draft-ietf-mpls-tp-gach-gal-01.txt   draft-ietf-mpls-tp-gach-gal-02.txt 
MPLS M. Bocci, Ed.
MPLS Working Group M. Bocci, Ed.
Internet-Draft M. Vigoureux, Ed. Internet-Draft M. Vigoureux, Ed.
Updates: 3032, 4385, 5085 Alcatel-Lucent Updates: 3032, 4385, 5085 Alcatel-Lucent
(if approved) G. Swallow (if approved) G. Swallow
Intended status: Standards Track D. Ward Intended status: Standards Track D. Ward
Expires: July 10, 2009 Cisco Expires: August 27, 2009 S. Bryant
Cisco
R. Aggarwal R. Aggarwal
Juniper Networks Juniper Networks
January 6, 2009 February 23, 2009
MPLS Generic Associated Channel MPLS Generic Associated Channel header
draft-ietf-mpls-tp-gach-gal-01 draft-ietf-mpls-tp-gach-gal-02
Status of this Memo Status of this Memo
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Abstract Abstract
This document generalises the applicability of the pseudowire This document generalises the applicability of the pseudowire (PW)
Associated Channel Header (ACH), enabling the realization of a Associated Channel Header (ACH), enabling the realization of a
control channel associated to MPLS Label Switched Paths (LSP), MPLS control channel associated to MPLS Label Switched Paths (LSPs) and
pseudowires (PW) and MPLS Sections. In order to identify the MPLS Sections in addition to MPLS pseudowires. In order to identify
presence of the Generic ACH (G-ACH), this document also assigns of the presence of this Associated Channel Header in the label stack,
one of the reserved MPLS label values to the 'Generic Associated this document also assigns one of the reserved MPLS label values to
channel header Label (GAL)', to be used as a label based exception the Generic Associated channel Label (GAL), to be used as a label
mechanism. based exception mechanism.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1]. document are to be interpreted as described in RFC 2119 [1].
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Contributing Authors . . . . . . . . . . . . . . . . . . . 5 1.1. Contributing Authors . . . . . . . . . . . . . . . . . . . 5
1.2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. Generic Associated Channel Header . . . . . . . . . . . . . . 6 2. Generic Associated Channel Header . . . . . . . . . . . . . . 6
2.1. Allocation of Channel Types . . . . . . . . . . . . . . . 7 2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Generalised Exception Mechanism . . . . . . . . . . . . . . . 7 2.2. Allocation of Channel Types . . . . . . . . . . . . . . . 7
3.1. Relationship with Existing MPLS OAM Alert Mechanisms . . . 8 3. ACH TLVs . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. GAL Applicability and Usage . . . . . . . . . . . . . . . 8 3.1. ACH TLV Payload Structure . . . . . . . . . . . . . . . . 8
3.2.1. GAL Processing . . . . . . . . . . . . . . . . . . . . 8 3.2. ACH TLV Header . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Relationship wth RFC 3429 . . . . . . . . . . . . . . . . 11 3.3. ACH TLV Object . . . . . . . . . . . . . . . . . . . . . . 9
4. Compatability . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Generalised Exception Mechanism . . . . . . . . . . . . . . . 9
5. Congestion Considerations . . . . . . . . . . . . . . . . . . 12 4.1. Relationship with Existing MPLS OAM Alert Mechanisms . . . 10
6. Security Consderations . . . . . . . . . . . . . . . . . . . . 12 4.2. GAL Applicability and Usage . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 4.2.1. GAL Processing . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 4.3. Relationship wth RFC 3429 . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5. Compatability . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 6. Congestion Considerations . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 14 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
There is a need for Operations, Administration and Maintenance (OAM) There is a need for Operations, Administration and Maintenance (OAM)
mechanisms that can be used for edge-to-edge (i.e. between mechanisms that can be used for fault detection, diagnostics,
originating and terminating LSRs or T-PEs) and segment (e.g. between maintenance and other functions on a PW and an LSP. These functions
any two LSRs or T-PEs/S-PEs along the path of a LSP or PW [15]) fault can be used between any two Label Edge Routers (LERs) / Label
detection, diagnostics, maintenance and other functions for a PW and Switching Router (LSRs) or Terminating Provider Edge routers (T-PEs)
a LSP. Some of these functions can be supported using tools such as / Switching Provider Edge routers (S-PEs) along the path of an LSP or
VCCV [2], BFD [3], or LSP-Ping [4]. However, a requirement has been PW respectively [15]. Some of these functions can be supported using
indicated to augment the set of maintenance functions, in particular existing tools such as Virtual Circuit Connectivity Verification
where MPLS networks are used for packet transport services and (VCCV) [2], Bidirectional Forwarding Detection for MPLS LSPs (BFD-
network operations [16]. Examples include performance monitoring, MPLS)[3], LSP-Ping [4], or BFD-VCCV [5]. However, a requirement has
automatic protection switching, and support for management and been indicated to augment this set of maintenance functions, in
signaling communication channels. These tools must be applicable to, particular when MPLS networks are used for packet transport services
and function in essentially the same manner (from an operational and transport network operations [16]. Examples of these functions
point of view) on both MPLS PWs and MPLS LSPs. They must also include performance monitoring, automatic protection switching, and
operate in-band on the PW or LSP such that they do not depend on PSN support for management and signaling communication channels. These
routing, user data traffic or ultimately on PSN or other dynamic tools MUST be applicable to, and function in essentially the same
control plane functions. manner (from an operational point of view) on MPLS PWs, MPLS LSPs and
MPLS Sections. They MUST also operate in-band on the PW or LSP such
that they do not depend on Packet Switched Network (PSN) routing or
on user data traffic, and MUST also not depend on dynamic control
plane functions.
