Configuring the Transmit Connect Speed Calculation Method

You can configure the method that the router uses to calculate the transmit connect speed of the subscriber’s access interface for a tunneled L2TP session. L2TP reports the transmit connect speed in L2TP Transmit (TX) Speed AVP 24. During the establishment of an L2TP tunnel session, the LAC sends AVP 24 to the LNS to convey the transmit speed of the subscriber’s access interface.

You can configure the calculation method for the transmit connect speed reported in L2TP Transmit (TX) Speed AVP 24 in any of the following ways. The first three methods—AAA domain maps, AAA tunnel groups, and RADIUS—are mutually exclusive.

AAA domain maps—Use the tx-connect-speed-method command from Domain Map Tunnel Configuration mode. For instructions, see Using AAA Domain Maps to Configure the Transmit Connect Speed Calculation Method.
AAA tunnel groups—Use the tx-connect-speed-method command from Tunnel Group Tunnel Configuration mode. For instructions, see Using AAA Tunnel Groups to Configure the Transmit Connect Speed Calculation Method .
AAA default tunnel parameters—Use the aaa tunnel tx-connect-speed-method command from Global Configuration mode. The router uses the calculation method specified with this command if the tunnel attributes returned from an AAA domain map, an AAA tunnel group, or a RADIUS authentication server do not include the transmit connect speed calculation method. For instructions, see Using AAA Default Tunnel Parameters to Configure the Transmit Connect Speed Calculation Method.
RADIUS Include the Tunnel-Tx-Speed-Method RADIUS attribute (Juniper Networks VSA 26-94) in RADIUS Access-Accept messages. For instructions, see Using AAA Default Tunnel Parameters to Configure the Transmit Connect Speed Calculation Method.

Transmit Connect Speed Calculation Methods

In previous releases, the router calculated the transmit speed of the subscriber’s access interface based only on statically configured settings for the underlying layer 2 access interface. With this feature, you can obtain a more accurate representation of the transmit connect speed by choosing a calculation method that reflects changes to the layer 2 interface due to statically configured settings, dynamically configured settings, or QoS settings.

You can choose one of the following methods for calculating the transmit connect speed that is reported in L2TP Transmit (TX) Speed AVP 24:

Static layer 2
Dynamic layer 2
QoS
Actual (lesser of dynamic layer 2 or QoS)

The following sections describe each of these calculation methods.

Note: Configuring the transmit connect speed calculation method has no effect on the operation of the L2TP Receive (RX) Speed AVP 38 or the Connect-Info RADIUS attribute [77] at the LAC.

Static Layer 2

The static layer 2 method calculates the transmit connect speed of the subscriber’s access interface based on the statically configured settings for the underlying layer 2 ATM 1483 or Ethernet interface. The static layer 2 method does not reflect changes to the transmit speed of the layer 2 interface due to dynamically configured settings or to QoS.

For ATM 1483 circuits, the static layer 2 value is based on the bandwidth that the connection requires. The router uses certain traffic parameters for each service category to determine the required bandwidth for the connection. For more information about how the router computes bandwidth for ATM 1483 circuits, see the Connection Admission Control section in the JunosE Link Layer Configuration Guide.

For Ethernet VLANs, the static layer 2 value is the advisory transmit speed of the VLAN subinterface, if configured with the vlan advisory-tx-speed command, or the speed of the underlying physical port if the advisory transmit speed is not configured.

If there is no explicit static configuration for the layer 2 interface, L2TP reports the speed of the underlying physical port as the transmit connect speed.

Dynamic Layer 2

The dynamic layer 2 method calculates the transmit connect speed of the subscriber’s access interface based on the dynamically configured settings for the underlying layer 2 interface.

If there is no dynamic configuration for the layer 2 interface, L2TP reports the transmit connect speed based on statically configured settings. If there is no static speed configuration for the layer 2 interface, L2TP reports the speed of the underlying physical port as the transmit connect speed.

