





Network Working Group                                       V. Mammoliti
Request for Comments: 5515                                  C. Pignataro
Category: Informational                                    Cisco Systems
                                                               P. Arberg
                                                        Redback Networks
                                                              J. Gibbons
                                                        Juniper Networks
                                                               P. Howard
                                                                May 2009


       Layer 2 Tunneling Protocol (L2TP) Access Line Information
                 Attribute Value Pair (AVP) Extensions

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   This document describes a set of Layer 2 Tunneling Protocol (L2TP)
   Attribute Value Pair (AVP) extensions designed to carry the
   subscriber Access Line identification and characterization
   information that arrives at the Broadband Remote Access Server (BRAS)
   with L2TP Access Concentrator (LAC) functionality.  It also describes
   a mechanism to report connection speed changes, after the initial
   connection speeds are sent during session establishment.  The primary
   purpose of this document is to provide a reference for DSL equipment
   vendors wishing to interoperate with other vendors' products.  The
   L2TP AVPs defined in this document are applicable to both L2TPv2 and
   L2TPv3.







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Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
      2.1. Requirements Language ......................................3
      2.2. Technical Terms and Acronyms ...............................4
   3. Access Line Information L2TP AVP Operation ......................5
   4. Additional L2TP Messages ........................................6
      4.1. Connect-Speed-Update-Notification (CSUN) ...................8
      4.2. Connect-Speed-Update-Request (CSURQ) .......................8
   5. Access Line Information L2TP Attribute Value Pair Extensions ....9
      5.1. Access Line Agent-Circuit-Id AVP ..........................10
      5.2. Access Line Agent-Remote-Id AVP ...........................11
      5.3. Access Line Actual-Data-Rate-Upstream AVP .................12
      5.4. Access Line Actual-Data-Rate-Downstream AVP ...............13
      5.5. Access Line Minimum-Data-Rate-Upstream AVP ................13
      5.6. Access Line Minimum-Data-Rate-Downstream AVP ..............14
      5.7. Access Line Attainable-Data-Rate-Upstream AVP .............14
      5.8. Access Line Attainable-Data-Rate-Downstream AVP ...........14
      5.9. Access Line Maximum-Data-Rate-Upstream AVP ................15
      5.10. Access Line Maximum-Data-Rate-Downstream AVP .............15
      5.11. Access Line Minimum-Data-Rate-Upstream-Low-Power AVP .....16
      5.12. Access Line Minimum-Data-Rate-Downstream-Low-Power AVP ...16
      5.13. Access Line Maximum-Interleaving-Delay-Upstream AVP ......17
      5.14. Access Line Actual-Interleaving-Delay-Upstream AVP .......17
      5.15. Access Line Maximum-Interleaving-Delay-Downstream AVP ....18
      5.16. Access Line Actual-Interleaving-Delay-Downstream AVP .....18
      5.17. Access Line Access-Loop-Encapsulation AVP ................19
      5.18. ANCP Access Line Type AVP ................................20
      5.19. Access Line IWF-Session AVP ..............................21
   6. Connect Speed Update L2TP Attribute Value Pair Extensions ......22
      6.1. Connect Speed Update AVP (CSUN, CSURQ) ....................22
      6.2. Connect Speed Update Enable AVP (ICRQ) ....................23
   7. Access Line Information AVP Mapping ............................24
      7.1. Summary of Access Line AVPs ...............................24
   8. IANA Considerations ............................................25
      8.1. Message Type AVP Values ...................................25
      8.2. Control Message Attribute Value Pairs (AVPs) ..............25
      8.3. Values for Access Line Information AVPs ...................25
   9. Security Considerations ........................................25
   10. Acknowledgements ..............................................26
   11. References ....................................................26
      11.1. Normative References .....................................26
      11.2. Informative References ...................................27







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1.  Introduction

   Access Nodes (ANs), referred to as Digital Subscriber Line Access
   Multiplexers (DSLAMs) in DSL, are adding enhancement features to
   forward, via in-band signaling, subscriber Access Line identification
   and characterization information to their connected upstream
   Broadband Remote Access Server (BRAS) with L2TP Access Concentrator
   (LAC) functionality.

   The Access Node/DSLAM may forward the information via one or more of
   the following methods:

   o  Vendor-Specific Point-to-Point Protocol over Ethernet (PPPoE) Tags
      [RFC2516].

   o  DHCP Relay Options [RFC3046] and Vendor-Specific Information
      Suboptions [RFC4243].

   o  Access Node Control Protocol [ANCP].

   Currently, this information is been collected on the BRAS and
   forwarded to a radius server via [RFC4679].

   This document describes the new additional L2TP AVPs that were
   created to forward the subscriber line identification and
   characterization information received at the BRAS/LAC to the
   terminating L2TP Network Server (LNS).  It also describes a mechanism
   by which the LAC may report connection speed changes to the LNS,
   after the initial connection speeds are sent by the LAC during
   session establishment.

   The L2TP AVPs defined in this document MAY be used with either an
   L2TPv2 [RFC2661] or L2TPv3 [RFC3931] implementation.

   The information acquired may be used to provide authentication,
   policy, and accounting functionality.  It may also be collected and
   used for management and troubleshooting purposes.

2.  Terminology

   The following sections define the usage and meaning of certain
   specialized terms in the context of this document.

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].



