draft-ietf-mpls-ldp-ip-pw-capability-07.txt   draft-ietf-mpls-ldp-ip-pw-capability-08.txt 
MPLS Working Group Kamran Raza
Internet Draft Sami Boutros
Intended status: Standards Track
Expires: October 26, 2014 Cisco Systems
April 27, 2014 MPLS Working Group Kamran Raza
Internet Draft Sami Boutros
Intended Status: Standards Track
Expires: April 18, 2015 Cisco Systems, Inc.
Controlling State Advertisements Of Non-negotiated LDP Applications October 15, 2014
draft-ietf-mpls-ldp-ip-pw-capability-07.txt Controlling State Advertisements Of Non-negotiated LDP Applications
Status of this Memo draft-ietf-mpls-ldp-ip-pw-capability-08.txt
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Abstract Abstract
There is no capability negotiation done for Label Distribution There is no capability negotiation done for Label Distribution
Protocol (LDP) applications that setup Label Switched Paths (LSPs) Protocol (LDP) applications that setup Label Switched Paths (LSPs) for
for IP prefixes or that signal Point-to-point (P2P) Pseudowires IP prefixes or that signal Point-to-point (P2P) Pseudowires (PWs) for
(PWs) for Layer 2 Virtual Private Networks (L2VPNs). When an LDP Layer 2 Virtual Private Networks (L2VPNs). When an LDP session comes
session comes up, an LDP speaker may unnecessarily advertise its up, an LDP speaker may unnecessarily advertise its local state for
local state for such LDP applications even when the peer session is such LDP applications even when the peer session is established for
established for some other applications like Multipoint LDP (mLDP) some other applications like Multipoint LDP (mLDP) or Inter-Chassis
or Inter-Chassis Communication Protocol (ICCP). This document Communication Protocol (ICCP). This document defines a solution by
defines a solution by which an LDP speaker announces to its peer its which an LDP speaker announces to its peer its disinterest in such
disinterest in such non-negotiated applications, thus disabling the non-negotiated applications, thus disabling the unnecessary
unnecessary advertisement of corresponding application state, which advertisement of corresponding application state, which would have
would have otherwise be advertised over the established LDP session. otherwise be advertised over the established LDP session.
Table of Contents Table of Contents
1. Introduction 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document 4 2. Conventions used in this document . . . . . . . . . . . . . . . 4
3. Non-negotiated LDP applications 4 3. Non-negotiated LDP applications . . . . . . . . . . . . . . . . 4
3.1. Non-interesting State 5 3.1. Non-interesting State . . . . . . . . . . . . . . . . . . . 4
4. Controlling State Advertisement 5 3.1.1 Prefix-LSPs . . . . . . . . . . . . . . . . . . . . . . 5
4.1. State Advertisement Control Capability 5 3.1.2 P2P-PWs . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Capabilities Procedures 8 4. Controlling State Advertisement . . . . . . . . . . . . . . . . 5
4.2.1. State Control Capability in an Initialization message 9 4.1. State Advertisement Control Capability . . . . . . . . . . 5
4.2.2. State Control capability in a Capability message 9 4.2. Capabilities Procedures . . . . . . . . . . . . . . . . . . 8
5. Operational Examples 9 4.2.1. State Control Capability in an Initialization message . 8
5.1. Disabling Prefix-LSPs and P2P-PWs apps on an ICCP session 9 4.2.2. State Control capability in a Capability message . . . 9
5.2. Disabling Prefix-LSPs app on a PW Targeted LDP session 10 5. Applicability Statement . . . . . . . . . . . . . . . . . . . . 9
5.3. Disabling Prefix-LSPs app dynamically on an LDP session 10 6. Operational Examples . . . . . . . . . . . . . . . . . . . . . 11
5.4. Disabling Prefix-LSPs app on an mLDP-only session 11 6.1. Disabling Prefix-LSPs and P2P-PWs on an ICCP session . . . 11
5.5. Disabling IPv4 or IPv6 Prefix-LSPs app on an dual-stack LSR 11 6.2. Disabling Prefix-LSPs on a L2VPN/PW T-LDP session . . . . . 11
6. Security Considerations 11 6.3. Disabling Prefix-LSPs dynamically on an established LDP
7. IANA Considerations 12 session . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8. References 12 6.4. Disabling Prefix-LSPs on an mLDP-only session . . . . . . . 12
8.1. Normative References 12 6.5. Disabling IPv4 or IPv6 Prefix-LSPs on a dual-stack LSR . . 12
8.2. Informative References 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgments 13 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1 Normative References . . . . . . . . . . . . . . . . . . . 13
9.2 Informative References . . . . . . . . . . . . . . . . . . 13
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
LDP Capabilities specification [RFC5561] introduced a mechanism to LDP Capabilities specification [RFC5561] introduced a mechanism to
negotiate LDP capabilities for a given feature between peer Label negotiate LDP capabilities for a given feature between peer Label
Switching Routers (LSRs). The capability mechanism insures that no Switching Routers (LSRs). The capability mechanism insures that no
unnecessary state is exchanged between peer LSRs unless the unnecessary state is exchanged between peer LSRs unless the
corresponding feature capability is successfully negotiated between corresponding feature capability is successfully negotiated between
the peers. the peers.
