Network Working Group A. Vainshtein (Axerra Networks) Internet Draft Y(J) Stein (RAD Data Communications) Expiration Date: March 2007 October 2006 Control Protocol Extensions for Setup of TDM Pseudowires draft-ietf-pwe3-tdm-control-protocol-extensi-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document defines extension to the PWE3 control protocol [RFC4447] and PWE3 IANA allocations [RFC4446] required for setup of TDM pseudowires. Vainshtein and Stein Standards Track [Page 1] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 TABLE OF CONTENTS 1. Introduction......................................................2 2. PW FEC for Setup of TDM PWs.......................................3 3. Interface Parameters for TDM PWs..................................3 3.1. CEP/TDM Payload Bytes (0x04)..................................3 3.2. CEP/TDM Bit-Rate (0x07).......................................4 3.3. Number of TDMoIP AAL1 cells per packet (0x0D - subject to IANA approval)..........................................................4 3.4. TDMoIP AAL1 mode (0x0E - subject to IANA approval)............5 3.5. TDMoIP AAL2 Options (0x0F - subject to IANA approval).........5 3.6. Fragmentation Indicator (0x09)................................6 3.7. TDM Options (0x0B)............................................6 4. Extending CESoPSN Basic NxDS0 Services with CE Application Signaling............................................................8 5. LDP Status Codes..................................................9 6. Using the PW Status TLV...........................................9 7. IANA Considerations..............................................10 8. Security Considerations..........................................10 9. Acknowledgements.................................................10 10. Disclaimer of Validity..........................................10 11. Normative References............................................11 12. Informational References........................................11 1. Introduction This document defines extension to the PWE3 control protocol [RFC4446] and PWE3 IANA allocations [RFC4446] required for setup of TDM pseudowires. Structure-agnostic TDM pseudowires have been specified in [RFC4553] and structure-aware ones in [PWE3-CESoPSN] and [PWE3-TDMoIP]. [RFC4447] defines extensions to LDP [RFC3036] that are required to exchange PW labels for PWs emulating various Layer 2 services (Ethernet, FR, ATM, HDLC etc.). Setup of TDM PWs requires both interpretation of the existing information elements of these extensions and exchange of additional information. Setup of TDM PWs using L2TPv3 will be defined in a separate document. Status of attachment circuits of TDM PWs can be exchanged between the terminating PEs using the mechanism defined in [RFC4447] without any changes. However, usage of these mechanisms with TDM PWs is NOT RECOMMENDED since indication of status of the TDM attachment circuits is carried in-band in the data plane. 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 RFC 2119. Vainshtein and Stein Expires March 2007 [Page 2] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 2. PW FEC for Setup of TDM PWs [RFC4447] uses LDP Label Mapping message [RFC3036] for advertising the FEC-to-PW Label binding, and defines two types of PW FEC that can be used for this purpose: 1. PWId FEC (FEC 128). This FEC contains: a) PW type b) Control bit (indicates presence of the control word) c) Group ID d) PW ID e) Interface parameters 2. Generalized PW FEC (FEC 129). This FEC contains only: a) PW type b) Control bit c) AGI, SAII and TAII that replace the PW ID The Group ID and the Interface parameters are contained in separate TLVs, called the PW Grouping TLV and the Interface Parameters TLV. Both types of PW FEC MAY be used for setup of TDM PWs with appropriate selection of PW types and interface parameters. The PW Types for TDM PWs are allocated in [RFC4446] as follows: o 0x0011 Structure-agnostic E1 over Packet [RFC4553] o 0x0012 Structure-agnostic T1 (DS1) over Packet [RFC4553] o 0x0013 Structure-agnostic E3 over Packet [RFC4553] o 0x0014 Structure-agnostic T3 (DS3) over