Virtual Circuit Connectivity Verification (VCCV) can use an VCCV can use an Associated Channel Header (ACH) to provide a PW-
associated channel to provide a control channel between a PW's associated control channel between a PW's end points, over which OAM
ingress and egress points and over which OAM and other control and other control messages can be exchanged. This document
messages can be exchanged. In this document, we propose a generic generalises the use of the ACH to enable the same associated control
associated channel header (G-ACH) to enable the same control channel channel mechanism to be used for Sections, LSPs and PWs. The
mechanism be used for MPLS Sections, LSPs and PWs. The associated associated control channel thus generalized is known as the Generic
channel header (ACH) specified in RFC 4385 [5] is used with Associated Channel (G-ACh). The ACH, specified in RFC 4385 [6], may
additional code points to support additional MPLS maintenance be used with additional code points to support additional MPLS
functions. maintenance functions on the G-ACh.
Generalizing the ACH mechanism to MPLS LSPs and MPLS Sections also Generalizing the associated control channel mechanism to LSPs and
requires a method to identify that a packet contains a G-ACH followed Sections also requires a method to identify that a packet contains an
by a non-service payload. This document therefore also defines a ACH followed by a non-service payload. Therefore, this document also
label based exception mechanism (the Generic Associated channel defines a label based exception mechanism that serves to inform an
header Label, or GAL) that serves to inform an LSR that a packet that LSR (or LER) that a packet it receives on an LSP or Section belongs
it receives on an LSP or section belongs to an associated channel. to an associated control channel for that LSP or Section.
RFC 4379 [4] and BFD for MPLS LSPs [3] have defined alert mechanisms RFC 4379 [4] and BFD-MPLS [3] define alert mechanisms that enable an
that enable a MPLS LSR to identify and process MPLS OAM packets when MPLS LSR to identify and process MPLS OAM packets when these are
the OAM packets are encapsulated in an IP header. These alert encapsulated in an IP header. These alert mechanisms are based on
mechanisms are based on TTL expiration and/or use an IP destination MPLS or PW label Time to Live (TTL) expiration and/or on the use of
address in the range 127/8. These mechanisms are the default an IP destination address in the range 127/8. These mechanisms are
mechanisms for identifying MPLS OAM packets when the OAM packets are the default mechanisms for identifying MPLS OAM packets when
encapsulated in an IP header. However it may not always be possible encapsulated in an IP header. However it may not always be possible
to use these mechanisms in some MPLS applications, (e.g. MPLS-TP to use these mechanisms in some MPLS applications, e.g. MPLS
[15]) particularly when IP based demultiplexing cannot be used. This Transport Profile (MPLS-TP) [15], particularly when IP based
document proposes an OPTIONAL mechanism that is RECOMMENDED for demultiplexing cannot be used. This document defines a mechanism
identifying and demultiplexing MPLS OAM and other maintenance that is RECOMMENDED for identifying and encapsulating MPLS OAM and
messages when IP based mechanisms such as those in [4] and [3] are other maintenance messages when IP based mechanisms such as those in
not available. [4] and [3] are not available. This mechanism MAY be used in
addition to IP-based mechanisms.
The G-ACH and GAL mechanisms are defined to work together. The GAL mechanism is defined to work together with the ACH for LSPs
and MPLS Sections.
Note that, in this document, maintenace functions and packets should Note that, in this document, maintenance functions and packets should
be understood in the broad sense, that is, as a set of FCAPS be understood in the broad sense. That is, a set of maintenance and
mechanisms that include OAM, Automatic Protection Switching (APS), management mechanisms that include OAM, Automatic Protection
Signalling Communication Channel (SCC) and Management Communication Switching (APS), Signalling Communication Channel (SCC) and
Channel (MCC) messages. Management Communication Channel (MCC) messages.
Note that the GAL and G-ACH are applicable to MPLS in general. Their Also note that the GAL and ACH are applicable to MPLS in general.
applicability to specific applications is outside the scope of this Their applicability to specific applications of MPLS is outside the
document. For example, the applicability of the GAL and G-ACH to scope of this document.
MPLS-TP is described in [15] and [17].
1.1. Contributing Authors 1.1. Contributing Authors
The editors gratefully acknowledge the contibution of Stewart Bryant, The editors gratefully acknowledge the contributions of Sami Boutros,
Italo Busi, Marc Lasserre, and Lieven Levrau. Italo Busi, Marc Lasserre, Lieven Levrau and Siva Sivabalan
1.2. Objectives 1.2. Objectives
This document proposes a mechanism to provide for the extended This document defines a mechanism that provides a solution to the
maintenance needs of emerging applications for MPLS. It creates a extended maintenance needs of emerging applications for MPLS. It
generic control channel identification mechanism that may be applied creates a generic control channel mechanism that may be applied to
to all MPLS LSPs, while maintaining compatibility with the PW MPLS LSPs and Sections, while maintaining compatibility with the PW
associated channel header (ACH) . It also normalizes the use of the associated channel. It also normalises the use of the ACH for PWs in
ACH for PWs in a transport context. a transport context, and defines a label based exception mechanism to
alert LERs/LSRs of the presence of an ACH after the bottom of the
stack.