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2.2.  Technical Terms and Acronyms

   Access Node/DSLAM

      The Access Node/DSLAM is a DSL signal terminator that contains a
      minimum of one Ethernet or ATM interface that serves as its
      upstream interface into which it aggregates traffic from several
      ATM-based (subscriber ports) or Ethernet-based downstream
      interfaces.

   BNG

      Broadband Network Gateway.  A BNG is an IP edge router where
      bandwidth and Quality-of-Service (QoS) policies are applied; the
      functions performed by a BRAS are a superset of those performed by
      a BNG.

   BRAS

      Broadband Remote Access Server.  A BRAS is a BNG and is the
      aggregation point for the subscriber traffic.  It provides
      aggregation capabilities (e.g., IP, PPP, Ethernet) between the
      access network and the core network.  Beyond its aggregation
      function, the BRAS is also an injection point for policy
      management and IP QoS in the access network.

   DSL

      Digital Subscriber Line.  DSL is a technology that allows digital
      data transmission over wires in the local telephone network.

   DSLAM

      Digital Subscriber Line Access Multiplexer.  DSLAM is a device
      that terminates DSL subscriber lines.  The data is aggregated and
      forwarded to ATM- or Ethernet-based aggregation networks.

   IWF

      Interworking Function.  The set of functions required for
      interconnecting two networks of different technologies (e.g., ATM
      and Ethernet).  IWF is utilized to enable the carriage of Point-
      to-Point Protocol over ATM (PPPoA) traffic over PPPoE.








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   LAC

      L2TP Access Concentrator.  If an L2TP Control Connection Endpoint
      (LCCE) is being used to cross-connect an L2TP session directly to
      a data link, we refer to it as an L2TP Access Concentrator (LAC).
      (See [RFC2661] and [RFC3931].)

   LCCE

      L2TP Control Connection Endpoint.  An L2TP node that exists at
      either end of an L2TP control connection.  May also be referred to
      as an LAC or LNS, depending on whether tunneled frames are
      processed at the data link (LAC) or network layer (LNS).  (See
      [RFC3931].)

   LNS

      L2TP Network Server.  If a given L2TP session is terminated at the
      L2TP node and the encapsulated network layer (L3) packet processed
      on a virtual interface, we refer to this L2TP node as an L2TP
      Network Server (LNS).  (See [RFC2661] and [RFC3931].)

3.  Access Line Information L2TP AVP Operation

   When the BRAS with LAC functionality receives the Access Line
   information from the Access Node and has determined that the session
   will be established with an LNS, the LAC will forward the information
   that it has collected in the newly defined L2TP AVPs.  The LAC will
   only forward the Access Line Information AVPs that have populated
   values.

   Access Line information from any of the above methods must be
   available at the BRAS prior to the start of session negotiation by
   the LAC.  This ensures Access Line parameters are reliably provided
   to the LNS and avoids additional call set-up delays.  Under the
   condition that the LAC has not received any Access Line information
   from any of the methods, as default behavior the LAC SHOULD establish
   the L2TP session without waiting for the Access Line information.  In
   this case, the LAC MUST NOT send any of the Access Line AVPs to the
   LNS.  The LAC MAY, as local policy, wait for the Access Line
   information from one or more of the methods before forwarding the
   information in the Access Line L2TP AVPs to the LNS.

   It is possible that the Access Node will only send a subset of the
   currently available line information defined.  The LAC MUST be able
   to limit and/or filter which AVPs, if any, are sent to the LNS.





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   It is also possible that the LAC may receive Access Line information
   from multiple sources and at different time intervals.  Local policy
   SHOULD determine which source(s) the LAC will accept.  The LAC SHOULD
   default to accepting ANCP-sourced parameters.

   The Access Line AVPs are sent as part of the L2TP Incoming-Call-
   Request (ICRQ) control message.  Connect Speed Update AVPs are sent
   as part of the Connect-Speed-Update-Notification (CSUN) or Connect-
   Speed-Update-Request (CSURQ) L2TP messages (see Sections 4, 4.1, and
   4.2).

   It is possible for the LAC to send updated Connect Speed
   characteristics to the LNS via the Connect Speed Update AVP in an
   L2TP Connect-Speed-Update-Notification (CSUN) control message (see
   Section 4.1).  To avoid unnecessary L2TP Connect-Speed-Update-Request
   and Connect-Speed-Update-Notification message exchanges between the
   LAC and LNS (e.g., during failover protocol recovery and
   resynchronization), the LAC signals in the session establishment
   exchange its ability and desire to provide speed updates during the
   life of the session.  This is achieved using a new AVP, Connect Speed
   Update Enable (see Section 6.2), sent in the L2TP Incoming-Call-
   Request (ICRQ) control message.  The absence of this AVP in the ICRQ
   message implies that the LAC will not be sending any speed updates
   during the life of the session.  If the LAC is configured to accept
   ANCP-sourced parameters, and supports providing speed updates during
   the life of a session, it MUST send the Connect Speed Update Enable
   AVP in the ICRQ, since this implies that speed updates may occur over
   the life of the connection.  If the LAC is configured to only accept
   PPPoE vendor-specific tags, it MUST NOT send the Connect Speed Update
   Enable AVP in the ICRQ, since the connection speed is only sent
   during PPPoE discovery and no further updates will occur during the
   life of the connection.

