Internet DRAFT - draft-ietf-pals-mpls-tp-dual-homing-coordination
draft-ietf-pals-mpls-tp-dual-homing-coordination
Network Working Group W. Cheng
Internet-Draft L. Wang
Intended status: Standards Track H. Li
Expires: October 28, 2017 China Mobile
J. Dong
Huawei Technologies
A. D'Alessandro
Telecom Italia
April 26, 2017
Dual-Homing Coordination for MPLS Transport Profile (MPLS-TP)
Pseudowires Protection
draft-ietf-pals-mpls-tp-dual-homing-coordination-06
Abstract
In some scenarios, MPLS Transport Profile (MPLS-TP) Pseudowires (PWs)
(RFC 5921) may be statically configured, when a dynamic control plane
is not available. A fast protection mechanism for MPLS-TP PWs is
needed to protect against the failure of an Attachment Circuit (AC),
the failure of a Provider Edge (PE), or a failure in the Packet
Switched Network (PSN). The framework and typical scenarios of dual-
homing PW local protection are described in [draft-ietf-pals-mpls-tp-
dual-homing-protection]. This document proposes a dual-homing
coordination mechanism for MPLS-TP PWs, which is used for state
exchange and switchover coordination between the dual-homing PEs for
dual-homing PW local protection.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 28, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Overview of the Proposed Solution . . . . . . . . . . . . . . 3
3. Protocol Extensions for Dual-Homing MPLS-TP PW Protection . . 4
3.1. Information Exchange Between Dual-Homing PEs . . . . . . 5
3.2. Protection Procedures . . . . . . . . . . . . . . . . . . 9
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
[RFC6372], [RFC6378] and [RFC7771] describe the framework and
mechanism of MPLS Transport Profile (MPLS-TP) linear protection,
which can provide protection for the MPLS Label Switched Path (LSP)
and Pseudowires (PWs) between the edge nodes. These mechanisms
cannot protect the failure of the Attachment Circuit (AC) or the edge
nodes. [RFC6718] and [RFC6870] specifies the PW redundancy framework
and mechanism for protecting the AC or edge node failure by adding
one or more edge nodes, but it requires PW switchover in case of an
AC failure, also PW redundancy relies on Packet Switched Network
(PSN) protection mechanisms to protect the failure of PW.
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In some scenarios such as mobile backhauling, the MPLS PWs are
provisioned with dual-homing topology, in which at least the CE node
on one side is dual-homed to two Provider Edge (PE) nodes. If a
failure occurs in the primary AC, operators usually prefer to perform
local switchover in the dual-homing PE side and keep the working
pseudowire unchanged if possible. This is to avoid massive PW
switchover in the mobile backhaul network due to the AC failure in
the mobile core site, which may in turn lead to congestion due to the
migration of traffic from the paths preferred by the network
planners. Similarly, as multiple PWs share the physical AC in the
mobile core site, it is preferable to keep using the working AC when
one working PW fails in the PSN network, which could avoid
unnecessary switchover for other PWs. A fast dual-homing PW
protection mechanism is needed to protect the failure in AC, the PE
node and the PSN network to meet the above requirements.
[I-D.ietf-pals-mpls-tp-dual-homing-protection] describes a framework
and several scenarios of dual-homing PW local protection. This
document proposes a dual-homing coordination mechanism for static
MPLS-TP PWs, which is used for information exchange and switchover
coordination between the dual-homing PEs for the dual-homing PW local
protection. The proposed mechanism has been implemented and deployed
in several mobile backhaul networks which use static MPLS-TP PWs for
the backhauling of mobile traffic from the radio access sites to the
core site.
2. Overview of the Proposed Solution
Linear protection mechanisms for MPLS-TP network are defined in
[RFC6378], [RFC7271] and [RFC7324]. When such mechanisms are applied
to PW linear protection [RFC7771], both the working PW and the
protection PW are terminated on the same PE node. In order to
provide dual-homing protection for MPLS-TP PWs, some additional
mechanisms are needed.
