Submitted to PPP Working Group Yves T'Joens INTERNET DRAFT Paolo Crivellari Laurent Hermans Bernard Sales Alcatel June 1999 Expires December, 1999 Layer Two Tunnelling Protocol : ATM access network extensions. Status of this memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months. Internet-Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet- Drafts as reference material or to cite them other than as a ``working draft'' or ``work in progress.'' The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To view the entire list of current Internet-Drafts, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directorieson ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au(Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Distribution of this memo is unlimited. Abstract [L2TP] specifies a protocol which permits the tunnelling of the link layer of PPP over packet based networks, to support remote access (mainly) by ISDN and PSTN networks. This document augments the procedures described in [L2TP] to further support ATM SVC or PVC based access networks. The extensions defined within this document allow for asymmetric bi-directional call establishment and service selection in the ATM access network. Table Of Contents T'Joens, et al. Expires December 1999 [Page 1] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 1. Introduction 1.1 Conventions 2. Assumptions 2.1 Topology 2.2 Connection Establishment 2.3 LCP Negotiation 3. ATM access enhanced procedures 3.1 ATM connectivity 3.2 Tunnel establishment 3.3 call establishment 3.4 Framing 4. Service model issues 4.1 Authentication 4.2 Authorization 5. New and extended AVPs 5.1 New AVP Summary 5.2 New AVP definition 5.3 Changed AVP Definition 6. IANA considerations 7. Security considerations 8. Acknowledgements 9. References 10. Contacts 1. Introduction [L2TP] is a tunnelling protocol that allows tunnelling of PPP sessions between a so called L2TP Access Concentrator (LAC) and an L2TP Network Server (LNS). The main focus of [L2TP] is on supporting HDLC based ISDN/PSTN access networks. This document augments the procedures described in [L2TP] to further support ATM SVC or PVC based access networks. Support for ATM access networks requires extensions to the present L2TP procedures along the following lines : (a) the traffic management aspects of ATM connections (e.g. assymetric bandwidth allocation and service category selection capabilities), (b) the addressing format to be used in switched ATM networks [AESA] and (c) the limititations imposed on LCP negotiation by transporting PPP over AAL5 over the access network segment of the PPP connection [PPPoA]. Within this draft, the necessary extensions to [L2TP] are defined to T'Joens, et al. Expires December 1999 [Page 2] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 cope with issues (a) and (b), issue (c) which is not specific to ATM may be solved as described in [L2TP_link]. 1.1 Conventions Throughout this document, the words that are used to define the significance of particular requirements are capitalised. These words are: o "MUST" This word or the adjective "REQUIRED" means that the item is an absolute requirement of this specification. o "MUST NOT" This phrase means that the item is an absolute prohibition of this specification. o "SHOULD" This word or the adjective "RECOMMENDED" means that there may exist valid reasons in particular circumstances to ignore this item, but the full implications should be understood and the case carefully weighed before choosing a different course. o "SHOULD NOT" This phrase means that there may exist valid reasons in particular circumstances when the listed behaviour is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behaviour described with this label. o "MAY" This word or the adjective "OPTIONAL" means that this item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because it enhances the product, for example; another vendor may omit the same item. 2. Assumptions In this section we describe some assumptions that have lead to the extensions described in this draft. 2.1 Topology The procedures as defined in [L2TP] apply mainly to access network T'Joens, et al. Expires December 1999 [Page 3] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 technology such as PSTN and ISDN, which may be respectively asynch. HDLC and synch HDLC based. The aim of this document is to extend L2TP support to allow for user / LAC communication based on ATM access network technology. 