4.  Additional L2TP Messages

   If the Access Line information changes while the session is still
   maintained, connection speed updates MAY be sent from the LAC to the
   LNS via an L2TP Connect-Speed-Update-Notification (CSUN) Message (see
   Section 4.1).  A new AVP, Connect Speed Update AVP (see Section 6.1),
   is included in the CSUN message to report connect speed updates for a
   specific session after the initial connection speeds are established
   (i.e., at session establishment via the Tx Connect Speed and Rx
   Connect Speed AVPs, Attribute Types 24 and 38, respectively, for
   L2TPv2 and 74 and 75, respectively, for L2TPv3).  The values
   established in the Connect Speed Update AVP (as well as the values
   for the initial Tx/Rx Connect Speeds AVPs) are based on LAC local
   policy.  For example, the LAC's local policy may use the Actual-Data-
   Rate-Upstream and Actual-Data-Rate-Downstream as its policy to report



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   connection speed updates.  For consistency, the same local policy
   SHOULD equally apply both to the initial connect speeds (conveyed
   during session establishment) and to the (optional) connect speed
   updates (sent after the establishment of the session).  The CSUN
   message MAY be sent periodically to the LNS based on local policy and
   may include more than one Connect Speed Update AVP.  The bulking of
   more than one Connect Speed Update AVP into the CSUN message serves
   the following purposes:

   o  Dampens the rate of changes sent to the LNS when Access Line
      parameter updates are received at a high rate for a given line.

   o  Efficiently forwards speed updates when Access Line parameter
      updates are received for many lines at the same time.

   o  Supports failover [RFC4951] protocol recovery and
      resynchronization.

   During failover recovery and resynchronization, to ensure the correct
   speeds have been applied to outstanding sessions on each tunnel, the
   LNS MAY issue a Connect-Speed-Update-Request (CSURQ) message (see
   Section 4.2) to the LAC containing one or more Session IDs.  In
   response to the CSURQ message, the LAC MUST issue a Connect-Speed-
   Update-Notification (CSUN) message (see Section 4.1) containing a
   Connect Speed Update AVP for each of the Session IDs requested in the
   CSURQ.  Note: In the CSUN response to the CSURQ, the LAC MUST NOT
   respond to unknown sessions, or to known sessions for which it did
   not issue a Connect Speed Update Enable AVP in the prior Incoming-
   Call-Request (ICRQ) control message for the session (see Sections 3
   and 6.2).

   This section defines two new Messages that are used with the IETF
   Vendor ID of 0 in the Message Type AVP.

      The following message types will be assigned to these new messages
      (see Section 8.1):

         28: (CSUN) Connect-Speed-Update-Notification

         29: (CSURQ) Connect-Speed-Update-Request

   The Mandatory (M) bit within the Message Type AVP SHOULD be clear
   (i.e., not set) for the CSUN and CSURQ control messages, to allow for
   an L2TP Control Connection Endpoint (LCCE) to maintain the control
   connection if the message type is unknown.






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4.1.  Connect-Speed-Update-Notification (CSUN)

   The Connect-Speed-Update-Notification (CSUN) is an L2TP control
   message sent by the LAC to the LNS to provide transmit and receive
   connection speed updates for one or more sessions.  The connection
   speed may change at any time during the life of the call; thus, the
   LNS SHOULD be able to update its connection speed on an active
   session.

   The following AVPs MUST be present in the CSUN:

      Message Type

      Connect Speed Update (more than one may be present in the CSUN)

   Note that the LAC MUST NOT include a Connect Speed Update AVP for
   which it did not send a Connect Speed Update Enable AVP in the prior
   Incoming-Call-Request (ICRQ) control message for the session.

4.2.  Connect-Speed-Update-Request (CSURQ)

   The Connect-Speed-Update-Request (CSURQ) is an L2TP control message
   sent by the LNS to the LAC to request the current transmit and
   receive connection speed for one or more sessions.  It MAY be issued
   at any time during the life of the tunnel and MUST only be issued for
   each outstanding session on each tunnel on which the LNS has already
   received a Connect Speed Update Enable AVP in the prior Incoming-
   Call-Request (ICRQ) control message for the session.  It is typically
   used as part of failover recovery and resynchronization to allow the
   LNS to verify it has the correct speeds for each outstanding session
   on each tunnel.

   The following AVPs MUST be present in the CSURQ:

      Message Type

      Connect Speed Update (more than one may be present in the CSURQ)

   The Current Tx Connect Speed and Current Rx Connect Speed fields in
   the Connect Speed Update AVP MUST be set to 0 when this AVP is used
   in the CSURQ message.

   In the CSUN response to the CSURQ, the LAC MUST NOT respond to
   unknown sessions or to known sessions for which it did not issue a
   Connect Speed Update Enable AVP in the prior Incoming-Call-Request
   (ICRQ) control message for the session.





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5.  Access Line Information L2TP Attribute Value Pair Extensions

   The Access Line information was initially defined in the DSL Forum
   Technical Report TR-101 [TR-101].  TR-101 defines the line
   characteristic that are sent from an Access Node.

   The following sections contain a list of the Access Line Information
   L2TP AVPs.  Included with each of the listed AVPs is a short
   description of the purpose of the AVPs.

