Internet DRAFT - draft-ietf-mpls-mldp-node-protection
draft-ietf-mpls-mldp-node-protection
Network Working Group IJ. Wijnands, Ed.
Internet-Draft K. Raza
Intended status: Standards Track Cisco Systems, Inc.
Expires: April 1, 2016 A. Atlas
Juniper Networks, Inc.
J. Tantsura
Ericsson
Q. Zhao
Huawei Technology
September 29, 2015
mLDP Node Protection
draft-ietf-mpls-mldp-node-protection-08
Abstract
This document describes procedures to support node protection for
Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths
(MP LSPs) that have been built by the "Multipoint Label Distribution
Protocol"(mLDP) [RFC6388]. In order to protect a node N, the Point
of Local Repair (PLR) Label Switched Router (LSR) of N must learn the
Merge Point (MPT) LSR(s) of node N such that traffic can be
redirected to them in case node N fails. Redirecting the traffic
around the failed node N depends on existing Point-to-Point (P2P)
Label Switched Paths (LSPs). The pre-established LSPs originate from
the PLR LSR and terminate on the MPT LSRs while bypassing LSR N.
Status of this Memo
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This Internet-Draft will expire on April 1, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. PLR Determination . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Transit node procedure . . . . . . . . . . . . . . . . . . 4
2.2. MP2MP root node procedure . . . . . . . . . . . . . . . . 5
2.3. PLR information encoding . . . . . . . . . . . . . . . . . 6
3. Using the tLDP session . . . . . . . . . . . . . . . . . . . . 8
4. Link or node failure . . . . . . . . . . . . . . . . . . . . . 10
4.1. Re-convergence after node/link failure . . . . . . . . . . 11
4.1.1. Node failure . . . . . . . . . . . . . . . . . . . . . 11
4.1.2. Link failure . . . . . . . . . . . . . . . . . . . . . 12
4.1.3. Switching to new primary path . . . . . . . . . . . . 12
5. mLDP Capabilities for Node Protection . . . . . . . . . . . . 13
5.1. PLR capability . . . . . . . . . . . . . . . . . . . . . . 13
5.2. MPT capability . . . . . . . . . . . . . . . . . . . . . . 13
5.3. The Protected LSR . . . . . . . . . . . . . . . . . . . . 13
5.4. The Node Protection Capability . . . . . . . . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 15
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
9. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
This document describes procedures to support node protection for
Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths
(MP LSPs) that have been built by the "Multipoint Label Distribution
Protocol"(mLDP) [RFC6388]. In order to protect a node N, the Point
of Local Repair (PLR) LSR of N must learn the Merge Point (MPT)
LSR(s) of node N such that traffic can be redirected to them in case
node N fails. Redirecting the traffic around the failed node N
depends on existing P2P LSPs. The pre-established LSPs originate
from the PLR LSR and terminate on the MPT LSRs while bypassing LSR N.
The procedures to setup these P2P LSPs are outside the scope of this
document, but one can imagine using Resource Reservation Protocol for
Traffic Engineering (RSVP-TE) [RFC5420] or Label Distribution
Protocol (LDP) Loop Free Alternative (LFA) [RFC5286] based techniques
to accomplish this.
The solution described in this document notifies the PLR(s) of the
MPT LST(s) via signalling using a Targeted LDP (tLDP) session
[RFC7060]. By having a tLDP session with the PLR, no additional
procedures need to be defined in order to support Make-Before-Break
(MBB), Graceful Restart (GR) and Typed Wildcard FEC support. All
this is achieved at the expense of having additional tLDP sessions
between each MPT and PLR LSR.
In order to allow a node to be protected against failure, the LSRs
providing the PLR and the MPT functionality as well as the protected
node MUST support the functionality described in this document. LDP
capability negotiation [RFC5561] is used to signal the availability
of the functionality between the participating nodes; these nodes
MUST support capability negotiation.
1.1. Conventions used in this document
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].
The terms "node" is used to refer to an LSR and used interchangeably.
The terms "PLR" and "MPT" are used as shorthand to refer to "PLR LSR"
and "MPT LSR" respectively.
1.2. Terminology
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mLDP: Multipoint extensions to LDP.
PLR: Point of Local Repair (the LSR that redirects the traffic to
one or more Merge Point LSRs).