Newly defined LDP features and applications, such as Typed Wildcard Newly defined LDP features and applications, such as Typed Wildcard
Forwarding Equivalence Class (FEC) [RFC5918], Inter-Chassis Forwarding Equivalence Class (FEC) [RFC5918], Inter-Chassis
Communication Protocol [ICCP], mLDP [RFC6388], and L2VPN Point-to- Communication Protocol [RFC7275], mLDP [RFC6388], and L2VPN Point-to-
multipoint (P2MP) PW [P2MP-PW] make use of LDP capabilities framework multipoint (P2MP) PW [P2MP-PW] make use of LDP capabilities framework
for their feature negotiation. However, the earlier LDP application for their feature negotiation. However, the earlier LDP application to
to establish LSPs for IP unicast prefixes, and application to signal establish LSPs for IP unicast prefixes, and application to signal
L2VPN P2P PW [RFC4447] [RFC4762] allowed LDP speakers to exchange L2VPN P2P PW [RFC4447] [RFC4762] allowed LDP speakers to exchange
application state without any capability negotiation, thus causing application state without any capability negotiation, thus causing
unnecessary state advertisement when a given application is not unnecessary state advertisement when a given application is not
enabled on one of the LDP speakers participating in a given session. enabled on one of the LDP speakers participating in a given session.
For example, when bringing up and using an LDP peer session with a For example, when bringing up and using an LDP peer session with a
remote Provider Edge (PE) LSR for purely ICCP signaling reasons, an remote Provider Edge (PE) LSR for purely ICCP signaling reasons, an
LDP speaker may unnecessarily advertise labels for IP (unicast) LDP speaker may unnecessarily advertise labels for IP (unicast)
prefixes to this ICCP related LDP peer. prefixes to this ICCP related LDP peer.
Another example of unnecessary state advertisement can be cited when Another example of unnecessary state advertisement can be cited when
LDP is to be deployed in an IP dual-stack environment. For instance, LDP is to be deployed in an IP dual-stack environment. For instance,
an LSR that is locally enabled to setup LSPs for both IPv4 and IPv6 an LSR that is locally enabled to setup LSPs for both IPv4 and IPv6
prefixes may advertise (address and label) bindings for both IPv4 and prefixes may advertise (address and label) bindings for both IPv4 and
IPv6 address families towards an LDP peer that is interested in IPv4 IPv6 address families towards an LDP peer that is interested in IPv4
bindings only. In this case, the advertisement of IPv6 bindings to bindings only. In this case, the advertisement of IPv6 bindings to the
the peer is unnecessary, as well as wasteful, from the point of view peer is unnecessary, as well as wasteful, from the point of view of
of LSR memory/CPU and network resource consumption. LSR memory/CPU and network resource consumption.
To avoid this unnecessary state advertisement and exchange, currently To avoid this unnecessary state advertisement and exchange, currently
an operator is typically required to configure and define filtering an operator is typically required to configure and define filtering
policies on the LSR, which introduces unnecessary operational policies on the LSR, which introduces unnecessary operational overhead
overhead and complexity for such deployments. and complexity for such deployments.
This document defines an LDP Capabilities [RFC5561] based solution by This document defines an LDP Capabilities [RFC5561] based solution by
which an LDP speaker may announce to its peer(s) its disinterest (or which an LDP speaker may announce to its peer(s) its disinterest (or
non-support) for state to setup IP Prefix LSPs and/or to signal L2VPN non-support) for state to setup IP Prefix LSPs and/or to signal L2VPN
P2P PW at the time of session establishment. This capability helps in P2P PW at the time of session establishment. This capability helps in
avoiding unnecessary state advertisement for such feature avoiding unnecessary state advertisement for such feature
applications. This document also states the mechanics to dynamically applications. This document also states the mechanics to dynamically
disable or enable the state advertisement for such applications disable or enable the state advertisement for such applications during
during the session lifetime. The non-interesting state of an the session lifetime. The non-interesting state of an application
application depends on the type of application and is described later depends on the type of application and is described later in section
in section 3.1. 3.1.
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119]. document are to be interpreted as described in RFC-2119 [RFC2119].
The term "IP" in this document refers to both IPv4 and IPv6 unicast The term "IP" in this document refers to both IPv4 and IPv6 unicast
address families. address families.