1.3. Scope 1.3. Scope
This document defines the encapsulation header for LSP, MPLS Section This document defines the encapsulation header for LSP, MPLS Section
and PW associated channel messages. and PW associated channel messages.
It does not define how associated channel capabilities are signaled It does not define how associated control channel capabilities are
or negotiated between LSRs or PEs, the operation of various OAM signaled or negotiated between LERs/LSRs or PEs, or the operation of
functions, nor how the messages transmitted on the associated various OAM functions.
channel.
This document does not deprecate existing MPLS and PW OAM mechanisms. This document does not deprecate existing MPLS and PW OAM mechanisms.
1.4. Terminology 1.4. Terminology
G-ACH: Generic Associated Channel Header ACH: Associated Channel Header
GAL: Generic Associated Channel Header Label G-ACh: Generic Associated Channel
MPLS Section: A network segment between two LSRs that are immediately
adjacent at the MPLS layer
Maintenance Packet: Any packet containing a message belonging to a GAL: G-ACh Label
maintenace protocol that is carried on a PW, LSP or MPLS Section
associated channel. Examples of such maintenance protocols include Maintenance packet: Any packet containing a message belonging to a
OAM functions, signaling communications or management communications. maintenance protocol that is carried on a PW, LSP or MPLS Section
associated control channel. Examples of such maintenance protocols
include OAM functions, signaling communications or management
communications.
The terms 'Section' and 'Concatenated Segment' are defined in [17].
2. Generic Associated Channel Header 2. Generic Associated Channel Header
VCCV [2] defines three MPLS Control Channel (CC) Types that may be VCCV [2] defines three MPLS Control Channel (CC) Types that may be
used to multiplex OAM messages onto a PW: CC Type 1 uses an used to exchange OAM messages through a PW: CC Type 1 uses an ACH and
associated channel header and is referred to as "In-band VCCV"; CC is referred to as "In-band VCCV"; CC Type 2 uses the MPLS Router
Type 2 uses the MPLS Router Alert Label to indicate VCCV packets and Alert Label to indicate VCCV packets and is referred to as "Out of
is referred to as "Out of Band VCCV"; CC Type 3 uses the TTL to force Band VCCV"; CC Type 3 uses the TTL to force the packet to be
the packet to be processed by the targeted router control plane and processed by the targeted router control plane and is referred to as
is referred to as "MPLS PW Label with TTL == 1". "MPLS PW Label with TTL == 1".
The use of the CC Type 1, currently limited to MPLS PWs, is here 2.1. Definition
extended to apply to MPLS LSPs as well as to MPLS Sections. This
associated channel header is called the Generic Associated Channel
Header (G- ACH). The PWE3 control word MUST be present in the
encapsulation of user packets when the G-ACH is used to demultiplex
the associated channel packet on a PW.
The CC Type 1 channel header is depicted in figure below: The use of the CC Type 1, previously limited to PWs, is here extended
to also apply to LSPs and to Sections. Note that for PWs, the PWE3
control word [6] MUST be present in the encapsulation of user packets
when the ACH is used to realize the associated control channel.
The CC Type 1 control channel header is depicted in figure below:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version|A| Reserved | Channel Type | |0 0 0 1|Version| Reserved | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Generic Associated Channel Header Figure 1: Associated Channel Header
In the above figure, the first nibble is set to 0001b to indicate a In the above figure, the first nibble is set to 0001b to indicate a
channel associated with a PW, a LSP or a Section. The Version field control channel associated with a PW, an LSP or a Section. The
is set to 0, as specified in RFC 4385 [5]. This draft allocates Bit Version field is set to 0, as specified in RFC 4385 [6]. Bits 8 to
8 of the ACH to the ACH TLV bit. This bit is set to 1 to indicate 14 of the G-ACH are reserved and MUST be set to 0 and ignored on
that an object defined in the ACH TLV registry immediately follows reception.
the G-ACH, otherwise it is set to 0. Bits 8 to 14 of the G-ACH are
reserved and MUST be set to 0..
Note that VCCV also includes mechanisms for negotiating the Control Note that VCCV also includes mechanisms for negotiating the Control
Channel and Connectivity Verification (i.e. OAM functions) Types Channel and Connectivity Verification (i.e. OAM functions) Types
between PEs. It is anticipated that similar mechanisms will be between PEs. It is anticipated that similar mechanisms will be
applied to existing MPLS LSPs. Such application will require further applied to LSPs. Such application will require further
specification. However, such specification is beyond the scope of specification. However, such specification is beyond the scope of
this document. this document.
2.1. Allocation of Channel Types 2.2. Allocation of Channel Types
The Channel Type field indicates the type of message carried on the The Channel Type field indicates the type of message carried on the
associated channel e.g. IPv4 or IPv6 if IP demultiplexing is used associated control channel e.g. IPv4 or IPv6 if IP demultiplexing is
for messages on the G-ACH, or OAM or other FCAPS function if IP used for messages sent on the associated control channel, or OAM or
demultiplexing is not used. For G-ACH packets where IP is not used other maintenance function if IP demultiplexing is not used. For
as the multiplexer, the Channel Type SHOULD indicate the specific associated control channel packets where IP is not used as the
maintenance protocol carried in the associated channel. multiplexer, the Channel Type SHOULD indicate the specific
maintenance protocol carried in the associated control channel.
