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<pre>Network Working Group A. Vainshtein
Request for Comments: 5287 ECI Telecom
Category: Standards Track Y(J). Stein
RAD Data Communications
August 2008
<span class="h1">Control Protocol Extensions for the Setup of</span>
<span class="h1">Time-Division Multiplexing (TDM) Pseudowires in MPLS Networks</span>
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This document defines extension to the Pseudowire Emulation Edge-to-
Edge (PWE3) control protocol <a href="./rfc4447">RFC 4447</a> and PWE3 IANA allocations <a href="./rfc4446">RFC</a>
<a href="./rfc4446">4446</a> required for the setup of Time-Division Multiplexing (TDM)
pseudowires in MPLS networks.
Table of Contents
<a href="#section-1">1</a>. Introduction ....................................................<a href="#page-2">2</a>
<a href="#section-2">2</a>. PW FEC for Setup of TDM PWs .....................................<a href="#page-2">2</a>
<a href="#section-3">3</a>. Interface Parameters for TDM PWs ................................<a href="#page-4">4</a>
<a href="#section-3.1">3.1</a>. Overview ...................................................<a href="#page-4">4</a>
<a href="#section-3.2">3.2</a>. CEP/TDM Payload Bytes ......................................<a href="#page-5">5</a>
<a href="#section-3.3">3.3</a>. CEP/TDM Bit-Rate (0x07) ....................................<a href="#page-5">5</a>
<a href="#section-3.4">3.4</a>. Number of TDMoIP AAL1 Cells per Packet .....................<a href="#page-6">6</a>
<a href="#section-3.5">3.5</a>. TDMoIP AAL1 Mode ...........................................<a href="#page-7">7</a>
<a href="#section-3.6">3.6</a>. TDMoIP AAL2 Options ........................................<a href="#page-7">7</a>
<a href="#section-3.7">3.7</a>. Fragmentation Indicator ....................................<a href="#page-8">8</a>
<a href="#section-3.8">3.8</a>. TDM Options ................................................<a href="#page-8">8</a>
4. Extending CESoPSN Basic NxDS0 Services with CE
Application Signaling ..........................................<a href="#page-11">11</a>
<a href="#section-5">5</a>. LDP Status Codes ...............................................<a href="#page-12">12</a>
<a href="#section-6">6</a>. Using the PW Status TLV ........................................<a href="#page-13">13</a>
<a href="#section-7">7</a>. IANA Considerations ............................................<a href="#page-13">13</a>
<a href="#section-8">8</a>. Security Considerations ........................................<a href="#page-14">14</a>
<a href="#section-9">9</a>. Acknowledgements ...............................................<a href="#page-14">14</a>
<a href="#section-10">10</a>. References ....................................................<a href="#page-14">14</a>
<a href="#section-10.1">10.1</a>. Normative References .....................................<a href="#page-14">14</a>
<a href="#section-10.2">10.2</a>. Informative References ...................................<a href="#page-14">14</a>
<span class="grey">Vainshtein & Stein Standards Track [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc5287">RFC 5287</a> Control Protocol Extensions for TDM Pseudowires August 2008</span>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
This document defines an extension to the PWE3 control protocol
[<a href="./rfc4447" title=""Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)"">RFC4447</a>] and PWE3 IANA allocations [<a href="./rfc4446" title=""IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)"">RFC4446</a>] required for the setup
of TDM pseudowires in MPLS networks.
Structure-agnostic TDM pseudowires have been specified in [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>],
and structure-aware ones have been specified in [<a href="./rfc5086" title=""Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)"">RFC5086</a>] and
[<a href="./rfc5087" title=""Time Division Multiplexing over IP (TDMoIP)"">RFC5087</a>].
[<a id="ref-RFC4447">RFC4447</a>] defines extensions to the Label Distribution Protocol (LDP)
[<a href="./rfc5036" title=""LDP Specification"">RFC5036</a>] that are required to exchange PW labels for PWs emulating
various Layer 2 services (Ethernet, Frame Relay (FR), Asynchronous
Transfer Mode (ATM), High-Level Data Link Control (HDLC), etc.). The
setup of TDM PWs requires both interpretation of the existing
information elements of these extensions and exchange of additional
information.
The setup of TDM PWs using L2TPv3 will be defined in a separate
document.
The status of attachment circuits of TDM PWs can be exchanged between
the terminating Provider Edges (PEs) using the PW Status mechanism
defined in [<a href="./rfc4447" title=""Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)"">RFC4447</a>] without any changes. However, usage of this
mechanism is NOT RECOMMENDED for TDM PWs since the indication of the
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 [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>].