3. Non-negotiated LDP applications 3. Non-negotiated LDP applications
For the applications that existed prior to the definition of LDP For the applications that existed prior to the definition of LDP
Capabilities framework [RFC5561], an LDP speaker typically Capabilities framework [RFC5561], an LDP speaker typically advertises,
advertises, without waiting for any capabilities exchange and without waiting for any capabilities exchange and negotiation, its
negotiation, its corresponding application state to its peers after corresponding application state to its peers after the session
the session establishment. These early LDP applications include: establishment. These early LDP applications include:
o IPv4/IPv6 Prefix LSPs Setup
o L2VPN P2P FEC128 and FEC129 PWs signaling o IPv4/IPv6 Prefix LSPs Setup
o L2VPN P2P FEC128 and FEC129 PWs signaling
This document onward uses following shorthand terms for these This document onward uses following shorthand terms for these earlier
earlier LDP applications: LDP applications:
o "Prefix-LSPs": Refers to an application that sets up LDP LSPs o "Prefix-LSPs": Refers to an application that sets up LDP LSPs
corresponding to IP routes/prefixes by advertising label corresponding to IP routes/prefixes by advertising label
bindings for Prefix FEC (as defined in RFC-5036). bindings for Prefix FEC (as defined in RFC-5036).
o "P2P-PWs": Refers to an application that signals FEC 128 and/or o "P2P-PWs": Refers to an application that signals FEC 128 and/or
FEC 129 L2VPN P2P Pseudowires using LDP (as defined in FEC 129 L2VPN P2P Pseudowires using LDP (as defined in RFC-4447).
RFC-4447).
To disable unnecessary state exchange for such LDP applications over To disable unnecessary state exchange for such LDP applications over
an established LDP session, a new capability is being introduced in an established LDP session, a new capability is being introduced in
this document. This new capability controls the advertisement of this document. This new capability controls the advertisement of
application state and enables an LDP speaker to notify its peer its application state and enables an LDP speaker to notify its peer its
disinterest in the state of one or more of these "Non-negotiated" disinterest in the state of one or more of these "Non-negotiated" LDP
LDP applications at the time of session establishment. Upon receipt applications at the time of session establishment. Upon receipt of
of such capability, the receiving LDP speaker, if supporting the such capability, the receiving LDP speaker, if supporting the
capability, disables the advertisement of the state related to the capability, disables the advertisement of the state related to the
application towards the sender of the capability. This new application towards the sender of the capability. This new capability
capability can also be sent later in a Capability message to either can also be sent later in a Capability message to either disable a
disable a previously enabled application's state advertisement or to previously enabled application's state advertisement or to enable a
enable a previously disabled application's state advertisement. previously disabled application's state advertisement.
3.1. Non-interesting State 3.1. Non-interesting State
A non-interesting state of a non-negotiated LDP application: A non-interesting state of a non-negotiated LDP application:
- is the application state which is of a no interest to an LSR and
need not be advertised to the LSR;
- is the application state which is of a no interest to an LSR
and need not be advertised to the LSR;
- need not be advertised in any of the LDP protocol messages; - need not be advertised in any of the LDP protocol messages;
- is dependent on application type and specified accordingly. - is dependent on application type and specified accordingly.
For Prefix-LSPs application type, the non-interesting state refers 3.1.1 Prefix-LSPs
to any state related to IP Prefix FEC (such as FEC label bindings,
LDP Status). This document, however, does not classify IP address
bindings as a non-interesting state and allows the advertisement of
IP Address bindings to facilitate other LDP applications (such as
mLDP) that depend on learning of peer addresses over an LDP session
for their correct operation.
For P2P-PWs application type, the non-interesting state refers to For Prefix-LSPs application type, the non-interesting state refers to
any state related to P2P PW FEC128/FEC129 (such as FEC label any state related to IP Prefix FEC (such as FEC label bindings, LDP
bindings, MAC [address] withdrawal, and LDP PW Status). Status). This document, however, does not classify IP address
bindings (advertised via ADDRESS message) as a non-interesting state
and allows the advertisement of IP Address bindings. The reason for
this allowance is that an LSR typically uses peer IP address(es) to
map an IP routing nexthop/address to an LDP peer for their
functionality. For example, mLDP [RFC6388] uses peer's IP address(es)
to determine its upstream LSR to reach Root node as well as to select
forwarding interface towards its downstream LSR. Hence in an mLDP-
only network, while it is desirable to disable advertisement of label
bindings for IP (unicast) Prefixes, disabling advertisement of IP
address bindings will break mLDP functionality. Similarly, other LDP
applications may also depend on learnt peer IP address and hence this
document does not put IP address binding into a non-interesting state
category to facilitate such LDP applications.
From now onward in this document, the term "state" will mean to 3.1.2 P2P-PWs
refer to the "non-interesting state" for an application, as defined
in this section. For P2P-PWs application type, the non-interesting state refers to any
state related to P2P PW FEC128/FEC129 (such as FEC label bindings,
MAC [address] withdrawal, and LDP PW Status). From now onward in this
document, the term "state" will mean to refer to the "non-interesting
state" for an application, as defined in this section.