Values for the Channel Type field currently used for VCCV are Values for the Channel Type field currently used for VCCV are
specified in RFC 4446 [6]. The functionality of any additional specified elsewhere, e.g. in RFC 4446 [7]and RFC 4385[6] .
channel types will be defined in another document. Each associated Additional Channel Type values and the associated maintenance
channel protocol solution document must specify the value to use for functionality will be defined in other documents. Each document
any additional channel types. specifying a protocol solution relying on the ACH MUST also specify
the applicable Channel Type field value.
Note that these values are allocated from the PW Associated Channel Note that these values are allocated from the PW Associated Channel
Type registry, but this document modifies the existing policy to Type registry, but this document modifies the existing policy to
accomodate a level of experimentation. See Section 7 for further accommodate a level of experimentation. See Section 8 for further
details. details.
3. Generalised Exception Mechanism 3. ACH TLVs
The above mechanism enables the multiplexing of various maintenace In some applications of the "In-band VCCV" associated control channel
packets onto a PW, LSP or Section and provides information on the it is necessary to include one or more ACH TLVs to provide additional
type of function being performed. In the case of a PW, the use of a context information to the maintenance packet. One use of these ACH
control word is negotiated or configured at the time of the PW TLVs might be to identify the source and/or intended destination of
establishment. A special case of the control word (the G-ACH) is the associated control channel maintenance message. However, the use
used to identify packets belonging to a PW associated channel. of this construct is not limited to providing addressing information
nor is the applicability restricted to transport network
applications.
Generalizing the ACH mechanism to MPLS LSPs and MPLS Sections also If the maintenance message MAY be preceded by one or more ACH TLVs,
requires a method to identify that a packet contains a G-ACH followed then this MUST be explicitly specified in the definition of an ACH
by a non-service payload. This document specifies that a label be Channel Type. If the ACH Channel Type definition does state that one
used and calls this special label the 'Generic Associated channel or more ACH TLVs MAY precede the maintenance message, an ACH TLV
header Label (GAL)'. One of the reserved label values defined in RFC Header MUST follow the ACH. If no ACH TLVs are required in a
3032 [7] is assigned for this purpose. The value of the label is to specific associated control channel packet, but the Channel Type
be allocated by IANA; this document suggests the value 13. nevertheless defines that ACH TLVs MAY be used, an ACH TLV Header
MUST be present but with a length field set to zero to indicate that
no ACH TLV follow this header.
The GAL provides a generalised exception mechanism to: If a channel type specification does not explicitly specify that ACH
TLVs MAY be used, then an ACH TLV Header MUST NOT be used.
o Differentiate specific packets (e.g. those containing OAM 3.1. ACH TLV Payload Structure
messages) from others, such as normal user-plane ones,
o Indicate that the Generic Associated Channel Header (G-ACH) This section defines and describes the structure of an ACH payload
appears immediately after the bottom of the label stack. when an ACH TLV Header is present. The structure of ACH TLVs that
MAY follow an ACH TLV Header is defined and described in the
following sections.
The 'Generic Associated channel header Label (GAL)' MUST only be used The following figure (Figure 2) shows the structure of a G-ACh packet
where both of these purposes are applicable. payload.
3.1. Relationship with Existing MPLS OAM Alert Mechanisms +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACH |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACH TLV Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
~ zero or more ACH TLVs ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
~ Maintenance Message ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RFC 4379 [4] and BFD for MPLS LSPs [3] have defined alert mechanisms Figure 2: ACH TLV Payload Structure
that enable a MPLS LSR to identify and process MPLS OAM packets when
the OAM packets are encapsulated in an IP header. These alert
mechanisms are based on TTL expiration and/or use an IP destination
address in the range 127/8.
These alert mechanisms SHOULD preferably be used in non MPLS-TP 3.2. ACH TLV Header
environments. The mechanism defined in this document MAY also be
used.
3.2. GAL Applicability and Usage The ACH TLV Header defines the length of the set of ACH TLVs that
follow.
The 'Generic Associated channel header Label (GAL)' MUST only be used 0 1 2 3
with Label Switched Paths (LSPs), with their associated Tandem 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
Connection Monitoring Entities (see [17] for definitions of TCMEs) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
and with MPLS Sections. | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The GAL applies to both P2P and P2MP LSPs, unless otherwise stated. Figure 3: ACH TLV Header
The length field specifies the length in octets of the complete set
of TLVs including TLVs that follow the ACH TLV header. A length of
zero indicates that no ACH TLV follow this header.
The reserved field is for future use and MUST be set to zero on
transmission and ignored on reception.
3.3. ACH TLV Object
An ACH TLV consists of a 16-bit Type field, followed by a 16-bit
Length field which specifies the number of octets of the Value field
which follows the Length field. This 32-bit word is followed by zero
or more octets of Value information. The format and semantics of the
value information are defined by the TLV Type as recorded in the TLV
Type registry. See Section 8 for further details. Note that the
Value field of ACH TLVs MAY contain sub-TLV objects.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
~ Value ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: ACH TLV Format
4. Generalised Exception Mechanism
Generalizing the associated channel mechanism to LSPs and Sections
also requires a method to identify that a packet contains an ACH
followed by a non-service payload. This document specifies that a
label is used for that purpose and calls this special label the G-ACh
Label (GAL). One of the reserved label values defined in RFC 3032
[8] is assigned for this purpose. The value of the label is to be
allocated by IANA; this document suggests the value 13.
