Network Working Group N. McGill Internet-Draft C. Pignataro Updates: 3931, 4349, 4454, 4591, Cisco Systems 4719 (if approved) April 13, 2009 Intended status: Standards Track Expires: October 15, 2009 L2TPv3 Extended Circuit Status Values draft-ietf-l2tpext-circuit-status-extensions-04 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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 and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "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. This Internet-Draft will expire on October 15, 2009. 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 defines additional Layer 2 Tunneling Protocol Version 3 McGill & Pignataro Expires October 15, 2009 [Page 1] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 (L2TPv3) bit values to be used within the "Circuit Status" Attribute Value Pair (AVP) to communicate more granular error states for Attachment Circuits (ACs) and Pseudowires (PWs). It also generalizes the Active bit and deprecates the use of the New bit in the "Circuit Status" AVP, updating RFC3931, RFC4349, RFC4454, RFC4591, and RFC4719. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Specification of Requirements . . . . . . . . . . . . . . 3 2. L2TPv3 Extended Circuit Status Values . . . . . . . . . . . . 3 3. Circuit Status Usage and Clarifications . . . . . . . . . . . 8 4. Updates to Existing RFCs . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1. Normative References . . . . . . . . . . . . . . . . . . . 10 8.2. Informative References . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 McGill & Pignataro Expires October 15, 2009 [Page 2] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 1. Introduction Currently the L2TPv3 Circuit Status AVP [RFC3931] is able to convey the UP/DOWN status of an access circuit. However, a finer granularity is often useful to determine the direction of the fault as has been added for MPLS-based pseudowires and used in the pseudowire control protocol using LDP, see Section 3.5 of [RFC4446] and Section 5.4.2 of [RFC4447]. Additionally, it is useful (in session-level redundancy scenarios) to be able to indicate if a pseudowire is in a standby state, where it is fully established by signaling and allows OAM, but is not switching data. Again, such functionality is available for MPLS- based pseudowires using LDP, see [I-D.ietf-pwe3-redundancy-bit]. This document provides extended circuit status bit values for L2TPv3 and adds them in a manner such that it is backwards compatible with the current Circuit Status AVP. These new bits are applicable to all pseudowires types that use the Circuit Status AVP. 1.1. Specification of Requirements 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]. 2. L2TPv3 Extended Circuit Status Values The Circuit Status AVP (ICRQ, ICRP, ICCN, OCRQ, OCRP, OCCN, SLI), Attribute Type 71, indicates the initial status of or a status change in the circuit to which the session is bound. The Attribute Value field for this AVP currently defined in [RFC3931] has the following format: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |N|A| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Bit Bit-Value Name ---------------------------------------------------------------- (A) 15 0x0001 Active (N) 14 0x0002 New As currently defined in [RFC3931] and replicated in [RFC4349], McGill & Pignataro Expires October 15, 2009 [Page 3] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 [RFC4454], [RFC4591], and [RFC4719], the two bits have the following meanings: o The A (Active) bit indicates whether the circuit is up/active/ ready (1) or down/inactive/not-ready (0). o The N (New) bit indicates whether the circuit status indication is for a new circuit (1) or an existing circuit (0). This document updates the semantics of the A and N bits as follows (see also Section 4): The A (Active) bit indicates whether the local pseudowire endpoint (both local attachment circuit and local PSN-facing pseudowire) has no faults present and is up/active/ready (1) or has faults present and is down/inactive/not-ready (0). The N (New) bit indicates if the notification is for a new circuit (1) or an existing circuit (0), and is provided to emulate (Frame Relay) NNI signaling between PEs. It MAY be used to convey that a circuit has been re-provisioned or newly provisioned at the PE, which can already be inferred from the L2TP control message type. It is therefore uncertain as to what use the receiving PE can make of this bit, although it MAY include logging. This document deprecates this bit as it is of little or no use, hence this bit SHOULD be ignored on receipt and is OPTIONAL to send. For reference, see Section 3.4 of [RFC4591] which does not specify any additional usage beyond the setting of in the ICRQ, ICRP (and OCRQ, OCRP) and clearing in all other control messages. This document also extends this bitmap of values to allow for finer granularity of local pseudowire (i.e., access circuit or PSN-facing endpoint) status reporting. The Attribute Value field for the Circuit Status AVP including the new values has the following format: McGill & Pignataro Expires October 15, 2009 [Page 4] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |S|E|I|T|R|0|A| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Bit