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This feature module describes the PPP over ATM SVCs feature. It includes information on the benefits of the new feature, supported platforms, related documents, and more.
This document includes the following sections:
The PPP over ATM SVCs feature provides support for PPP on ATM switched virtual circuits (SVCs). Before this feature, PPP was supported over ATM permanent virtual circuits (PVCs) only.
With this new feature, each time an end user initiates a connection to a Network Access Provider (NAP) or Network Service Provider (NSP), an ATM SVC is established using a configured ATM address. A PPP session is then established over the SVC. By using PPP, the NAPs and NSPs can authenticate users and provide suitable access to the various services being offered. Whereas PVCs require that services and destination addresses be predetermined, the PPP over ATM SVCs feature allows users to choose services and the quality of those services dynamically on the basis of destination address.
Figure 1 shows a typical network topology for PPP over ATM SVCs terminating at an NAP.
Figure 2 shows a typical network topology of PPP over ATM SVCs terminating at an NSP.
The PPP over ATM SVCs feature works by associating each PPP session with a virtual-access interface. Each virtual-access interface is associated with an SVC. The SVCs use static maps that hold information about the encapsulation type and virtual template number. A single static map can accept multiple PPP over ATM SVC calls.
More Efficient DSL Provisioning
As the demand for digital subscriber line (DSL) services increases, setting up an ATM PVC between each subscriber and NAP or NSP becomes a cumbersome and inefficient means of deployment. The PPP over ATM SVCs feature reduces the cost of provisioning and enhances manageability of DSL services for NAPs and NSPs by enabling DSL service to be established on SVCs in addition to PVCs.
Flexibility
The PPP over ATM SVCs feature provides flexibility by allowing end users to select services and QOS dynamically on the basis of destination address.
The PPP over ATM SVCs feature does not support PPP over ATM SVC dialout mode.
Standards
No new or modified standards are supported by this feature.
MIBs
No new or modified MIBs are supported by this feature.
For descriptions of supported MIBs and how to use MIBs, see the Cisco MIB web site on Cisco Connection Online (CCO) at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
RFCs
RFC 2364, PPP over AAL5.
See the following sections for configuration tasks for the PPP over ATM SVCs feature. Each task in the list is identified as optional or required.
To configure PPP over an ATM SVC, use the following commands beginning in global configuration mode:
| Command | Purpose | |
|---|---|---|
Step 1 | interface atm slot/0 or interface atm slot/port-adaptor/0 or interface atm number or interface atm slot/port | Specifies an ATM interface and enters interface configuration mode. To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation. |
Step 2 | svc [name] | Creates an ATM SVC. |
Step 3 | encapsulation aal5auto | Specifies encapsulation auto, which allows the SVC to use either aal5snap or aal5mux encapsulation types. |
Step 4 | protocol ppp virtual-template | Specifies that PPP is established over the ATM SVC using the configuration from the specified virtual template. |
Step 5 | max vc | Specifies the maximum number of SVCs that can be established using the current configuration. |
Step 6 | max bandwidth | Specifies the total amount of bandwidth available to all SVCs in the current configuration. |
To set the network service access point (NSAP) address for the ATM interface, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
atm nsap-address nsap-address | Sets the NSAP address for an ATM interface. |
When configuring an SVC, you must use the atm nsap-address command to define the source NSAP address. It identifies a particular port on the ATM network and must be unique across the network.
To create and configure a virtual template, use the following commands beginning in global configuration mode:
| Command | Purpose | |
|---|---|---|
Step 1 | interface virtual-template number | Creates a virtual template and enters interface configuration mode. |
Step 2 | ip unnumbered type number | (Optional) Enables IP on the interface without assigning a specific IP address. |
Other optional configuration commands can be added to the virtual template configuration. For example, you can enable the PPP authentication on the virtual template using the pppauthenticationchap command. Refer to the "Configuring Virtual Template Interfaces" chapter in the Cisco IOS Dial Services Configuration Guide: Network Services for additional information about configuring the virtual template.
