draft-ietf-mpls-tp-li-lb-07.txt   draft-ietf-mpls-tp-li-lb-08.txt 
Network Working Group Sami Boutros (Ed.) Network Working Group Sami Boutros (Ed.)
Internet Draft Siva Sivabalan (Ed.) Internet Draft Siva Sivabalan (Ed.)
Intended status: Standards Track Cisco Systems, Inc. Intended status: Standards Track Cisco Systems, Inc.
Updates: 6371 (if approved) Updates: 6371 (if approved)
Expires: April 3, 2012 Rahul Aggarwal (Ed.) Expires: April 24, 2012 Rahul Aggarwal (Ed.)
Arktan, Inc. Arktan, Inc.
Martin Vigoureux (Ed.) Martin Vigoureux (Ed.)
Alcatel-Lucent Alcatel-Lucent
Xuehui Dai (Ed.) Xuehui Dai (Ed.)
ZTE Corporation ZTE Corporation
October 3, 2011 October 24, 2011
MPLS Transport Profile lock Instruct and Loopback Functions MPLS Transport Profile lock Instruct and Loopback Functions
draft-ietf-mpls-tp-li-lb-07.txt draft-ietf-mpls-tp-li-lb-08.txt
Abstract Abstract
Two useful Operations, Administration, and Maintenance (OAM) Two useful Operations, Administration, and Maintenance (OAM)
functions in a transport network are "lock" and "loopback". The lock functions in a transport network are "lock" and "loopback". The lock
function enables an operator to lock a transport path such that it function enables an operator to lock a transport path such that it
does not carry client traffic, but can continue to carry OAM messages does not carry client traffic, but can continue to carry OAM messages
and may carry test traffic. The loopback function allows an operator and may carry test traffic. The loopback function allows an operator
to set a specific node on the transport path into loopback mode such to set a specific node on the transport path into loopback mode such
that it returns all received data. that it returns all received data.
This document specifies the lock function for MPLS networks and This document specifies the lock function for MPLS networks and
describes how the loopback function operates in MPLS networks. describes how the loopback function operates in MPLS networks.
This document updates RFC 6371 section 7.1.1. This document updates RFC 6371 section 7.1.1 and 7.1.2.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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Two useful Operations, Administration, and Maintenance (OAM) Two useful Operations, Administration, and Maintenance (OAM)
functions in a transport network are "lock" and "loopback". This functions in a transport network are "lock" and "loopback". This
document discusses these functions in the context of MPLS networks. document discusses these functions in the context of MPLS networks.
- The lock function enables an operator to lock a transport path such - The lock function enables an operator to lock a transport path such
that it does not carry client traffic. As per RFC 5860 [1], lock is that it does not carry client traffic. As per RFC 5860 [1], lock is
an administrative state in which it is expected that no client an administrative state in which it is expected that no client
traffic may be carried. However, test traffic and OAM messages can traffic may be carried. However, test traffic and OAM messages can
still be mapped onto the locked transport path. The lock function still be mapped onto the locked transport path. The lock function
may be applied to to Label Switched Paths (LSPs), Pseudowires (PWs) may be applied to to Label Switched Paths (LSPs), Pseudowires (PWs)
(including multi-segment Pseudowires) (MS-PWs), and MPLS Sections (including multi-segment Pseudowires) (MS-PWs), and bidirectional
as defined in RFC 5960 [9]). MPLS Sections as defined in RFC 5960 [9]).
- The loopback function allows an operator to set a specific node on - The loopback function allows an operator to set a specific node on
a transport path into loopback mode such that it returns all a transport path into loopback mode such that it returns all
received data. Loopback can be applied at a Maintenance Entity received data. Loopback can be applied at a Maintenance Entity
Group End Point (MEP) or a Maintenance Entity Group Intermediate Group End Point (MEP) or a Maintenance Entity Group Intermediate
Point (MIP) on a co-routed bidirectional LSP, PW or MPLS Point (MIP) on a co-routed bidirectional LSP, on a PW, or on an
Section. It can also be applied at a MEP on an associated bidirectional MPLS Section. It can also be applied at a MEP on an
bidirectional LSP, PW or MPLS Section. associated bidirectional LSP.
