wdiff rfc8223.alt-original rfc8223.txt

MPLS Working Group Santosh
Internet Engineering Task Force (IETF) S. Esale
INTERNET-DRAFT Raveendra
Request for Comments: 8223 R. Torvi
Updates: 7473 (if approved) Juniper Networks
Intended Status: Proposed Standard Luay
Category: Standards Track L. Jalil
Expires: December 29, 2017
ISSN: 2070-1721 Verizon
Uma
U. Chunduri
Huawei
Kamran
K. Raza
Cisco Systems, Inc.
June 27,
August 2017

Application-aware

Application-Aware Targeted LDP
draft-ietf-mpls-app-aware-tldp-09

Abstract

Recent targeted Targeted Label Distribution Protocol (tLDP) applications applications, such
as remote loop-free alternate (LFA) Loop-Free Alternates (LFAs) and BGP auto discovered
pseudowire auto-discovered
pseudowires, may automatically establish a tLDP session to with any
Label Switching Router (LSR) in a network. The initiating LSR has
information about the targeted applications to administratively
control initiation of the session. However, the responding LSR has
no such information to control acceptance of this session. This
document defines a mechanism to advertise and negotiate the Targeted Applications
Application Capability (TAC) during LDP session initialization. As
the responding LSR becomes aware of targeted applications, it may
establish a limited number of tLDP sessions for certain applications.
In addition, each targeted application is mapped to LDP Forwarding
Equivalence Class (FEC) Elements elements to advertise only necessary LDP FEC- FEC
label bindings over the session. This document updates RFC 7473 for
enabling advertisement of LDP FEC-label FEC label bindings over the session.

Status of this This Memo

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The list Section 2 of RFC 7841.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 ....................................................3
1.1. Conventions Used in This Document . . . . . . . . . . . . . 4
1.2 ..........................4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 ................................................4
2. Targeted Application Capability . . . . . . . . . . . . . . . . 5
2.1 .................................5
2.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 ...................................................5
2.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 .................................................5
2.3. LDP message procedures . . . . . . . . . . . . . . . . . . . 8
2.3.1 Message Procedures .....................................8
2.3.1. Initialization message . . . . . . . . . . . . . . . . . 8
2.3.2 Message ..............................8
2.3.2. Capability message . . . . . . . . . . . . . . . . . . . 9 Message ..................................8
3. Targeted Application FEC Advertisement Procedures . . . . . . . 9 ...............9
4. Interaction of Targeted Application Capabilities and State
Advertisement Control Capabilities . . . . . . . . . . . . . . 10 .............................10
5. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1 Cases ......................................................12
5.1. Remote LFA Automatic Targeted session . . . . . . . . . . . 12
5.2 Session .....................12
5.2. FEC 129 Auto Discovery Auto-discovery Targeted session . . . . . . . . . . 13
5.3 Session ...................13
5.3. LDP over RSVP and Remote LFA targeted session . . . . . . . 13
5.4 Targeted Session .............13
5.4. mLDP node protection targeted session . . . . . . . . . . . 13 Node Protection Targeted Session .....................13
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 14 ........................................14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14 ............................................14
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 15
9. Contributing Authors . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1 .....................................................15
8.1. Normative References . . . . . . . . . . . . . . . . . . . 16
10.2 ......................................15
8.2. Informative References . . . . . . . . . . . . . . . . . . 16 ....................................16
Acknowledgments ...................................................17
Contributors ......................................................17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17

1 ................................................18

1. Introduction

LDP uses the extended discovery Extended Discovery mechanism to establish the tLDP
Targeted LDP (tLDP) adjacency and subsequent session session, as described in
[RFC5036]. A LSR Label Switching Router (LSR) initiates extended discovery Extended
Discovery by sending a tLDP Hello to a specific address. The remote
LSR decides to either accept or ignore the tLDP Hello based on local
configuration only. Targeted LDP A tLDP application is an application that uses a
tLDP session to exchange information such as
FEC-Label FEC label bindings
("FEC" stands for "Forwarding Equivalence Class") with a peer LSR in
the network. For an application such as FEC 128 pseudowire, the
remote LSR is configured with the source LSR address so that it can
use that information to accept or ignore a given tLDP Hello.