In MPLS-TP PW dual-homing protection, the linear protection mechanism
as defined in [RFC6378] [RFC7271] and [RFC7324] on the single-homing
PE (e.g. PE3 in Figure 1) is not changed, while on the dual-homing
side, the working PW and protection PW are terminated on two dual-
homing PEs (e.g. PE1 and PE2 in Figure 1) respectively to protect a
failure occuring in a PE or a connected AC. As described in
[I-D.ietf-pals-mpls-tp-dual-homing-protection], a dedicated Dual-Node
Interconnection (DNI) PW is used between the two dual-homing PE nodes
to forward the traffic. In order to utilize the linear protection
mechanism [RFC7771] in the dual-homing PEs scenario, coordination
between the dual-homing PE nodes is needed, so that the dual-homing
PEs can switch the connection between the AC, the service PW and the
DNI-PW properly in a coordinated fashion by the forwarder.
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+----------------------------------+
| PE1 |
+----------------------------------+ +----+
| | | Working | |
X Forwarder + Service X-------------X |
/| | PW | Service PW1 | |
AC1 / +--------+--------+ | | |
/ | DNI PW | | | |
+---* +--------X--------+----------------+ | | +---+
| | ^ | | | |
|CE1| | DNI PW |PE3 +---|CE2|
| | | | | | |
| | V | | | |
+---* +--------X--------+----------------+ | | +---+
\ | DNI PW | | | |
AC2 \ +--------+--------+ | Protection | |
\| | Service X-------------X |
X Forwarder + PW | Service PW2 | |
| | | +----+
+----------------------------------+
| PE2 |
+----------------------------------+
Figure 1. Dual-homing Protection with DNI-PW
3. Protocol Extensions for Dual-Homing MPLS-TP PW Protection
In dual-homing MPLS-TP PW local protection, the forwarding state of
the dual-homing PEs are determined by the forwarding state machine in
Table 1.
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+-----------+---------+--------+---------------------+
|Service PW | AC | DNI PW | Forwarding Behavior |
+-----------+---------+--------+---------------------+
| Active | Active | Up |Service PW <-> AC |
+-----------+---------+--------+---------------------+
| Active | Standby | Up |Service PW <-> DNI PW|
+-----------+---------+--------+---------------------+
| Standby | Active | Up | DNI PW <-> AC |
+-----------+---------+--------+---------------------+
| Standby | Standby | Up | Drop all packets |
+-----------+---------+--------+---------------------+
| Active | Active | Down |Service PW <-> AC |
+-----------+---------+--------+---------------------+
| Active | Standby | Down | Drop all packets |
+-----------+---------+--------+---------------------+
| Standby | Active | Down | Drop all packets |
+-----------+---------+--------+---------------------+
| Standby | Standby | Down | Drop all packets |
+-----------+---------+--------+---------------------+
Table 1. Dual-homing PE Forwarding State Machine
In order to achieve the dual-homing MPLS-TP PW protection,
coordination between the dual-homing PE nodes is needed to exchange
the PW status and protection coordination requests.
3.1. Information Exchange Between Dual-Homing PEs
The coordination information will be sent on the DNI PW over the
Generic Associated Channel (G-ACh) as described in [RFC5586]. A new
G-ACh channel type is defined for the dual-homing coordination
between the dual-homing PEs of MPLS-TP PWs. This channel type can be
used for the exchange of different types of information between the
dual-homing PEs. This document uses this channel type for the
exchange of PW status and switchover coordination between the dual-
homing PEs. Other potential usages of this channel type are for
further study and are out of the scope of this document.
The MPLS-TP Dual-Homing Coordination (DHC) message is sent on the DNI
PW between the dual-homing PEs. The format of the MPLS-TP DHC
message is shown below:
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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 0 0 1|Version| Reserved | DHC Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dual-Homing PEs Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. MPLS-TP Dual-Homing Coordination Message
The first 4-octets is the common G-ACh header as specified in
[RFC5586]. The DHC Channel Type is the G-ACh channel type code point
to be assigned by IANA.
The Dual-Homing Group ID is a 4-octet unsigned integer to identify
the dual-homing group which the dual-homing PEs belong to. It MUST
be the same at both PEs in the same group.
The TLV Length field specifies the total length in octets of the
subsequent TLVs.
In this document, two TLVs are defined in MPLS-TP Dual-Homing
Coordination message for dual-homing MPLS-TP PW protection:
Type Description Length
1 PW Status 20 Bytes
2 Dual-Node Switching 16 Bytes
The PW Status TLV is used by a dual-homing PE to report its service
PW status to the other dual-homing PE in the same dual-homing group.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=1 (PW Status) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Dual-homing PE Node_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Dual-homing PE Node_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DNI PW-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service PW Status |D|F|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3. PW Status TLV
- The Length field specifies the length in octets of the value field
of the TLV.