MPT: Merge Point (the LSR that merges the backup LSP with primary
LSP. Note, there can be multiple MPT LSRs for a single MP-LSP
node protection).
tLDP: Targeted LDP.
MP LSP: Multi-Point LSP (either a P2MP or MP2MP LSP).
root node: The root of either a P2MP or MP2MP LSP as defined in
[RFC6388].
2. PLR Determination
In order for a MPT to establish a tLDP session with a PLR, it first
has to learn the PLR for a particular MP LSP. It is the
responsibility of the protected node N to advertise the address of
the PLR to the MPT. The PLR address for a MP LSP on node N is the
address of the upstream LDP peer, but only when node N is NOT the
root node of the MP2MP LSP. If the upstream LDP peer is unable to
function as PLR, the procedures in this document do not apply and are
out of the scope. If node N is the root node, the procedures are
slightly different as described in Section 2.2. The procedures that
follow assume that all the participating nodes (N, PLRs, MPTs) are
enabled (e.g., by a user configuration) to support and implement the
PLR determination feature.
The procedures as documented in this document requires the protected
node to be directly connected to the PLR and MPT nodes. This is
because mLDP depends on unicast routing to determine the upstream LSR
and unicast routing (by default) only has information about the next-
hop and not beyond that. Support for non-directly connected PLR and
MPT nodes is outside the scope of this document.
2.1. Transit node procedure
Find below the procedures for when the protected node is a transit
node along the path to the root.
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root
^
|
(LSR1)
. | .
. | .
. (N) .
. / \ .
. / \.
(LSR2) (LSR3)
| |
Figure 1.
N: The node being protected,
...: Backup LSPs from LSR1 to LSR2 and LSR3.
Node N uses the root address of the MP LSP to determine the upstream
LSR for a given MP LSP following the procedures as documented in
[RFC6388] section 2.4.1.1. The upstream LSR in figure 1 is LSR1
because it is the first hop along the shortest path to reach the root
address. After determining the upstream LSR, node N (which has the
node protection feature enabled) MUST advertise the address of LSR1
as the PLR address to the downstream members of the MP LSP (i.e.,
LSR2 and LSR3) if the given downstream member has announced support
for node protection (see Section 5 during Capability negotiation).
For the format and encoding of PLR address information, see
Section 2.3.
Note, in order for the protected traffic to reach nodes LSR2 and
LSR3, LSR1 MUST have two unidirectinal LSPs to LSR2 and LSR3,
bypassing node N. The procedures for setting up these LSPs are
outside the scope of this documemnt.
2.2. MP2MP root node procedure
Find below the procedures for when the protected node is the root of
a MP2MP LSP. Consider figure 2 below;
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|
(LSR1)
. | .
. | .
. (N) . root
. / \ .
. / \.
(LSR2)....(LSR3)
| |
Figure 2.
N: The MP2MP root node being protected.
...: Backup LSPs between LSR1, LSR2 and LSR3.
Assume that LSR1, LSR2 and LSR3 are all members of a MP2MP LSP for
which N is the root node. Since N is the root of the MP2MP LSP,
there is no upstream LSR and no 'single' PLR LSR for protecting node
N. In order to protect node N, all the directly connected members of
the MP2MP must participate in protecting node N by acting both as PLR
and MPT LSR. An LSR will act as MPT for traffic coming from the
other LSR(s) and it will act as PLR for traffic it is sending to the
other LSR(s). Since node N knows the members of the MP2MP LSP, it
will advertise the member list to its directly connected members,
excluding the member it is sending to. For example, node N will
advertise {LSR3,LSR1} list to LSR2 excluding LSR2 from it. Instead
of advertising a single PLR when node N is not the root, a list of
PLRs is advertised using the procedures documented in Section 2.3.
It should be noted that the MP2MP root node protection mechanism
doesn't replace the Root Node Redundancy (RNR) procedures as
described in [RFC6388] section 7. The node protection procedures in
this document will help in restoring traffic for the existing MP2MP
LSPs after node failure, but a new root node has to be elected
eventually in order to allow new MP2MP LSPs to be created.
Note, in order for the protected traffic to be exchanged between
nodes LSR1, LSR2 and LSR3, bidirectional LSPs have to exist between
the LSRs, bypassing node N. The procedures for setting up these LSPs
are outside the scope of this documemnt.