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. PW FEC for Setup of TDM PWs</span>
[<a id="ref-RFC4447">RFC4447</a>] uses the LDP Label Mapping message [<a href="./rfc5036" title=""LDP Specification"">RFC5036</a>] for
advertising the FEC-to-PW Label binding, and defines two types of PW
Forwarding Equivalence Classes (FECs) 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
<span class="grey">Vainshtein & Stein Standards Track [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc5287">RFC 5287</a> Control Protocol Extensions for TDM Pseudowires August 2008</span>
e) Interface parameters Sub-TLV
2. Generalized PW FEC (FEC 129). This FEC contains only:
a) PW type
b) Control bit
c) Attachment Group Identifier (AGI), Source Attachment Individual
Identifier (SAII), and Target Attachment Individual Identifier
(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.
Either of these types of PW FEC MAY be used for the setup of TDM PWs
with the appropriate selection of PW types and interface parameters.
The PW types for TDM PWs are allocated in [<a href="./rfc4446" title=""IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)"">RFC4446</a>] as follows:
o 0x0011 Structure-agnostic E1 over Packet [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>]
o 0x0012 Structure-agnostic T1 (DS1) over Packet [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>]
o 0x0013 Structure-agnostic E3 over Packet [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>]
o 0x0014 Structure-agnostic T3 (DS3) over Packet [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>]
o 0x0015 CESoPSN basic mode [<a href="./rfc5086" title=""Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)"">RFC5086</a>]
o 0x0016 TDMoIP AAL1 mode [<a href="./rfc5087" title=""Time Division Multiplexing over IP (TDMoIP)"">RFC5087</a>]
o 0x0017 CESoPSN TDM with CAS [<a href="./rfc5086" title=""Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)"">RFC5086</a>]
o 0x0018 TDMoIP AAL2 mode [<a href="./rfc5087" title=""Time Division Multiplexing over IP (TDMoIP)"">RFC5087</a>]
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.
PW type 0x0012 MUST also be used for the setup of structure-agnostic
TDM PWs between a pair of J1 attachment circuits (see [<a href="./rfc4805" title=""Definitions of Managed Objects for the DS1, J1, E1, DS2, and E2 Interface Types"">RFC4805</a>]).
<span class="grey">Vainshtein & Stein Standards Track [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc5287">RFC 5287</a> Control Protocol Extensions for TDM Pseudowires August 2008</span>
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Interface Parameters for TDM PWs</span>
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Overview</span>
The interface parameters that are relevant for the setup of the TDM
PWs are listed below.
-------------------------------------------------------------
| Interface Parameter | Sub-TLV ID | Length | Description |
|-----------------------|------------|--------|-------------|
| CEP/TDM Payload Bytes | 0x04 | 4 |<a href="#section-3.2">Section 3.2</a> |
|-----------------------|------------|--------|-------------|
| CEP/TDM Bit-Rate | 0x07 | 6 |<a href="#section-3.3">Section 3.3</a> |
|-----------------------|------------|--------|-------------|
| Number of TDMoIP AAL1 | 0x0E | 4 |<a href="#section-3.4">Section 3.4</a> |
| Cells per Packet | | | |
|-----------------------|-------=----|--------|-------------|
| TDMoIP AAL1 Mode | 0x10 | 4 |<a href="#section-3.5">Section 3.5</a> |
|-----------------------|------------|--------|-------------|
| TDMoIP AAL2 Options | 0x11 | 8 or |<a href="#section-3.6">Section 3.6</a> |
| | | larger | |
| | |see note| |
|-----------------------|------------|--------|-------------|
| Fragmentation | 0x09 | 4 |<a href="#section-3.7">Section 3.7</a> |
| Indicator | | | |
|-----------------------|------------|--------|-------------|
| TDM Options | 0x0B | 4, 8, |<a href="#section-3.8">Section 3.8</a> |
| | | or 12 | |
-------------------------------------------------------------
If not explicitly indicated otherwise in the appropriate description,
the value of the interface parameter is interpreted as an unsigned
integer of the appropriate size (16 or 32 bits).
Note: The length of basic TDMoIP AAL2 Options interface parameter is
8 bytes, and when the optional Channel ID (CID) mapping bases field
is used, there is one additional byte for each trunk transported.
Thus, if 1 trunk is being supported, this message occupies 9 bytes.