However, applications such as Remote LFA remote Loop-Free Alternates (LFAs) and
BGP auto discovered
pseudowire auto-discovered pseudowires automatically initiate asymmetric extended discovery
Extended Discovery to any LSR in a network based on local state only.
With these applications, the remote LSR is not explicitly configured
with the source LSR address. So So, the remote LSR either responds or ignores to
all tLDP Hellos. Hellos or ignores them.

In addition, since the session is initiated and established after
adjacency formation, the responding LSR has no information on
targeted applications
information available to from which it can choose a session
with a targeted application that it is configured to support. Also,
the initiating LSR may employ a limit per application on locally
initiated automatic tLDP sessions,
however sessions; however, the responding LSR has
no such information to employ a similar limit on the incoming tLDP
sessions. Further, the responding LSR does not know whether the
source LSR is establishing a tLDP session for configured, configured
applications, automatic applications, or both applications. both.

This document proposes and describes a solution to advertise the
Targeted Application Capability (TAC), consisting of a list of
targeted application
list, applications, during initialization of a tLDP session. It
also defines a mechanism to enable an a new application and disable an
old application after session establishment. This capability
advertisement provides the responding LSR with the necessary
information to control the acceptance of tLDP sessions
per application. For instance, an LSR may accept all BGP auto discovered
auto-discovered tLDP sessions as defined described in [RFC6074] but may only
accept a limited number of Remote remote LFA tLDP sessions as
defined described
in [RFC7490] [RFC7490].

Also, the targeted LDP tLDP application is mapped to LDP FEC element type types to
advertise specific application FECs only, avoiding the advertisement
of other unnecessary FECs over a tLDP session.

1.1

1.1. Conventions Used in This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119
BCP 14 [RFC2119] and RFC 8174 [RFC8174] when, and only when, they appear in all
capitals, as shown here.

1.2

1.2. Terminology

In addition to the terminology defined in [RFC7473], this document
uses the following terms:

tLDP : Targeted LDP
TAC : Targeted Application Capability
TAE : Targeted Application Element
TA-Id : Targeted Application Identifier
SAC : State Advertisement Control Capability
LSR : Label Switching Router
mLDP : Multipoint LDP
PQ node : Remote-LFA nexthops Remote LFA next hops
RSVP-TE : RSVP Traffic Engineering
P2MP : Point-to-Multipoint
PW : Pseudowire
P2P-PW : Point-to-point Psuedowire Point-to-Point Pseudowire
MP2MP : Multipoint-to-Multipoint
HSMP LSP: Hub and Spoke Multipoint Label Switched Path
LSP : Label Switched Path
MP2P : Multipoint-to-point Multipoint-to-Point
MPT : Merge Point

2. Targeted Application Capability

2.1

2.1. Encoding

An LSR MAY advertise that it is capable of negotiating a targeted LDP tLDP
application list over a tLDP session by using the Capability
Advertisement capability
advertisement as defined in [RFC5561] and encoded 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| TLV Code Point | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved | |
+-+-+-+-+-+-+-+-+ Capability Data |
| +-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This document defines a new optional capability TLV of type TBD1
called 'Targeted Application Capability (TAC)'.

Flag "U" MUST be set to 1 to indicate that this capability must be
silently ignored if unknown. The TAC's Capability Data field
contains the Targeted Application Element (TAE) information information, encoded
as follows:

Targeted Application Element(TAE)

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Targ. Appl. Id TA-Id |E| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Targeted Application Identifier (TA-Id):
a 16 bit

TA-Id: A 16-bit Targeted Application Identifier value.

E-bit: The enable bit indicates

E: E-bit (Enable bit). Indicates whether the sender is
advertising or withdrawing the TAE. The E-bit value is used
as follows:

1 - The TAE is advertising the targeted application.
0 - The TAE is withdrawing the targeted application.