- The Destination Dual-homing PE Node_ID is the 32-bit identifier of
the receiver PE [RFC6370] which supports both IPv4 and IPv6
environments. Usually it is the same as the LSR-ID of the receiver
PE.
- The Source Dual-homing PE Node_ID is the 32-bit identifier of the
sending PE [RFC6370] which supports both IPv4 and IPv6 environments.
Usually it is the same as the LSR-ID of the sending PE.
- The DNI PW-ID field contains the 32-bit PW ID [RFC4447] of the DNI
PW.
- The Flags field contains 32 bit flags, in which:
o The P (Protection) bit indicates whether the Source Dual-homing PE
is the working PE (P=0) or the protection PE (P=1).
o Other bits are reserved for future use, which MUST be set to 0 on
transmission and MUST be ignored upon receipt.
- The Service PW Status field indicates the status of the Service PW
between the sending PE and the remote PE. Currently two bits are
defined in the Service PW Status field:
o F bit: If set, it indicates Signal Fail (SF) [RFC6378] on the
service PW. It can be either a local request generated by the PE
itself or a remote request received from the remote PE.
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o D bit: If set, it indicates Signal Degrade (SD) [RFC6378] on the
service PW. It can be either a local request or a remote request
received from the remote PE.
o Other bits are reserved for future use, which MUST be set to 0 on
transmission and MUST be ignored upon receipt.
The Dual-Node Switching TLV is used by one dual-homing PE to send
protection state coordination to the other PE in the same dual-homing
group.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=2 (Dual-Node Switching) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Dual-homing PE Node_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Dual-homing PE Node_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DNI PW-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |S|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4. Dual-Node Switching TLV
- The Length field specifies the length in octets of the value field
of the TLV.
- The Destination Dual-homing PE Node_ID is the 32-bit identifier of
the receiver PE [RFC6370]. Usually it is the same as the LSR-ID of
the receiver PE.
- The Source Dual-homing PE Node_ID is the 32-bit identifier of the
sending PE [RFC6370]. Usually it is the same as the LSR-ID of the
sending PE.
- The DNI PW-ID field contains the 32-bit PW-ID [RFC4447] of the DNI
PW.
- The Flags field contains 32 bit flags, in which:
o The P (Protection) bit indicates whether the Source Dual-homing PE
is the working PE or the protection PE. It is set to 1 when the
Source PE of the dual-node switching request is the protection PE.
o The S (PW Switching) bit indicates which service PW is used for
forwarding traffic. It is set to 0 when traffic will be
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transported on the working PW, and is set to 1 if traffic will be
transported on the protection PW. The value of the S bit is
determined by the protection coordination mechanism between the
dual-homing PEs and the remote PE.
o Other bits are reserved for future use, which MUST be set to 0 on
transmission and MUST be ignored upon receipt.
When a change of the service PW status is detected by one of the
dual-homing PEs, it MUST be reflected in the PW Status TLV and sent
to the other dual-homing PE as quickly as possible to allow for fast
protection switching using 3 consecutive DHC messages. This set of
three messages allows for fast protection switching even if one or
two of these packets are lost or corrupted. After the transmission
of the three rapid messages, the dual-homing PE MUST send the most
recently transmitted service PW status periodically to the other
dual-homing PE on a continual basis using the DHC message.
When one dual-homing PE determines that the active service PW needs
to be switched from the working PW to the protection PW, It MUST send
the Dual-Node Switching TLV to the other dual-homing PE as quickly as
possible to allow for fast protection switching using 3 consecutive
DHC messages. After the transmission of the three messages, the
protection PW would become the active service PW, and the dual-homing
PE MUST send the most recently transmitted Dual-Node Switching TLV
periodically to the other dual-homing PE on a continual basis using
the DHC message.
It is RECOMMENDED that the default interval of the first three rapid
DHC messages is 3.3 ms similar to [RFC6378], and the default interval
of the subsequent messages is 1 second. Both the default interval of
the three consecutive messages as well as the default interval of the
periodical messages SHALL be configurable by the operator.
3.2. Protection Procedures
The dual-homing MPLS-TP PW protection mechanism can be deployed with
the existing AC redundancy mechanisms. On the PSN network side, PSN
tunnel protection mechanism is not required, as the dual-homing PW
protection can also protect if a failure occurs in the PSN network.