2.2 Connection Establishment Due to the wide variety of existing signalling protocols and ATM service categories, and their support or non-support within ATM based access networks, this document takes as approach to provide for a flexible identification of ATM connection characteristics while establishing outgoing and incoming L2TP calls. The procedures as defined within this document allow the allocation of asymmetric bandwidth and service category selection in terms of real or non-real time requirements on the ATM portion of the access network. As such, the detailed signalling protocol specific information elements that are necessary for switched VC service, are not negotiated during call establishment over the L2TP tunnel. In order to identify the endpoint of the ATM connection within the ATM access network, SVCs can be established on the basis of the ATM end system addressing format [AESA]. For PVC based services, the PVC can either be referred to by using the ATM end system addressing procedure (Dialed Number), or by making use of a textual name (Service Name). The latter is inspired by the procedures defined within [Auto_PVC]. 2.3 LCP negotiation The procedures described within this draft may be combined with the procedures described in [L2TP_link] to limit LCP negotiation between LNS and user, so as to enforce PPP over AAL5 specific LCP negotiation [PPPoA]. 3. ATM access enhanced procedures In order to illustrate the procedures specified within this draft, this section will provide a description of what might happen when a Virtual dial-up client initiates access through a (switched) ATM access network. Note that the emphasis is on the changes proposed within this draft relative to [L2TP]. 3.1 ATM connectivity Prior to initiating the PPP protocol layer, a Virtual Connection (VC) MUST be established between the user and the Network Access Server (LAC). This virtual connection MAY either be a preconfigured T'Joens, et al. Expires December 1999 [Page 4] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 Permanent VC(PVC), where the access network provider, NAS and user agree beforehand on the characteristics of the PVC, or MAY be an on- demand switched VC(SVC), where the negotiation between user, network and NAS takes place by means of an ATM signalling protocol. Note that for establishing PVCs, alternative use may be made of the procedures as described in [Auto_PVC]. In both cases, the user is referred to as the Virtual dial-in user. Prior to accepting the switched connection from the Virtual dial-in user, the LAC MAY check with the LNS whether the call should be accepted. In the latter situation, the LAC MAY determine based upon parameters available within the call establishment message that this concerns a virtual dial in user, or MAY undertake a partial authentication of the end system/user, in order to bind the end system/user with a specific LNS. 3.2 Tunnel establishment If no tunnel connection currently exists to the desired LNS, one is initiated. During the tunnel establishment, LNS and LAC indicate bearer and framing capabilities to each other, according to normal procedures. The bearer capability is extended to allow the identification of ATM devices in the LAC. This allows the LNS to use the extensions as defined within this draft to support ATM based outgoing calls. If no compatibility between LNS and LAC exists according to the extensions defined within this draft, no tunnel establishment can take place. This would be because the LAC does not support any bearer capability which is expected by the LNS, or vice versa. It is however encouraged that LAC or LNS implementations would allow for seamless interworking with peer devices which do not implement the extensions defined within this draft. This could be implemented by allowing a gracefull fallback to Digital bearer capability. 3.3 call establishment During incoming and outgoing broadband call establishment, the following extensions are defined to existing procedures. During OCRQ, the LNS MUST indicate to the LAC minimum and maximum speeds for receive and transmit traffic (from the LAC perspective). This is to allow for the bi-directional asymmetric nature of ATM traffic contracts. Note that in order to support UBR connections between LAC and user, the Minimum BPS MUST be set to zero. T'Joens, et al. Expires December 1999 [Page 5] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 Further during OCRQ, the LNS MAY indicate to the LAC the required service category, i.e., real time (rt) or non-real time (nrt) transport services. The combination of minimum and maximum receive and transmit speed, and the indication of the required service category allows the LAC to establish an ATM connection according to its own capabilities, and the ATM access network capabilities, however within the service requirement for the PPP layer. Real time connectivity can be provided by either CBR or rt-VBR ATM service categories, non-real time connectivity can be provided by UBR, nrt-VBR, ABR or GFR ATM service categories. Further the LNS MUST indicate to the LAC in OCRQ message the dialed number according to the format described in this