QoS

The QoS method calculates the transmit connect speed of the subscriber’s access interface based on settings determined by static or dynamic QoS configurations. This calculation is based on the interface columns that QoS uses to build scheduler profiles for L2TP sessions. For example, a typical interface column might consist of an L2TP session over an Ethernet VLAN over a Gigabit Ethernet interface.

You can configure QoS to control the rate of any logical interface in the interface column. For those logical interfaces with a rate controlled by QoS, QoS reports this configured rate as the transmit connect speed for that interface. For those logical interfaces that do not have a QoS-configured rate, QoS reports the speed of the underlying physical port as the transmit connect speed.

For more information, see QoS and L2TP TX Speed AVP 24 Overview in JunosE Quality of Service Configuration Guide.

Actual

The actual method calculates the transmit connect speed of the subscriber’s access interface as the lesser of the following two values:

Value using the dynamic layer 2 calculation method
Value using the QoS calculation method

Transmit Connect Speed Calculation Examples

The examples in this section illustrate how the router uses the methods described in Transmit Connect Speed Calculation Methods to calculate the transmit connect speed.

Example 1: L2TP Session over ATM 1483 Interface

In this example, an L2TP session is established over an ATM 1483 subinterface on an OC3/STM1 ATM IOA. The configuration has the following characteristics:

There is no explicit static configuration for the layer 2 (ATM 1483) interface.
A transmit connect speed of 10 Mbps is provided dynamically from a RADIUS authentication server when the subscriber logs in.
The transmit connect speed calculated by QoS is 5 Mbps.

Based on these characteristics, Table 79 lists the transmit connect speed value reported in L2TP Transmit (TX) Speed AVP 24 for each calculation method, and the reason why L2TP reports this value.

Table 79: Transmit Connect Speeds for L2TP over ATM 1483 Example

Calculation Method	Transmit Connect Speed Reported in AVP 24	Reason
Static layer 2	155 Mbps	L2TP reports the speed of the underlying OC3 physical port because there is no explicit static configuration for the layer 2 interface.
Dynamic layer 2	10 Mbps	L2TP reports the transmit connect speed provided by RADIUS.
QoS	5 Mbps	L2TP reports the transmit connect speed calculated by QoS.
Actual	5 Mbps	L2TP reports the lesser of the dynamic layer 2 speed (10 Mbps) or the QoS speed (5 Mbps).

Example 2: L2TP Session over Ethernet VLAN Interface

In this example, an L2TP session is established over a PPPoE subinterface over an Ethernet VLAN subinterface. The configuration has the following characteristics:

The Ethernet VLAN subinterface is configured with an advisory transmit speed of 100 Mbps.
The dynamic layer 2 setting does not apply to the VLAN subinterface.
The transmit connect speed calculated by QoS is 10 Mbps.

Based on these characteristics, Table 80 lists the transmit connect speed value reported in L2TP Transmit (TX) Speed AVP 24 for each calculation method, and the reason why L2TP reports this value.

Table 80: Transmit Connect Speeds for L2TP over Ethernet Example

Calculation Method	Transmit Connect Speed Reported in AVP 24	Reason
Static layer 2	100 Mbps	L2TP reports the advisory transmit speed configured on the VLAN subinterface. If configured, the advisory transmit speed takes precedence over the physical port speed for a VLAN subinterface.
Dynamic layer 2	100 Mbps	L2TP reports the static layer 2 value because the dynamic layer 2 setting does not apply to a VLAN subinterface.
QoS	10 Mbps	L2TP reports the transmit connect speed calculated by QoS.
Actual	10 Mbps	L2TP reports the lesser of the dynamic layer 2 speed (100 Mbps) or the QoS speed (10 Mbps).

Transmit Connect Speed Reporting Considerations

The following considerations affect the transmit connect speed value reported in L2TP Transmit (TX) Speed AVP 24 when you use this feature.

Session Termination for Dynamic Speed Timeout

Under certain heavy load conditions, the router might be unable to obtain the dynamic-layer2 value for the transmit connect speed of the subscriber’s access interface. In this situation, the LAC sends the LNS an L2TP Call-Disconnect-Notify (CDN) message to terminate the L2TP session.