2.3. PLR information encoding
The upstream LSR address is conveyed via an LDP Notification message
with an MP Status TLV, where the MP status TLV contains a new "PLR
Status Value Element" that specifies the address of the PLR.
The new "PLR Status Value Element" is encoded as follows;
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PLR Status Element:
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 = TBA-1 | Length | Addr Family |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Addr Fam cont | Num PLR entry | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| PLR entry (1 or more) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where
Type: PLR Status Value Element (Type TBA-1 to be assigned by IANA)
Length: The Length field is an unsigned integer that encodes the
length of the Status Value following the Length field. The
encoded Length varies based on the Addr Family and the number of
PLR entries.
Addr Family: Two octet quantity containing a value from IANA's
[AFI] registry that encodes the address family for the PLR Address
encoded in the PLR entry.
Num PLR entry: Element as an unsigned, integer followed by that
number of "PLR entry" fields in the format specified below.
The format of a "PLR Entry" is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| Reserved | PLR address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ PLR address (cont) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where
A bit: 0 = Withdraw, 1 = Add.
Reserved: 15 bits, MUST be zero on transmit and ignored on receipt
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PLR address: PLR Address encoded according to Address Family field
encoded in the PLR Status Value Element. Note, the length of the
PLR address field is specific to the Address Family that is
encoded.
The size of a "PLR Entry" is the 2 octets ("A bit + Reserved") + PLR
address length. The length of the PLR address is dependent on the
Address Family as encoded in the PLR Status Value Element. The size
of a "PLR entry" is 6 octets and 18 octets respectively for an IPv4
PLR address and an IPv6 PLR address.
If the PLR address on N changes for a given MP LSP, N needs to
trigger a new PLR Status to update the MPT(s). Node N can advertise
or withdraw a given PLR from its PLR set by setting the "A bit" to 1
or 0 respectively in the corresponding PLR entry. Removing a PLR
address is likely due to a link failure; see the procedures as
documented in Section 4.1. To remove all PLR addresses belonging to
the encoded Address Family, an LSR N MUST encode a PLR Status Value
Element with no PLR entry and "Num PLR entry" field MUST be set to
zero.
Both the PLR Status and an MP FEC TLV [RFC5036] MUST be included in
the LDP Notification message so that a receiver is able to associate
the PLR Status with the MP LSP.
3. Using the tLDP session
The receipt of a PLR MP Status (with PLR addresses) for a MP LSP on a
receiving LSR makes it an MPT for node protection. If not already
established, the MPT LSR MUST establish a tLDP session with all of
the learned PLR addresses using the procedures as documented in
[RFC7060].
Using Figure 1 as the reference topology, let us assume that both
LSR2 and LSR3 are MPTs and have established a tLDP session with the
PLR being LSR1. Assume that both LSR2 and LSR3 have a FEC <R,X> with
a upstream LSR N and label Ln assigned to FEC towards N. The MPTs
will create a secondary upstream LSR (using the received PLR address)
and assigned a Label Lpx to FEC <R,X> towards PLR for it. The MPTs
will do that for each PLR address that was learned for the MP LSP.
In this example, the MPTs will have a FEC <R,X> with two local labels
associated with it. Label Ln that was assigned to N using the the
normal mLDP procedures, and Label Lpx that was assigned to PLR (LSR1)
for the purpose of node protection. Note, when the protected node is
a MP2MP root node, there will be an upstream LSR for each PLR address
that was advertised along with a unique Label Lpx.
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The receipt of a FEC Label Mapping alone over the tLDP session from
MPT on a PLR conveys the label information but does not convey the
node being protected. The information about a protected node is
known to the MPT LSR and needs to be communicated to the PLR as well.
For this reason, the FEC Label Mapping (FEC <R,X> : Lpx) sent by the
MPT over the tLDP session to the PLR MUST include a Status TLV with
MP Status and a new LDP MP status Value Element called the "Protected
Node Status Value Element". This new value element is used to
specify the address of the node being protected. The "Protected Node
Status Value Element" has the following format;
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBA-2 | Length | Addr Family |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Addr Fam cont | Node address ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type : Protected Node Status Value Element (Type TBA-2 to be
assigned by IANA)
Length: The Length field is an unsigned integer that encodes the
length of the Status Value following the Length field. The
encoded Length varies based on the Address Family and is 6 octets
(for Address Family + IPv4 address and 18 octets for Address
Family + IPv6 address.