   The AVPs follow the standard method of encoding AVPs as follows:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |M|H| rsvd  |      Length       |           Vendor ID           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Attribute Type        |Attribute Value, if Required ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     ... (Until Length is reached)                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The M bit for all the AVPs defined in this document SHOULD be set to
   0 to allow for backwards compatibility with LNSs that do not support
   the Access Line Information AVP extensions hereby defined.  However,
   if it is desired to prevent the establishment of the L2TP session if
   the peer LNS does not support the Access Line Information AVP
   extensions, the M bit MAY be set to 1.  See Section 4.2 of [RFC2661]
   and Section 5.2 of [RFC3931].

   All the AVPs defined in this document MAY be hidden (the H bit MAY be
   0 or 1).

   The Length (before hiding) of all the listed AVPs is 6 plus the
   length of the Attribute Value, if one is required, in octets.

   The Vendor ID for all the listed AVPs (Sections 5.1 through 5.19) is
   that of the IANA assigned ADSL Forum Vendor ID, decimal 3561
   [IANA.enterprise-numbers].

   All the listed AVPs (Section 5.1 through Section 5.19) MAY be present
   in the following messages unless otherwise stipulated:

      Incoming-Call-Request (ICRQ)

   The Value of the AVP contains information about the Access Line to
   which the subscriber is attached.




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   With the exception of the Connect Speed Update AVP (see Section 6.1),
   all new AVPs specifying a data rate or speed expressed in bits per
   second (bps) will be sent as 64-bits to provide extensibility to
   support future increases in subscriber connection speeds.  These new
   AVPs that specify a 64-bit "Data-Rate" are defined from Section 5.3
   to Section 5.12, both inclusive.  Whenever a speed value sent in an
   AVP fits within 32 bits, the upper 32 bits MUST be transmitted as 0s.

   The various Data-Rates and Interleaving-Delays used in the subsequent
   Sections 5.3 through 5.16 are defined in Section 3.9.4 of [TR-101].
   The qualifiers used with these Data-Rates and Interleaving-Delays
   have the following meanings:

   o  Actual      Actual rate or delay of an access loop

   o  Attainable  Maximum value that can be achieved by the equipment

   o  Minimum     Minimum value configured by the operator

   o  Maximum     Maximum value configured by the operator

5.1.  Access Line Agent-Circuit-Id AVP

   The Access Line Agent-Circuit-Id AVP, Attribute Type 1, contains
   information describing the subscriber agent circuit ID corresponding
   to the logical access loop port of the Access Node/DSLAM from which a
   subscriber's requests are initiated.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Agent-Circuit-Id ... (2 to 63 octets)
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Agent-Circuit-Id is of arbitrary length, but MUST be greater than
   1 octet and not greater than 63 octets.

   The Length (before hiding) of this AVP is 6 plus the length of the
   Agent-Circuit-Id.

   The Agent-Circuit-Id contains information about the Access Node/DSLAM
   to which the subscriber is attached, along with a unique identifier
   for the subscriber's DSL port on that Access Node/DSLAM.  The Agent-






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   Circuit-Id contains a locally administered string representing the
   access loop logical port, and its syntax is defined in Section 3.9.3
   of [TR-101].  The text string is encoded in the UTF-8 charset
   [RFC3629].

   An exemplary description of the Agent-Circuit-Id string format
   follows for background purposes.  The LAC MUST treat the string as an
   opaque value and MUST NOT manipulate or enforce the format of the
   string based on the description here or in TR-101 [TR-101].

   Default syntax for the string is defined in [TR-101].  The examples
   in this section are included only for illustrative purposes.  The
   exact syntax of the string is implementation dependent; however, a
   typical practice is to subdivide it into two or more space-separated
   components, one to identify the Access Node and another the
   subscriber line on that node, with perhaps an indication of whether
   that line is Ethernet or ATM.  Example formats for this string are
   shown below.

      "Access-Node-Identifier atm slot/port:vpi.vci"
      (when ATM/DSL is used)

      "Access-Node-Identifier eth slot/port[:vlan-id]"
      (when Ethernet/DSL is used)

   The syntax for the string is defined in [TR-101].  An example showing
   the slot and port field encoding is given below:

      "Relay-identifier atm 3/0:100.33"
      (slot = 3, port = 0, vpi = 100, vci = 33)

   The Access-Node-Identifier is a unique ASCII string that does not
   include 'space' characters.  The syntax of the slot and port fields
   reflects typical practices currently in place.  The slot identifier
   does not exceed 6 characters in length, and the port identifier does
   not exceed 3 characters in length using a '/' as a delimiter.

   The exact manner in which slots are identified is Access Node/DSLAM
   implementation dependent.  The vpi, vci, and vlan-id fields (when
   applicable) are related to a given access loop (U-interface).

5.2.  Access Line Agent-Remote-Id AVP

   The Access Line Agent-Remote-Id AVP, Attribute Type 2, contains an
   operator-specific, statically configured string that uniquely
   identifies the subscriber on the associated access loop of the Access
   Node/DSLAM.




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   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Agent-Remote-Id ... (2 to 63 octets)
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Agent-Remote-Id is of arbitrary length, but MUST be greater than
   1 octet and not greater than 63 octets.

   The Length (before hiding) of this AVP is 6 plus the length of the
   Agent-Remote-Id.

   The Agent-Remote-Id contains information sent from the Access Node/
   DSLAM from which the subscriber is attached, to further refine the
   access loop logical port identification with a user.  The content of
   this message is entirely open to the service provider's discretion.
   For example, it MAY contain a subscriber billing ID or telephone
   number.  The LAC MUST treat the string as an opaque value and MUST
   NOT manipulate or enforce its format.  The text string is defined in
   [TR-101], and is encoded in the UTF-8 charset [RFC3629].