Loopback is used to test the integrity of the transport path to and Loopback is used to test the integrity of the transport path to and
from the node that is performing loopback. It requires that the from the node that is performing loopback. It requires that the
transport is locked and that a MEP on the transport path sends test transport is locked and that a MEP on the transport path sends test
data which it also validates on receipt. data which it also validates on receipt.
This document specifies the lock function for MPLS networks and This document specifies the lock function for MPLS networks and
describes how the loopback function operates in MPLS networks. describes how the loopback function operates in MPLS networks.
This document updates RFC 6371 section 7.1.1 [6]. This document updates RFC 6371 section 7.1.1 [6].
1.1. Updates RFC 6371 1.1. Updates RFC 6371
This document updates section 7.1.1 of RFC 6371 [6]. This document updates section 7.1.1 and 7.1.2 of RFC 6371 [6].
That framework makes the assumption that the Lock Instruct message is That framework makes the assumption that the Lock Instruct message is
used to independently enable locking and requires a response message. used to independently enable locking and requires a response message.
The mechanism defined in this document requires that a lock The mechanism defined in this document requires that a lock
instruction is sent by management to both ends of the locked instruction is sent by management to both ends of the locked
transport path and that the Lock Instruct message does not require a transport path and that the Lock Instruct message does not require a
response. response.
2. Terminology and Conventions 2. Terminology and Conventions
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MPLS-TP: MPLS Transport Profile MPLS-TP: MPLS Transport Profile
MPLS-TP LSP: Bidirectional Label Switch Path MPLS-TP LSP: Bidirectional Label Switch Path
TLV: Type Length Value TLV: Type Length Value
TTL: Time To Live TTL: Time To Live
LI: Lock Instruct LI: Lock Instruct
NMS: Network Management System
Transport path: MPLS-TP LSP or MPLS PW Transport path: MPLS-TP LSP or MPLS PW
3. Lock Function 3. Lock Function
Lock is used to request a MEP to take a transport path out of service Lock is used to request a MEP to take a transport path out of service
for administrative reasons. For example, Lock can be used to allow for administrative reasons. For example, Lock can be used to allow
some form of maintenance to be done for a transport path. Lock is some form of maintenance to be done for a transport path. Lock is
also a prerequisite of the Loopback function described in Section 4. also a prerequisite of the Loopback function described in Section 4.
The NMS or a management process initiates a Lock by sending a Lock The NMS or a management process initiates a Lock by sending a Lock
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that is, it stops injecting or forwarding traffic onto the transport that is, it stops injecting or forwarding traffic onto the transport
path. path.
To properly lock a transport path (for example, to ensure that a To properly lock a transport path (for example, to ensure that a
loopback test can be performed), both directions of the transport loopback test can be performed), both directions of the transport
path must be taken out of service so a Lock command is sent to the path must be taken out of service so a Lock command is sent to the
MEPs at both ends of the path. This ensures that no traffic is sent MEPs at both ends of the path. This ensures that no traffic is sent
in either direction. Thus, the Lock function can be realized entirely in either direction. Thus, the Lock function can be realized entirely
using the management plane. using the management plane.
However, despatch of messages in the management plane to the two MEPs However, dispatch of messages in the management plane to the two MEPs
may present coordination challenges. It is desirable that the lock be may present coordination challenges. It is desirable that the lock be
achieved in a coordinated way within a tight window, and this may be achieved in a coordinated way within a tight window, and this may be
difficult with a busy management plane. In order to provide difficult with a busy management plane. In order to provide
additional coordination, an LI OAM message can additionally be sent. additional coordination, an LI OAM message can additionally be sent.
A MEP locks a transport path when it receives a command from a A MEP locks a transport path when it receives a command from a
management process or when it receives an LI message as described in management process or when it receives an LI message as described in
Section 6. Section 6.
This document defines an LI message for MPLS OAM. The LI message is This document defines an LI message for MPLS OAM. The LI message is
based on a new ACH Type as well as an existing TLV. This is a common based on a new ACH Type as well as an existing TLV. This is a common
mechanism applicable to lock LSPs, PW, and MPLS Sections. mechanism applicable to lock LSPs, PWs, and bidirectional MPLS
Sections.