2.2

2.2. Procedures

At tLDP session establishment time, a an LSR MAY include a new
capability TLV, the TAC TLV, as an optional TLV in the LDP
Initialization message. The TAC TLV's Capability data MAY consist of
zero or more
TAEs TAEs, each pertaining to a unique TA-Id that a an LSR
supports over the session. If the receiver LSR receives the same
TA-Id in more than one TAE, it MUST process the first element and
ignore the duplicate elements. If the receiver LSR receives an
unknown TA-Id in the TAE, it MUST silently ignore such a TAE and
continue processing the rest of the TLV.

If the receiver LSR does not receive the TAC TLV in the
Initialization message or it does not understand the TAC TLV, the TAC
negotiation is considered unsuccessful and the session establishment
proceeds as per [RFC5036]. On the receipt of a valid TAC TLV, an LSR
MUST generate its own TAC TLV with TAEs consisting of unique TA-Ids
that it supports over the tLDP session. If there is at least one TAE
common TAE between the TAC TLV it has received and its own, the
session MUST proceed to establishment as per [RFC5036]. If not, A an
LSR MUST send a 'Session Rejected/Targeted Application Capability Mis-Match'
Mismatch' Notification message to the peer and close the session.
The initiating LSR SHOULD tear down the corresponding tLDP adjacency
after sent sending or receipt of receiving a 'Session Rejected/Targeted Application
Capability Mis-Match' Mismatch' Notification message to or from the responding
LSR
LSR, respectively.

If both of the peers support the TAC TLV, an LSR decides to establish
or close a tLDP session based on the negotiated list of targeted application
list.
applications. For example, an initiating LSR advertises A, B B, and C
as TA-Ids, and the responding LSR advertises C, D D, and E as TA-Ids. Then
Then, the negotiated TA-Id as per both the LSRs is C. Another In another
example, an initiating LSR advertises A, B B, and C as TA-Ids, and the
responding LSR, which acts as a passive LSR, advertises all of the
applications - -- A, B, C, D D, and E - -- as TA-Ids that it supports over
this session. Then
the The negotiated targeted applications as per both the LSRs
are then A, B B, and C. Finally, If if the initiating LSR advertises A, B
B, and C as a TA-
Ids TA-Ids and the responding LSR advertises D and E as
TA-Ids, then the negotiated targeted applications as per both the LSRs
are none. "none". Therefore, if the intersection of the sets of received
and sent TA-Id TA-Ids is null, then the LSR sends a 'Session
Rejected/Targeted Application Capability Mis-Match' Mismatch' Notification
message to the peer LSR and closes the session.

When the responding LSR playing the active role [RFC5036] in LDP
session establishment receives a 'Session Rejected/Targeted
Application Capability Mis-Match' Mismatch' Notification message, it MUST set
its session setup retry interval to a maximum value, as such 0xffff. value -- that is,
0xFFFF. The session MAY stay in NON EXISTENT a non-existent state. When it
detects a change in the initiating LSR or local LSR configuration
pertaining to the TAC TLV, it MUST clear the session setup back off backoff
delay associated with the session to re-attempt the reattempt session establishment. A
An LSR detects the configuration change on the other LSR with the upon receipt
of a tLDP Hello message that has a higher configuration sequence
number than the earlier tLDP Hello message.

When the initiating LSR playing the active role in LDP session
establishment receives a 'Session Rejected/Targeted Application
Capability Mis-Match' Mismatch' Notification message, either it MUST either (1) close
the session and tear down the corresponding tLDP adjacency or it MUST (2) set
its session setup retry interval to a maximum value, as such 0xffff. value -- that is,
0xFFFF.

If the initiating LSR decides to tear down the associated tLDP
adjacency, the session is closed on the initiating LSR as well as the
responding LSR. It MAY also take appropriate actions. For instance,
if an automatic session intended to support the Remote remote LFA
application is rejected by the responding LSR, the initiating LSR may
inform the IGP to calculate another PQ node [RFC7490] for the route
or set of routes. More specific actions are a local matter and are
outside the scope of this document.

If the initiating LSR sets the session setup retry interval to
maximum, the session MAY stay in a non-existent state. When this LSR
detects a change in the responding LSR configuration or its own
configuration pertaining to the TAC TLV, it MUST clear the session
setup
back off backoff delay associated with the session in order to re-attempt the reattempt
session establishment.