Since there can be no more than 248 CIDs in a given PW, this can
never exceed 256 (this when each channel comes from a different
trunk). 248 channels translates to less than 9 E1s, and so, for this
case, the length is
<span class="grey">Vainshtein & Stein Standards Track [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc5287">RFC 5287</a> Control Protocol Extensions for TDM Pseudowires August 2008</span>
no more than 17 bytes. A single PE is not required to support more
than 10 AAL2 PWs (i.e., up to 2480 individual channels, which is more
than carried by a fully populated STM1). Thus, the memory required
to store all the AAL2 mapping information is typically between 80 and
170 bytes per PE.
<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. CEP/TDM Payload Bytes</span>
This parameter is used for the setup of all SAToP and CESoPSN PWs
(i.e., PW types 0x0011, 0x0012, 0x0013, 0x0014, 0x0015, and 0x0017)
and employs the following semantics:
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
[<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>], [<a href="./rfc5086" title=""Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)"">RFC5086</a>]) 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 for a T1 or J1 trunk).
ii) The size of the signaling sub-structure is not accounted for
in the specified value P.
5. This parameter MUST NOT be used for the setup of TDMoIP PWs (i.e.,
PWs with PW types 0x0016 and 0x0018).
<span class="h3"><a class="selflink" id="section-3.3" href="#section-3.3">3.3</a>. CEP/TDM Bit-Rate (0x07)</span>
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:
<span class="grey">Vainshtein & Stein Standards Track [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc5287">RFC 5287</a> Control Protocol Extensions for TDM Pseudowires August 2008</span>
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 [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>]:
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
or J1 circuit (1,544 Mbit/s) in units of 64 kbit/s. The values
mentioned above are used for convenience.
Note: A 4-byte space is reserved for this parameter for compatibility
with [<a href="./rfc4842" title=""Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP)"">RFC4842</a>].
<span class="h3"><a class="selflink" id="section-3.4" href="#section-3.4">3.4</a>. Number of TDMoIP AAL1 Cells per Packet</span>
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 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).
<span class="grey">Vainshtein & Stein Standards Track [Page 6]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-7" ></span>
<span class="grey"><a href="./rfc5287">RFC 5287</a> Control Protocol Extensions for TDM Pseudowires August 2008</span>
<span class="h3"><a class="selflink" id="section-3.5" href="#section-3.5">3.5</a>. TDMoIP AAL1 Mode</span>
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.
<span class="h3"><a class="selflink" id="section-3.6" href="#section-3.6">3.6</a>. TDMoIP AAL2 Options</span>
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x11 | Length | V | ENCODING |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CID mapping bases |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in this parameter are defined as follows:
V defines the Voice Activity Detection (VAD) capabilities. Its
values have the following significance:
0 means that activity is only indicated 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. Other specific values that can be used in
this field are beyond the scope of this specification, but the two
directions MUST match for the PW setup to succeed.
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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.
CID mapping bases is an OPTIONAL parameter; its existence and length
are determined by the length field. If the mapping of AAL2 CID
values to a physical interface and time slot is statically
configured, or if AAL2 switching [<a href="#ref-Q.2630.1" title="December 1999">Q.2630.1</a>] 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.
<span class="h3"><a class="selflink" id="section-3.7" href="#section-3.7">3.7</a>. Fragmentation Indicator</span>
This interface parameter is specified in [<a href="./rfc4446" title=""IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)"">RFC4446</a>], and its usage is
explained in [<a href="./rfc4623" title=""Pseudowire Emulation Edge-to- Edge (PWE3) Fragmentation and Reassembly"">RFC4623</a>]. It MUST be omitted in the FEC of all TDM PWs
excluding trunk-specific NxDS0 services with CAS using the CESoPSN
encapsulation. In the 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).
<span class="h3"><a class="selflink" id="section-3.8" href="#section-3.8">3.8</a>. TDM Options</span>
This is a new interface parameter. Its Interface Parameter ID (0x0B)
has been assigned by IANA, and its format is shown in Figure 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 Sub-TLV
The fields shown in this diagram are used as follows:
Parameter ID Identifies the TDM PW Options interface
parameter, 0x0B.
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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 endpoint
cannot meet this requirement, the Label Mapping
message containing the FEC in question MUST be
rejected with the appropriate status code (see
<a href="#section-4">Section 4</a> below).
D The Differential 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 endpoint cannot meet this
requirement, the Label Mapping message containing
the FEC in question MUST be rejected with the
appropriate status code (see <a href="#section-4">Section 4</a> 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 [<a href="./rfc5086" title=""Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)"">RFC5086</a>]):
o '00' for PWs that do not use signaling packets
o '01' for CESoPSN PWs carrying TDM data packets
and expecting Customer Edge (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
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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 the 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, which 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. A value of 0 means that the 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 the Synchronization source
ID (SSRC ID) in the RTP header expected by the PW
endpoint distributing this FEC. A value of 0
means that the SSRC ID value check will not be
used for detecting misconnections.