Addr Family: Two octet quantity containing a value from IANA's
[AFI] registry that encodes the address family for the Node
Address.
Node address: Protected node address encoded according to Address
Family field.
When a PLR receives a Label Mapping for FEC <R,X> that includes a
Protected Node Status, it will only use that label binding once the
Node advertised in the Status value becomes unreachable. If the LSP
is a MP2MP LSP, the PLR would have assigned a Label Mapping for the
upstream MP2MP FEC Element to the MPT ([RFC6388] section 3) for FEC
<R,X>. This label binding on the MPT MUST only be used once node N
becomes unreachable.
The procedures to determine if a node is unreachable is a local
decision and not spelled out in this document. Typically link
failure or Bidirectional Forwarding Detection (BFD) can be used to
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determine and detect node unreachability.
4. Link or node failure
Consider the following topology;
root
^
|
. (LSR1)
. / | .
. (M) | .
. \ | .
. (N) .
. / \ .
. / \.
(LSR2) (LSR3)
| |
Figure 3.
N: The node being protected
M: The backup node to protect link LSR1 - N
...; Backup LSPs from LSR1 to LSR2 and LSR3.
Assume that LSR1 is the PLR for protected node N, LSR2 and LSR3 are
MPTs for node N. When LSR1 discovers that node N is unreachable, it
cannot immediately determine whether it is the link from LSR1 to N or
the actual node N that has failed. In Figure 3, the link between
LSR1 and N is also protected using Fast ReRoute (FRR) [RFC4090] link
protection via node M. LSR1 MAY potentially invoke both protection
mechanisms at the same time, that is redirection of the traffic using
link protection via node M to N, and for node protection directly to
LSR1 and LSR2. If only the link failed, LSR2 and LSR3 will receive
the packets twice due to the two protection mechanisms. To prevent
duplicate packets being forwarded to the receivers on the tree, LSR2
and LSR3 need to determine from which upstream node they should
accept the packets. This can be either from the primary upstream LSR
N or from the secondary upstream LSR1, but never both at the same
time. The selection between the primary upstream LSR or (one or
more) secondary upstream LSRs (on LSR2 and LSR3) is based on the
reachability of the protected node N. As long as N is reachable from
an MPT, the MPT should accept and forward the MPLS packets from N.
Once N becomes unreachable, the LSPs from secondary upstream PLR LSRs
(LSR1 in our example) are activated. Note that detecting if N is
unreachable is a local decision and not spelled out in this document.
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Typically link failure or Bidirectional Forwarding Detection (BFD)
can be used to determine and detect node unreachability.
4.1. Re-convergence after node/link failure
Consider the following topology;
root
^
_ |
/. (LSR1)
/. /. | .\
/. (M). | .\
(P). \. | .\
\. ( N ) .(Q)
\. / \ ./
\. / \ ./
(LSR2) (LSR3)
| |
Figure 4.
N: The node being protected.
M: The backup node to protect link 'LSR1 - N'.
P and Q: The nodes on the new primary path after failure of node N.
...: P2P backup LSPs.
Assume that LSR1 has detected that Node N is unreachable and invoked
both the Link Protection and Node Protection procedures as described
in this example. LSR1 is acting as PLR and sending traffic over both
the backup P2P LSP to node N (via M) and the P2P LSPs directly to
LSR2 and LSR3, acting as MPT LSRs. The sequence of events is
dependent on whether the link from LSR1 to N has failed or node N
itself. The nodes downstream from the protected node (and
participating in node protection) MUST have the capability to
determine that the protected node has become unreachable. Otherwise
the procedures below can not be applied.
4.1.1. Node failure
If node N failed, both LSR2 and LSR3 will have changed the primary
upstream LSR to the secondary upstream LSR (LSR1) due to node N being
unreachable. With that, the label bindings previously assigned to
LSR1 will be activated on the MPTs (LSR2 and LSR3) and the label
binding to N will be disabled. Traffic is now switched over to the
label bindings that were installed for node protection.