After a tLDP session using the TAC mechanism has been established with TAC capability, established,
the initiating and responding LSR LSRs MUST distribute FEC-label FEC label bindings
for the negotiated applications only. For instance, if the tLDP
session is established for a BGP auto discovered auto-discovered pseudowire, only FEC
129 label bindings MUST be distributed over the session. Similarly, a
an LSR operating in downstream on demand on-demand mode MUST request FEC-label FEC label
bindings for the negotiated applications only.

If the Targeted Application Capability TAC and the Dynamic Capability,
described in [RFC5561], Capability [RFC5561] are negotiated during
session initialization, the TAC MAY be re-negotiated renegotiated after session
establishment by sending an updated TAC TLV in the LDP Capability
message. The updated TAC TLV carries TA-Ids with an incremental
update only. The updated TLV MUST consist of one or more TAEs with
the E-bit set (1) or E-bit off (0), to advertise or withdraw the new
application and the old application application, respectively. This may lead to
advertisements or withdrawals of certain types of FEC-Label FEC label bindings
over the session or tear down to teardown of the tLDP adjacency and
subsequently and,
subsequently, the session.

The Targeted Application Capability TAC is advertised on the tLDP session only. If the tLDP session
changes to a link session, a an LSR SHOULD withdraw it with S bit the S-bit
set to 0. Similarly, if the link session changes to tLDP, a an LSR
SHOULD advertise it via the Capability message. If the capability
negotiation fails, this may lead to destruction of the tLDP session.

By default, an LSR SHOULD accept tLDP hellos Hellos in order to then accept
or reject the tLDP session based on the application information.

In addition, an LSR SHOULD allow the configuration of any TA-Id in
order to facilitate the use of private TA-Id's usage TA-Ids by a network operator.

2.3

2.3. LDP message procedures

2.3.1 Message Procedures

2.3.1. Initialization message Message

1. The S-bit of the Targeted Application Capability TAC TLV MUST be set to 1 to advertise Targeted Application Capability the TAC and
SHOULD be ignored on the receipt receipt, as defined described in [RFC5561] [RFC5561].

2. The E-bit of the Targeted Application Element TAE MUST be set to 1 to enable Targeted the targeted
application and SHOULD be ignored on the receipt.

3. An LSR MAY add the State Advertisement Control Capability by
mapping Targeted
Application Element the TAE to the State Advertisement Control (SAC) Elements elements
as defined in Section 4.

2.3.2

2.3.2. Capability message

The Message

After a change to local configuration, the initiating or responding
LSR may re-negotiate renegotiate the TAC after local
configuration change with via the Capability message.

1. The S-bit of the TAC is set to 1 or 0 to advertise or withdraw it.

2. After the configuration change, If if there is no common TAE between
its new TAE list and peers the peer's TAE list, the LSR MUST send a
'Session Rejected/Targeted Application Capability Mis-Match' Mismatch'
Notification message and close the session.

3. If there is a common TAE, a an LSR MAY also update the SAC
Capability based on the updated TAC TAC, as described in section 4 Section 4,
and send the updated TAC and SAC capabilities Capability in a Capability
message to the peer.

4. A receiving LSR processes the Capability message with the TAC TLV.
If the S-bit is set to 0, the TAC is disabled for the session.

5. If the S-bit is set to 1, a the LSR process processes a list of TAEs from
TACs capability
the TAC's data with the E-bit set to 1 or 0 to update the
peer's TAE.

3. Targeted Application FEC Advertisement Procedures

The targeted LDP tLDP application MUST be mapped to LDP FEC element types as
follows to advertise only necessary LDP FEC-Label FEC label bindings over the
tLDP session.

* Intra-area FECs : FECs: FECs that are on the shortest path shortest-path tree and
are not leafs of the shortest path shortest-path tree.

4. Interaction of Targeted Application Capabilities and State
Advertisement Control Capabilities

As described in this document, the set of TAEs negotiated between two
LDP peers advertising the TAC represents the willingness of both
peers to advertise state information for a set of applications. The
set of applications negotiated by the TAC mechanism is symmetric
between the two LDP peers. In the absence of further mechanisms, two
LDP peers will both advertise state information for the same set of
applications.