The GAL provides an alert based exception mechanism to:
o differentiate specific packets (e.g. maintenance messages) from
others, such as normal user-plane ones,
o indicate that the ACH appears immediately after the bottom of the
label stack.
The GAL MUST only be used where both of these purposes apply.
4.1. Relationship with Existing MPLS OAM Alert Mechanisms
RFC 4379 [4] and BFD-MPLS [3] have defined alert mechanisms that
enable a MPLS LSR to identify and process MPLS OAM packets when the
OAM packets are encapsulated in an IP header. These alert mechanisms
are based on TTL expiration and/or use an IP destination address in
the range 127/8.
These alert mechanisms SHOULD be used in non MPLS-TP environments,
although the mechanism defined in this document MAY also be used.
4.2. GAL Applicability and Usage
The GAL MUST only be used with LSPs, concatenated segments of LSPs,
and with Sections.
In MPLS-TP, the GAL MUST always be at the bottom of the label stack In MPLS-TP, the GAL MUST always be at the bottom of the label stack
(i.e. S bit set to 1). However, in other MPLS environments, this (i.e. S bit set to 1). However, in other MPLS environments, this
document places no restrictions on where the GAL may appear within document places no restrictions on where the GAL may appear within
the label stack. the label stack.
The GAL MUST NOT appear in the label stack when transporting normal The GAL MUST NOT appear in the label stack when transporting normal
user-plane packets. Furthermore, the GAL MUST only appear once in user-plane packets. Furthermore, when present, the GAL MUST only
the label stack for packets on the generic associated channel. appear once in the label stack.
3.2.1. GAL Processing 4.2.1. GAL Processing
The Traffic Class (TC) field (formerly known as the EXP field) of the The Traffic Class (TC) field (formerly known as the EXP field) of the
label stack entry containing the GAL follows the definition and label stack entry containing the GAL follows the definition and
processing rules specified and referenced in [8]. processing rules specified and referenced in [9].
The Time-To-Live (TTL) field of the label stack entry that contains The Time-To-Live (TTL) field of the label stack entry that contains
the GAL follows the definition and processing rules specified in [9]. the GAL follows the definition and processing rules specified in
[10].
3.2.1.1. MPLS Section 4.2.1.1. MPLS Label Switched Paths and Segments
The following figure (Figure 2) depicts two MPLS LSRs immediately The following figure (Figure 5) depicts two LERs (A and D) and two
adjacent at the MPLS layer. LSRs (B and C) for a given LSP which is established from A to D and
switched in B and C.
+---+ +---+ +---+ +---+ +---+ +---+
| A |-------------| Z | | A |-------------| B |-------------| C |-------------| D |
+---+ +---+ +---+ +---+ +---+ +---+
Figure 2: Maintenance over an MPLS Section Associated Channel Figure 5: MPLS-TP maintenance over a LSP
With regards to the MPLS Section, both LERs are Maintenance End In this example, a G-ACh exists on an LSP that extends between LERs A
Points (see [17] for definitions of MEPs). and D, via LSRs B and C. Only these nodes may insert, extract or
process packets on this G-ACh.
The following figure (Figure 3) depicts the format of a labelled OAM The following figure (Figure 6) depicts the format of a MPLS-TP
packet on an associated channel when used for MPLS Section maintenance message when used for an LSP.
maintenance.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL | TC |S| TTL | | GAL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Generic-ACH | | ACH |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . | ACH TLV Header (if present) |
. Maintenance Message . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. | | ~
~ Zero or more ACH TLVs ~
~ (if present) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
~ Maintenance Message ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Maintenance Packet Format for MPLS Section Figure 6: MPLS-TP maintenance message format for a LSP
To send a MPLS-TP maintenance packet on an associated channel of the Note that it is possible that the LSP may be tunnelled in another LSP
MPLS Section, the head-end LSR (A) of the MPLS Section generates a (e.g. if a MPLS Tunnel exists between B and C), and as such other
maintenance packet with a G-ACH to which it pushes a GAL. labels may be present in the label stack.
o The TTL field of the GAL SHOULD be set to 1. To send a maintenance message on the LSP associated control channel,
the LER (A) generates a maintenance message, to which it MAY
prepended an ACH TLV header and appropriate ACH TLVs, and with a ACH
to which it pushes a GAL and finally the LSP label.
o The S bit of the GAL MUST be set to 1 in MPLS-TP. o The TTL field of the GAL MUST be set to at least 1. The exact
value of the TTL is application specific.
The maintenance packet, the G-ACH and the GAL SHOULD NOT be modified o The S bit of the GAL MUST be set according to its position in the
towards the tail-end LSR (Z). Upon reception of the labelled packet, label stack.
the tail-end LSR (Z), after having checked the GAL fields, SHOULD
pass the whole packet to the appropriate processing entity.
3.2.1.2. Label Switched Paths o The setting of the TC field is application specific.
The following figure (Figure 4) depicts four LSRs. A LSP is The maintenance message, the ACH or the GAL SHOULD NOT be modified
established from A to D and switched in B and C. towards the targeted destination. Upon reception of the labelled
packet, the targeted destination, after having checked both the LSP
label and GAL fields, SHOULD pass the whole maintenance message to
the appropriate processing entity.