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4.1.2. Link failure
If the link 'LSR1 - N' has failed, both LSR2 and LSR3 will not change
the primary upstream LSR because node N is still reachable. LSR2 and
LSR3 will receive traffic over two different bindings, the primary
label binding assigned to node N (due to link protection via node M)
as well as over the binding assigned to LSR1 for the node protection.
Since the secondary upstream LSRs have not been activated, the
traffic received due to node protection will be dropped. Node N will
re-converge and update LSR2 and LSR3 (Section 2.3) with the
information that the PLR address (LSR1) is no longer applicable and
must be removed. In response, LSR2 and LSR3 MUST send a Label
Withdraw to LSR1 to withdraw the label binding. This will stop the
traffic being forwarded over the backup P2P LSPs for node protection.
LSR1 will respond back with a Label Release as soon as the binding
has been removed.
4.1.3. Switching to new primary path
The network will eventually re-converge and a new best path to the
root will be found by LSR2 and LSR3. LSR2 will find that P is its
new primary upstream LSR to reach the Root and LSR3 will find Q. Note
that although the current active upstream LSR can either be node N or
LSR1 (depending on link or node failure), it does not matter for the
following procedures. Both LSR2 and LSR3 SHOULD use the Make-Before-
Break (MBB) procedures as described in [RFC6388] section 8 to switch
to the new primary upstream node. As soon as the new primary
upstream LSRs P and Q are activated, a Label Withdraw message MUST be
sent to the old upstream LSR. Note that an upstream LSR switchover
from a tLDP neighbor to a directly connected LDP neighbor is no
different compared to switching between two directly connected
neighbors. After the Label Withdraw message has been received by
LSR1 or node N, forwarding will stop and a Label Release will be
sent.
When it is determined that after re-convergence there is no more
interest in the tLDP session between the MPT and the PLR, the tLDP
session MAY be taken down. It is possible that having no more
interest in the tLDP session is temporarily due to link flapping. In
order to avoid the tLDP session from flapping, it is RECOMMENDED to
apply a delay before tearing down the session. Determining the delay
is a local implementation matter. If the operator is not concerned
with the tLDP session flapping and/or other procedures are in place
to avoid this altogether, there is no need to apply the delay.
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5. mLDP Capabilities for Node Protection
In order to describe the capabilities of the participating LSRs, this
document is organizing it per role in the network i.e., Point of
Local Repair (PLR), Merge Point (MPT), and Protected Node (as
depicted in Fig 1).
5.1. PLR capability
A PLR node should handle the following conditions;
1. Accept an incoming tLDP session from the MPT LSR.
2. Support the receipt of a "Protected Node Status Value Element"
status in a MP Status TLV over tLDP session.
3. Upon node failure detection, capable of switching traffic towards
one or more MPT(s) over P2P LSP (bypassing N) using the labels
previously advertised for MP LSPs over the tLDP session.
An LSR capable of performing these actions will advertise it self as
PLR capable in the Node Protection capability (see Section 5.4).
This is a unidirectional capability announced from PLR to the
protected LSR.
5.2. MPT capability
An MPT node should handle the following conditions;
1. Support the receipt of "PLR Status Value Element" in a MP Status
TLV from a protected node N.
2. Support to transmit "Protected Node Status Value Element" in a MP
Status TLV to a PLR.
A LSR capable of performing these actions will advertise itself as
MPT capable in the Node Protection capability (see Section 5.4).
This is a unidirectional capability from MPT to the protected LSR.
5.3. The Protected LSR
A protected node should handle the following conditions;
1. Determine the PLR and MPT capability for directly connected
upstream and downstream LSRs for a given MP FEC.
2. Support transmitting of "PLR Status Value Element" in a MP Status
TLV to one or more downstream MPT LSRs.
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The protected LSR does not advertise any capability for mLDP Node
Protection because it does not need to receive any of the defined MP
Status values as described above. However, the protected node does
play an important role in the signaling and setup of the node
protection. For a given FEC, the protected node can only send PLR
information to a downstream LSR if the PLR has signaled the PLR
capability and the downstream LSR has signaled the MPT capability.
When the downstream LSR (acting as MPT) receives the PLR status, it
can implicitly infer that the advertised LSR(s) are PLR capable. The
MPT LSR can now proceed with setting up a tLDP session with the
PLR(s) and MP LSP node protection signaling.
5.4. The Node Protection Capability
We define a single capability "MP Node Protection Capability" to
announce the PLR and MPT capability.
