One document matched: draft-ietf-l2tpext-tdm-04.txt
Differences from draft-ietf-l2tpext-tdm-03.txt
L2TP TDM November 2007
Network Working Group A. Vainshtein
Internet Draft Axerra Networks
Document: draft-ietf-l2tpext-tdm-04.txt S. Galtzur
Rawflow
Creation Date: 2007-11-19
Intended Status: Proposed Standard
Expires: May 2008
Layer Two Tunneling Protocol - Setup of TDM Pseudowires
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/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document defines extensions to the Layer Two Tunneling Protocol
(L2TP) for support of structure-agnostic and structure-aware TDM
pseudowires.
Conventions used in this document
In this document we refer to control plane as the packets that
contain control information (via AVP) and the mechanism that handles
these packets.
In this document we refer to the data plane as the packets that
contain transported user data.
Vainshtein and Galtzur Expires - May 2008 [Page 1]
L2TP TDM November 2007
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 [RFC2119].
Table of Contents
1. Introduction...................................................2
2. L2TP Extension.................................................2
2.1 TDM PW AVP (ICRQ, OCRQ)...................................3
2.2 RTP AVP (ICRQ, OCRQ, ICRP, OCRP)..........................5
2.3 Changes in the Control Connection AVPs.....................6
2.4 Changes in the Session Connection AVPs.....................6
3. Creation of the TDM Pseudowire Session.........................6
4. IANA Considerations............................................7
Security Considerations...........................................8
Copyright notice..................................................8
Normative references.............................................10
Informative references...........................................10
Authors' Addresses...............................................10
1. Introduction
This document defines extensions to the Layer Two Tunneling Protocol
Version 3(L2TPv3) for support of structure-agnostic [RFC4553] and
structure-aware [PWE3-CESoPSN] TDM pseudowires. Encapsulation of the
structure-agnostic TDM PWs over L2TPv3 is described in [RFC4553],
Figure 2b. Encapsulation of the structure-aware TDM PWs over L2TPv3
is described in [PWE3-CESoPSN], Figures 1c (TDM data packets) and 4a
(CE application signaling packets). However, the order of the CESoPSN
Control Word (CW) and RTP header (if it is used) MUST match between
the TDM data and CE signaling packets.
Setup of structure-aware pseudowires using encapsulations described
in [PWE3-TDMoIP] has been left for further study.
Setup and maintenance of TDM PWs in MPLS networks using LDP is
described in [PWE3-TDM-CTR].
2. L2TP Extension
The L2TP Control Connection is responsible for 3 main operations:
1. Establishment and validation of a pseudowire (PW) session.
2. Ending (tearing down) of a pseudowire session.
3. Transferring of End Point status.
Vainshtein and Galtzur Expires - May 2008 [Page 2]
L2TP TDM November 2007
Tearing down of session for a TDM pseudowire is identical to
[RFC3931].
[PWE3-CESoPSN] and [RFC4553] describe how to transfer the Attachment
Circuit (AC) status via the data plane. This is therefore NOT
RECOMMENDED to use the Set-Link-Info (SLI) message described in
[RFC3931] for conveying this status with the PWs in question.
[RFC3931] specifies that the Circuit Status AVP MUST be present in
the ICRQ/ICRP messages. It also specifies that the N bit in this AVP
should be set during the PW setup even if the specific AC does not
provide any way to convey the "new AC" indication. Accordingly, the
Circuit Status AVP for the PWs in question, when used in the
ICRQ/ICRP messages, MUST always have both N and A bits set.
The next sections describe the extensions to the L2TP for
establishment and validation of TDM pseudowire sessions.
There are 2 new AVPs for the Session Connection Messages. One AVP
describe the TDM pseudowire attributes. The second AVP describe the
RTP attributes for this TDM pseudowire.
2.1 TDM PW AVP (ICRQ, OCRQ)
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 (IETF) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Type (AVP-TBA-1) | Reserved |SP |CAS|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bit Rate | Payload Bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This AVP MAY be hidden (the H bit MAY be 0 or 1). The M bit for this
AVP SHOULD be set to 0. The Length (before hiding) of this AVP is
12.
The Bit Rate field contains the value that represents the bit rate of
the local AC in the units of 64 Kbit/s encoded as an unsigned 16-bit
integer. Its usage for all types of TDM PWs implies the following
semantics:
1) 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 for the basic mode
ii) MUST be set to 25 for the "Octet-aligned T1" mode
c) Structure-agnostic E3 emulation - 535
Vainshtein and Galtzur Expires - May 2008 [Page 3]
L2TP TDM November 2007
d) Structure-agnostic T3 emulation - 699
2) For CESoPSN PWs this parameter MUST be set to the number of DS0
channels in the corresponding attachment circuit.
Note: For structure-agnostic T1 emulation the values 24 and 25 do not
reflect the exact bit rate, and are used for convenience only.
Note: The semantics of the Bit Rate field defined above are
consistent with those of the Bit Rate Interface Attribute as defined
in [PWE3-TDM-CTR].
The Payload Bytes field contains the value that represents the number
of the TDM Payload bytes in the PW packet and is used with the
following semantics:
1) For structure-agnostic emulation any value of the payload bytes can
be specified.