+---+ +---+ +---+ +---+ 4.2.1.2. MPLS Section
| A |-------------| B |-------------| C |-------------| D |
+---+ +---+ +---+ +---+
Figure 4: Maintenance over an LSP Associated Channel The following figure (Figure 7) depicts an example of a MPLS Section.
LERs A and D are Maintenance End Points (MEPs) with respect to this +---+ +---+
LSP. Furthermore, LSRs B and C could also be Maintenance | A |-------------| Z |
Intermediate Points (MIPs) with respect to this LSP (see [17] for +---+ +---+
definitions of MEPs and MIPs).
The following figure (Figure 5) depicts the format of a labelled Figure 7: Maintenance over an MPLS Section
maintenance packet when used for a MPLS-TP LSP.
With regard to the MPLS Section, a G-ACh exists between A and Z. Only
A and Z can insert, extract or process packets on this G-ACh.
The following figure (Figure 8) depicts the format of a maintenance
message when used for a MPLS Section. The GAL MAY provide the
exception mechanism for a control channel in its own right without
being associated with a specific LSP, thus providing maintenance
related communications across a specific link interconnecting two
LSRs. In this case, the GAL is the only label in the stack.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL | TC |S| TTL | | GAL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Generic-ACH | | ACH |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . | ACH TLV Header (if present) |
. Maintenance Message . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. | | ~
~ Zero or more ACH TLVs ~
~ (if present) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
~ Maintenance Message ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Maintenance Packet Format for MPLS-TP LSP Figure 8: Maintenance message format for a MPLS Section
Note that it is possible that the LSP MAY also be tunnelled in
another LSP (e.g. if a MPLS Tunnel exists between B and C), and as
such other labels MAY be present above it in the label stack.
To send a maintenance packet on the LSP associated channel, the head-
end LSR (A) generates a OAM message with a G-ACH on which it first
pushes a GAL followed by the LSP label.
o The TTL field of the GAL SHOULD be set to 1. To send a maintenance message on a control channel associated to the
Section, the head-end LSR (A) of the Section generates a maintenance
message, to which it MAY prepend an ACH TLV Header and appropriate
ACH TLVs, and with a ACH to which it pushes a GAL.
o The S bit of the GAL SHOULD be set to 1 in MPLS-TP. o The TTL field of the GAL MUST be set to at least 1. The exact
value of the TTL is application specific.
The maintenance message, the G-ACH or the GAL SHOULD NOT be modified o The S bit of the GAL MUST be set according to its position in the
towards the targeted destination. Upon reception of the labelled label stack. For MPLS Sections, the S bit MUST be set to 1.
packet, the targeted destination, after having checked both the LSP
label and GAL fields, SHOULD pass the whole packet to the appropriate
processing entity.
3.2.1.3. Tandem Connection Monitoring Entity o The setting of the TC field is application specific.
Tandem Connection Monitoring will be specified in a separate The maintenance message, the ACH and the GAL SHOULD NOT be modified
document. towards the tail-end LSR (Z). Upon reception of the labelled packet,
the tail-end LSR (Z), after having checked the GAL fields, SHOULD
pass the whole packet to the appropriate processing entity.
3.3. Relationship wth RFC 3429 4.3. Relationship wth RFC 3429
RFC 3429 [18] describes the assignment of one of the reserved label RFC 3429 [18] describes the assignment of one of the reserved label
values, defined in RFC 3032 [7], to the 'OAM Alert Label' that is values, defined in RFC 3032 [8], to the 'OAM Alert Label' that is
used by user-plane MPLS OAM functions for the identification of MPLS used by user-plane MPLS OAM functions for the identification of MPLS
OAM packets. The value of 14 is used for that purpose. OAM packets. The value of 14 is used for that purpose.
Both this document and RFC 3429 [18] therefore describe the Both this document and RFC 3429 [18] therefore describe the
assignment of reserved label values for similar purposes. The assignment of reserved label values for similar purposes. The
rationale for the assignment of a new reserved label can be rationale for the assignment of a new reserved label can be
summarized as follows: summarized as follows:
o Unlike the mechanisms described and referenced in RFC 3429 [18], o Unlike the mechanisms described and referenced in RFC 3429 [18],
MPLS-TP OAM packet payloads will not reside immediately after the MPLS-TP maintenance messages will not reside immediately after the
GAL but instead behind the G-ACH, which itself resides immediately GAL but instead behind the ACH, which itself resides after the
after the bottom of the label stack when the GAL is present. This bottom of the label stack. This ensures that OAM, using the
ensures that OAM using the generic associated channel complies G-ACh, complies with RFC 4928 [11].
with RFC 4928 [10].
o The set of maintenance functions potentially operated in the o The set of maintenance functions potentially operated in the
context of the generic associated channel is wider than the set of context of the G-ACh is wider than the set of OAM functions
OAM functions referenced in RFC 3429 [18]. referenced in RFC 3429 [18].
o It has been reported that there are existing implementations and o It has been reported that there are existing implementations and
running deployments using the 'OAM Alert Label' as described in running deployments using the 'OAM Alert Label' as described in
RFC 3429 [18]. It is therefore not possible to modify the 'OAM RFC 3429 [18]. It is therefore not possible to modify the 'OAM
Alert Label' allocation, purpose or usage. Nevertheless, it is Alert Label' allocation, purpose or usage. Nevertheless, it is
RECOMMENDED by this document that no further OAM extensions based RECOMMENDED by this document that no further OAM extensions based
on 'OAM Alert Label' (Label 14) usage be specified or developed. on 'OAM Alert Label' (Label 14) usage be specified or developed.