4. Loopback Function 4. Loopback Function
This section provides a description of the Loopback function within This section provides a description of the Loopback function within
an MPLS network. This function is achieved through management an MPLS network. This function is achieved through management
commands and so there is no protocol specification necessary. commands and so there is no protocol specification necessary.
However, the Loopback function is dependent on the Lock function and However, the Loopback function is dependent on the Lock function and
so it is appropriate to describe it in this document. so it is appropriate to describe it in this document.
The Loopback function is used to test the integrity of a transport The Loopback function is used to test the integrity of a transport
path from a MEP up any other node in the same MEG. This is achieved path from a MEP up any other node in the same MEG. This is achieved
by setting the target node into loopback mode, and transmitting a by setting the target node into loopback mode, and transmitting a
pattern of test data from the MEP. The target node loops all received pattern of test data from the MEP. The target node loops all received
data back toward the originator, and the MEP extracts the test data data back toward the originator, and the MEP extracts the test data
and compares it with what it sent. and compares it with what it sent.
Loopback is a function that enables a receiving MEP to return traffic Loopback is a function that enables a receiving MEP or MIP to return
to the sending MEP when in the loopback state. This state corresponds traffic to the sending MEP when in the loopback state. This state
to the situation where, at a given node, a forwarding plane loop is corresponds to the situation where, at a given node, a forwarding
configured and the incoming direction of a transport path is cross- plane loop is configured and the incoming direction of a transport
connected to the outgoing reverse direction. Therefore, except in the path is cross-connected to the outgoing reverse direction. Therefore,
case of early TTL expiry, traffic sent by the source will be received except in the case of early TTL expiry, traffic sent by the source
by that source. will be received by that source.
Data plane loopback is an out-of-service function, as required in Data plane loopback is an out-of-service function, as required in
section 2.2.5 of RFC 5860 [1]. This function loops back all traffic section 2.2.5 of RFC 5860 [1]. This function loops back all traffic
(including user data and OAM). The traffic can be originated from one (including user data and OAM). The traffic can be originated from one
internal point at the ingress of a transport path within an interface internal point at the ingress of a transport path within an interface
or inserted from input port of an interface using an external test or inserted from input port of an interface using an external test
equipment. The traffic is looped back unmodified (other than normal equipment. The traffic is looped back unmodified (other than normal
per hop processing such as TTL decrement) in the direction of the per hop processing such as TTL decrement) in the direction of the
point of origin by an interface at either an intermediate node or a point of origin by an interface at either an intermediate node or a
terminating node. terminating node.
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It should be noted that data plane loopback function itself is It should be noted that data plane loopback function itself is
applied to data plane loopback points residing on different applied to data plane loopback points residing on different
interfaces from MIPs/MEPs. All traffic (including both payload and interfaces from MIPs/MEPs. All traffic (including both payload and
OAM) received on the looped back interface is sent on the reverse OAM) received on the looped back interface is sent on the reverse
direction of the transport path. direction of the transport path.
For data plane loopback at an intermediate point in a transport For data plane loopback at an intermediate point in a transport
path, the loopback needs to be configured to occur at either the path, the loopback needs to be configured to occur at either the
ingress or egress interface. This is done using management. ingress or egress interface. This is done using management.
The Loopback can be performed using a management plane. Management The management plane can be used to configure the Loopback function.
plane must ensure that the two MEPs are locked before performing the The management plane must ensure that the two MEPs are locked before
loopback function. it requests setting MEP or MIP in the loopback state.
The nature of test data and the use of loopback traffic to measure The nature of test data and the use of loopback traffic to measure
packet loss, delay, and delay variation is outside the scope of this packet loss, delay, and delay variation is outside the scope of this
document. document.
4.1. Operational Prerequisites 4.1. Operational Prerequisites
Obviously, for the Loopback function to operate, there are several Obviously, for the Loopback function to operate, there are several
prerequisites: prerequisites:
- There must be a return path, so transport path under test must e - There must be a return path, so transport path under test must be
bidirectional. bidirectional.