4. Controlling State Advertisement 4. Controlling State Advertisement
To control advertisement of non-interesting state related to non- To control advertisement of non-interesting state related to non-
negotiated LDP applications defined in section 3, a new capability negotiated LDP applications defined in section 3, a new capability
TLV is defined as follows. TLV is defined as follows.
4.1. State Advertisement Control Capability 4.1. State Advertisement Control Capability
The "State Advertisement Control Capability" is a new Capability The "State Advertisement Control Capability" is a new Capability
Parameter TLV defined in accordance with section 3 of LDP Parameter TLV defined in accordance with section 3 of LDP
Capabilities specification [RFC5561]. The format of this new TLV is Capabilities specification [RFC5561]. The format of this new TLV is
as follows: as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| State Adv. Ctrl Cap.(IANA)| Length | |U|F|State Adv. Ctrl. Cap (IANA)| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved | | |S| Reserved | |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| | | |
~ State Advertisement Control Element(s) ~ ~ State Advertisement Control Element(s) ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Format of an "State Advertisement Control Capability" TLV Figure 1: Format of an "State Advertisement Control Capability" TLV
The value of the U-bit for the TLV MUST be set to 1 so that a The value of the U-bit for the TLV MUST be set to 1 so that a
receiver MUST silently ignore this TLV if unknown to it, and receiver MUST silently ignore this TLV if unknown to it, and continue
continue processing the rest of the message. Whereas, The value of processing the rest of the message. Whereas, The value of F-bit MUST
F-bit MUST be set to 0. Once advertised, this capability cannot be be set to 0. Once advertised, this capability cannot be withdrawn;
withdrawn; thus S-bit MUST be set to 1 in an Initialization and thus S-bit MUST be set to 1 in an Initialization and Capability
Capability message. message.
The capability data associated with this State Advertisement Control The capability data associated with this State Advertisement Control
(SAC) Capability TLV is one or more State Advertisement Control (SAC) Capability TLV is one or more State Advertisement Control
Elements, where each element indicates enabling/disabling of Elements, where each element indicates enabling/disabling of
advertisement of non-interesting state for a given application. The advertisement of non-interesting state for a given application. The
format of a SAC Element is defined as follows: format of a SAC Element is defined as follows:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|D| App |Unused | |D| App |Unused |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 2: Format of "State Advertisement Control Element" Figure 2: Format of "State Advertisement Control Element"
Where: Where:
D bit: Controls the advertisement of the state specified in "App" D bit: Controls the advertisement of the state specified in "App"
field: field:
1: Disable state advertisement 1: Disable state advertisement
0: Enable state advertisement 0: Enable state advertisement
When sent in an Initialization message, D bit MUST be set to 1. When sent in an Initialization message, D bit MUST be set
to 1.
App: Defines the application type whose state advertisement is to be App: Defines the application type whose state advertisement is to be
controlled. The value of this field is defined as follows: controlled. The value of this field is defined as follows:
1: IPv4 Prefix-LSPs (LSPs for IPv4 prefixes) 1: IPv4 Prefix-LSPs (LSPs for IPv4 prefixes)
2: IPv6 Prefix-LSPs (LSPs for IPv6 prefixes) 2: IPv6 Prefix-LSPs (LSPs for IPv6 prefixes)
3: FEC128 P2P-PW (L2VPN PWid FEC signaling) 3: FEC128 P2P-PW (L2VPN PWid FEC signaling)
4: FEC129 P2P-PW (L2VPN Generalized PWid FEC signaling) 4: FEC129 P2P-PW (L2VPN Generalized PWid FEC signaling)
Any other value in this field MUST be treated as an error. Any other value in this field MUST be treated as an error.
Unused: MBZ on transmit and ignored on receipt. Unused: MBZ on transmit and ignored on receipt.
The "Length" field of SAC Capability TLV depends on the number of The "Length" field of SAC Capability TLV depends on the number of SAC
SAC Elements present in the TLV. For example, if there are two Elements present in the TLV. For example, if there are two elements
elements present, then the Length field is set to 3 octets. A present, then the Length field is set to 3 octets. A receiver of this
receiver of this capability TLV can deduce number of elements capability TLV can deduce number of elements present in the TLV by
present in the TLV by using the Length field. using the Length field.
From now onward, this document uses the term "element" to refer to a From now onward, this document uses the term "element" to refer to a
SAC Element. SAC Element.
