch will not drop cells due to congestion. | |
UBR.3 | Best effort, Tagging | Traffic conformance is only applied to tag all cells as CLP1. A "best effort" attempt is made to deliver all traffic, but there is no guarantee the switch will not drop cells due to congestion. | |
ABR | ABR.1 | PCR CLP=0 MCR CLP=0 | Traffic conformance is based on PCR of the CLP=0 cell stream, as well as the MCR of the CLP=0 cell stream with no |
rt-VBR | VBR.1 | PCR CLP=0+1 SCR CLP=0 MBS CLP=0 Tagging | Traffic conformance is based on the PCR of the CLP=0+1 aggregate cell stream, as well as the SCR and MBS of the CLP=0 cell stream with tagging enabled. |
VBR.2 | PCR CLP=0+1 SCR CLP=0 MBS CLP=0 No tagging | Traffic conformance is based on the PCR of the CLP=0+1 aggregate cell stream, as well as the SCR and MBS of the CLP=0 cell stream with no tagging. | |
VBR.3 | PCR CLP=0+1 SCR CLP=0+1 MBS CLP=0+1 | Traffic conformance is based on the PCR, SCR, and MBS of the CLP=0+1 cell stream with no tagging. |
The following ATM service requirements apply only to ATM SPVC connections. These requirements appear only on the ATM SPVC Service Subset Viewer.
The Z select type specifies whether or not CPC will use the values in the Z VPI and Z VCI fields when attempting to provision the requested SPVC. If you select Required, CPC will use the values. If you select Any, CPC will use any available VPI or VCI.
The retry interval is the amount of time (in seconds) that CPC will wait after attempting, unsuccessfully, to provision a requested SPVC before attempting to provision the SPVC again.
The retry alarm threshold is the number of times CPC will attempt, unsuccessfully, to provision a requested SPVC before raising an alarm.
The retry limit is the number times CPC will attempt, unsuccessfully, to provision a requested SPVC.
The failure timeout is the amount of time (in seconds) that the SPVC will remain connected without traffic before the connection is destroyed and re-created.
You can create Service object profiles for the various types of ATM services. When you use a Service object profile CPC uses the values that you have specified to create the service you are creating. Profiles provide an easy way to store information about the various types of ATM services that you will be provisioning.
Figure 12-1 shows the ATM Service Profile Object Viewer.
Figure 12-2 shows the ATM SPVC Service Profile Object Viewer.
The attributes for which you can provide values in the ATM Service object profile are outlined in Table 12-1 below. Not all of these attributes need to be specified for every type of service, refer to Table 12-1 for a list.
| Attribute | Description | Acceptable Values | Default Value |
|---|---|---|---|
SE Profile Name | This is the name of the service element profile for the equipment module. Note that if you do not specify a name here the default service element profile for each of the networks your service is traversing will be used. |
| Default |
Circuit Type1 | Select either a virtual circuit or a virtual path. | VC or VP | VC |
SPVC Type2 | Select either a virtual circuit or a virtual path. | VC or VP | VP |
Service Class | This is the ATM service category. | one of CBR, ABR, UBR, rt-VBR, | CBR |
Recovery | This is the recovery priority for NNI resiliency. | 0...n where 0 is infinitely low priority, 1 has the highest priority, and n is lower. | 5 |
SPVC Failure Timeout2 | This is the amount of time (in seconds) that the SPVC will remain connected without traffic before the connection is destroyed and re-created. | integer |
|
SCR (cells/s) | This is the sustainable cell rate, which is the maximum average cell transmission rate that is allowed over a given period of time on a given circuit. It allows the network to allocate sufficient resources for guaranteeing that network performance objectives are met. |
| 0 |
PCR (cells/s) | This is the peak cell rate, which is the maximum allowed cell transmission rate (expressed in cells per second). It defines the shortest time period between cells and provides the highest guarantee that network performance objectives (based on cell loss ratio) will be met. |
| 0 |
MCR (cells/s) | This is the minimum cell rate, which is the minimum allocated bandwidth for a connection. |
| 0 |
MBS | Maximum burst size is the maximum number of cells that can be received at the PCR. This allows a burst of cells to arrive at a rate higher than the SCR. If the burst is larger than anticipated, the additional cells are either tagged or dropped. This parameters applies only to VBR traffic. |
| 0 |
CDVT | Cell Delay Variation Tolerance establishes the time scale over which the PCR is policed. This is set to allow for jitter (CDV). |
| 3000 |
CDV (Microseconds) | Cell delay variation (CDV) represents the difference between the maximum CTD and the minimum CTD. |
| 75 |
Max CTD (Microseconds) | Cell transfer delay is the time elapsed between departure time of a cell from the generating endsystem and the arrival time at the destination. |
| 0 |
CLR | The cell loss ratio QoS parameter is defined on a per connection basis as the number of lost cells divided by the total number of transmitted cells. |
| 10 |
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Application folder to highlight it.
Step 4 Click the ATM Service Profile folder to highlight it if you wish to create an ATM PVC service profile. Or, click the ATM SPVC Service Profile folder to highlight it if you wish to create an ATM SPVC service profile.