Alternatively, Length can be set to 8 in this
case.
Notes:
1. This interface parameter MAY be omitted in the following cases:
a) SAToP PWs that do not use RTP header [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>].
b) Basic CESoPSN NxDS0 services without CE application signaling
[<a href="./rfc5086" title=""Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)"">RFC5086</a>].
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.
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2. This interface parameter MUST be present in the following cases:
a) All TDM PWs that use RTP headers.
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 <a href="#section-4">Section 4</a> 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 possibly the Differential timestamping mode are
used, the value of the Length field MUST be set to 8 or 12 in
order to accommodate the Timestamping Clock Frequency and SSRC
fields.
4. Usage or non-usage of the RTP header MUST match for the two
directions making up the TDM PW. However, it is possible to use
the Differential timestamping mode in just one direction.
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Extending CESoPSN Basic NxDS0 Services with CE Application Signaling</span>
[<a id="ref-RFC5086">RFC5086</a>] states that basic NxDS0 services can be extended to carry
CE application signaling (e.g., CAS) in special signaling packets
carried in a separate PW.
The following rules define the setup of matching pairs of CESoPSN PWs
using the PW ID FEC and the extensions defined above:
1. The two PWs MUST:
a) Have the same PW type.
b) Use the same setup method (i.e., either both use the PWId FEC,
or both use the Generalized PW FEC).
c) Have the same values of all the Interface Parameters listed in
<a href="#section-3.1">Section 3.1</a> above with the exception of the code point in the
SP field of the TDM Options parameter:
i) For the PW carrying TDM data packets, the SP bits MUST be
set to '01'.
ii) For the PW carrying the signaling packets, the SP bits MUST
set to '10'.
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2. If the PWId FEC has been used:
a) The value of PW ID for the CESoPSN PW carrying TDM data packets
MUST be even.
b) The value of PW ID for the CESoPSN PW carrying CE application
signaling MUST be the next (odd) value after the (even) PW ID
of the CESoPSN PW carrying TDM data packets.
When using the Generalized PW FEC for the setup of the two PWs, no
specific rules for matching the two FECs are defined.
Implementation-specific mechanisms MAY be employed to verify the
proper matching of the TDM data PW with its associated CE signaling
PW.
If one of the two associated PWs has been established and the other
failed to be established, or for any reason fails after having been
established, the established PW MUST be torn down.
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. LDP Status Codes</span>
In addition to the status codes defined in Sections <a href="#section-5.1">5.1</a> and <a href="#section-7.2">7.2</a> of
[<a href="./rfc4447" title=""Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)"">RFC4447</a>], the following status codes defined in [<a href="./rfc4446" title=""IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)"">RFC4446</a>] MUST be
used to indicate the reason of failure to establish a TDM PW:
1. Incompatible bit-rate:
a) In the case of a mismatch of T1 encapsulation modes (basic vs.
octet-aligned).
b) In the case of a mismatch in the number of timeslots for NxDS0
basic services or trunk-specific NxDS0 services with CAS.
2. CEP/TDM misconfiguration:
a) In the case of a mismatch in the desired usage of RTP header.
b) In the case of a mismatch of the desired Timestamping Clock
Frequency.
c) In the case of a 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.
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e) In the case of TDMoIP AAL1 PWs with different AAL1 modes
specified by the endpoints.
3. The generic misconfiguration error MAY be used to indicate any
setup failure not covered above.
In cases 2a, 2b, 2c, and 2e above, the user MAY reconfigure the
endpoints and attempt to set up the PW once again.
In the case of 2d, the failure is fatal.
Note that setting of the Control bit (see <a href="#section-2">Section 2</a> above) to zero
MUST result in an LDP status of "Illegal C-Bit".
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Using the PW Status TLV</span>
The TDM PW control word carries status indications for both
attachment circuits (L and M fields) and the PSN (R field) indication
(see [<a href="./rfc4553" title=""Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)"">RFC4553</a>], [<a href="./rfc5086" title=""Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)"">RFC5086</a>], and [<a href="./rfc5087" title=""Time Division Multiplexing over IP (TDMoIP)"">RFC5087</a>]). Similar functionality is
available via use of the PW Status TLV (see <a href="./rfc4447#section-5.4.2">Section 5.4.2 of
[RFC4447]</a>). If the latter mechanism is employed, the signaling PE
sends its peer a PW Status TLV for this PW, setting the appropriate
bits (see <a href="./rfc4446#section-3.5">Section 3.5 of [RFC4446]</a>):
o Pseudowire Not Forwarding
o Local Attachment Circuit (ingress) Receive Fault
o Local Attachment Circuit (egress) Transmit Fault
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, a Status TLV with all of
the above bits set SHOULD be sent.