Packet [RFC4553] o 0x0015 CESoPSN basic mode [PWE3-CESoPSN] o 0x0016 TDMoIP AAL1 mode [PWE3-TDMoIP] o 0x0017 CESoPSN TDM with CAS [PWE3-CESoPSN] o 0x0018 TDMoIP AAL2 mode [PWE3-TDMoIP] The two endpoints MUST agree on the PW type, as both directions of the PW are required to be of the same type. The Control bit MUST always be set for TDM PWs since all TDM PW encapsulations always use a control word. 3. Interface Parameters for TDM PWs 3.1. CEP/TDM Payload Bytes (0x04) This parameter is used for setup of all SAToP and CESoPSN PWs (i.e. PW types 0x0011, 0x0012, 0x0013, 0x0014, 0x0015 and 0x0017) and employs the following semantics: This parameter is used for setup of all SAToP and CESoPSN PWs (i.e. PW types 0x0011, 0x0012, 0x0013, 0x0014, 0x0015 and 0x0017) with the following semantics: Vainshtein and Stein Expires March 2007 [Page 3] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 1. The two endpoints of a TDM PW MUST agree on the same value of this parameter for the PW to be set up successfully. 2. Presence of this parameter in the PWId FEC or in the Interface Parameters Field TLV is OPTIONAL. If this parameter is omitted, default payload size defined for the corresponding service (see [RFC4553], [PWE3-CESoPSN]) MUST be assumed 3. For structure-agnostic emulation, any value consistent with the MTU of the underlying PSN MAY be specified 4. For CESoPSN PWs: a) The specified value P MUST be an integer multiple of N, where N is the number of timeslots in the attachment circuit b) For trunk-specific NxDS0 with CAS: i) (P/N) MUST be an integer factor of the number of frames per corresponding trunk multiframe (i.e. 16 for an E1 trunk and 24 of a T1 trunk) ii) The size of the signaling sub-structure is not accounted for in the specified value P. 3.2. CEP/TDM Bit-Rate (0x07) This interface parameter represents the bit-rate of the TDM service in multiples of the "basic" 64 Kbit/s rate. Its usage for all types of TDM PWs assumes the following semantics: 1. This interface parameter MAY be omitted if the attachment circuit bit-rate can be unambiguously derived from the PW Type (i.e. for structure-agnostic emulation of E1, E3 and T3 circuits). If this value is omitted for the structure-agnostic emulation of T1 PW Type, the basic emulation mode MUST be assumed. 2. If present, only the following values MUST be specified for structure-agnostic emulation (see [RFC4553]: a) Structure-agnostic E1 emulation - 32 b) Structure-agnostic T1 emulation: i) MUST be set to 24 in the basic emulation mode ii) MUST be set to 25 for the "Octet-aligned T1" emulation mode c) Structure-agnostic E3 emulation - 535 d) Structure-agnostic T3 emulation - 699 3. For all kinds of structure-aware emulation, this parameter MUST be set to N where N is the number of DS0 channels in the corresponding attachment circuit. Note: The value 24 does not represent the actual bit-rate of the T1 circuit (1,544 Mbit/s) in units of 64 kbit/s. The values mentioned above are used for convenience. 3.3. Number of TDMoIP AAL1 cells per packet (0x0D - subject to IANA approval) This parameter MAY be present for TDMoIP AAL1 mode PWs (PW type 0x0016) and specifies the number of 48-byte AAL1 PDUs per MPLS packet. Any values consistent with the MTU of the underlying PSN MAY be specified. If this parameter is not specified it defaults to 1 PDU per packet for Vainshtein and Stein Expires March 2007 [Page 4] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 low bit-rates (CEP/TDM Bit-Rate less than or equal to 32), and to 5 for high bit-rates (CEP/TDM Bit-Rate of 535 or 699). 