4. Compatability 5. Compatability
An LER, LSR or PE MUST discard received G-ACH packets if it is not G- Procedures for handling a packet received with an invalid incoming
ACH capable, if it is not capable of processing packets on the label are specified in RFC 3031[12].
indicated G-ACH channel, or if it has not, through means outside the
scope of this document, indicated to the sending LSR, LER or PE that
it will process G-ACH packets received on the indicated channel. The
LER, LSR or PE MAY increment an error counter and MAY also optionally
issue a system and/or SNMP notification.
5. Congestion Considerations An LER, LSR or PE MUST discard received associated channel packets on
which all of the MPLS or PW labels have been popped if any one of the
following conditions is true:
o It is not capable of processing packets on the Channel Type
indicated by the ACH of the received packet.
o It has not, through means outside the scope of this document,
indicated to the sending LSR, LER or PE that it will process
associated channel packets on the Channel Type indicated by the
ACH of the received packet.
o If the ACH was indicated by the presence of a GAL, and the first
nibble of the ACH of the received packet is not 0b0001.
o The ACH version is not recognised.
In addition, it MAY increment an error counter and MAY also
optionally issue a system and/or SNMP notification.
6. Congestion Considerations
The congestion considerations detailed in RFC 5085 [2] apply. The congestion considerations detailed in RFC 5085 [2] apply.
Further generic associated channel-specific congestion considerations
will be detailed in a future revision of this document.
6. Security Consderations 7. Security Considerations
The security considerations detailed in RFC 5085 [2], the MPLS The security considerations for the associated control channel are
architecture [11], the PWE3 architecture [12] and the MPLS-TP described in RFC 4385[6]. Further security considerations MUST be
framework [15] apply. described in the relevant associated channel type specification.
7. IANA Considerations RFC 5085 [2] provides data plane related security considerations.
These also apply to a G-ACh, whether the alert mechanism uses a GAL
or only an ACH.
This document requests that IANA allocates a Label value, to the 8. IANA Considerations
'Generic Associated channel header Label (GAL)', from the pool of
reserved labels, and suggests this value to be 13.
Channel Types for the Generic Associated Channel are allocated from This document requests that IANA allocates a label value, to the GAL,
the IANA PW Associated Channel Type registry [6]. The PW Associated from the pool of reserved labels, and suggests this value to be 13.
Channel Types for the Associated Channel Header are allocated from
the IANA PW Associated Channel Type registry [7]. The PW Associated
Channel Type registry is currently allocated based on the IETF Channel Type registry is currently allocated based on the IETF
consensus process, described in[13]. This allocation process was consensus process, described in[13]. This allocation process was
chosen based on the consensus reached in the PWE3 working group that chosen based on the consensus reached in the PWE3 working group that
pseudowire associated channel mechanisms should be reviewed by the pseudowire associated channel mechanisms should be reviewed by the
IETF and only those that are consistent with the PWE3 architecture IETF and only those that are consistent with the PWE3 architecture
and requirements should be allocated a code point. and requirements should be allocated a code point.
However, a requirement has emerged (see [16]) to allow for However, a requirement has emerged (see [16]) to allow for
optimizations or extensions to OAM and other control protocols optimizations or extensions to OAM and other control protocols
running in an associated channel to be experimented with without running in an associated channel to be experimented without resorting
resorting to the IETF standards process, by supporting experimental to the IETF standards process, by supporting experimental code
code points. This would prevent code points used for such functions points. This would prevent code points used for such functions from
from being used from the range allocated through the IETF standards being used from the range allocated through the IETF standards and
and thus protects an installed base of equipment from potential thus protects an installed base of equipment from potential
inadvertent overloading of code points. In order to support this inadvertent overloading of code points. In order to support this
requirement, this document requests that the code-point allocation requirement, this document requests that the code point allocation
scheme for the PW Associated Channel Type be changed as follows: scheme for the PW Associated Channel Type be changed as follows:
0 - 32751 : IETF Consensus 0 - 32751 : IETF Consensus
32752 - 32767 : Experimental 32752 - 32767 : Experimental
Code points in the experimental range MUST be used according to the Code points in the experimental range MUST be used according to the
guidelines of RFC 3692 [14]. Experimental OAM functions MUST be guidelines of RFC 3692 [14]. Experimental OAM functions MUST be
disabled by default. The channel type value used for a given disabled by default. The Channel Type value used for a given
experimental OAM function MUST be configurable, and care MUST be experimental OAM function MUST be configurable, and care MUST be
taken to ensure that different OAM functions that are not taken to ensure that different OAM functions that are not inter-
interoperable are configured to use different channel type values. operable are configured to use different Channel Type values.
8. Acknowledgements The PW Associated Channel Type registry needs to be updated to
include a column indicating whether the ACH is followed by a ACH TLV
header (Yes/No). There are two ACH Channel Type code-points
currently assigned and in both cases no ACH TLV header is used. Thus
the new format of the PW Channel Type registry is:
Registry:
Value Description TLV Follows Reference
----- ---------------------------- ----------- ---------
0x21 ACH carries an IPv4 packet No [RFC4385]
0x57 ACH carries an IPv6 packet No [RFC4385]
Figure 9: PW Channel Type registry
IANA is requested create a new registry called the Associated Channel
TLV Registry. The allocation policy for this registry is IETF
consensus. This registry MUST record the following information.