As described in [RFC7473], State Advertisement Control(SAC) the SAC TLV can be used by an LDP speaker
to communicate its interest or disinterest in receiving state
information from a given peer for a particular application. Two LDP
peers can use the SAC mechanism to create asymmetric advertisement advertisements
of state information between the two peers.

The TAC negotiation facilitates the awareness of targeted
applications to both of the peers. It enables them to advertise only
necessary LDP FEC-label FEC label bindings corresponding to negotiated
applications. With the SAC, the responding LSR is not aware of
targeted applications. Thus Thus, it may be unable to communicate its
interest or disinterest to receive in receiving state information from the peer.
Therefore, when the responding LSR is not aware of targeted
applications such a as remote LFA LFAs and BGP auto discovered auto-discovered pseudowires,
the TAC mechanism should be used used, and when the responding LSR is
aware (with appropriate configuration) of targeted applications such
as FEC 128 pseudowire, the SAC mechanism should be used. Also Also, after
the TAC mechanism makes the responding LSR aware of targeted application,
applications, the SAC mechanism may be used to communicate its
disinterest in receiving state information from the peer for a
particular negotiated application, creating asymmetric
advertisements.

Thus, the TAC mechanism enables two LDP peers to symmetrically
advertise state information for negotiated targeted applications.
Further, the SAC mechanism enables both of them to asymmetrically
disable receipt of state information for some of the already already-
negotiated targeted applications. Collectively, both the TAC mechanism
and the SAC
mechanisms mechanism can both be used to control the FEC-label FEC label
bindings that are advertised over the tLDP session. For instance,
suppose that the initiating LSR establishes a tLDP session to session, using the
TAC mechanism, with the responding LSR for
Remote remote LFA and FEC 129 PW
targeted applications with TAC. So applications. So, each LSR advertises the corresponding FEC-Label FEC
label bindings. Further, suppose that the initiating LSR is not the
PQ node for the responding LSRs Remote LSR's remote LFA IGP calculations. In
such a case, the responding LSR may use the SAC mechanism to convey
its disinterest in receiving state information for Remote remote LFA targeted LDP application. tLDP
applications.

For a given tLDP session, the TAC mechanism can be used without the
SAC mechanism, and the SAC mechanism can be used without the TAC
mechanism. It is useful to discuss the behavior that occurs when the
TAC and SAC mechanisms are used on the same tLDP session. The TAC
mechanism MUST take precedence over the SAC mechanism with respect to
enabling applications for which state information will be advertised.
For a tLDP session using the TAC mechanism, the LDP peers MUST NOT
advertise state information for an application that has not been
negotiated in the most recent TAE list (referred to as an un-
negotiated a
non-negotiated application). This is true even if one of the peers
announces its interest in receiving state information that
corresponds to the un-negotiated non-negotiated application by sending a SAC TLV.
In other words, when the TAC mechanism is being used, the SAC
mechanism cannot and should not enable state information advertisement
advertisements for applications that have not been enabled by TAC. the TAC
mechanism.

On the other hand, the SAC mechanism MUST take precedence over the
TAC mechanism with respect to disabling state information
advertisements. If an LDP speaker has announced its disinterest in
receiving state information for a given application to a given peer
using the SAC mechanism, its peer MUST NOT send state information for
that application, even if the two peers have negotiated that the
corresponding application via the TAC mechanism.

For the purposes of determining the correspondence between targeted
applications defined in this document and application state as
defined in [RFC7473] [RFC7473], an LSR MUST use the following mappings:

LDPv4 Tunneling - IPv4 Prefix-LSPs
LDPv6 Tunneling - IPv6 Prefix-LSPs
LDPv4 Remote LFA - IPv4 Prefix-LSPs
LDPv6 Remote LFA - IPv6 Prefix-LSPs
LDP FEC 128 PW - FEC128 FEC 128 P2P-PW
LDP FEC 129 PW - FEC129 FEC 129 P2P-PW

An LSR MUST map Targeted Application the targeted application to the LDP capability
as follows:

mLDP Tunneling - P2MP Capability, MP2MP Capability Capability, and HSMP LSP
Capability TLV

mLDP node protection Node Protection - P2MP Capability, MP2MP Capability Capability, and HSMP
LSP Capability TLV