- The node in loopback mode must be on both the forward and return - The node in loopback mode must be on both the forward and return
paths. This possible for all MEPs and MIPs on a co-routed paths. This is possible for all MEPs and MIPs on a co-routed
bidirectional LSP, PW, or MPLS Section, but is only bidirectional LSP, on a PW, or on a bidirectional MPLS Section, but
possible on for MEPs on associated bidirectional LSPs, PW, is only possible on for MEPs on associated bidirectional LSPs.
or MPLS Sections.
- The transport path cannot deliver client data when one of its nodes - The transport path cannot deliver client data when one of its nodes
is in loopback mode, so it is important that the transport path is is in loopback mode, so it is important that the transport path is
locked before loopback is enabled. locked before loopback is enabled.
- Management plane coordination between the node in loopback mode and - Management plane coordination between the node in loopback mode and
the MEP sending test data is required. The MEP must not send test the MEP sending test data is required. The MEP must not send test
data until loopback has been properly configured because this would data until loopback has been properly configured because this would
result in the test data continuing toward the destination. result in the test data continuing toward the destination.
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MEP Source ID TLV: This is one of the three MEP Source ID TLVs MEP Source ID TLV: This is one of the three MEP Source ID TLVs
defined in [3] and identifies the MEP that originated the LI message. defined in [3] and identifies the MEP that originated the LI message.
6. Operation of the Lock Function 6. Operation of the Lock Function
6.1. Locking a Transport Path 6.1. Locking a Transport Path
When a MEP receives a Lock command from an NMS or through some other When a MEP receives a Lock command from an NMS or through some other
management process, it MUST take the transport path out of service. management process, it MUST take the transport path out of service.
That is, it MUST stop injecting or forwarding traffic onto the LSP, That is, it MUST stop injecting or forwarding traffic onto the LSP,
PW, or Section that has been locked. PW, or bidirectional Section that has been locked.
As soon as the transport path has been locked, the MEP MUST send an As soon as the transport path has been locked, the MEP MUST send an
LI message targeting the MEP at the other end of the locked transport LI message targeting the MEP at the other end of the locked transport
path. The source MEP MUST set the Refresh Timer value in the LI path. The source MEP MUST set the Refresh Timer value in the LI
message and MUST retransmit the LI message at the frequency indicated message and MUST retransmit the LI message at the frequency indicated
by the value set. by the value set.
When locking a transport path, the NMS or management process is When locking a transport path, the NMS or management process is
required to send a Lock command to both ends of the transport path. required to send a Lock command to both ends of the transport path.
Thus a MEP may receive either the management command or an LI message Thus a MEP may receive either the management command or an LI message
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6.2. UnLocking a Transport Path 6.2. UnLocking a Transport Path
Unlock is used to request a MEP to bring the previously locked Unlock is used to request a MEP to bring the previously locked
transport path back in service. transport path back in service.
When a MEP receives an Unlocked command from a management process it When a MEP receives an Unlocked command from a management process it
MUST cease sending LI messages. However, as described in Section 6.1, MUST cease sending LI messages. However, as described in Section 6.1,
if the MEP is still receiving LI messages, the transport path MUST if the MEP is still receiving LI messages, the transport path MUST
remain out of service. Thus, to unlock a transport path, the remain out of service. Thus, to unlock a transport path, the
management process has to send an Unlock command to the MEPs at management process has to send an Unlock command to the MEPs at
either end. both ends.
When a MEP has been unlocked and has not received an LI message for a When a MEP has been unlocked and has not received an LI message for a
multiple of 3.5 times the Refresh Timer on the LI message (or has multiple of 3.5 times the Refresh Timer on the LI message (or has
never received an LI message), the MEP unlocks the transport path and never received an LI message), the MEP unlocks the transport path and
puts it back into service. puts it back into service.
7. Security Considerations 7. Security Considerations
MPLS-TP is a subset of MPLS and so builds upon many of the aspects of MPLS-TP is a subset of MPLS and so builds upon many of the aspects of
the security model of MPLS. MPLS networks make the assumption that it the security model of MPLS. MPLS networks make the assumption that it
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