Step 5 Click the Object Viewer button on the toolbar.
Step 6 Click to highlight an empty cell in the Service Profile Subset Viewer. Enter the required attribute values and specify a name for a new Service Profile.
Step 7 Save the profile by clicking the save button on the toolbar.
Step 8 Apply the Transaction by clicking on the apply button on the toolbar.
Step 2 Double-click the ATM Service Application folder to open it.
Step 3 Click the ATM Service Profile folder to highlight it if you wish to modify an ATM PVC service profile. Or, click the SPVC Service Profile folder to highlight it if you wish to create an ATM SPVC service profile.
Step 4 Click the Object Viewer button on the toolbar.
Step 5 Click the cell of the attribute that you want to modify, and enter the new value.
Step 6 Save the modified profile by clicking the save button on the toolbar.
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Application folder to open it.
Step 4 Double-click a type of profile that contains a specific profile that you want to delete (i.e. ATM Service Profile).
Step 5 Click the specific profile and click the delete button on the toolbar.
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Application folder to open it.
Step 4 Click the ATM Service folder to highlight it if you wish to create an ATM PVC service. Or, click the ATM SPVC Service folder to highlight it if you wish to create an ATM SPVC service.
Step 5 Click the Object Viewer button on the toolbar.
Step 6 Click to highlight an empty cell in the ATM Service Object Viewer. Enter the required attribute values and specify a name for a new Service. The required values are:
Step 7 Save the service by clicking the save button on the toolbar.
Step 8 Apply the Transaction by clicking the apply button on the toolbar.
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Application folder to open it.
Step 4 Double-click the ATM Service folder to highlight it if you wish to delete an ATM PVC service or double-click the ATM SPVC Service Profile folder if you wish to delete an ATM SPVC service.
Step 5 Click the specific Service object to highlight it.
Step 6 Click the delete button on the toolbar.
Step 7 Apply the Transaction by clicking the apply button on the toolbar.
Figure 12-3 shows the ATM SPVC Service Object Viewer.
Figure 12-4 shows the ATM Service Object Viewer.
CPC supports the creation of ATM Virtual Links, CPC can thread a path between Service Object endpoints using ATM Virtual Links in addition to NNI Links, Similar to an NNI Link, the Virtual Link connects two distinct networks. The connection is made by at ATM Virtual Link Service Object, and can then be treated as fabric by other Services.
There are two types of ATM Virtual Links: An ATM Virtual Link of type VC can be used to multiplex other protocols (such as 802.x using [RFC 1483]: an ATM Virtual Link of type VC is a Virtual Path which can be used to multiplex Virtual Channels (VCs). An ATM Virtual Link of type VC or VP may be either Managed (endpoints are on distinct NNI Links) or Unmanaged (endpoints are not on any NNI Links).
To find more information on creating ATM Virtual Links, through FTI, refer to the Cisco Provisioning Center Programmer's Guide.
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Application folder to open it.
Step 4 Double-click the Virtual Link Service Profile folder to highlight it.
Step 5 Click the Object Viewer button on the toolbar.
Step 6 Click to highlight an empty cell in the Service Profile Subset Viewer. Enter the required attribute values and specify a name for a new Service Profile.
Step 7 Save the profile by clicking the save button on the toolbar.
Step 8 Apply the Transaction by clicking the apply button on the toolbar.
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Application folder to open it.
Step 4 Double-click the Virtual Link Service folder to highlight it.
Step 5 Click the specific Object Viewer object to highlight it.
Step 6 Click to highlight an empty cell in the Virtual Link Service Object Viewer. Enter the required attribute values and specify a name for a new link. The required attribute values are described under "Creating an ATM Service."
Step 7 Save the link by clicking the save button on the toolbar.
Step 8 Apply the Transaction by clicking the apply button on the toolbar.
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Pack folder to open it.
Step 4 Double-click the Virtual Link Service folder to highlight it.
Step 5 Click the Subset Viewer button on the toolbar.
Step 6 Click the get list button on the toolbar.
Step 7 Click the link you wish to modify to highlight it.
Step 8 Make the required modifications to the attribute values and save the link by clicking the save button on the toolbar.
Step 9 Apply the Transaction by clicking the apply button on the toolbar.
 |
Note You cannot modify an ATM VC Virtual Link or an ATM VP Virtual Link after it has been created. |
Step 2 Double-click the Service Application folder to open it.
Step 3 Double-click the ATM Service Pack folder to open it.
Step 4 Double-click the Virtual Link Service folder to highlight it.
Step 5 Click the Object Viewer button on the toolbar.
Step 6 Click the link you wish to delete to highlight it.
Step 7 Click the delete button on the toolbar.
Step 8 Apply the Transaction by clicking the apply button to the toolbar.
Figure 12-5 shows the ATM Virtual Link Profile Object Viewer.
Figure 12-6 shows the ATM Virtual Link Service Object Viewer.
Posted: Thu Aug 3 16:41:26 PDT 2000
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