2) For CESoPSN PWs:
a) The specified value MUST be an integer multiple of number of
DS0 channels in the corresponding attachment circuit.
b) In addition to that, for trunk-specific NxDS0 with CAS,
(Payload Bytes/number of DS0 channels) MUST be an integer
factor of the number of frames per corresponding trunk
multiframe.
The Reserved bits are reserved. They MUST be set to 0 on transmission
and MUST be ignored on reception.
The SP bits define support for the CESoPSN application signaling
packets (see [PWE3-CESoPSN]) and MUST be used as following:
1) Set to '00' for TDM PWs that do not use signaling packets
2) Set to '01' for the CESoPSN PWs carrying TDM data packets and
expecting CE application signaling packets in a separate PW
3) Set to '10' for a PW carrying CE application signaling packets with
the data packets in a separate PW
4) Set to '11' for e CESoPSN PW carrying both TDM data and signaling
packets.
The CAS bits define the trunk type for trunk-specific CESoPSN
services with CAS. These bits:
1) MUST be set to 0 for all pseudowire types excluding trunk-specific
CESoPSN with CAS
2) For trunk-specific CESoPSN with CAS these bits bust be set to:
a) '01' in the case of an E1 trunk
b) '10' in the case of a T1/ESF trunk
c) '11' in the case of a T1/SF trunk.
Vainshtein and Galtzur Expires - May 2008 [Page 4]
L2TP TDM November 2007
2.2 RTP AVP (ICRQ, OCRQ, ICRP, OCRP)
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 (IETF) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Type (AVP-TBA-2) |D| PT |C| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Timestamp Clock Frequency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Presence of this AVP indicates that the RTP header is used in the TDM
pseudowire encapsulation. Use or non-use of the RTP header MUST match
for the two directions of a TDM PW. This AVP MAY be hidden (the H bit
MAY be 0 or 1). The M bit for this AVP SHOULD be set to 0. The
Length (before hiding) of this AVP is 16.
The D bit indicates the timestamping mode (absolute or differential)
in the RTP header. These modes are described in, e.g., in [RFC4553],
Section 4.3.2. If the D bit is set to 1 then the Differential
timestamping mode is used, otherwise the Absolute timestamping mode
is used. Timestamping modes can be used independently for the two
directions of a TDM PW.
The C bit indicates the ordering of the RTP header and the control
word as following:
o If the C bit is set to 1 the RTP header appears after the control
word in the data channel of the TDM pseudowire. This mode is
described as SAToP/CESoPSN encapsulation over IPv4/IPv6 PSN with
L2TPv3 demultiplexing in [RFC4553] and [PWE3-CESoPSN] respectively.
o If the C bit is set to 0 the RTP header appears before the control
word. This mode described as the old mode of the SAToP/CESoPSN
encapsulation over L2TPv3 in [RFC4553], Appendix A, and [PWE3-
CESoPSN], Annex C, respectively.
PT is the payload type expected in the RTP header. Value of zero
indicates that the payload type is ignored and will not be used to
detect malformed packets.
Timestamp Clock Frequency is the clock frequency used for the time
stamping in 8 KHz.
SSRC indicates the expected value of SSRC ID in the RTP header. A
zero in this field means that SSRC ID will not be used for detecting
misconnections. Since L2TP provides an alternative security mechanism
Vainshtein and Galtzur Expires - May 2008 [Page 5]
L2TP TDM November 2007
via the cookies, if the cookie length is larger then zero the SSRC
SHOULD be zero.
2.3 Changes in the Control Connection AVPs
Control Connection that support TDM MUST add the appropriate PW Type
value to the list in the Pseudowire Capabilities List AVP. The exact
value is TBA by IANA and is listed in the next section.
2.4 Changes in the Session Connection AVPs
PW Type AVP should be set to one of the following values:
1. Structure-agnostic emulation [RFC4553] of:
a. E1 circuits - TBA-SAToP-E1 by IANA. The value 0x0011 is
suggested for alignment with [RFC4446]
b. T1 circuits - TBA-SAToP-T1 by IANA. The value 0x0012 is
suggested for alignment with [RFC4446]
c. E3 circuits - TBA-SAToP-E3 by IANA. The value 0x0013 is
suggested for alignment with [RFC4446]
d. T3 circuits - TBA-SAToP-T3 by IANA. The value 0x0014 is
suggested for alignment with [RFC4446]
2. Structure-aware emulation [PWE3-CESoPSN] of:
a. CESoPSN basic mode - TBA-CESoPSN-Basic by IANA. The value
0x0015 is suggested for alignment with [RFC4446]
b. Trunk-specific CESoPSN service with CAS - TBA-CESoPSN-CAS by
IANA. The value 0x0017 is suggested for alignment with
[RFC4446].
TDM pseudowires use their own control word. Therefore the L2-
Specific Sublayer AVP MUST either be omitted or set to zero.
TDM pseudowires use their own sequencing. Therefore the Data
Sequencing AVP MUST either be omitted or set to zero.