3.4. TDMoIP AAL1 mode (0x0E - subject to IANA approval) This parameter MAY be present for TDMoIP AAL1 mode PWs (PW type 0x0016) and specifies the AAL1 mode. If this parameter is not present, the AAL1 mode defaults to "structured". When specified, the values have the following significance: 0 unstructured AAL1 2 structured AAL1 3 structured AAL1 with CAS. The two endpoints MUST agree on the TDMoIP AAL1 mode. 3.5. TDMoIP AAL2 Options (0x0F - subject to IANA approval) This parameter MUST be present for TDMoIP AAL2 mode PWs (PW type 0x0018) and 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0F | Length | V | ENCODING | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Maximum Duration | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CID mapping bases | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The fields in this parameter are defined as follows: V defines the VAD capabilities. Its values have the following significance: 0 means that the CID is only switched by signaling 1 means that voice activity detection is employed 3 means this channel is always active. In particular, this channel may be used for timing recovery. Encoding specifies native signal processing performed on the payload. When no native signal processing is performed (i.e. G.711 encoding) this field MUST be zero. Maximum Duration specifies the maximum time allowed for filling an AAL2 PDU, in units of 125 microseconds. For unencoded 64 kbps channels this numerically equals the maximum number of bytes per PDU, and MUST be less than 64. For other encoding parameters, larger values may be attained. Vainshtein and Stein Expires March 2007 [Page 5] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 CID mapping bases is an OPTIONAL parameter, its existence and length determined by the length field. If the mapping of AAL2 CID values to physical interface and time slot is statically configured, or if AAL2 switching [Q.2630.1] is employed, this parameter MUST NOT appear. When it is present, and the channels belong to N physical interfaces (i.e. N E1s or T1s), it MUST be N bytes in length. Each byte represents a number to be subtracted from the CID to get the timeslot number for each physical interface. For example, if the CID mapping bases parameter consists of the bytes 20 and 60, this signifies that timeslot 1 of trunk 1 corresponds to CID 21 and timeslot 1 of trunk 2 is called 61. 3.6. Fragmentation Indicator (0x09) This interface parameter is specified in [RFC4446] and its usage is explained in [RFC4623]. It MUST be omitted in the FEC of all TDM PWs excluding trunk-specific NxDS0 services with CAS using the CESoPSN encapsulation. In case of these services, it MUST be present in the PW FEC if the payload size specified value P differs from Nx(number of frames per trunk multiframe). 3.7. TDM Options (0x0B) This is a new interface parameter. Its Interface Parameter ID has to be assigned by IANA, and its format is shown in Fig. 1 below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parameter ID | Length |R|D|F|X|SP |CAS| RSVD-1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| PT | RSVD-2 | FREQ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1. Format of the TDM Options Interface Parameter The fields shown in this diagram are used as follows: Vainshtein and Stein Expires March 2007 [Page 6] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 Parameter ID Identifies the TDM PW Options interface parameter, value TBA by IANA Length 4, 8 or 12 (see below) R The RTP Header Usage bit: if set, indicates that the PW endpoint distributing this FEC expects to receive RTP header in the encapsulation. RTP header will be used only if both endpoints expect to receive it. If this bit is cleared, Length MUST be set to 4, otherwise it MUST be either 8 or 12 (see below). If the peer PW end point cannot meet this requirement, the Label Mapping message containing the FEC in question MUST be rejected with the appropriate status code (see Section 4 below). D The Dynamic Timestamping Mode bit: if set, indicates that the PW endpoint distributing this FEC expects the peer to use Differential timestamping mode in the packets sent to it. If the peer PW end point cannot meet this requirement, the Label Mapping message containing the FEC in question MUST be rejected with the appropriate status code (see Section 4 below). F, X Reserved for future extensions. MUST be cleared when distributed and MUST be ignored upon reception SP Encodes support for the CESoPSN signaling packets (see [PWE3-CESoPSN]): o '00' for PWs that do not use signaling packets o '01' for CESoPSN PWs carrying TDM data packets and expecting CE application signaling packets in a separate PW o '10' for a PW carrying CE application signaling packets