5. Use cases

5.1 Cases

5.1. Remote LFA Automatic Targeted session Session

The LSR determines that it needs to form an automatic tLDP session to
with a remote LSR based on IGP calculation as described in [RFC7490]
or some other mechanism, which is mechanism outside the scope of this document. The LSR
forms the tLDP adjacency and constructs an Initialization message
with the TAC TLV with consisting of the TAE as Remote the remote LFA during
session establishment. The receiver LSR processes the LDP
Initialization message and verifies whether it is configured to
accept a Remote remote LFA tLDP session. If it is, it may further verify
that establishing such a session does not exceed the configured limit
for Remote remote LFA sessions. If all of these conditions are met, the
receiver LSR may respond back with an Initialization message with the
TAC corresponding to Remote the remote LFA, and subsequently the session
may be established.

After the session using the TAC mechanism has been established with TAC capability, established, the
sender and receiver LSR LSRs distribute IPv4 or IPv6 FEC label bindings
over the session. Further, the receiver LSR may determine that it
does not need these FEC label bindings. So So, it may disable the
receipt of these FEC label bindings by mapping targeted application element the TAE to state control capability the State
Advertisement Control Capability as described in section Section 4.

5.2

5.2. FEC 129 Auto Discovery Auto-discovery Targeted session Session

BGP auto discovery auto-discovery may determine whether the LSR needs to initiate an
auto-discovery tLDP session with a border LSR. Multiple LSRs may try
to form an auto discovered auto-discovered tLDP session with a border LSR. So, a
service provider may want to limit the number of auto discovered auto-discovered tLDP
sessions that a border LSR can accept. As described in Section 2,
LDP may convey targeted applications with the TAC TLV to a border
LSR. A border LSR may establish or reject the tLDP session based on
local administrative policy. Also, as the receiver LSR becomes aware
of targeted applications, it can also employ an administrative policy
for security. For instance, it can employ a policy to accept all
auto-discovered session sessions from source-list. a source addresses list.

Moreover, the sender and receiver LSR LSRs must exchange FEC 129 label
bindings only over the tLDP session.

5.3

5.3. LDP over RSVP and Remote LFA targeted session

A Targeted Session

An LSR may want to establish a tLDP session to with a remote LSR for LDP
over RSVP
LDP-over-RSVP tunneling and Remote remote LFA applications. The sender LSR
may add both of these applications as a unique Targeted Application Element TAE in the Targeted Application Capability TAC data of
a TAC TLV. The receiver LSR may have reached a configured limit for
accepting Remote remote LFA automatic tLDP sessions, but it may have been
configured to accept LDP over RSVP LDP-over-RSVP tunneling. In such a case, the
tLDP session is formed for both LDP over RSVP LDP-over-RSVP tunneling and Remote remote
LFA applications applications, as both need the same FECs - IPv4 or IPv6 -- IPv4, IPv6, or both.

5.4

5.4. mLDP node protection targeted session Node Protection Targeted Session

A merge point Merge Point (MPT) LSR may determine that it needs to form an
automatic tLDP session to with the upstream point of local repair (PLR)
LSR for MP2P and MP2MP LSP [RFC6388] node protection as described in the
[RFC7715]. The MPT LSR may add a new targeted LDP tLDP application - -- mLDP
protection
- -- as a unique TAE in the Targeted Application Capability Data TAC data of a TAC TLV and send
it in the Initialization message to the PLR. If the PLR is
configured for mLDP node protection and establishing this session
does not exceed the limit of either mLDP node protection sessions or
automatic tLDP sessions, the PLR may decide to accept this session.
Also, the PLR may respond back with the initialization Initialization message with a
TAC TLV that has one of the TAEs as - mLDP protection, and the session
proceeds to establishment as per [RFC5036].

6. Security Considerations

The Capability procedure procedures described in this document does do not introduce any change
changes to LDP Security Considerations section security considerations as described in [RFC5036].