For more information about supported L2TP terminate reasons, see AAA Terminate Reasons.

Advisory Speed Precedence for VLANs over Bridged Ethernet

For interface columns that consist of an L2TP session over an Ethernet VLAN subinterface over a bridged Ethernet interface, the advisory transmit speed of the VLAN subinterface, if configured with the vlan advisory-tx-speed command, takes precedence over the physical port speed of the underlying layer 2 ATM 1483 interface. As a result, if the advisory transmit speed is configured for the VLAN subinterface, L2TP reports this value as the transmit connect speed regardless of the port speed of the ATM 1483 interface.

Using AAA Domain Maps to Configure the Transmit Connect Speed Calculation Method

To configure the transmit connect speed calculation method for a tunneled L2TP session associated with an AAA domain map:

Access Domain Map Tunnel Configuration mode.
host1(config)#aaa domain-map sunnyvale.com host1(config-domain-map)#router-name lac host1(config-domain-map)#tunnel 5 host1(config-domain-map-tunnel)#
For more information about how to map a domain to an L2TP tunnel from Domain Map Tunnel Configuration mode, see Mapping a User Domain Name to an L2TP Tunnel Overview.
From Domain Map Tunnel Configuration mode, configure the calculation method for the transmit connect speed of the subscriber’s access interface.
host1(config-domain-map-tunnel)#tx-connect-speed-method dynamic-layer2

(Optional) Use the show aaa domain-map command to verify configuration of the transmit connect speed calculation method.

host1(config-domain-map-tunnel)#run show aaa domain-map

Domain: sunnyvale.com; router-name: lac; ipv6-router-name: default
                                                                 Tunnel
Tunnel   Tunnel   Tunnel   Tunnel   Tunnel    Tunnel    Tunnel   Client
 Tag      Peer    Source    Type    Medium   Password     Id      Name
------   ------   ------   ------   ------   --------   ------   ------
5        <null>   <null>   l2tp     ipv4     <null>     <null>   <null>
         Tunnel                 Tunnel                     Tunnel
Tunnel   Server     Tunnel       Max                       Virtual
 Tag      Name    Preference   Sessions     Tunnel RWS     Router
------   ------   ----------   --------   --------------   -------
5        <null>   2000         0          system chooses   <null>
          Tunnel    Tunnel        Tunnel
Tunnel   Failover   Switch          Tx
 Tag      Resync    Profile    Speed Method
------   --------   -------   --------------
5        <null>     <null>    dynamic layer2

Using AAA Tunnel Groups to Configure the Transmit Connect Speed Calculation Method

To configure the transmit connect speed calculation method for a tunneled L2TP session associated with an AAA tunnel group:

Access Tunnel Group Tunnel Configuration mode.
host1(config)#aaa tunnel-group boston host1(config-tunnel-group)#tunnel 3 host1(config-tunnel-group-tunnel)#
For more information about how to map a domain to an L2TP tunnel from Tunnel Group Tunnel Configuration mode, see Mapping a User Domain Name to an L2TP Tunnel Overview.
From Tunnel Group Tunnel Configuration mode, configure the calculation method for the transmit connect speed of the subscriber’s access interface.
host1(config-tunnel-group-tunnel)#tx-connect-speed-method qos

(Optional) Use the show aaa tunnel-group command to verify configuration of the transmit connect speed calculation method.

host1(config-tunnel-group-tunnel)#run show aaa tunnel-group

Tunnel Group: boston
                                                                 Tunnel
Tunnel   Tunnel   Tunnel   Tunnel   Tunnel    Tunnel    Tunnel   Client
 Tag      Peer    Source    Type    Medium   Password     Id      Name
------   ------   ------   ------   ------   --------   ------   ------
3        <null>   <null>   l2tp     ipv4     <null>     <null>   <null>
         Tunnel                 Tunnel                     Tunnel
Tunnel   Server     Tunnel       Max                       Virtual
 Tag      Name    Preference   Sessions     Tunnel RWS     Router
------   ------   ----------   --------   --------------   -------
3        <null>   2000         0          system chooses   <null>
                              Tunnel
          Tunnel    Tunnel      Tx
Tunnel   Failover   Switch    Speed
 Tag      Resync    Profile   Method
------   --------   -------   ------
3        <null>     <null>    qos