This section uses the one-side dual-homing scenario as an example to
describe the dual-homing PW protection procedures, the procedures for
two-side dual-homing scenario would be similar.
On the dual-homing PE side, the role of working and protection PE are
set by the management system or local configuration. The service PW
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connecting to the working PE is the working PW, and the service PW
connecting to the protection PE is called the protection PW.
On the single-homing PE side, it treats the working PW and protection
PW as if they terminate on the same remote PE node, thus normal MPLS-
TP protection coordination procedures still apply on the single-
homing PE.
The forwarding behavior of the dual-homing PEs is determined by the
components shown in the figure below:
+---------------------------------+ +-----+
| PE1 (Working PE) | | |
+---------------------------------+ PW1 | |
| | | Working | |
+ Forwarder + Service X<-------->X |
/| | PW | | |
/ +--------+--------+ | | |
AC1 / | DNI PW | | | |
/ +--------X--------+---------------+ | |
+-----+/ AC ^ DNI PW | | +---+
| CE1 |redundancy | | PE3 +--|CE2|
+-----+ mechanism | DHC message | | +---+
\ V exchange | |
AC2 \ +--------X--------+---------------+ | |
\ | DNI PW | | | |
\ +--------+--------+ | PW2 | |
\| | Service |Protection| |
+ Forwarder + PW X<-------->X |
| | | PSC | |
+---------------------------------+ message | |
| PE2 (Protection PE) | exchange | |
+---------------------------------+ +-----+
Figure 5. Components of one-side dual-homing PW protection
In Figure 5, for each dual-homing PE, the service PW is the PW used
to carry service between the dual-homing PE and the remote PE. The
state of the service PW is determined by the Operation Administration
and Maintanence (OAM) mechanisms between the dual-homing PEs and the
remote PE.
The DNI PW is provisioned between the two dual-homing PE nodes. It
is used to bridge traffic when a failure occurs in the PSN network or
in the ACs. The state of the DNI PW is determined by the OAM
mechanism between the dual-homing PEs. Since the DNI PW is used to
carry both the DHC messages and the service traffic during protection
switching, it is important to ensure the robustness of the DNI PW.
In order to avoid the DNI PW failure due to the failure of a
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particular link, it is RECOMMENDED that multiple diverse links be
deployed between the dual-homing PEs and the underlay LSP protection
mechanism SHOULD be enabled.
The AC is the link which connects a dual-homing PE to the dual-homed
CE. The status of AC is determined by the existing AC redundancy
mechanisms, this is out of the scope of this document.
In order to perform dual-homing PW local protection, the service PW
status and Dual-node switching coordination requests are exchanged
between the dual-homing PEs using the DHC message defined in
Section 3.1.
Whenever a change of service PW status is detected by a dual-homing
PE, it MUST be reflected in the PW Status TLV and sent to the other
dual-homing PE immediately using the 3 consecutive DHC messages.
After the transmission of the three rapid messages, the dual-homing
PE MUST send the most recently transmitted service PW status
periodically to the other dual-homing PE on a continual basis using
the DHC message. This way, both dual-homing PEs have the status of
the working and protection PW consistently.
When there is a switchover request either generated locally or
received on the protection PW from the remote PE, based on the status
of the working and protection service PW, along with the local and
remote request of the protection coordination between the dual-homing
PEs and the remote PE, the active/standby state of the service PW can
be determined by the dual-homing PEs. As the remote protection
coordination request is transmitted over the protection path, in this
case the active/standby status of the service PW is determined by the
protection PE in the dual-homing group.
If it is determined on one dual-homing PE that switchover of service
PW is needed, this dual-homing PE MUST set the S bit in the Dual-Node
Switching TLV and send it to the other dual-homing PE immediately
using the 3 consecutive DHC messages. With the exchange of service
PW status and the switching request, both dual-homing PEs are
consistent on the Active/Standby forwarding status of the working and
protection service PWs. The status of the DNI PW is determined by PW
OAM mechanism as defined in [RFC5085], and the status of ACs are
determined by existing AC redundancy mechanisms, both are out of the
scope of this document. The forwarding behavior on the dual-homing
PE nodes is determined by the forwarding state machine as shown in
Table 1 .