As described in [RFC5036], DoS attacks via Extended Hellos, which are
required to establish a tLDP session, can be addressed by filtering
Extended Hellos using access lists that define addresses with which
Extended Discovery is permitted. Further, as described in section
Section 5.2 of this document, a an LSR can employ a policy to accept
all auto-
discovered auto-discovered Extended Hellos from the configured source
addresses list.

Also

Also, for the two LSRs supporting the TAC, the tLDP session is only
established after successful negotiation of the TAC. The initiating
and receiving LSR LSRs MUST only advertise TA-Ids that they support. In support --
in other words, what they are configured for over the tLDP session.

7. IANA Considerations

This document requires

IANA has assigned the assignment of a new following code point for a the new Capability
Parameter TLVs TLV defined in this document. The code point has been
assigned from the IANA managed LDP registry "TLV Type Name Space", corresponding to the advertisement Space" sub-registry of the Targeted
Applications capability. IANA is requested to assign the lowest
available value after 0x050B. "Label
Distribution Protocol (LDP) Parameters" registry.

Value Description Reference
----- --------------------------------
------ ------------------------------- ---------
TBD1
0x050F Targeted Applications capability [this document]

This document requires the assignment of Application Capability RFC 8223

IANA has assigned a new code point for a status code from the IANA managed registry "STATUS CODE NAME SPACE"
on "Status Code Name Space"
sub-registry of the Label "Label Distribution Protocol (LDP) Parameters page,
corresponding to the notification of session Rejected/Targeted
Application Capability Mis-Match. IANA is requested to assign the
lowest available value after 0x0000004B. Parameters"
registry.

Value E Description Reference
----- - --------------------------------
---------- --- ----------------------------------- ---------
TBD2
0x0000004C 1 Session Rejected/Targeted
Application Capability Mis-Match [this document]

This document also creates Mismatch RFC 8223
IANA has created a new name space 'the LDP registry called "LDP Targeted Application Identifier' on
Identifier" in the Label "Label Distribution Protocol (LDP)
Parameters page, that is to be managed by IANA. Parameters"
registry. The range is 0x0001-
0xFFFE, with 0x0001-0xFFFE. Values in the following values requested range
0x0001-0x1FFF in this document. registry shall be allocated according to the
"IETF Review" procedure [RFC8126]; values in the range 0x2000-0xF7FF
shall be allocated according to the "First Come First Served"
procedure [RFC8126]. The initial values are as follows.

Value Description Reference
-------- -------------------------
--------------- ------------------------------- ---------
0x0000 Reserved [this document] RFC 8223
0x0001 LDPv4 Tunneling [this document] RFC 8223
0x0002 LDPv6 Tunneling [this document] RFC 8223
0x0003 mLDP Tunneling [this document] RFC 8223
0x0004 LDPv4 Remote LFA [this document] RFC 8223
0x0005 LDPv6 Remote LFA [this document] RFC 8223
0x0006 LDP FEC 128 PW [this document] RFC 8223
0x0007 LDP FEC 129 PW [this document] RFC 8223
0x0008 LDP Session Protection [this document] RFC 8223
0x0009 LDP ICCP [this document] RFC 8223
0x000A LDP P2MP PW [this document] RFC 8223
0x000B mLDP Node Protection [this document] RFC 8223
0x000C LDPv4 Intra-area FECs [this document] RFC 8223
0x000D LDPv6 Intra-area FECs [this document]
0x0001 - 0x1FFF Available for assignment
by IETF Review
0x2000 - 0F7FF Available for assignment
as first come first served
0xF800 - 0xFBFF RFC 8223
0x000E-0xF7FF Unassigned
0xF800-0xFBFF Available for private use
0xFC00 - 0xFFFE Private Use
0xFC00-0xFFFE Available for experimental use Experimental Use
0xFFFF Reserved [this document] RFC 8223

8. Acknowledgments

The authors wish to thank Nischal Sheth, Hassan Hosseini, Kishore
Tiruveedhul, Loa Andersson, Eric Rosen, Yakov Rekhter, Thomas
Beckhaus, Tarek Saad, Lizhong Jin and Bruno Decraene for doing the
detailed review. Thanks to Manish Gupta and Martin Ehlers for their
input to this work and many helpful suggestions.