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. IANA Considerations</span>
Most of the IANA assignments required by this document are already
listed in [<a href="./rfc4446" title=""IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)"">RFC4446</a>]. Additional assignments have been made for four
Interface Parameter Sub-TLV types (see <a href="#section-3.1">Section 3.1</a>):
o TDM Options (0x0B)
o Number of TDMoIP AAL1 cells per packet (0x0E)
o TDMoIP AAL1 mode (0x10)
o TDMoIP AAL2 Options (0x11)
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<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. Security Considerations</span>
This document does not have any additional impact on the security of
PWs above that of basic LDP-based setup of PWs specified in
[<a href="./rfc4447" title=""Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)"">RFC4447</a>].
<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. Acknowledgements</span>
Sharon Galtzur has reviewed one of the previous versions of this
document. Y. (J.) Stein would like to thank Barak Schlosser for
helpful discussions.
<span class="h2"><a class="selflink" id="section-10" href="#section-10">10</a>. References</span>
<span class="h3"><a class="selflink" id="section-10.1" href="#section-10.1">10.1</a>. Normative References</span>
[<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.
[<a id="ref-RFC5036">RFC5036</a>] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", <a href="./rfc5036">RFC 5036</a>, October 2007.
[<a id="ref-RFC4447">RFC4447</a>] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the
Label Distribution Protocol (LDP)", <a href="./rfc4447">RFC 4447</a>, April 2006.
[<a id="ref-RFC4446">RFC4446</a>] Martini, L., "IANA Allocations for Pseudowire Edge to Edge
Emulation (PWE3)", <a href="https://www.rfc-editor.org/bcp/bcp116">BCP 116</a>, <a href="./rfc4446">RFC 4446</a>, April 2006.
[<a id="ref-RFC4623">RFC4623</a>] Malis, A. and M. Townsley, "Pseudowire Emulation Edge-to-
Edge (PWE3) Fragmentation and Reassembly", <a href="./rfc4623">RFC 4623</a>,
August 2006.
[<a id="ref-RFC4553">RFC4553</a>] Vainshtein, A., Ed., and YJ. Stein, Ed., "Structure-
Agnostic Time Division Multiplexing (TDM) over Packet
(SAToP)", <a href="./rfc4553">RFC 4553</a>, June 2006.
<span class="h3"><a class="selflink" id="section-10.2" href="#section-10.2">10.2</a>. Informative References</span>
[<a id="ref-RFC5086">RFC5086</a>] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and
P. Pate, "Structure-Aware Time Division Multiplexed (TDM)
Circuit Emulation Service over Packet Switched Network
(CESoPSN)", <a href="./rfc5086">RFC 5086</a>, December 2007.
[<a id="ref-RFC5087">RFC5087</a>] Y(J). Stein, Shashoua, R., Insler, R., and M. Anavi, "Time
Division Multiplexing over IP (TDMoIP)", <a href="./rfc5087">RFC 5087</a>,
December 2007.
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<span class="grey"><a href="./rfc5287">RFC 5287</a> Control Protocol Extensions for TDM Pseudowires August 2008</span>
[<a id="ref-Q.2630.1">Q.2630.1</a>] ITU-T Recommendation Q.2630.1, December 1999, AAL type 2
signaling protocol - Capability set 1
[<a id="ref-RFC4805">RFC4805</a>] Nicklass, O., Ed., "Definitions of Managed Objects for the
DS1, J1, E1, DS2, and E2 Interface Types", <a href="./rfc4805">RFC 4805</a>, March
2007.
[<a id="ref-RFC4842">RFC4842</a>] Malis, A., Pate, P., Cohen, R., Ed., and D. Zelig,
"Synchronous Optical Network/Synchronous Digital Hierarchy
(SONET/SDH) Circuit Emulation over Packet (CEP)", <a href="./rfc4842">RFC</a>
<a href="./rfc4842">4842</a>, April 2007.
Authors' Addresses
Alexander ("Sasha") Vainshtein
ECI Telecom
30 ha-Sivim St.,
PO Box 500 Petah-Tiqva, 49517 Israel
EMail: Alexander.Vainshtein@ecitele.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
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Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a>, 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.
Intellectual Property
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 <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and <a href="https://www.rfc-editor.org/bcp/bcp79">BCP 79</a>.
Copies of IPR disclosures made to the IETF Secretariat and any
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such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
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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 & Stein Standards Track [Page 16]
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