Using the topology in Figure 5 as an example, in normal state, the
working PW (PW1) is in active state, the protection PW (PW2) is in
standby state, the DNI PW is up, and AC1 is in active state according
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to the AC redundancy mechanism. According to the forwarding state
machine in Table 1, traffic will be forwarded through the working PW
(PW1) and the primary AC (AC1). No traffic will go through the
protection PE (PE2) or the DNI PW, as both the protection PW (PW2)
and the AC connecting to PE2 are in standby state.
If a failure occurs in AC1, the state of AC2 changes to active
according to the AC redundancy mechanism, while there is no change in
the state of the working and protection PWs. According to the
forwarding state machine in Table 1, PE1 starts to forward traffic
between the working PW and the DNI PW, and PE2 starts to forward
traffic between AC2 and the DNI PW. It should be noted that in this
case only AC switchover takes place, in the PSN network traffic is
still forwarded using the working PW.
If a failure in the PSN network brings PW1 down, the failure can be
detected by PE1 or PE3 using existing OAM mechanisms. If PE1 detects
the failure of PW1, it MUST inform PE2 the state of working PW using
the PW Status TLV in the DHC messages and change the forwarding
status of PW1 to standby. On receipt of the DHC message, PE2 SHOULD
change the forwarding status of PW2 to active. Then according to the
forwarding state machine in Table 1, PE1 SHOULD set up the connection
between the DNI PW and AC1, and PE2 SHOULD set up the connection
between PW2 and the DNI PW. According to the linear protection
mechanism [RFC6378], PE2 also sends an appropriate protection
coordination message [RFC6378] over the protection PW (PW2) to PE3
for the remote side to switchover from PW1 to PW2. If PE3 detects
the failure of PW1, according to linear protection mechanism
[RFC6378], it sends a protection coordination message on the
protection PW (PW2) to inform PE2 of the failure on the working PW.
Upon receipt of the message, PE2 SHOULD change the forwarding status
of PW2 to active and set up the connection according to the
forwarding state machine in Table 1. PE2 SHOULD send a DHC message
to PE1 with the S bit set in the Dual-Node Switching TLV to
coordinate the switchover on PE1 and PE2. This is useful for a
unidirectional failure which cannot be detected by PE1.
If a failure brings the working PE (PE1) down, the failure can be
detected by both PE2 and PE3 using existing OAM mechanisms. Both PE2
and PE3 SHOULD change the forwarding status of PW2 to active, and
send a protection coordination message [RFC6378] on the protection PW
(PW2) to inform the remote side to switchover. According to the
existing AC redundancy mechanisms, the status of AC1 changes to
standby, and the state of AC2 changes to active. According to the
forwarding state machine in Table 1, PE2 starts to forward traffic
between the PW2 and AC2.
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4. IANA Considerations
This document requests that IANA assigns one new channel type for
"MPLS-TP Dual-Homing Coordination message" from the "MPLS Generalized
Associated Channel (G-ACh) Types (including Pseudowire Associated
Channel Types)" registry of the "Generic Associated Channel (G-ACh)
Parameters" registry.
Value Description Reference
TBD MPLS-TP Dual-Homing Coordination message [This document]
This document requests that IANA creates a new sub-registry called
"MPLS-TP DHC TLVs" in the "Generic Associated Channel (G-ACh)
Parameters" registry, with fields and initial allocations as follows:
Type Description Length Reference
0x00 Reserved
0x01 PW Status 20 Bytes [this document]
0x02 Dual-Node Switching 16 Bytes [this document]
The allocation policy for this registry is IETF Review as specified
in [RFC5226].
5. Security Considerations
MPLS-TP is a subset of MPLS and so builds upon many of the aspects of
the security model of MPLS. Please refer to [RFC5920] for generic
MPLS security issues and methods for securing traffic privacy and
integrity.
The DHC message defined in this document contains control
information, if it is injected or modified by an attacker, the dual-
homing PEs might not agree on which PE should be used to deliver the
CE traffic, and this could be used as a denial of service attack
against the CE. It is important that the DHC message is used within
a trusted MPLS-TP network domain as described in [RFC6941].
The DHC message is carried in the G-ACh [RFC5586], so it is dependent
on the security of the G-ACh itself. The G-ACh is a generalization
of the Associated Channel defined in [RFC4385]. Thus, this document
relies on the security mechanisms provided for the Associated Channel
as described in those two documents.
As described in the security considerations of [RFC6378], the G-ACh
is essentially connection oriented so injection or modification of
control messages requires the subversion of a transit node. Such
subversion is generally considered hard in connection oriented MPLS
networks and impossible to protect against at the protocol level.