As described earlier, SAC Capability TLV MAY be included by an LDP As described earlier, SAC Capability TLV MAY be included by an LDP
speaker in an Initialization message to signal to its peer LSR that speaker in an Initialization message to signal to its peer LSR that
state exchange for one or more application(s) need to be disabled on state exchange for one or more application(s) need to be disabled on
the given peer session. This TLV can also be sent later in a the given peer session. This TLV can also be sent later in a
Capability message to selectively enable or disable these Capability message to selectively enable or disable these
applications. If there are more than one elements present in a SAC applications. If there are more than one elements present in a SAC
Capability TLV, the elements MUST belong to distinct app types and Capability TLV, the elements MUST belong to distinct app types and
an app type MUST NOT appear more than once. If a receiver the an app type MUST NOT appear more than once. If a receiver
receives such a malformed TLV, it SHOULD discard this TLV and receives such a malformed TLV, it SHOULD discard this TLV and
continue processing rest of the message. If an LSR receives a continue processing rest of the message. If an LSR receives a message
message with a SAC capability TLV containing an element with "App" with a SAC capability TLV containing an element with "App" field set
field set to a value other than defined above, the receiver MUST to a value other than defined above, the receiver MUST ignore and
ignore and discard the element and continue processing the rest of discard the element and continue processing the rest of the TLV.
the TLV.
To control more than one application state, a sender LSR can either To control more than one application state, a sender LSR can either
send a single capability TLV in a message with multiple elements send a single capability TLV in a message with multiple elements
present, or can send separate messages with capability TLV present, or can send separate messages with capability TLV specifying
specifying one or more elements. A receiving LSR, however, MUST one or more elements. A receiving LSR, however, MUST treat each
treat each incoming capability TLV with an element corresponding to incoming capability TLV with an element corresponding to a given
a given application type as an update to its existing policy for the application type as an update to its existing policy for the given
given type. type.
To understand capability updates from an example, let us consider 2 To understand capability updates from an example, let us consider 2
LSRs, S (LDP speaker) and P (LDP peer), both of which support all LSRs, S (LDP speaker) and P (LDP peer), both of which support all the
the non-negotiated applications listed earlier. By default, these non-negotiated applications listed earlier. By default, these LSR
LSR will advertise state for these applications, as configured, to will advertise state for these applications, as configured, to their
their peer as soon as an LDP session is established. Now assume that peer as soon as an LDP session is established. Now assume that P
P receives from S a SAC capability in an Initialization message with receives from S a SAC capability in an Initialization message with
"IPv6 Prefix-LSPs" and "FEC129 P2P-PW" applications disabled. This "IPv6 Prefix-LSPs" and "FEC129 P2P-PW" applications disabled. This
updates P's outbound policy towards S to advertise state related to updates P's outbound policy towards S to advertise state related to
only IPv4 Prefix-LSPs and FEC128 P2P-PW applications. Later, P only IPv4 Prefix-LSPs and FEC128 P2P-PW applications. Later, P
receives another capability update from S via a Capability message receives another capability update from S via a Capability message
with "IPv6 Prefix-LSPs" enabled and "FEC128 P2P-PWs" disabled. This with "IPv6 Prefix-LSPs" enabled and "FEC128 P2P-PWs" disabled. This
results in P's outbound policy towards S to advertise both IPv4 and results in P's outbound policy towards S to advertise both IPv4 and
IPv6 Prefix-LSPs application state, and disable both FEC128 and IPv6 Prefix-LSPs application state, and disable both FEC128 and
FEC129 P2P-PWs signaling. Finally, P receives another update from S FEC129 P2P-PWs signaling. Finally, P receives another update from S
via a Capability message that specifies to disable all four non- via a Capability message that specifies to disable all four non-
negotiated applications state, resulting in P outbound policy negotiated applications state, resulting in P outbound policy towards
towards S to block/disable state for all these applications, and S to block/disable state for all these applications, and only
only advertise state for any other application, as applicable. advertise state for any other application, as applicable.
4.2. Capabilities Procedures 4.2. Capabilities Procedures
The SAC capability conveys the desire of an LSR to disable the The SAC capability conveys the desire of an LSR to disable the
receipt of unwanted/unnecessary state from its LDP peer. This receipt of unwanted/unnecessary state from its LDP peer. This
capability is unilateral and unidirectional in nature, and a capability is unilateral and unidirectional in nature, and a
receiving LSR is not required to send a similar capability TLV in an receiving LSR is not required to send a similar capability TLV in an
Initialization or Capability message towards the sender of this Initialization or Capability message towards the sender of this
capability. This unilateral behavior conforms to the procedures capability. This unilateral behavior conforms to the procedures
defined in the Section 6 of LDP Capabilities [RFC5561]. defined in the Section 6 of LDP Capabilities [RFC5561].