To verify the configuration of PPP over ATM SVCs, use the following privileged EXEC command:
| Command | Purpose |
|---|---|
Router#show atm svc ppp | Displays information about each SVC configured for PPP over ATM. |
Use the command listed in the section "Verifying PPP over ATM SVCs" to monitor the PPP over ATM SVCs feature.
This section provides an example of the configuration of PPP over an ATM SVC.
In the following example, ATM interface 2/0/0 is configured to accept ATM SVC calls whose called party address is 47.00918100000000400B0A2501.0060837B4740.00. The same ATM NSAP address can be configured on other physical ATM interfaces as well. When a PPP session is established, a virtual access interface is created and cloned with the configuration from virtual template 1. All PPP sessions established on this ATM interface will use the ip address of loopback interface 0. A maximum of 100 SVCs can be established using this configuration. SVCs established using this configuration cannot take up more than 50 Mbps in total bandwidth.
interface ATM 2/0/0 svc anna encapsulation aal5auto protocol ppp virtual-template 1 max vc 100 max bandwidth 50000 atm nsap 47.00918100000000400B0A2501.0060837B4740.00 ! interface virtual-template 1 ip unnumbered loopback 0 ! interface loopback 0 ip address 10.7.1.1 255.255.255.0
This section documents the following new and modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.1 command reference.
To configure the ATM adaptation layer (AAL) and encapsulation type for an ATM permanent virtual circuit (PVC), switched virtual circuit (SVC), virtual circuit (VC) class, or VC bundle, use the encapsulation aal5 command in the appropriate command mode. To remove an encapsulation from a PVC, SVC, VC class, or VC bundle, use the no form of this command.
encapsulation aal5encap [virtual-template number] |
Note To configure Integrated Local Management Interface (ILMI), QSAAL, or Switched Multimegabit Data Service (SMDS) encapsulations for an ATM PVC, use the pvc command. |
Syntax Description
encap AAL and encapsulation type. When mux is specified, a protocol is required. Possible values for the encap argument are as follows: auto—For PPP over ATM SVCs only. The auto keyword enables an ATM SVC to use either aal5snap or aal5mux encapsulation. ciscoppp—For Cisco Point-to-Point Protocol (PPP) over ATM. Supported on ATM PVCs only. mux apollo—For a multiplex (MUX)-type VC using the Apollo protocol. mux appletalk—For a MUX-type VC using the AppleTalk mux decnet—For a MUX-type VC using the DECnet protocol. mux frame—For a MUX-type VC for Frame Relay-ATM Internetworking on the Cisco MC3810 router. mux frame-relay—For a MUX-type virtual circuit for Frame Relay-ATM Network Interworking (FRF.5) on the Cisco MC3810. mux fr-atm-srv—For a MUX-type virtual circuit for Frame Relay-ATM Service Interworking (FRF.8) on the Cisco MC3810. mux ip—For a MUX-type VC using the IP protocol. mux ipx—For a MUX-type VC using the IPX mux ppp—For a MUX-type virtual circuit running IETF-compliant PPP over ATM. You must use the virtual-template number argument to identify the virtual template. (If you need to establish a virtual template, use the interface virtual-template command.) The mux ppp keyword applies to ATM PVCs only. mux vines—For a MUX-type VC using the VINES protocol. mux voice—For a MUX-type VC for Voice over ATM on the Cisco MC3810 router.
protocol.
protocol.
Syntax Description
mux xns—For a MUX-type VC using the XNS nlpid—Allows ATM interfaces to interoperate with High-Speed Serial Interfaces (HSSIs) that are using an ATM data service unit (ADSU) and running ATM-Data Exchange Interface (DXI). Supported on ATM PVCs only. snap—The only encapsulation supported for Inverse ARP. virtual-template number (Optional) (This argument is required for ciscoppp encapsulation only.) Specifies the number used to identify the virtual template.
protocol.
Logical Link Control/Subnetwork Access Protocol (LLC/SNAP) precedes the protocol datagram.
Defaults
The global default encapsulation is snap. See the "Usage Guidelines" section for other default characteristics.