Note: The Control Word (CW) used in the SAToP and CESoPSN
encapsulations over L2TPv3 effectively represents a dedicated L2-
Specific Sub-layer.
3. Creation of the TDM Pseudowire Session
When LCCE wants to open a Session for TDM PW it MUST include the TDM
PW AVP (in any case) and the RTP AVP (if and only if the RTP header
is used) in the ICRQ or OCRQ message. The LCCE peer must validate
the TDM PW AVP and make sure it can meet the requirements derived
from the RTP AVP (if it exist). If the peer agrees with the TDM AVP
it will send an appropriate ICRP or OCRP message with the matching
RTP AVP (if needed). The Initiator need to validate that it can
supply the requirements derived from the received RTP AVP.
Vainshtein and Galtzur Expires - May 2008 [Page 6]
L2TP TDM November 2007
The two peers MUST agree on the values in the TDM PW AVP:
1. Bit Rate values MUST be equal on both sides. If they are
different, the connection will be rejected with return code RC-
TBD-1 and error code EC-TBD-1.
2. In the case of trunk-specific CESoPSN with CAS, the trunk type (as
encoded in the CAS bits of the TDM AVP) MUST be the same for the
two sides. Otherwise the connection will be rejected with return
code RC-TBD-1 and error code EC-TBD-2.
3. If one side does not support the payload bytes value proposed by
the other one, the connection will be rejected with return code
RC-TBD-1 and error code EC-TBD-3.
4. If one side cannot send RTP header requested by the other side,
the connection will be rejected with return code RC-TBD-1 and
error code EC-TBD-4.
5. If one side can send RTP header but not with the requested
timestamp clock frequency, the connection will be rejected with
return code RC-TBD-1 and error code EC-TBD-5.
If CESoPSN basic NxDS0 PW is extended to support CE application
signaling in a separate PW instance, then the two PW instances:
1. MUST use the same PW type
2. MUST use the same values in all the fields of the TDM AVP
excluding the SP field which must be set to '01' for teh TDM data
PW and to '10' for the PW carrying CE application signaling
3. MUST both use or not use RTP header (and accordingly, include or
not include the RTP AVP).
4. IANA Considerations
This draft requires assignment of the following values by IANA:
PW types listed in Section 2.1 above. It is RECOMMENDED to use the
same values as defined in [RFC4446].
New attribute value pair IDs:
1. AVP-TBD-1 - TDM Pseudowire AVP
2. AVP-TBD-2 - RTP AVP
New return codes and error codes:
1. RC-TBD-1 - return code to indicate connection refused because of
TDM PW parameters. The exact error code is as follows.
2. EC-TBD-1 - indicate Bit Rate values disagree.
Vainshtein and Galtzur Expires - May 2008 [Page 7]
L2TP TDM November 2007
3. EC-TBD-2 - indicate different trunk types in the case of trunk-
specific CESoPSN with CAS
4. EC-TBD-3 - requested payload size too big or too small.
5. EC-TBD-4 - RTP header cannot be generated.
6. EC-TBD-5 - requested timestamp clock frequency cannot be generated
5. Security Considerations
This document specifies only the L2TPv3-based control plane for setup
of TDM PWs. Within this scope, there are no additional security
considerations on top of those discussed in [RFC3931].
Common data plane security considerations for the TDM PWs have been
discussed in some detail in both [RFC4553] and [PWE3-CESoPSN]. On top
of these, the L2TPv3-based data plane provides additional security
mechanisms based on usage of cookies.
Copyright notice
Copyright (C) The IETF Trust (2007).
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, THE IETF TRUST 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.
Vainshtein and Galtzur Expires - May 2008 [Page 8]
L2TP TDM November 2007
IPR Validity Disclaimer
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 Galtzur Expires - May 2008 [Page 9]
L2TP TDM November 2007
Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[RFC3931] J. Lau, M. Townsley, I. Goyret, Layer Two Tunneling
Protocol - Version 3 (L2TPv3), March 2005
Informative 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
[RFC4553] A. Vainshtein, Y. Stein, Structure-Agnostic TDM over
Packet (SAToP), RFC 4553, June 2006
[PWE3-TDMoIP] Y. Stein et al, TDM over IP, Work in progress, draft-
ietf-pwe3-tdmoip-06.txt, December 2006.
[RFC4446] L. Martini, M. Townsley, IANA Allocations for pseudo
Wire Edge to Edge Emulation (PWE3), RFC 4446,
April 2006
[PWE3-TDM-CTR] A. Vainshtein, Y. Stein, Control Protocol Extensions
for Setup of TDM Pseudowires in MPLS Networks, Work in
Progress, November 2007,
draft-ietf-pwe3-tdm-control-prootocol-extensi-06.txt
Authors' Addresses
Sharon Galtzur
Rawflow Inc.
The Old Pump House, 19 Hooper St.,
London E1 8BU,
UK
Email: sharon@rawflow.com
Alexander Vainshtein,
Axerra Networks,
24 Raoul Wallenberg St.,
Tel Aviv, Israel
Email: sasha@axerra.com
Vainshtein and Galtzur Expires - May 2008 [Page 10]
| PAFTECH AB 2003-2026 | 2026-04-21 23:06:04 |