5.3.  Access Line Actual-Data-Rate-Upstream AVP

   The Access Line Actual-Data-Rate-Upstream AVP, Attribute Type 129,
   contains the actual upstream train rate of a subscriber's
   synchronized Access link.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Actual-Data-Rate-Upstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Actual-Data-Rate-Upstream is an 8-octet value.

   The Actual-Data-Rate-Upstream AVP contains an 8-octet unsigned
   integer, indicating the subscriber's actual data rate upstream of a
   synchronized Access link.  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.





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5.4.  Access Line Actual-Data-Rate-Downstream AVP

   The Access Line Actual-Data-Rate-Downstream AVP, Attribute Type 130,
   contains the actual downstream train rate of a subscriber's
   synchronized Access link.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Actual-Data-Rate-Downstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Actual-Data-Rate-Downstream AVP contains an 8-octet unsigned
   integer, indicating the subscriber's actual data rate downstream of a
   synchronized Access link.  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.

5.5.  Access Line Minimum-Data-Rate-Upstream AVP

   The Access Line Minimum-Data-Rate-Upstream AVP, Attribute Type 131,
   contains the subscriber's operator-configured minimum upstream data
   rate.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Minimum-Data-Rate-Upstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Minimum-Data-Rate-Upstream AVP contains an 8-octet unsigned
   integer, indicating the subscriber's minimum upstream data rate (as
   configured by the operator).  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.








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5.6.  Access Line Minimum-Data-Rate-Downstream AVP

   The Access Line Minimum-Data-Rate-Downstream AVP, Attribute Type 132,
   contains the subscriber's operator-configured minimum downstream data
   rate.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Minimum-Data-Rate-Downstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Minimum-Data-Rate-Downstream AVP contains an 8-octet unsigned
   integer, indicating the subscriber's minimum downstream data rate (as
   configured by the operator).  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.

5.7.  Access Line Attainable-Data-Rate-Upstream AVP

   The Access Line Attainable-Data-Rate-Upstream AVP, Attribute Type
   133, contains the subscriber's actual attainable upstream data rate.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Attainable-Data-Rate-Upstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Attainable-Data-Rate-Upstream AVP contains an 8-octet unsigned
   integer, indicating the subscriber's Access Line actual attainable
   upstream data rate.  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.

5.8.  Access Line Attainable-Data-Rate-Downstream AVP

   The Access Line Attainable-Data-Rate-Downstream AVP, Attribute Type
   134, contains the subscriber's actual attainable downstream data
   rate.



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   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Attainable-Data-Rate-Downstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Attainable-Data-Rate-Downstream AVP contains an 8-octet unsigned
   integer, indicating the subscriber's Access Line actual DSL
   attainable downstream data rate.  The rate is coded in bits per
   second.

   The Length (before hiding) of this AVP is 14.

5.9.  Access Line Maximum-Data-Rate-Upstream AVP

   The Access Line Maximum-Data-Rate-Upstream AVP, Attribute Type 135,
   contains the subscriber's maximum upstream data rate, as configured
   by the operator.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Maximum-Data-Rate-Upstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Maximum-Data-Rate-Upstream AVP contains an 8-octet unsigned
   integer, indicating the numeric value of the subscriber's Access Line
   maximum upstream data rate.  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.

5.10.  Access Line Maximum-Data-Rate-Downstream AVP

   The Access Line Maximum-Data-Rate-Downstream AVP, Attribute Type 136,
   contains the subscriber's maximum downstream data rate, as configured
   by the operator.







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   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Maximum-Data-Rate-Downstream
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Maximum-Data-Rate-Downstream AVP contains an 8-octet unsigned
   integer, indicating the numeric value of the subscriber's Access Line
   maximum downstream data rate.  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.

5.11.  Access Line Minimum-Data-Rate-Upstream-Low-Power AVP

   The Access Line Minimum-Data-Rate-Upstream-Low-Power AVP, Attribute
   Type 137, contains the subscriber's minimum upstream data rate in low
   power state, as configured by the operator.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Minimum-Data-Rate-Upstream-Low-Power
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Minimum-Data-Rate-Upstream-Low-Power AVP contains an 8-octet
   unsigned integer, indicating the numeric value of the subscriber's
   Access Line minimum upstream data rate when in low power state
   (L1/L2).  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.

5.12.  Access Line Minimum-Data-Rate-Downstream-Low-Power AVP

   The Access Line Minimum-Data-Rate-Downstream-Low-Power AVP, Attribute
   Type 138, contains the subscriber's minimum downstream data rate in
   low power state, as configured by the operator.







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   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Minimum-Data-Rate-Downstream-Low-Power
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         ... in bps (64 bits)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Minimum-Data-Rate-Downstream-Low-Power AVP contains an 8-octet
   unsigned integer, indicating the numeric value of the subscriber's
   Access Line minimum downstream data rate when in low power state
   (L1/L2).  The rate is coded in bits per second.

   The Length (before hiding) of this AVP is 14.

5.13.  Access Line Maximum-Interleaving-Delay-Upstream AVP

   The Access Line Maximum-Interleaving-Delay-Upstream AVP, Attribute
   Type 139, contains the subscriber's maximum one-way upstream
   interleaving delay, as configured by the operator.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Maximum-Interleaving-Delay-Upstream               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Maximum-Interleaving-Delay-Upstream AVP contains a 4-octet
   unsigned integer, indicating the numeric value in milliseconds of the
   subscriber's Access Line maximum one-way upstream interleaving delay.