Command Modes
Interface-ATM-VC configuration (for an ATM PVC or SVC)
VC-class configuration (for a VC class)
Bundle configuration (for a VC bundle)
Command History
11.3 T This command was introduced. 12(0)3T 12.0(7)T 12.1(3)T The auto keyword was added to provide encapsulation configuration for PPP over ATM SVCs.
Release
Modification
Usage Guidelines
A VC bundle can have only one encapsulation configured for it: either snap or mux.
Use one of the mux encapsulation options to dedicate the specified PVC to a single protocol; use the snap encapsulation option to multiplex two or more protocols over the same PVC. Whether you select mux or snap encapsulation might depend on practical considerations, such as the type of network and the pricing offered by the network. If the pricing of the network depends on the number of PVCs set up, snap might be the appropriate choice. If pricing depends on the number of bytes transmitted, mux might be the appropriate choice because it has slightly less overhead.
To use this command to configure a VC bundle, first enter the bundle subinterface configuration command to create a new bundle or modify an existing one and to enter bundle configuration mode.
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Note When a VC is a member of a VC bundle, configuration using the encapsulation aal5 command in VC class mode no longer applies to the VC. Bundle configuration takes precedence. |
When configuring Cisco PPP over ATM, specify the ciscoppp encapsulation for the encap argument and specify the virtual template number.
It is possible to implicitly create a virtual template when configuring Cisco PPP over ATM. In other words, if the parameters of the virtual template are not explicitly defined before you configure the ATM PVC, the PPP interface will be brought up using default values from the virtual template identified. However, some parameters (such as an IP address) take effect only if they are specified before the PPP interface comes up. Therefore, we recommend that you explicitly create and configure the virtual template before configuring the ATM PVC to ensure such parameters take effect.
If you specify virtual template parameters after the ATM PVC is configured, you should enter a shutdown command followed by a no shutdown command on the ATM subinterface to restart the interface, causing the newly configured parameters (such as an IP address) to take effect.
If the encapsulation aal5 command is not explicitly configured on an ATM PVC, SVC, or VC bundle, the VC inherits the following default configuration (listed in order of precedence from lowest to highest):
Examples
The following example configures an ATM SVC called "chicago" with encapsulation "auto." Encapsulation auto enables the SVC to use PPP and either aal5snap or aal5mux encapsulation.
svc chicago encapsulation aal5auto
The following example configures an ATM PVC with VPI 0 and VCI 33 for a MUX-type encapsulation using IP:
pvc 0/33
encapsulation aal5mux ip
The following example configures a bundle called chicago for aal5snap encapsulation:
bundle chicago
encapsulation aal5snap
Related Commands
broadcast Configures broadcast packet duplication and transmission for an ATM VC class, PVC, SVC, or VC bundle. class-int Assigns a VC class to an ATM main interface or subinterface. class-vc Assigns a VC class to an ATM PVC, SVC, or VC bundle member. inarp Configures the Inverse ARP time period for an ATM PVC, VC class, or VC bundle. oam-bundle Enables end-to-end F5 OAM loopback cell generation and OAM1 management for a virtual circuit class that can be applied to a virtual circuit bundle. oam retry Configures parameters related to OAM management for an ATM PVC, SVC, VC class, or VC bundle. protocol (ATM) Configures a static map for an ATM PVC, SVC, VC class, or VC bundle. Enables Inverse ARP or Inverse ARP broadcasts on an ATM PVC by configuring Inverse ARP directly on the PVC, on the VC bundle, or in a VC class (applies to IP and IPX protocols only).
Command
Description
1OAM = Operation, administration, and maintenance.
To specify the total amount of outgoing bandwidth available to SVCs in the current configuration, use the max bandwidth interface-ATM-VC command. To remove the current bandwidth setting, use the no form of this command.
max bandwidth kbps
Syntax Description
kbps Total amount of outgoing bandwidth in kilobits per second available to all SVCs in the current configuration.
Defaults
No default behavior or values.
Command Modes
Interface-ATM-VC configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
Only the guaranteed cell rate of an SVC is counted toward the maximum bandwidth.
