Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Network administrators use queueing to manage congestion on a router interface or a permanent virtual circuit (PVC). In an ATM environment, the congestion point might not be the interface itself, but the PVC because of the traffic parameters, including the available bit rate (ABR), the constant bit rate (CBR), and the variable bit rate (VBR) associated with the PVC. For real-time traffic, such as voice flows, to be transmitted in a timely manner, the data rate must not exceed the traffic parameters, or packets might be dropped, thereby affecting voice quality. Fancy queueing such as class-based weighted fair queueing (CBWFQ), low latency queueing (LLQ), or weighted fair queueing (WFQ), can run on the PVC to provide the quality of service (QoS) guarantees for the traffic.

In previous releases, RSVP reservations were not constrained by the traffic parameters of the flow's outbound PVC. As a result, oversubscription could occur when the sum of the RSVP traffic and other traffic exceeded the PVC's capacity.

The RSVP support for ATM/PVCs feature allows RSVP to function with per-PVC queueing for voice-like flows. Specifically, RSVP can install reservations on PVCs defined at the interface and subinterface levels. There is no limit to the number of PVCs that can be configured per interface or subinterface.

• RSVP Bandwidth Allocation and Modular QoS Command Line Interface (CLI)
  
• Benefits of RSVP Support for ATM PVCs
  
• Restrictions
  

• Cisco 3600 series (Cisco 3620, 3640, and 3660)
• Cisco 3810 multiservice access concentrator
• Cisco 7200 series

The network must support the following Cisco IOS features before RSVP support for ATM/PVCs is enabled:

• Resource Reservation Protocol (RSVP)
• Weighted fair queueing (WFQ)

See the following sections for configuration tasks for the RSVP support for ATM/PVCs feature. Each task in the list indicates whether the task is optional or required.

• Creating a PVC (Required)
• Defining ATM QoS Traffic Parameters for a PVC (Required)
• Defining a Policy Map for WFQ (Required)
• Applying a Policy Map to a PVC (Required)
• Enabling RSVP on an Interface (Required)
• Configuring a Path (Optional)
• Configuring a Reservation (Optional)

• Creating a PVC
  
• Defining ATM QoS Traffic Parameters for a PVC
  
• Defining a Policy Map for WFQ
  
• Applying a Policy Map to a PVC
  
• Enabling RSVP on an Interface
  
• Configuring a Path
  
• Configuring a Reservation
  
• Verifying RSVP Support for ATM PVCs Configuration
  

To monitor and maintain RSVP support for ATM/PVCs, use the following commands in EXEC mode:

Router# show ip rsvp installed

Router# show ip rsvp installed detail

Router# show queueing [custom | fair | priority | random-detect [interface serial-number]]

Router# show atm pvc [vpi/vci  |  name  |  interface atm   interface-number]

• Point-to-Point Configuration
  
• Multipoint Configuration
  

AAL --ATM adaptation layer. AAL defines the conversion of user information into cells. AAL1 and AAL2 handle isochronous traffic, such as voice and video; AAL3/4 and AAL5 pertain to data communications through the segmentation and reassembly of packets.

ABR --Available bit rate. A QoS class defined by the ATM Forum for ATM networks. ABR is used for connections that do not require timing relationships between source and destination. ABR provides no guarantees in terms of cell loss or delay, providing only best-effort service. Traffic sources adjust their transmission rate in response to information they receive describing the status of the network and its capability to successfully deliver data.

admission control --The process in which an RSVP reservation is accepted or rejected based on end-to-end available network resources.

Asynchronous Transfer Mode --See ATM.

ATM --Asynchronous Transfer Mode. A cell-based data transfer technique in which channel demand determines packet allocation. This is an international standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.

available bit rate --See ABR.

bandwidth --The difference between the highest and lowest frequencies available for network signals. This term also describes the rated throughput capacity of a given network medium or protocol.

CBR --Constant bit rate. A QoS class defined by the ATM Forum for ATM networks. CBR is used for connections that depend on precise clocking to ensure undistorted delivery.

CBWFQ -- Class-based weighted fair queueing. A queueing mechanism that extends the standard WFQ functionality to provide support for user-defined traffic classes.

Class-based weighted fair queueing -- See CBWFQ .

constant bit rate --See CBR.

flow --A stream of data traveling between two endpoints across a network (for example, from one LAN station to another). Multiple flows can be transmitted on a single circuit.

ILMI --Interim Local Management Interface. Described in the ATM Forum's UNI specification, ILMI allows end users to retrieve basic information, such as status and configuration about virtual connections and addresses, for a particular UNI.

Interim Local Management Interface --See ILMI.

latency --The delay between the time a device receives a packet and the time that the packet is forwarded out the destination port.

MUX --A multiplexing device that combines multiple signals for transmission over a single line. The signals are demultiplexed, or separated, at the receiving end.

payload --The portion of a cell, frame, or packet that contains upper-layer information (data).

permanent virtual circuit --See PVC.

point-to-multipoint connection --One of two fundamental connection types. It is a unidirectional connection in which a single source end system (known as a root node) connects to multiple destination end systems (known as leaves).

point-to-point connection --One of two fundamental connection types. It is a unidirectional or bidirectional connection between two end systems.

PQ --Priority queue. A routing feature in which frames in an output queue are assigned priority based on various characteristics such as packet size and interface type.

priority queue --See PQ.

PVC --Permanent virtual circuit or connection. A virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and teardown in situations where certain virtual circuits must exist all the time.

QoS --Quality of service. A measure of performance for a transmission system that reflects its transmission quality and service availability.

quality of service --See QoS.

reservable bandwidth pool --The amount of bandwidth on a link that features can set aside in order to provide QoS guarantees.

Resource Reservation Protocol --See RSVP.

RSVP --Resource Reservation Protocol. A protocol for reserving network resources to provide quality of service guarantees to application flows.

SNAP --Subnetwork Access Protocol. An Internet protocol that operates between a network entity in the subnetwork and a network entity in the end system. SNAP specifies a standard method of encapsulating IP datagrams and ARP messages on IEEE networks. The SNAP entity in the end system makes use of the services of the subnetwork and performs three key functions: data transfer, connection management, and QoS selection.

subnetwork access protocol --See SNAP.

SVC --Switched virtual circuit or connection. A virtual circuit that is dynamically established on demand and is torn down when transmission is complete. SVCs are used in situations where data transmission is sporadic.

switched virtual circuit --See SVC.

variable bit rate --See VBR.

VBR --Variable bit rate. A QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a real time (RT) class and a non-real time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections where there is no fixed timing relationship between samples, but where a guaranteed QoS is still needed.

VC --Virtual circuit. A logical circuit created to ensure reliable communication between two network devices. A virtual circuit can be either permanent (PVC) or switched (SVC).

virtual circuit --See VC.

Voice over IP --See VoIP.

VoIP --Voice over IP. The ability to carry normal telephony-style voice over an IP-based internet maintaining telephone-like functionality, reliability, and voice quality.

weighted fair queueing --See WFQ.

WFQ --Weighted fair queueing. A queue management algorithm that provides a certain fraction of link bandwidth to each of several queues, based on relative bandwidth applied to each of the queues.