document (NSAP format). When the dialed number carries an all zero payload, the LAC SHOULD look at the Service Name AVP to bind the tunnel call to an PVC. 3.4 Framing Within this document the PPP PDU refers to the concatenation of PPP protocol ID, PPP Information and PPP padding fields. In the direction of user to LNS, the PPP PDU will be carried on top of an AAL5 connection between user and LAC. The LAC MUST strip off the AAL5 specific fields based on the encapsulation mechanism in use on the ATM connection, i.e. VC multiplexed or LLC encapsulated [PPPoA], and MUST encapsulate the PPP PDU with address and control field, as per HDLC procedures, on the L2TP tunnel. In the direction of LNS to user, the PPP PDU will be carried on top of an AAL5 connection between LAC and user. The LAC MUST strip the PPP PDU from the address and control field on the L2TP tunnel, and insert the AAL5 specific fields based on the encapsulation mechanism in use on the ATM connection, i.e. VC multiplexed or LLC encapsulated. 4. Service model issues 4.1 Authentication In case of ATM switched VC establishment, calling party number information may be used for first level authentication much in the same way as for PSTN or ISDN access. In case of permanent VC establishment, authentication may not be an issue from the LAC side, because of the permanent character of the VC. Bilateral agreement between LAC and LNS providers may eliminate the authentication phase T'Joens, et al. Expires December 1999 [Page 6] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 in the latter case. 4.2 Authorization Because of the flexibility of establishing ATM connections with varying parameters, some authorization may be required prior to accepting the establishment of a switched ATM connection from the user with certain ATM traffic parameters. This authorization may be performed against the ATM specific authentication information (e.g. calling line id), or may be performed after partial authentication of the user at the PPP level. Non authorized access requests result in connection release. 5. New and extended AVPs 5.1 New AVP Summary The following table lists the extra AVPs that are defined within this document. The "attr" column indicates the integer value assigned to this attribute. Note that the attribute value is relative compared to the vendor ID. The "M" column indicates the setting of the "Mandatory" bit of the AVP header for each attribute. The "LEN" column indicates the size of the AVP including the AVP header. A "+" in this column indicates that the length varies depending upon the length of the actual contents of the value field. The usage list for each entry indicates the message types that utilize each AVP. An abbreviation shown in mixed or upper case letters indicates that the corresponding AVP MUST be present in this message type. All lower case indicates that the AVP MAY optionally appear in this message type. Some AVPs MAY be present only when a corresponding optional AVP or specific setting within the AVP is present, these AVPs are shown in lower case as well. Attr M Len Attribute Name (usage) x 0 10 Rx Minimum BPS (OCRQ) 32-bit integer indicating the lowest acceptable line speed for the call in the receive direction. Rx indicates the user to LAC direction. x 0 10 Rx Maximum BPS (OCRQ) 32-bit integer indicating the highest acceptable line speed for call in the receive direction. Rx indicates the user to LAC direction. x 0 6+ ATM Cause Code (cdn) 16-bit cause code, 1 octet cause message, and optional ASCII advisory message. x 0 8 Service Category (ocrq, icrq) T'Joens, et al. Expires December 1999 [Page 7] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 The Service Category indicates the service expected for the call, e.g., real time or non-real time. x 0 6+ Service Name (ocrq, icrq) The Service Name indicates the service name linked to a preestablished PVC. 5.2 New AVP definition The following lists the new AVPs defined within this draft, and describes the expected behaviour when this AVP would be present within a message. Rx Minimum BPS 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0|0|0|0|0| 10 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | x | BPS (H) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BPS (L) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Rx Minimum BPS AVP encodes the lowest acceptable line speed for this call in the receive direction, for these cases where asymmetric transmission is required. This AVP MAY be included within the OCRQ, and SHOULD only be included when the LAC indicated ATM support in the bearer capabilities AVP during tunnel establishment. Rx Maximum BPS 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0|0|0|0|0| 10 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | x | BPS (H) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BPS (L) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ T'Joens, et al. Expires December 1999 [Page 8] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 The Rx Maximum BPS AVP encodes the highest acceptable line speed for this call in the receive direction, for these cases where asymmetric transmission is required. This AVP MAY be included within the OCRQ, and SHOULD only be included when the LAC indicated ATM support in the bearer capabilities AVP during tunnel establishment. Service Category 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0|0|0|0|0| 8 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | x |0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|S| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Service Category provides optional extra information on the Quality of Service expected for the call establishment. The S bit indicates either non real time (S bit set to 0) or real time (S bit set to 1) service requirement. The other bit fields are reserved for future use. The Service Category AVP MAY be present in OCRQ and ICRQ messages, and SHOULD only be included when the LAC indicated ATM support in the bearer capabilities AVP during tunnel establishment. Service Name 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0|0|0|0|0| 6+len name | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | x | name | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | name (ctd) .... +-+-+-+-+-+-+-+-+-+-+-+-+- The Service Name field allows for the exchange of a textual name for referring to a PVC. The service name AVP MAY only be T'Joens, et al. Expires December 1999 [Page 9] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 provided when the Dialed Number field is encoded as all zeros. The service name AVP MAY be present in OCRQ and ICRQ messages, and SHOULD only be included when the LAC indicated ATM support in the bearer capabilities AVP during tunnel establishment. ATM Cause Code 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0|0|0|0|0| 6 + len.Cause Code| 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | x | Cause Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cause Code (cont'd) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The ATM Cause code AVP indicates the Cause Code as specified in [UNI], for ATM connection establishment failures. The ATM Cause Code AVP MUST be present in the CDN message. 5.3 Changed AVP Definition The following AVPs see their contents changed relative to [L2TP] in order to support ATM access awareness. Bearer Capabilities 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0|0|0|0|0| 10 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 4 | 0x00 | 0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x00 |0|0|0|0|0|B|A|D| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The bearer Capabilities AVP within a SCCRQ or SCCRP indicates the bearer capabilities that the sender of this message can provide for outgoing calls. If bit B is set, broadband access is supported (ATM), if bit A is set, analogue access is supported. If bit D is set, Digital access is supported. T'Joens, et al. Expires December 1999 [Page 10] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 This AVP provides the peer with an indication of the bearer device types supported by the hardware interfaces of the sender for outgoing calls. An LNS SHOULD NOT initiate an outgoing call specifying a value in the Bearer Type AVP for a device type not advertised in the Bearer Capabilities AVP it received from the LAC during control connection establishment. Attempts to do so will result in the call being rejected. In these cases where the LAC only supports the B bit, and the LNS would not recognize the B bit, no outgoing calls are possible. Note that when the LAC only has ATM based devices, it may still opt for fall back to digital bearer types. (Tx) Minimum BPS The (Tx) Minimum BPS AVP encodes the lowest acceptable line speed for this call in the transmit direction. The (Tx) Minimum BPS AVP MAY be used in OCRQ. If the Rx Minimum BPS is not available in the message, then symmetric transmission is implied, with both minimum receive and transmit bit-rates equal to Minimum BPS. (Tx) Minimum BPS is set in bits/second, and may be mapped to the PCR in cells/second for ATM based traffic. Note that the PCR is a mandatory parameter for all service capabilities in ATM signalling. The exact mapping to signalling IEs is outside the scope of this draft. (Tx) Maximum BPS (Tx) Maximum BPS AVP encodes the highest acceptable line speed for this call in the transmit direction. The (Tx) Maximum BPS AVP MAY be used in OCRQ. If the Rx Maximum BPS AVP is not available in the message, then symmetric transmission is implied, with both maximum receive and transmit bitrates equal to Maximum BPS. (Tx) Maximum BPS is