Bit-Value Name ----------------------------------------------------------------- (A) 15 0x0001 Active: Pseudowire has no faults (N) 14 0x0002 New [use deprecated] (R) 13 0x0004 Local Attachment Circuit (ingress) Receive Fault (T) 12 0x0008 Local Attachment Circuit (egress) Transmit Fault (I) 11 0x0010 Local PSN-facing PW (ingress) Receive Fault (E) 10 0x0020 Local PSN-facing PW (egress) Transmit Fault (S) 9 0x0040 Pseudowire is in Standby mode The new bits values have the following meanings: (R), Local Attachment Circuit (ingress) Receive Fault Fault Here | | | +----------------------+ +----------------------+ | Rx| LCCE |Egress | Peer LCCE | --X-->| |-------->| | | L2TPv3 | [PSN] | L2TPv3 | Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit | <-----| |<--------| | +----------------------+ +----------------------+ An alarm or fault has occurred at the local attachment circuit such that it is unable to receive traffic. It can still transmit traffic. McGill & Pignataro Expires October 15, 2009 [Page 5] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 (T), Local Attachment Circuit (egress) Transmit Fault +----------------------+ +----------------------+ Rx| LCCE |Egress | Peer LCCE | ----->| |-------->| | | L2TPv3 | [PSN] | L2TPv3 | Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit | <--X--| |<--------| | | +----------------------+ +----------------------+ | | Fault Here A fault has occurred at the local attachment circuit such that it is unable to transmit traffic. It can still receive traffic. (I), Local PSN-facing PW (ingress) Receive Fault +----------------------+ +----------------------+ Rx| LCCE |Egress | Peer LCCE | ----->| |-------->| | | L2TPv3 | [PSN] | L2TPv3 | Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit | <-----| |<---X----| | +----------------------+ | +----------------------+ | | Fault Here A fault has occurred in the receive direction between the local endpoint and the remote L2TP endpoint. Note that a fault at the session level would not necessarily trigger an L2TP control connection timeout. The means of detecting this fault are outside the scope of this document; as an example, detection may be via PW Type-specific means, BFD, or other methods. McGill & Pignataro Expires October 15, 2009 [Page 6] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 (E), Local PSN-facing PW (egress) Transmit Fault Fault Here | | +----------------------+ | +----------------------+ Rx| LCCE |Egress| | Peer LCCE | ----->| |------X->| | | L2TPv3 | [PSN] | L2TPv3 | Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit | <-----| |<--------| | +----------------------+ +----------------------+ A fault has occurred in the transmit direction between the local endpoint and the remote L2TP endpoint. Note that a fault at the session level would not necessarily trigger an L2TP control connection timeout. The means of detecting this fault are outside the scope of this document; as an example, detection may be via PW Type-specific means, BFD, or other methods. (S), Pseudowire is in Standby mode Standby | | +----------------------+ | +----------------------+ Rx| LCCE |Egress | Peer LCCE | ----->| |---X---->| | | L2TPv3 | [PSN] | L2TPv3 | Tx| Circuit Pseudowire |Ingress | Pseudowire Circuit | <-----| |<--X-----| | +----------------------+ | +----------------------+ | | Standby The pseudowire has been placed into a standby mode which means that although it was signaled (setup of the PW) and is operational, it is NOT switching user traffic. Any received user traffic SHOULD be dropped. User traffic MUST NOT be transmitted. A standby pseudowire also allows for means to check its data plane liveness, to ensure its ability to switch data packets end-to-end. This is achieved for example as detailed in [RFC5085] or [I-D.ietf-pwe3-vccv-bfd]. However, data is not forwarded from an Access Circuit (AC) into the L2TPv3 session, or from the L2TPv3 McGill & Pignataro Expires October 15, 2009 [Page 7] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 session out of the AC. 3. Circuit Status Usage and Clarifications The following are clarifications regarding the usage of the Circuit Status AVP bits: o The (R), (T), (I) and (E) bits are collectively referred to as "fault status bits". o [RFC3931] defined the (A) bit as pertaining to local access circuit state only. This draft redefines it as meaning that "no faults are present on the local pseudowire endpoint." o If multiple faults occur, all the fault status bits corresponding to each fault MUST be set (i.e., they MUST be bitwise-OR-d together). o The (A) bit MUST NOT be set until all fault status bits are cleared. This behavior allows an endpoint to be backwards compatible with a remote endpoint that does not understand these new status bits. o If any of the fault status bits are set, then the (A) bit MUST be cleared. That is, the fault status bits (R, T, I, E) are a more granular definition of (A), such that OR-ing the bits provides an inverted (A). o If (A) is clear and the fault status bits (R, T, I, E) are clear, it means that there is no extended circuit status. That is, the circuit is down/inactive/not-ready (from the (A) bit), without a more granular (extended) indication. o The (S) bit can be set in conjunction with any other bit, including (A). A pseudowire endpoint in Standby (S bit set) can be up/active/ready (A bit set) or experiencing a fault (A bit cleared and (R, T, I, E) bit(s) set). o Leaving standby mode is indicated by the clearing of the (S) bit. o The usage of the (N) bit has been deprecated. 