   The Length (before hiding) of this AVP is 10.

5.14.  Access Line Actual-Interleaving-Delay-Upstream AVP

   The Access Line Actual-Interleaving-Delay-Upstream AVP, Attribute
   Type 140, contains the subscriber's actual one-way upstream
   interleaving delay.









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   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Actual-Interleaving-Delay-Upstream                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Actual-Interleaving-Delay-Upstream AVP contains a 4-octet
   unsigned integer, indicating the numeric value in milliseconds of the
   subscriber's Access Line actual upstream interleaving delay.

   The Length (before hiding) of this AVP is 10.

5.15.  Access Line Maximum-Interleaving-Delay-Downstream AVP

   The Access Line Maximum-Interleaving-Delay-Downstream AVP, Attribute
   Type 141, contains the subscriber's maximum one-way downstream
   interleaving delay, as configured by the operator.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Maximum-Interleaving-Delay-Downstream               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Maximum-Interleaving-Delay-Downstream AVP contains a 4-octet
   unsigned integer, indicating the numeric value in milliseconds of the
   subscriber's Access Line maximum one-way downstream interleaving
   delay.

   The Length (before hiding) of this AVP is 10.

5.16.  Access Line Actual-Interleaving-Delay-Downstream AVP

   The Access Line Actual-Interleaving-Delay-Downstream AVP, Attribute
   Type 142, contains the subscriber's actual one-way downstream
   interleaving delay.











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   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Actual-Interleaving-Delay-Downstream               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Actual-Interleaving-Delay-Downstream AVP contains a 4-octet
   unsigned integer, indicating the numeric value in milliseconds of the
   subscriber's Access Line actual downstream interleaving delay.

   The Length (before hiding) of this AVP is 10.

5.17.  Access Line Access-Loop-Encapsulation AVP

   The Access Line Access-Loop-Encapsulation AVP, Attribute Type 144,
   describes the encapsulation(s) used by the subscriber on the access
   loop.

   The Length (before hiding) of this AVP is 9.

   The Access-Loop-Encapsulation value is comprised of three 1-octet
   values representing the Data Link, Encapsulation 1, and Encapsulation
   2, respectively.

   The Access-Loop-Encapsulation value is 3 octets in length, logically
   divided into three 1-octet sub-fields, each containing its own
   enumeration value, as shown in the following diagram:


              0                   1                   2
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |   Data Link   |    Encaps 1   |    Encaps 2   |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Valid values for the sub-fields are as follows:

      Data Link

         0x00 ATM AAL5

         0x01 Ethernet







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      Encaps 1

         0x00 NA - Not Available

         0x01 Untagged Ethernet

         0x02 Single-Tagged Ethernet

      Encaps 2

         0x00 NA - Not Available

         0x01 PPPoA LLC

         0x02 PPPoA Null

         0x03 IP over ATM (IPoA) LLC

         0x04 IPoA Null

         0x05 Ethernet over AAL5 LLC with Frame Check Sequence (FCS)

         0x06 Ethernet over AAL5 LLC without FCS

         0x07 Ethernet over AAL5 Null with FCS

         0x08 Ethernet over AAL5 Null without FCS

5.18.  ANCP Access Line Type AVP

   The ANCP Access Line Type AVP, Attribute Type 145, describes the
   transmission systems on access loop to the subscriber.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      ANCP-Access-Line-Type                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Length (before hiding) of this AVP is 10.  The ANCP Access Line
   Type AVP defines the type of transmission system used.








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   The ANCP Access Line Type AVP contains a 1-octet field encoding the
   Transmission System, followed by a 3-octet reserved field (MUST be
   zero), and is 4 octets in length.  It indicates the transmission
   systems on access loop to the subscriber.  The current valid values
   only utilize the 1-octet field.

   Valid values are as follows:

      Transmission system:

         0x01 ADSL1

         0x02 ADSL2

         0x03 ADSL2+

         0x04 VDSL1

         0x05 VDSL2

         0x06 SDSL

         0x07 UNKNOWN

5.19.  Access Line IWF-Session AVP

   The Access Line IWF-Session AVP, Attribute Type 254, indicates if an
   Interworking Function has been performed with respect to the
   subscriber's session.

   The Attribute Value field for this AVP has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Inter-Working Function                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Inter-Working Function is a 4-octet value.

      Valid values for this field are as follows:

         0x00 IWF not performed

         0x01 IWF performed

   The Length (before hiding) of this AVP is 10.




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6.  Connect Speed Update L2TP Attribute Value Pair Extensions

   The following sections define Connect Speed Update related AVPs.
   These AVPs (Section 6.1 and Section 6.2) use the IETF Vendor ID of 0.

   The M bit for these AVPs SHOULD be set to 0.  However, if it is
   desired to prevent the establishment or tear down the established
   L2TP session if the peer LNS does not support the Connect Speed
   Update AVP extensions, the M bit MAY be set to 1.  See Section 4.2 of
   [RFC2661] and Section 5.2 of [RFC3931].