Examples
In following example, an SVC called "anna" on ATM interface 2/0/0 is configured using the max bandwidth command to allow a maximum of 50 Mbps of bandwidth to be used by all of the SVCs in this configuration:
interface ATM 2/0/0 svc anna encapsulation aal5auto protocol ppp virtual-template 1 max bandwidth 50000
Related Commands
max vc Specifies the maximum number of SVCs that can be established using the current configuration svc Creates an ATM SVC.
Command
Description
To specify the maximum number of SVCs that can be established using the current configuration, use the max vc interface-ATM-VC command. To restore the maximum number of SVCs to the default setting, use the no form of this command.
max vc number
Syntax Description
number Maximum number of SVCs to be established using the current SVC configuration.
Defaults
4096 SVCs.
Command Modes
Interface-ATM-VC configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
In following example, an SVC called "anna" on ATM interface 2/0/0 is configured using the max vc command to allow a maximum of 100 SVCs to be established using this configuration:
interface ATM 2/0/0 svc anna encapsulation aal5auto protocol ppp virtual-template 1 max vc 100
Related Commands
max bandwidth Specifies the maximum amount of bandwidth available to all SVCs in the current configuration. svc Creates an ATM SVC.
Command
Description
To display information about each SVC configured for PPP over ATM, use the show atm svc ppp privileged EXEC command.
show atm svc pppSyntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following is sample output for the show atm svc ppp command:
Router# show atm svc ppp ATM Int. VCD/Name VPI VCI Type VCSt VA VASt 2/0.1 10 0 60 SVC UP 1 UP
Table 1 describes the fields shown in the displays.
| Field | Description |
|---|---|
ATM Int. | Interface on which the SVC is configured. |
VCD/Name | Virtual circuit descriptor (VCD) or name associated with the SVC. |
VPI | Virtual path identifier. |
VCI | Virtual channel identifier. |
Type | Type of virtual circuit. |
VCSt | Virtual circuit state. |
VA | Virtual access interface number. |
VASt | Virtual access interface state. |
To create an ATM switched virtual circuit (SVC) and specify the destination network service access point (NSAP) address on a main interface or subinterface, use the svc interface configuration command. To disable the SVC, use the no form of this command.
svc [name] [nsap address]
Syntax Description
name (Optional) The name of the SVC and map. The name can be up to 16 characters long. nsap address (Optional) The destination ATM NSAP address. Must be exactly 40 hexadecimal digits long and in the correct format. See the "Usage Guidelines" section.
Defaults
No NSAP address is defined.
Command Modes
Interface configuration
Command History
11.3 This command was introduced. 12.1(3)T This command was modified to allow an SVC to be created without a specific NSAP address associated with it.
Release
Modification
Usage Guidelines
Once you specify a name for an SVC, you can reenter the interface-ATM-VC configuration mode by simply entering svc name. You can remove an NSAP address and any associated parameters by entering no svc name or no svc nsap address.
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Note After configuring the parameters for an ATM SVC, you must exit the interface-ATM-VC configuration mode in order to enable the SVC settings. |
Creating an SVC without a specific NSAP address will allow a router to accept calls from any ATM address, and allow multiple VCs to be set up using the same configuration.
Examples
The following example creates an SVC called "chicago" on ATM interface 2/0/0:
interface atm 2/0/0 svc chicago
The following example creates an SVC with the name "lion" and specifies the 40-digit hexadecimal destination ATM NSAP address:
svc lion nsap 47.0091.81.000000.0040.0B0A.2501.ABC1.3333.3333.05
ATM—Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays.
DSL—Digital subscriber line. Public network technology that delivers high bandwidth over conventional copper wiring at limited distances.
NSAP—Network service access point. Network addresses, as specified by ISO. An NSAP is the point at which OSI Network Service is made available to a transport layer (Layer 4) entry.
PPP—Point-to-point protocol. Successor to SLIP that provides router-to-router and host-to-network connections over synchronous and asynchronous circuits.
PVC—Permanent virtual circuit. Virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and teardown in situations in which certain virtual circuits must exist all the time.
SVC—Switched virtual circuit. Virtual circuit that is dynamically established on demand and is torn down when transmission is complete.
Posted: Tue Sep 19 18:05:51 PDT 2000
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