set in bits/second, and may be mapped to the PCR in cells/second for ATM based traffic. Note that the PCR is a mandatory parameter for all service capabilities in ATM signalling. The exact mapping to signalling IEs is outside the scope of this draft. Bearer Type T'Joens, et al. Expires December 1999 [Page 11] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0|0|0|0|0| 10 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 18 | 0x00 | 0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x00 |0|0|0|0|0|B|A|D| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The bearer type AVP encodes the bearer type for the requested call. The bearer type AVP MUST be present in the OCRQ, and MAY be present in the ICRQ. If bit B is set, broadband access is requested (ATM), if bit A is set, analogue access is requested. If bit D is set, Digital access is requested. Note that in the OCRQ all 3 bits (B,A,D) may be set indicating that the call may be of either type. The B bit SHOULD only be set if the Broadband capability was indicated during tunnel establishment. Dialed Number 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0|0|0|0|0| 26 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 21 | NSAP | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NSAP (cont'd) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NSAP (cont'd) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NSAP (cont'd) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NSAP (cont'd) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NSAP (cont'd) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Dialed Number AVP indicates the number that should be used to address the virtual dial in user. The Dialed number AVP MUST be present in OCRQ, and MAY be present in ICRQ. The Dialed number AVP SHOULD be interpreted as binary encoded when the B T'Joens, et al. Expires December 1999 [Page 12] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 bit is set in the Bearer Type AVP. The NSAP binary encoded address provides a broader range of address encapsulation methods than an ASCII field. In the NSAP field, which MUST have the length of 20 octets, the addressing protocol used (E.164, ICD, DCC) is specified as defined in [AESA]. If the Dialed Number AVP carries an all zero NSAP address, the Service Name AVP MAY provide further information to bind the L2TP call to a specific VC connection. See also [Auto_PVC]. Sub-Address see Dialed Number. If the Dialed Number carries an all zero NSAP address, the Sub-Address should be neglected on receipt. 6. IANA Considerations This document requires 5 new type values for the following AVPs : - Rx Minimum BPS - Rx Maximum BPS - ATM Cause Code - Service Category - Service Name This document further defines a new bit (B) in the bearer capabilities and bearer type AVPs. This document defines a flag field in the Service Category AVP, only one bit in this flag has been assigned witin this document (S). 7. Security Considerations No extra security risk outside these specified by [L2TP] are foreseen. 8. Acknowledgements The authors would like to thank Juha Heinanen (Telia) and David Allen (Nortel Networks) for their constructive discussion on the draft during the Minneapolis IETF meeting. 9. References [L2TP] K. Hamzeh, T. Kolar, M. Littlewood, G. Singh Pall, J. Taarud, A. Valencia, A. Rubens, W.M. Townsley, B. Palter, W. Verthein "Layer Two Tunnelling Protocol (L2TP)", RFC xxxx, July 1999 [PPP] W. Simpson, "The Point-to-Point Protocol (PPP)", STD 51, RFC 1661, July 1994 T'Joens, et al. Expires December 1999 [Page 13] Internet Draft draft-ietf-pppext-l2tp-atmext-01.txt June 1999 [PPPoA] G. Gross, M. Kaycee, A. Lin, A. Malis, J. Stephens, "PPP over AAL5", RFC 2364, July 1998 [UNI] User-Network Interface (UNI) Specification, Version 4.0, ATM Forum, July, 1996 [AESA] ATM Forum Addressing : Reference Guide, version 1.0, ATM Forum, Final Ballot, January 1999 [PPP_HDLC] W. Simpson, "PPP in HDLC-like Framing", STD 51, RFC 1662, July 1994 [L2TP_link] M. Townsley, W. Palter, "L2TP Link Extensions", Internet Draft, November 1998, [Auto_PVC] ATM Forum, "Auto-configuration of PVCs", af-nm-0122.000, March 1999 10. Contacts Yves T'joens Alcatel Corporate Research Center Francis Wellesplein 1, 2018 Antwerp, Belgium Phone : +32 3 240 7890 E-mail : yves.tjoens@alcatel.be Paolo Crivellari Alcatel Access Systems Division Francis Wellesplein 1, 2018 Antwerp, Belgium Phone : +32 3 240 3319 E-mail : pcri@sebb.bel.alcatel.be Laurent Hermans Alcatel Corporate Research Center Francis Wellesplein 1, 2018 Antwerp, Belgium Phone : +32 3 240 8671 E-mail : hermanla@rc.bel.alcatel.be Bernard Sales Alcatel Corporate Research Center Francis Wellesplein 1, 2018 Antwerp, Belgium Phone : +32 3 240 9574 E-mail : bernard.sales@btmaa.bel.alcatel.be T'Joens, et al. Expires December 1999 [Page 14]