There are no initial entries.
Name Type Length Description Reference
(octets)
Figure 10: PW ACH TLV registry
9. Acknowledgements
The authors would like to thank all members of the teams (the Joint The authors would like to thank all members of the teams (the Joint
Working Team, the MPLS Interoperability Design Team in IETF and the Working Team, the MPLS Interoperability Design Team in IETF and the
T-MPLS Ad Hoc Group in ITU-T) involved in the definition and MPLS-TP Ad-Hoc Team in ITU-T) involved in the definition and
specification of MPLS Transport Profile. specification of MPLS Transport Profile.
9. References 10. References
9.1. Normative References 10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit [2] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007. Pseudowires", RFC 5085, December 2007.
[3] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD [3] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD
For MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress), For MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress),
June 2008. June 2008.
[4] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label [4] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label
Switched (MPLS) Data Plane Failures", RFC 4379, February 2006. Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.
[5] Bryant, S., Swallow, G., Martini, L., and D. McPherson, [5] 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.
[6] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use
over an MPLS PSN", RFC 4385, February 2006. over an MPLS PSN", RFC 4385, February 2006.
[6] Martini, L., "IANA Allocations for Pseudowire Edge to Edge [7] Martini, L., "IANA Allocations for Pseudowire Edge to Edge
Emulation (PWE3)", BCP 116, RFC 4446, April 2006. Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
[7] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, [8] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci,
D., Li, T., and A. Conta, "MPLS Label Stack Encoding", D., Li, T., and A. Conta, "MPLS Label Stack Encoding",
RFC 3032, January 2001. RFC 3032, January 2001.
[8] Andersson, L. and R. Asati, "Multi-Protocol Label Switching [9] Andersson, L. and R. Asati, "Multi-Protocol Label Switching
(MPLS) label stack entry: "EXP" field renamed to "Traffic (MPLS) label stack entry: "EXP" field renamed to "Traffic
Class" field", draft-ietf-mpls-cosfield-def-08 (work in Class" field", draft-ietf-mpls-cosfield-def-08 (work in
progress), December 2008. progress), December 2008.
[9] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in [10] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in
Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, Multi-Protocol Label Switching (MPLS) Networks", RFC 3443,
January 2003. January 2003.
[10] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal Cost [11] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal Cost
Multipath Treatment in MPLS Networks", BCP 128, RFC 4928, Multipath Treatment in MPLS Networks", BCP 128, RFC 4928,
June 2007. June 2007.
[11] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label [12] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label
Switching Architecture", RFC 3031, January 2001. Switching Architecture", RFC 3031, January 2001.
[12] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge
(PWE3) Architecture", RFC 3985, March 2005.
[13] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [13] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
October 1998.
[14] Narten, T., "Assigning Experimental and Testing Numbers [14] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692, January 2004. Considered Useful", BCP 82, RFC 3692, January 2004.
9.2. Informative References 10.2. Informative References
[15] Bocci, M., Bryant, S., and L. Levrau, "A Framework for MPLS in [15] Bocci, M., Bryant, S., and L. Levrau, "A Framework for MPLS in
Transport Networks", draft-ietf-mpls-tp-framework-00 (work in Transport Networks", draft-ietf-mpls-tp-framework-00 (work in
progress), November 2008. progress), November 2008.
[16] Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in [16] Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in
MPLS Transport Networks", MPLS Transport Networks",
draft-ietf-mpls-tp-oam-requirements-00 (work in progress), draft-ietf-mpls-tp-oam-requirements-00 (work in progress),
December 2008. December 2008.
[17] Busi, I. and B. Niven-Jenkins, "MPLS-TP OAM Framework and [17] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and
Overview", draft-busi-mpls-tp-oam-framework-00 (work in S. Ueno, "MPLS-TP Requirements",
progress), October 2008. draft-ietf-mpls-tp-requirements-04 (work in progress),
February 2009.
[18] Ohta, H., "Assignment of the 'OAM Alert Label' for [18] Ohta, H., "Assignment of the 'OAM Alert Label' for
Multiprotocol Label Switching Architecture (MPLS) Operation and Multiprotocol Label Switching Architecture (MPLS) Operation and
Maintenance (OAM) Functions", RFC 3429, November 2002. Maintenance (OAM) Functions", RFC 3429, November 2002.
Authors' Addresses Authors' Addresses
Matthew Bocci (editor) Matthew Bocci (editor)
Alcatel-Lucent Alcatel-Lucent
Voyager Place, Shoppenhangers Road
Maidenhead, Berks SL6 2PJ
UK
Email: matthew.bocci@alcatel-lucent.com Email: matthew.bocci@alcatel-lucent.com
Martin Vigoureux (editor) Martin Vigoureux (editor)
Alcatel-Lucent Alcatel-Lucent
Route de Villejust
Nozay, 91620
France
Email: martin.vigoureux@alcatel-lucent.com Email: martin.vigoureux@alcatel-lucent.com
George Swallow George Swallow
Cisco Cisco
Email: swallow@cisco.com Email: swallow@cisco.com
David Ward David Ward
Cisco Cisco
Email: dward@cisco.com Email: dward@cisco.com
Stewart Bryant
Cisco
Email: stbryant@cisco.com
Rahul Aggarwal Rahul Aggarwal
Juniper Networks Juniper Networks
Email: rahul@juniper.net Email: rahul@juniper.net
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