The format of the capability parameter TLV is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type = TBA-3 | Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved |P|M| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where
U/F bits: MUST be set to 1 and 0 respectively (as per [RFC5561])
Type: MP Node Protection Capability (Type = TBA-3 to be assigned
by IANA)
Length: Unsigned integer, MUST be set to 2.
S bit: Set to 1 to announce and 0 to withdraw the capability (as
per [RFC5561])
P bit: Set to 1 to indicate the PLR is capable of MP LSP node
protection
M bit: Set to 1 to indicate the MPT is capable of MP LSP node
protection
Reserved: MUST be zero on transmit and ignored on receipt
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The above capability can be sent in an LDP Initialization message to
announce capability at the session establishment time, or it can be
sent in LDP Capability message to dynamically update (announce or
withdraw) its capability towards its peer using procedures specified
in [RFC5561].
An LSR that supports the PLR functionality LSR MAY send this
capability to its downstream MP peers with "P" bit set; whereas, an
LSR that supports an the MPT functionality MAY send this capability
to its upstream peer with "M" bit set. Moreover, an LSR that
supports both the PLR and MPT functionality MAY sent this capability
to its peers with both "P" and "M" bit set.
6. Security Considerations
The procedures in this document add two new TLVs to existing LDP
messages. Those TLVs can be protected by the mechanisms that are
used to protect LDP messages as described in [RFC6388] and [RFC5920].
If it were possible to attack the mechanisms described in this
document an LSR (a PLR or a MPT) could be induced to support a large
number of tLDP sessions and set up an even larger number of LSPs.
The security mechanisms in [RFC6388] and [RFC5920] are believed to be
adequate, but an implementation could provide additional protection
by counting such protection sessions and LSPs and producing a log
message to the operator if a threshold is crossed.
7. IANA considerations
IANA is requested to allocate two new code points from the "LDP MP
Status Value Element type" registry within the Label Distribution
Protocol (LDP) Parameters;
Value | Name | Reference
------+----------------------------------------+-----------
TBA-1 | PLR Status Value Element | this doc
------+----------------------------------------+-----------
TBA-2 | Protected Node Status Value Element | this doc
IANA is requested to assign a new code points for a new Capability
Parameter TLV. The code point should be assigned from the IETF
Consensus range of the "TLV Type Name Space" registry within the LDP
Parameters. The lowest available new code point after 0x0970 should
be used.
Value | Description | Reference | Notes/Reg Date
------+-------------------------------+-----------+---------------
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TBA-3 | MP Node Protection Capability | This doc |
8. Acknowledgments
The authors like to thank Nagendra Kumar, Duan Hong, Martin
Vigoureux, Kenji Fujihira, Loa Andersson and Ben Campbell for their
comments on this document. Also, many thanks to Elwyn Davies and
Adrian Farrel for the detailed review and contribution to this
document.
9. Contributor Addresses
Below is a list of other contributing authors in alphabetical order:
Eric Rosen
Juniper Networks, Inc.
10 Technology Park Drive
Westford
MA 01886
USA
erosen@juniper.net
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
[RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
Le Roux, "LDP Capabilities", RFC 5561, July 2009.
[RFC7060] Napierala, M., Rosen, E., and IJ. Wijnands, "Using LDP
Multipoint Extensions on Targeted LDP Sessions", RFC 7060,
November 2013.
[AFI] "IANA, Address Family Identifier (AFIs), http://
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www.iana.org/assignments/address-family-numbers/address-
family-numbers.xhtml", July 2013.
10.2. Informative References
[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
May 2005.
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
Authors' Addresses
IJsbrand Wijnands (editor)
Cisco Systems, Inc.
De kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
Kamran Raza
Cisco Systems, Inc.
2000 Innovation Drive
Ottawa Ontario K2K-3E8
Canada
Email: skraza@cisco.com
Alia Atlas
Juniper Networks, Inc.
10 Technology Park Drive
Westford MA 01886
USA
Email: akatlas@juniper.net
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Jeff Tantsura
Ericsson
300 Holger Way
San Jose CA 95134
USA
Email: jeff.tantsura@ericsson.com
Quintin Zhao
Huawei Technology
125 Nagog Technology Park
Acton MA 01719
USA
Email: quintin.zhao@huawei.com
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