9. Contributing Authors

Chris Bowers
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
USA
EMail: cbowers@juniper.net

Zhenbin Li
Huawei
Bld No.156 Beiqing Rd
Beijing 100095
China
Email: lizhenbin@huawei.com

10. References

10.1

8.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007,
<http://www.rfc-editor.org/info/rfc5036>. <https://www.rfc-editor.org/info/rfc5036>.

[RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
Le Roux, "LDP Capabilities", RFC 5561,
DOI 10.17487/RFC5561, July 2009,
<http://www.rfc-editor.org/info/rfc5561>.
<https://www.rfc-editor.org/info/rfc5561>.

[RFC7473] Kamran Raza, Sami K. and S. Boutros, "Controlling State Advertisements
of Non-negotiated LDP Applications", RFC 7473,
DOI 10.17487/RFC7473, March 2015, <http://www.rfc-
editor.org/info/rfc7473>.
<https://www.rfc-editor.org/info/rfc7473>.

[RFC7715] IJ. Wijnands, E. Rosen, K. IJ., Ed., Raza, J. Tantsura, A. K., Atlas, A., Tantsura, J., and
Q. Zhao, "mLDP "Multipoint LDP (mLDP) Node Protection",
RFC 7715, DOI 10.17487/RFC7715, January 2016,
<http://www.rfc-editor.org/info/rfc7715>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
<https://www.rfc-editor.org/info/rfc7715>.

[RFC8174] B. Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC8174, RFC 8174,
DOI 10.17487/RFC8174, May 2017, <http://www.rfc-
editor.org/info/rfc8174>.

10.2
<https://www.rfc-editor.org/info/rfc8174>.

8.2. Informative References

[RFC7490] S. Bryant, C. Filsfils, S. Previdi, M. Shand, N. So,
"Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
April 2015.

[RFC6074] E. Rosen, B. E., Davie, V. B., Radoaca, V., and W. Luo,
"Provisioning, Auto-Discovery, and Signaling in Layer 2
Virtual Private Networks (L2VPNs)", RFC 6074,
DOI 10.17487/RFC6074, January 2011. 2011,
<https://www.rfc-editor.org/info/rfc6074>.

[RFC6388] IJ. Wijnands, I. IJ., Ed., Minei, K. I., Ed., Kompella, K., and B.
Thomas, "Label Distribution Protocol Extensions for
Point-to-Multipoint and Multipoint-to-Multipoint Label
Switched Paths", RFC 6388, DOI 10.17487/RFC6388,
November 2011.

8. 2011, <https://www.rfc-editor.org/info/rfc6388>.

[RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
RFC 7490, DOI 10.17487/RFC7490, April 2015,
<https://www.rfc-editor.org/info/rfc7490>.

[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.

Acknowledgments

The authors wish to thank Nischal Sheth, Hassan Hosseini, Kishore
Tiruveedhul,
Tiruveedhula, Loa Andersson, Eric Rosen, Yakov Rekhter, Thomas
Beckhaus, Tarek Saad, Lizhong Jin Jin, and Bruno Decraene for doing the their
detailed review. reviews. Thanks to Manish Gupta and Martin Ehlers for their
input to this work and many helpful suggestions.

9. Contributing Authors

Contributors

The following people contributed substantially to the content of this
document and should be considered co-authors:

Chris Bowers
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
USA
EMail:
United States of America
Email: cbowers@juniper.net

Zhenbin Li
Huawei
Bld No.156
Bldg. No. 156 Beiqing Rd Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com

Authors' Addresses

Santosh Esale
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
USA
EMail:
United States of America

Email: sesale@juniper.net

Raveendra Torvi
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
EMail:
United States of America

Email: rtorvi@juniper.net

Luay Jalil
Verizon
1201 E East Arapaho Rd Road
Richardson, TX 75081
USA
United States of America

Email: luay.jalil@verizon.com

Uma Chunduri
Huawei
2330 Central Expy Expressway
Santa Clara, CA 95050
USA
United States of America

Email: uma.chunduri@huawei.com

Kamran Raza
Cisco Systems, Inc.
2000 Innovation Drive
Ottawa, ON K2K-3E8
Canada
E-mail:

Email: skraza@cisco.com