6.1.  Connect Speed Update AVP (CSUN, CSURQ)

   The Connect Speed Update AVP, Attribute Type 97, contains the updated
   connection speeds for this session.  The format is consistent with
   that of the Tx Connect Speed and Rx Connect Speed AVPs for L2TPv2
   (Attribute Types 24 and 38, respectively) and L2TPv3 (Attribute Types
   74 and 75, respectively).  Hence, there is a separate format defined
   for L2TPv2 and L2TPv3.

   The Attribute Value field for this AVP has the following format for
   L2TPv2 Tunnels:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Reserved             |      Remote Session Id        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Current Tx Connect Speed in bps                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Current Rx Connect Speed in bps                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



















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   The Attribute Value field for this AVP has the following format for
   L2TPv3 Tunnels:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Remote Session Id                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Current Tx Connect Speed in bps...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                ...Current Tx Connect Speed in bps (64 bits)         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Current Rx Connect Speed in bps...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                ...Current Rx Connect Speed in bps (64 bits)         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Remote Session Id is the remote session id relative to the sender
   (i.e., the identifier that was assigned to this session by the peer).
   The Current Tx Connect Speed is a 4-octet value (L2TPv2) or an
   8-octet value (L2TPv3) representing the current transmit connect
   speed, from the perspective of the LAC (e.g., data flowing from the
   LAC to the remote system).  The rate is encoded in bits per second.
   The Current Rx Connect Speed is a 4-octet value (L2TPv2) or an
   8-octet value (L2TPv3) representing the current receive connect
   speed, from the perspective of the LAC (e.g., data flowing from the
   remote system to the LAC).  The rate is encoded in bits per second.

   The Length (before hiding) of this AVP is 18 (L2TPv2) or 26 (L2TPv3).

6.2.  Connect Speed Update Enable AVP (ICRQ)

   The Connect Speed Update Enable AVP, Attribute Type 98, indicates
   whether the LAC intends to send speed updates to the LNS during the
   life of the session.  The Connect Speed Update Enable AVP is a
   boolean AVP.  Presence of this AVP indicates that the LAC MAY send
   speed updates using CSUN (see Section 4.1) during the life of the
   session, and the LNS SHOULD query for the current connection speed
   via the CSURQ (see Section 4.2) during failover synchronization.
   Absence of this AVP indicates that the LAC will not be sending speed
   updates using CSUN (see Section 4.1) during the life of the session,
   and the LNS MUST NOT query for the current connection speed via the
   CSURQ (see Section 4.2) during failover synchronization.

   The Length (before hiding) of this AVP is 6.






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7.  Access Line Information AVP Mapping

   The Access Line information that is obtained from the Access Node/
   DSLAM is required to be mapped into the Access Line AVPs.  The Access
   Line information can be obtained via:

   o  Vendor-Specific PPPoE Tags [RFC2516].

   o  DHCP Relay Options [RFC3046] and Vendor-Specific Information
      Suboptions [RFC4243].

   o  ANCP [ANCP].

7.1.  Summary of Access Line AVPs

   Table 1 summarizes the Access Line AVPs defined in Sections 5.1
   through 5.19.

       +-----------------+----------------------------------------+
       | Access Line AVP | Name                                   |
       +-----------------+----------------------------------------+
       |        1 (0x01) | Agent-Circuit-Id                       |
       |        2 (0x02) | Agent-Remote-Id                        |
       |      129 (0x81) | Actual-Data-Rate-Upstream              |
       |      130 (0x82) | Actual-Data-Rate-Downstream            |
       |      131 (0x83) | Minimum-Data-Rate-Upstream             |
       |      132 (0x84) | Minimum-Data-Rate-Downstream           |
       |      133 (0x85) | Attainable-Data-Rate-Upstream          |
       |      134 (0x86) | Attainable-Data-Rate-Downstream        |
       |      135 (0x87) | Maximum-Data-Rate-Upstream             |
       |      136 (0x88) | Maximum-Data-Rate-Downstream           |
       |      137 (0x89) | Minimum-Data-Rate-Upstream-Low-Power   |
       |      138 (0x8A) | Minimum-Data-Rate-Downstream-Low-Power |
       |      139 (0x8B) | Maximum-Interleaving-Delay-Upstream    |
       |      140 (0x8C) | Actual-Interleaving-Delay-Upstream     |
       |      141 (0x8D) | Maximum-Interleaving-Delay-Downstream  |
       |      142 (0x8E) | Actual-Interleaving-Delay-Downstream   |
       |      144 (0x90) | Access-Loop-Encapsulation              |
       |      145 (0x91) | ANCP Access Line Type                  |
       |      254 (0xFE) | IWF-Session                            |
       +-----------------+----------------------------------------+

                     Table 1: Access Line AVP Summary








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8.  IANA Considerations

   Sections 8.1 and 8.2 describe request for new values in
   [IANA.l2tp-parameters], for registries already managed by IANA
   assignable through Expert Review according to [RFC3438].  Section 8.3
   describes number spaces not managed by IANA.

8.1.  Message Type AVP Values

   This number space is managed by IANA as per [RFC3438].  There are two
   new message types, defined in Sections 4.1 and 4.2, to be allocated
   for this specification.

      Message Type AVP (Attribute Type 0) Values

         28: (CSUN) Connect-Speed-Update-Notification

         29: (CSURQ) Connect-Speed-Update-Request

8.2.  Control Message Attribute Value Pairs (AVPs)

   This number space is managed by IANA as per [RFC3438].  There are two
   new AVPs, defined in Sections 6.1 and 6.2, to be allocated for this
   specification.