Using AAA Default Tunnel Parameters to Configure the Transmit Connect Speed Calculation Method

You can configure the transmit connect speed calculation method as a default AAA tunnel parameter by using the aaa tunnel tx-connect-speed-method command from Global Configuration mode. This command applies the specified calculation method to all tunneled L2TP sessions associated with a particular virtual router, and thereby alleviates the need for you to configure the transmit connect speed calculation method for each individual subscriber.

Configuring the calculation method as a default AAA tunnel parameter for a virtual router has lower precedence than using AAA domain maps, AAA tunnel groups, or RADIUS to configure the transmit connect speed calculation method. The router uses the calculation method specified with the aaa tunnel tx-connect-speed-method command if the tunnel attributes returned from an AAA domain map, an AAA tunnel group, or a RADIUS authentication server do not include the transmit connect speed calculation method.

To configure the transmit connect speed calculation method for all tunneled L2TP sessions associated with a particular virtual router:

Create the virtual router for which you want to configure the transmit connect speed calculation method.
host1(config)#virtual-router north
For more information about configuring and using virtual routers, see the Configuring Virtual Routers chapter in the JunosE System Basics Configuration Guide.
Configure the transmit connect speed calculation method in the context of this virtual router.
host1:north(config)#aaa tunnel tx-connect-speed-method qos
- To specify the calculation method for the transmit connect speed, use one of the following keywords, as described in Using AAA Tunnel Groups to Configure the Transmit Connect Speed Calculation Method :
  - static-layer2
  - dynamic-layer2
  - qos
  - actual

(Optional) Use the show aaa tunnel-parameters command to verify configuration of the transmit connect speed calculation method.

host1:north(config)#run show aaa tunnel-parameters
Tunnel password is <NULL>
Tunnel client-name is <NULL>
Tunnel nas-port-method is none
Tunnel switch-profile is boston
Tunnel tx-connect-speed-method is qos
Tunnel nas-port ignore disabled
Tunnel nas-port-type ignore disabled
Tunnel assignmentId format is assignmentId
Tunnel calling number format is fixed

Using RADIUS to Configure the Transmit Connect Speed Calculation Method

On the LAC, the router can receive tunnel configuration attributes through a RADIUS authentication server. To use RADIUS to configure the transmit connect speed calculation method for a subscriber’s access interface, you can configure RADIUS to include the Tunnel-Tx-Speed-Method RADIUS attribute (Juniper Networks VSA 26-94) in RADIUS Access-Accept messages.

Table 81 describes the Tunnel-Tx-Speed-Method RADIUS attribute. For more information about RADIUS Access-Accept messages, see Subscriber AAA Access Messages Overview. For a description of the RADIUS attributes supported by JunosE Software, see RADIUS IETF Attributes.

Table 81: Tunnel--Tx-Speed-Method RADIUS Attribute

Attribute Number	Attribute Name	Description	Length	Subtype Length	Value
[26-94]	Tunnel-Tx-Speed-Method	The method that the router uses to calculate the transmit connect speed of the subscriber’s access interface	12	6	integer: 1 = static-layer2; TX speed based on static layer 2 settings 2 =dynamic-layer2; TX speed based on dynamic layer 2 settings 3 = qos; TX speed based on QoS settings 4 = actual; TX speed that is the lesser of the dynamic-layer2 value or the qos value

Attribute Number

Attribute Name

Description

Length

Subtype Length

Value

[26-94]

Tunnel-Tx-Speed-Method

The method that the router uses to calculate the transmit connect speed of the subscriber’s access interface

integer:

1 = static-layer2; TX speed based on static layer 2 settings
2 =dynamic-layer2; TX speed based on dynamic layer 2 settings
3 = qos; TX speed based on QoS settings
4 = actual; TX speed that is the lesser of the dynamic-layer2 value or the qos value