4. Updates to Existing RFCs This document updates existing RFCs that define (either generically or in the context of a specific set of PW Types) the Active and New McGill & Pignataro Expires October 15, 2009 [Page 8] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 bits of the Circuit Status AVP. The Active and New bits of the Circuit Status AVP are specified in Section 5.4.5 of [RFC3931]. Those definitions are adapted to specific Attachment Circuits and replicated in Section 3.4 of [RFC4349] (HDLC Frames over L2TPv3), Section 8 of [RFC4454] (ATM over L2TPv3), Section 3.4 of [RFC4591] (Frame Relay over L2TPv3), and Section 2.3.3 of [RFC4719] (Ethernet Frames over L2TPv3). This document updates the definitions in all these five references to say: The A (Active) bit indicates whether the local pseudowire endpoint (both local attachment circuit and local PSN-facing pseudowire) has no faults present and is up/active/ready (1) or has faults present and is down/inactive/not-ready (0). The N (New) bit usage is deprecated, it SHOULD be ignored on receipt and is OPTIONAL to send. This document also updates Section 2.2 (bullet c) of [RFC4719], removing the following two sentences: For ICRQ and ICRP, the Circuit Status AVP MUST indicate that the circuit status is for a new circuit (refer to N bit in Section 2.3.3). For ICCN and SLI (refer to Section 2.3.2), the Circuit Status AVP MUST indicate that the circuit status is for an existing circuit (refer to N bit in Section 2.3.3) and reflect the current status of the link (refer to A bit in Section 2.3.3). And finally, updates Section 3.1 of [RFC4349], Section 3.1 of [RFC4454], Section 3.1 of [RFC4591], and Section 2.2 of [RFC4719] with the following paragraph addition: The usage of the N bit in the Circuit Status AVP is deprecated. Therefore, for ICRQ and ICRP the Circuit Status AVP need not indicate on sending (nor check on receipt) that the circuit status is for a new circuit, and for ICCN and SLI the Circuit Status AVP need not indicate on sending (nor check on receipt) that the circuit status is for an existing circuit. 5. Security Considerations No additional security considerations exist with extending this attribute. McGill & Pignataro Expires October 15, 2009 [Page 9] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 6. IANA Considerations The Circuit Status Bits number space reachable at [IANA.l2tp-parameters] is managed by IANA as per Section 10.7 of [RFC3931]. Five new bits (bits 9 through 13) and one updated bit (bit 14) are requested to be assigned as follows: Circuit Status Bits - per [RFC3931] ------------------- Bit 9 - S (Standby) bit Bit 10 - E (Local PSN-facing PW (egress) Tx Fault) bit Bit 11 - I (Local PSN-facing PW (ingress) Rx Fault) bit Bit 12 - T (Local AC (egress) Tx Fault) bit Bit 13 - R (Local AC (ingress) Rx Fault) bit Bit 14 - N (New) bit [use deprecated] 7. Acknowledgements The authors wish to thank Muhammad Yousuf, Mark Townsley, George Wilkie, Prashant Jhingran, Pawel Sowinski, and Ignacio Goyret for useful comments received. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005. [RFC4349] Pignataro, C. and M. Townsley, "High-Level Data Link Control (HDLC) Frames over Layer 2 Tunneling Protocol, Version 3 (L2TPv3)", RFC 4349, February 2006. [RFC4454] Singh, S., Townsley, M., and C. Pignataro, "Asynchronous Transfer Mode (ATM) over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4454, May 2006. [RFC4591] Townsley, M., Wilkie, G., Booth, S., Bryant, S., and J. Lau, "Frame Relay over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4591, August 2006. [RFC4719] Aggarwal, R., Townsley, M., and M. Dos Santos, "Transport McGill & Pignataro Expires October 15, 2009 [Page 10] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 of Ethernet Frames over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4719, November 2006. 8.2. Informative References [I-D.ietf-pwe3-redundancy-bit] Muley, P., Bocci, M., and L. Martini, "Preferential Forwarding Status bit definition", draft-ietf-pwe3-redundancy-bit-01 (work in progress), September 2008. [I-D.ietf-pwe3-vccv-bfd] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)", draft-ietf-pwe3-vccv-bfd-03 (work in progress), February 2009. [IANA.l2tp-parameters] Internet Assigned Numbers Authority, "Layer Two Tunneling Protocol "L2TP"", March 2009, . [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006. [RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006. [RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007. Authors' Addresses Neil McGill Cisco Systems 7025-4 Kit Creek Rd PO Box 14987 Research Triangle Park, NC 27709 USA Email: nmcgill@cisco.com McGill & Pignataro Expires October 15, 2009 [Page 11] Internet-Draft L2TPv3 Extended Circuit Status Values April 2009 Carlos Pignataro Cisco Systems 7200-12 Kit Creek Road PO Box 14987 Research Triangle Park, NC 27709 USA Email: cpignata@cisco.com McGill & Pignataro Expires October 15, 2009 [Page 12]