with the data packets in a separate PW o '11' - for CESoPSN PWs carrying TDM data and CE application signaling on the same PW CAS MUST be cleared for all types of TDM PWs excluding trunk-specific NxDS0 services with CAS. For these services it encodes the trunk framing like following: o '01' - an E1 trunk o '10' - a T1/ESF trunk o '11' - a T1 SF trunk RSVD-1 and RSVD-2 Reserved bits, MUST be set to 0 by the PW endpoint distributing this FEC and MUST be ignored by the receiver PT Indicates the value of Payload Type in the RTP header expected by the PW endpoint distributing this FEC. Value 0 means that PT value check will not be used for detecting malformed packets FREQ Frequency of timestamping clock in units of 8 kHz SSRC Indicates the value of SSRC ID in the RTP header expected by the PW endpoint distributing this FEC. Value 0 means that SSRC ID value check will not be used for detecting misconnections. Alternatively, Length can be set to 8 in this case. Vainshtein and Stein Expires March 2007 [Page 7] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 Notes: 1. This interface parameter MAY be omitted in the following cases: a) SAToP PWs that do not use RTP header [RFC4553] b) Basic CESoPSN NxDS0 services without CE application signaling [PWE3-CESoPSN] c) TDMoIP AAL1 mode 0 or 2 PWs that do not use RTP. d) TDMoIP AAL2 PWs that do not relay CAS signaling and do not use RTP. 2. This interface parameter MUST be present in the following cases: a) All TDM PWs that use RTP header b) CESoPSN PWs that carry basic NxDS0 services and use CESoPSN signaling packets to carry CE application signaling. This case is discussed in detail in Section 4 below c) CESoPSN PWs that carry trunk-specific NxDS0 services with CAS d) TDMoIP AAL1 mode 1 PWs e) TDMoIP AAL2 PWs that relay CAS signaling. 3. If RTP header and Differential timestamping mode are used, the value of the Length field MUST be set to 8 or 12 in order to include at least the Timestamping Clock Frequency field in the value 4. A TDM PW encapsulation MUST either use or not use RTP in both directions. However, it is possible to use Differential timestamping mode in just one direction of the PW. 4. Extending CESoPSN Basic NxDS0 Services with CE Application Signaling [PWE3-CESoPSN] defines that basic NxDS0 services can be extended to carry also CE application signaling (e.g., CAS) in separate signaling packets carried in a separate PW. The following rules define setup of matching pairs of CESoPSN PWs using the PW Id FEC and the extensions defined above: 1. The value of PW ID for the CESoPSN PW carrying TDM data packets MUST be even 2. The value of PW ID for the CESoPSN PW carrying CE application signaling MUST be the next odd value for the (even) value of PW ID for the CESoPSN PW carrying TDM data packets 3. The two PWs MUST: a) Have the same PW Type b) Have the same values of all the Interface Parameters with the exception of the code point in the SP field of the TDM Options parameter. i) The PWId FEC of the PW carrying TDM data packets must be marked with SP bits set to '01' in this field ii) The PWId FEC of the PW carrying CE signaling packets must be marked with SP bits set to '10' in this field. Vainshtein and Stein Expires March 2007 [Page 8] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 If only one of the two PWs required to carry a CESoPSN basic NxDS0 service and associated CE signaling packets has been established and the other one failed, the established PW MUST be torn down. Setup of CESoPSN PWs with CE application signaling using the Generalized PW FEC is left for further study. 