After this capability is successfully negotiated (i.e. sent by an After this capability is successfully negotiated (i.e. sent by an LSR
LSR and received/understood by its peer), then the receiving LSR and received/understood by its peer), then the receiving LSR MUST NOT
MUST NOT advertise any state related to the disabled applications advertise any state related to the disabled applications towards the
towards the capability sending LSR until and unless these capability sending LSR until and unless these application states are
application states are explicitly enabled again via a capability explicitly enabled again via a capability update. Upon receipt of a
update. Upon receipt of a capability update to disable an enabled capability update to disable an enabled application [state] during
application [state] during the lifetime of a session, the receiving the lifetime of a session, the receiving LSR MUST also withdraw from
LSR MUST also withdraw from the peer any previously advertised state the peer any previously advertised state corresponding to the
corresponding to the disabled application. disabled application.
If a receiving LDP speaker does not understand the SAC capability If a receiving LDP speaker does not understand the SAC capability
TLV, then it MUST respond to the sender with "Unsupported TLV" TLV, then it MUST respond to the sender with "Unsupported TLV"
notification as described in LDP Capabilities [RFC5561]. If a notification as described in LDP Capabilities [RFC5561]. If a
receiving LDP speaker does not understand or does not support an receiving LDP speaker does not understand or does not support an
application specified in an application control element, it SHOULD application specified in an application control element, it SHOULD
silently ignore/skip such an element and continue processing rest of silently ignore/skip such an element and continue processing rest of
the TLV. the TLV.
4.2.1. State Control Capability in an Initialization message 4.2.1. State Control Capability in an Initialization message
LDP Capabilities [RFC5561] framework dictates that the S-bit of LDP Capabilities [RFC5561] framework dictates that the S-bit of
capability parameter in an Initialization message MUST be set to 1 capability parameter in an Initialization message MUST be set to 1
and SHOULD be ignored on receipt. and SHOULD be ignored on receipt.
An LDP speaker determines (e.g. via some local configuration or An LDP speaker determines (e.g. via some local configuration or
default policy) if it needs to disable Prefix-LSPs and/or P2P-PWs default policy) if it needs to disable Prefix-LSPs and/or P2P-PWs
applications with a peer LSR. If there is a need to disable, then applications with a peer LSR. If there is a need to disable, then the
the SAC TLV needs to be included in the Initialization message with SAC TLV needs to be included in the Initialization message with
respective SAC elements included with their D bit set to 1. respective SAC elements included with their D bit set to 1.
An LDP speaker that supports the SAC capability MUST interpret the An LDP speaker that supports the SAC capability MUST interpret the
capability TLV in a received Initialization message such that it capability TLV in a received Initialization message such that it
disables the advertisement of the application state towards the disables the advertisement of the application state towards the
capability sending LSR for Prefix-LSPs and/or P2P-PWs applications capability sending LSR for Prefix-LSPs and/or P2P-PWs applications if
if their SAC element's D bit is set to 1. their SAC element's D bit is set to 1.
4.2.2. State Control capability in a Capability message 4.2.2. State Control capability in a Capability message
If the LDP peer supports "Dynamic Announcement Capability" If the LDP peer supports "Dynamic Announcement Capability" [RFC5561],
[RFC5561], then an LDP speaker may send SAC capability in a then an LDP speaker may send SAC capability in a Capability message
Capability message towards the peer. Once advertised, these towards the peer. Once advertised, these capabilities cannot be
capabilities cannot be withdrawn and hence the S-bit of the TLV MUST withdrawn and hence the S-bit of the TLV MUST be set to 1 when sent
be set to 1 when sent in a Capability message. in a Capability message.
An LDP speaker may decide to send this TLV towards an LDP peer if An LDP speaker may decide to send this TLV towards an LDP peer if one
one or more of its Prefix-LSPs and/or P2P-PWs applications get or more of its Prefix-LSPs and/or P2P-PWs applications get disabled,
disabled, or if previously disabled application gets enabled again. or if previously disabled application gets enabled again. In this
In this case, the LDP speaker constructs the TLV with appropriate case, the LDP speaker constructs the TLV with appropriate SAC
SAC element(s) and sends the corresponding capability TLV in a element(s) and sends the corresponding capability TLV in a Capability
Capability message. message.
Upon receipt of this TLV in a Capability message, the receiving LDP Upon receipt of this TLV in a Capability message, the receiving LDP
speaker reacts in the same manner as it reacts upon the receipt of speaker reacts in the same manner as it reacts upon the receipt of
this TLV in an Initialization message. Additionally, the peer this TLV in an Initialization message. Additionally, the peer
withdraws/advertises the application state from/to the capability withdraws/advertises the application state from/to the capability
sending LDP speaker according to the capability update. sending LDP speaker according to the capability update.
5. Operational Examples 5. Applicability Statement
5.1. Disabling Prefix-LSPs and P2P-PWs applications on an ICCP session The procedures defined in this document may result in disabling
announcement of label bindings for IP Prefixes and/or P2P PW FECs,
and hence should be used with caution and discretion. This document
recommends that this new SAC capability and its procedures SHOULD be
enabled on an LSR only via a configuration knob. This knob could
either be a global LDP knob or be implemented per LDP neighbor.