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Management level techniques are more appropriate. The procedures and
protocol extensions defined in this document do not affect the
security model of MPLS-TP linear protection as defined in [RFC6378].
Uniqueness of the identifiers defined in this document is guaranteed
by the assigner (e.g. the operator). Failure by an assigner to use
unique values within the specified scoping for any of the identifiers
defined herein could result in operational problems. Please refer to
[RFC6370] for more details about the uniqueness of the identifiers.
6. Contributors
The following individuals substantially contributed to the content of
this document:
Kai Liu
Huawei Technologies
Email: alex.liukai@huawei.com
Shahram Davari
Broadcom Corporation
davari@broadcom.com
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the
Label Distribution Protocol (LDP)", RFC 4447,
DOI 10.17487/RFC4447, April 2006,
<http://www.rfc-editor.org/info/rfc4447>.
[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
Circuit Connectivity Verification (VCCV): A Control
Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
December 2007, <http://www.rfc-editor.org/info/rfc5085>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<http://www.rfc-editor.org/info/rfc5586>.
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[RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
Profile (MPLS-TP) Identifiers", RFC 6370,
DOI 10.17487/RFC6370, September 2011,
<http://www.rfc-editor.org/info/rfc6370>.
[RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS-
TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378,
October 2011, <http://www.rfc-editor.org/info/rfc6378>.
[RFC7271] Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H.,
D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS
Transport Profile (MPLS-TP) Linear Protection to Match the
Operational Expectations of Synchronous Digital Hierarchy,
Optical Transport Network, and Ethernet Transport Network
Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014,
<http://www.rfc-editor.org/info/rfc7271>.
[RFC7324] Osborne, E., "Updates to MPLS Transport Profile Linear
Protection", RFC 7324, DOI 10.17487/RFC7324, July 2014,
<http://www.rfc-editor.org/info/rfc7324>.
7.2. Informative References
[I-D.ietf-pals-mpls-tp-dual-homing-protection]
Cheng, W., Wang, L., Li, H., Davari, S., and J. Dong,
"Dual-Homing Protection for MPLS and MPLS-TP Pseudowires",
draft-ietf-pals-mpls-tp-dual-homing-protection-05 (work in
progress), January 2017.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <http://www.rfc-editor.org/info/rfc4385>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<http://www.rfc-editor.org/info/rfc5920>.
[RFC6372] Sprecher, N., Ed. and A. Farrel, Ed., "MPLS Transport
Profile (MPLS-TP) Survivability Framework", RFC 6372,
DOI 10.17487/RFC6372, September 2011,
<http://www.rfc-editor.org/info/rfc6372>.
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[RFC6718] Muley, P., Aissaoui, M., and M. Bocci, "Pseudowire
Redundancy", RFC 6718, DOI 10.17487/RFC6718, August 2012,
<http://www.rfc-editor.org/info/rfc6718>.
[RFC6870] Muley, P., Ed. and M. Aissaoui, Ed., "Pseudowire
Preferential Forwarding Status Bit", RFC 6870,
DOI 10.17487/RFC6870, February 2013,
<http://www.rfc-editor.org/info/rfc6870>.
[RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed.,
and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP)
Security Framework", RFC 6941, DOI 10.17487/RFC6941, April
2013, <http://www.rfc-editor.org/info/rfc6941>.
[RFC7771] Malis, A., Ed., Andersson, L., van Helvoort, H., Shin, J.,
Wang, L., and A. D'Alessandro, "Switching Provider Edge
(S-PE) Protection for MPLS and MPLS Transport Profile
(MPLS-TP) Static Multi-Segment Pseudowires", RFC 7771,
DOI 10.17487/RFC7771, January 2016,
<http://www.rfc-editor.org/info/rfc7771>.
Authors' Addresses
Weiqiang Cheng
China Mobile
No.32 Xuanwumen West Street
Beijing 100053
China
Email: chengweiqiang@chinamobile.com
Lei Wang
China Mobile
No.32 Xuanwumen West Street
Beijing 100053
China
Email: Wangleiyj@chinamobile.com
Han Li
China Mobile
No.32 Xuanwumen West Street
Beijing 100053
China
Email: Lihan@chinamobile.com
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Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: jie.dong@huawei.com
Alessandro D'Alessandro
Telecom Italia
via Reiss Romoli, 274
Torino 10148
Italy
Email: alessandro.dalessandro@telecomitalia.it
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