5. LDP Status Codes In addition to the status codes defined in section 5.3 of [RFC4447], the following status codes defined in [RFC4446] MUST be used to indicate the reason of failure to establish a TDM PW: 1. Incompatible bit rate: a) In the case of mismatch of T1 encapsulation modes (basic vs. octet-aligned) b) In case of mismatch in the number of timeslots for NxDS0 basic services or trunk-specific NxDS0 services with CAS 2. CEP/TDM mis-configuration: a) In the case of mismatch in the desired usage of RTP header b) In the case of mismatch of the desired timestamping clock frequency c) In the case of mismatch of expected signaling packets behavior for basic CESoPSN NxDS0 services extended to carry CE application signaling in separate signaling packets d) In the case of trunk-specific NxDS0 services with CAS if the framing types of the trunks are different e) In the case of TDMoIP AAL1 PWs with different AAL1 modes specified by the end points In cases 2a, 2b, 2c and 2e above, the user MAY reconfigure the end points and attempt to setup the PW once again. In the case 2d the failure is fatal. Note that setting of the Control bit (see section 2 above) to zero MUST result in an LDP status of "Illegal C-Bit". 6. Using the PW Status TLV The TDM PW control word carries status indications for both attachment circuits (L and M fields) and the PSN (R field) (see [RFC4553], [PWE3- CESoPSN] and [PWE3-TDMoIP]). Similar functionality is available via use of the PW Status TLV (see [RFC4447], Section 5.4.2). If the latter mechanism is employed, the signaling PE sends to its peer a PW Status TLV, setting the appropriate bits (see [RFC4446], Section 3.5): o Pseudowire Not Forwarding o Local Attachment Circuit (ingress) Receive Fault o Local Attachment Circuit (egress) Transmit Fault Vainshtein and Stein Expires March 2007 [Page 9] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 o Local PSN-facing PW (ingress) Receive Fault o Local PSN-facing PW (egress) Transmit Fault. As long as the TDM PW interworking function is operational, usage of the Status TLV is NOT RECOMMENDED in order to avoid contention between status indications reported by the data and control plane. However, if the TDM PW interworking function (IWF) itself fails while the PWE3 control plane remains operational, Status TLV with all of the above bits set SHOULD be sent. 7. IANA Considerations Most of the IANA assignments required by this draft are already listed in [RFC4446]. Additional assignments are required for three Interface Parameters Sub-TLV type values (see Sections 3.3, 3.4 and 3.5): o Number of TDMoIP AAL1 cells per packet (suggested value - 0x0D) o TDMoIP AAL1 mode (suggested value - 0x0E) o TDMoIP AAL2 Options (suggested value - 0x0F). 8. Security Considerations This draft does not have any additional impact on security of PWs above that of basic LDP setup of PWs. 9. Acknowledgements AV thanks Sharon Galtzur for reviewing the previous version of this text. 10. Disclaimer of Validity The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Vainshtein and Stein Expires March 2007 [Page 10] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 11. Normative References [RFC2119] S. Bradner, Key Words in RFCs to Indicate Requirement Levels, RFC 2119, IETF, 1997 [RFC3036] L. Andersson et al, LDP Specification, RFC 3036, IETF, 2001 [RFC4447] L. Martini et al, Pseudowire Setup and Maintenance using LDP, Work in progress, June 2005, RFC 4447, IETF, 2006 [RFC4446] L. Martini, IANA Allocations for pseudowire Edge to Edge Emulation (PWE3), RFC 4446, IETF, 2006 [RFC4623] A. Malis, M. Townsley, PWE3 Fragmentation and Reassembly, Work in progress, RFC 4623, IETF, 2006 [RFC4553] A. Vainshtein, Y. Stein, Structure-Agnostic TDM over Packet (SAToP), RFC 4553, IETF, 2006 12. Informational References [PWE3-CESoPSN] A. Vainshtein et al, Structure-aware TDM Circuit Emulation Service over Packet Switched Network (CESoPSN), Work in progress, May 2006, draft-ietf-pwe3-cesopsn-07.txt [PWE3-TDMoIP] Y(J) Stein et al, TDM over IP, Work in progress, June 2005,draft-ietf-pwe3-tdmoip-05.txt [Q.2630.1] ITU-T Recommendation Q.2630.1, December 1999, AAL type 2 signaling protocol - Capability set 1 Vainshtein and Stein Expires March 2007 [Page 11] Control Protocol Extensions for Setup of TDM Pseudowires October 2006 Authors' Addresses Alexander ("Sasha") Vainshtein Axerra Networks 24 Raoul Wallenberg St., Tel Aviv 69719 ISRAEL Phone: + 972 3 765-9993 Email: sasha@axerra.com Yaakov (Jonathan) Stein RAD Data Communications 24 Raoul Wallenberg St., Bldg C Tel Aviv 69719 ISRAEL Phone: +972 3 645-5389 Email: yaakov_s@rad.com Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Vainshtein and Stein Expires March 2007 [Page 12]