Hence, it is recommended that an operator SHOULD enable this
capability and its associated procedures on an LSR towards a neighbor
only if it is known that such bindings advertisement and exchange
with the neighbor is unnecessary and wasteful.
Following table summarizes a non-exhaustive list of typical LDP
session types on which this new SAC capability and its procedures are
expected to be applied to disable advertisement of non-interesting
state:
+===============================+================================+
| Session Type(s) | Non-interesting State |
+===============================+================================+
| P2P-PW FEC128-only | IP Prefix LSPs + P2P-PW FEC129 |
|-------------------------------|--------------------------------|
| P2P-PW only (FEC128/129) | IP Prefix LSPs |
|-------------------------------|--------------------------------|
| IPv4-only on a Dual-Stack LSR | IPv6 Prefix LSPs + P2P-PW |
|-------------------------------|--------------------------------|
| IPv6-only on a Dual-Stack LSR | IPv4 Prefix LSPs + P2P-PW |
|-------------------------------|--------------------------------|
| mLDP-only | IP Prefix LSPs + P2P-PW |
|-------------------------------|--------------------------------|
| ICCP-only | IP Prefix LSPs + P2P-PW |
+-------------------------------+--------------------------------+
It is to be noted that if an application state needs changing after
session initialization (e.g. to enable previously disabled
application or to disable previously enabled application), the
procedures defined in this document expect LSR peers to support LDP
"Dynamic Announcement" Capability to announce the change in SAC
capability via LDP Capability message. However, if any of the peering
LSR does not support this capability, the alternate option is to
force reset the LDP session to advertise the new SAC capability
accordingly during the following session initialization.
Following are some more important points that an operator need to
consider regarding the applicability of this new capability and
associated procedures defined in this document:
- An operator SHOULD disable Prefix-LSPs state on any Targeted LDP (T-LDP)
session that is established for ICCP-only and/or PW-only purposes.
- An operator MUST NOT disable Prefix-LSPs state on any T-LDP session
that is established for remote LFA FRR [RLFA] reasons.
- In a remote LFA FRR [RLFA] enabled network, it is RECOMMENDED to
not disable Prefix-LSPs state on a T-LDP session even if the current
session type is PW-only and/or ICCP-only. This is recommended because
any remote/T-LDP neighbor could potentially be picked as a remote LFA
PQ node.
- This capability SHOULD be enabled for Prefix-LSPs in the
scenarios when it is desirable to disable (or enable)
advertisement of "all" the prefix label bindings. For scenarios
when a "subset" of bindings need to be filtered, the existing
filtering procedures pertaining to label binding announcement
should be used.
- It is allowed to use label advertisement filtering policies in
conjunction with the procedures defined in this document for
Prefix-LSPs. In such cases, the label bindings will be announced
as per the label filtering policy for the given neighbor when
Prefix-LSP application is enabled.
6. Operational Examples
6.1. Disabling Prefix-LSPs and P2P-PWs on an ICCP session
Consider two PE routers, LSR1 and LSR2, which understand/support SAC Consider two PE routers, LSR1 and LSR2, which understand/support SAC
capability TLV, and have an established LDP session to exchange ICCP capability TLV, and have an established LDP session to exchange ICCP
state related to dual-homed devices connected to these LSRs. Let us state related to dual-homed devices connected to these LSRs. Let us
assume that both LSRs are provisioned not to exchange any state for assume that both LSRs are provisioned not to exchange any state for
Prefix-LSPs (IPv4/IPv6) and P2P-PWs (FEC128/129) application. Prefix-LSPs (IPv4/IPv6) and P2P-PWs (FEC128/129) application.
To indicate their disinterest in these applications, the LSRs will
To indicate their disinterest in these applications, the LSRs will
include a SAC capability TLV (with 4 SAC elements corresponding to include a SAC capability TLV (with 4 SAC elements corresponding to
these 4 applications with D bit set to 1 for each one) in the these 4 applications with D bit set to 1 for each one) in the
Initialization message. Upon receipt of this TLV in Initialization Initialization message. Upon receipt of this TLV in Initialization
message, the receiving LSR will disable the advertisement of message, the receiving LSR will disable the advertisement of
IPv4/IPv6 label bindings, as well as P2P PW FEC128/129 signaling, IPv4/IPv6 label bindings, as well as P2P PW FEC128/129 signaling,
towards its peer after session establishment. towards its peer after session establishment.
5.2. Disabling Prefix-LSPs application on a PW Targeted LDP session 6.2. Disabling Prefix-LSPs on a L2VPN/PW T-LDP session
Now, consider LSR1 and LSR2 have an established Targeted LDP (T-LDP) Now, consider LSR1 and LSR2 have an established T-LDP session for
session for P2P-PWs application to exchange label bindings for P2P-PWs application to exchange label bindings for FEC 128/129. Given
FEC 128/129. Given that there is no need to exchange IP Prefix label that there is no need to exchange IP label bindings amongst the PE
bindings amongst the PE LSRs over a PW T-LDP session in most typical LSRs over a PW T-LDP session in most typical deployments, let us
deployments, let us assume that LSRs are provisioned to disable assume that LSRs are provisioned to disable IPv4/IPv6 Prefix-LSPs
IPv4/IPv6 Prefix-LSPs application state on the given PW session. application state on the given PW session.