      Control Message Attribute Value Pairs (AVPs)

         97: Connect Speed Update AVP

         98: Connect Speed Update Enable AVP

8.3.  Values for Access Line Information AVPs

   The Access Line Information AVPs use the Vendor ID of 3561 for the
   ADSL Forum (now Broadband Forum).  The number spaces in these Values
   and their new allocations (e.g., enumerated values for the Access
   Line Access-Loop-Encapsulation AVP and ANCP Access Line Type AVP) are
   managed by the Broadband Forum.

9.  Security Considerations

   The security of these AVP relies on an implied trust relationship
   between the Access Node/DSLAM and the BRAS/LAC, and between the LAC
   and the LNS.  The identifiers that are inserted by the Access Node/
   DSLAM are unconditionally trusted; the BRAS does not perform any
   validity check on the information received before forwarding the
   information.




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   These AVPs are intended to be used in environments in which the
   network infrastructure (the Access Node/DSLAM, the BRAS/LAC, the LNS,
   and the entire network in which those devices reside) is trusted and
   secure.

   Careful consideration should be given to the potential security
   vulnerabilities that are present in this model before deploying this
   option in actual networks.

   The AVPs described in this document are used to carry identification
   and characterization of subscriber Access Line, and to report
   connection speed changes.  If used in a non-secure environment, they
   could reveal such information.  The Tunnel (Control Connection)
   security considerations are covered in Section 9.1 of [RFC2661] and
   Section 8.l of [RFC3931].  Additionally, the hiding of AVP attribute
   values mechanism can be used to hide the value of the AVPs described
   in this document, if they are deemed sensitive in some environments.
   AVP hiding is described in Section 4.3 of [RFC2661] and Section 5.3
   of [RFC3931].

   The Attributes described in this document neither increase nor
   decrease the security of the L2TP protocol.

   It is possible to utilize [RFC3193] "Securing L2TP with IPsec" to
   increase the security by utilizing IPsec to provide for tunnel
   authentication, privacy protection, integrity checking and replay
   protection.

10.  Acknowledgements

   Many thanks to Wojciech Dec and the others of the Broadband Forum
   (previously the DSL Forum) Architecture and Transport Working Group
   for their help in putting together this document.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2661]  Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn,
              G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"",
              RFC 2661, August 1999.

   [RFC3438]  Townsley, W., "Layer Two Tunneling Protocol (L2TP)
              Internet Assigned Numbers Authority (IANA) Considerations
              Update", BCP 68, RFC 3438, December 2002.



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   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.

   [TR-101]   DSL Forum, "Migration to Ethernet-Based DSL Aggregation",
              TR 101, April 2006, <http://www.broadband-forum.org/
              technical/download/TR-101.pdf>.

11.2.  Informative References

   [ANCP]     Wadhwa, S., Moisand, J., Subramanian, S., Haag, T., Voigt,
              N., and R. Maglione, "Protocol for Access Node Control
              Mechanism in Broadband Networks", Work in Progress,
              March 2009.

   [IANA.enterprise-numbers]
              Internet Assigned Numbers Authority, "PRIVATE ENTERPRISE
              NUMBERS", <http://www.iana.org>.

   [IANA.l2tp-parameters]
              Internet Assigned Numbers Authority, "Layer Two Tunneling
              Protocol 'L2TP'", <http://www.iana.org>.

   [RFC2516]  Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D.,
              and R. Wheeler, "A Method for Transmitting PPP Over
              Ethernet (PPPoE)", RFC 2516, February 1999.

   [RFC3046]  Patrick, M., "DHCP Relay Agent Information Option",
              RFC 3046, January 2001.

   [RFC3193]  Patel, B., Aboba, B., Dixon, W., Zorn, G., and S. Booth,
              "Securing L2TP using IPsec", RFC 3193, November 2001.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC4243]  Stapp, M., Johnson, R., and T. Palaniappan, "Vendor-
              Specific Information Suboption for the Dynamic Host
              Configuration Protocol (DHCP) Relay Agent Option",
              RFC 4243, December 2005.

   [RFC4679]  Mammoliti, V., Zorn, G., Arberg, P., and R. Rennison, "DSL
              Forum Vendor-Specific RADIUS Attributes", RFC 4679,
              September 2006.

   [RFC4951]  Jain, V., "Fail Over Extensions for Layer 2 Tunneling
              Protocol (L2TP) "failover"", RFC 4951, August 2007.





Mammoliti, et al.            Informational                     [Page 27]

RFC 5515            L2TP Access Line AVP Extensions             May 2009


Authors' Addresses

   Vince Mammoliti
   Cisco Systems
   181 Bay Street, Suite 3400
   Toronto, ON  M5J 2T3
   Canada

   EMaill: vince@cisco.com


   Carlos Pignataro
   Cisco Systems
   7200 Kit Creek Road
   PO Box 14987
   Research Triangle Park, NC  27709
   USA

   EMail: cpignata@cisco.com


   Peter Arberg
   Redback Networks
   300 Holger Way
   San Jose, CA  95134
   USA

   EMail: parberg@redback.com


   John Gibbons
   Juniper Networks
   10 Technology Park Drive
   Westford, MA  01886
   USA

   EMail: jgibbons@juniper.net


   Paul Howard

   EMail: howsoft@mindspring.com









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