To indicate their disinterest in Prefix-LSPs application over a PW To indicate their disinterest in Prefix-LSPs application over a PW T-
T-LDP session, the LSRs will follow/apply the same procedures as LDP session, the LSRs will follow/apply the same procedures as
described in previous section. As a result, only P2P-PWs related described in previous section. As a result, only P2P-PWs related
state will be exchanged between these LSRs over this T-LDP session. state will be exchanged between these LSRs over this T-LDP session.
5.3. Disabling Prefix-LSPs application dynamically on an established 6.3. Disabling Prefix-LSPs dynamically on an established LDP session
LDP session
Assume that LSRs from previous sections were initially provisioned Assume that LSRs from previous sections were initially provisioned to
to exchange both Prefix-LSPs and P2P-PWs state over the session exchange both Prefix-LSPs and P2P-PWs state over the session between
between them, and also support "Dynamic Announcement" Capability them, and also support "Dynamic Announcement" Capability [RFC5561].
[RFC5561]. Now, assume that LSR1 is dynamically provisioned to Now, assume that LSR1 is dynamically provisioned to disable
disable (IPv4/IPv6) Prefix-LSPs over T-LDP session with LSR2. In (IPv4/IPv6) Prefix-LSPs over T-LDP session with LSR2. In this case,
this case, LSR1 will send SAC capability TLV in a Capability message LSR1 will send SAC capability TLV in a Capability message towards
towards LSR2 with application control elements defined for IPv4 and LSR2 with application control elements defined for IPv4 and IPv6
IPv6 Prefix-LSPs with D bit set to 1. Upon receipt of this TLV, LSR2 Prefix-LSPs with D bit set to 1. Upon receipt of this TLV, LSR2 will
will disable Prefix-LSPs application state(s) towards LSR1 and disable Prefix-LSPs application state(s) towards LSR1 and withdraw
withdraw all previously advertised application state from LSR1. To all previously advertised application state from LSR1. To withdraw
withdraw label bindings from its peer, LSR2 MAY use a single Prefix label bindings from its peer, LSR2 MAY use a single Prefix FEC Typed
FEC Typed Wildcard Label Withdraw message [RFC5918] if the peer Wildcard Label Withdraw message [RFC5918] if the peer supports Typed
supports Typed Wildcard FEC capability. Wildcard FEC capability.
This dynamic disability of Prefix-LSPs application does not impact This dynamic disability of Prefix-LSPs application does not impact
L2VPN P2P-PWs application on the given session, and both LSRs should L2VPN P2P-PWs application on the given session, and both LSRs should
continue to exchange PW Signaling application related state. continue to exchange PW Signaling application related state.
5.4. Disabling Prefix-LSPs application on an mLDP-only session 6.4. Disabling Prefix-LSPs on an mLDP-only session
Now assume that LSR1 and LSR2 have formed an LDP session to exchange Now assume that LSR1 and LSR2 have formed an LDP session to exchange
mLDP state only. In typical deployments, LSR1 and LSR2 also exchange mLDP state only. In typical deployments, LSR1 and LSR2 also exchange
bindings for IP (unicast) prefixes upon mLDP session, which is bindings for IP (unicast) prefixes upon mLDP session, which is
unnecessary and wasteful for an mLDP-only LSR. unnecessary and wasteful for an mLDP-only LSR.
Using the procedures defined earlier, an LSR can indicate its Using the procedures defined earlier, an LSR can indicate its
disinterest in Prefix-LSPs application state to its peer upon disinterest in Prefix-LSPs application state to its peer upon session
session establishment time or dynamically later via LDP capabilities establishment time or dynamically later via LDP capabilities update.
update.
Reference to section 3.1, the peer disables the advertisement of any Reference to section 3.1, the peer disables the advertisement of any
state related to IP Prefix FECs, but still advertises IP address state related to IP Prefix FECs, but still advertises IP address
bindings that are required for the correct operation of mLDP. bindings that are required for the correct operation of mLDP.
5.5. Disabling IPv4 or IPv6 Prefix-LSPs application on an dual-stack LSR 6.5. Disabling IPv4 or IPv6 Prefix-LSPs on a dual-stack LSR
In IP dual-stack scenarios, LSR2 may advertise unnecessary state In IP dual-stack scenarios, LSR2 may advertise unnecessary state
(e.g. IPv6 prefix label bindings) towards peer LSR1 corresponding to (e.g. IPv6 prefix label bindings) towards peer LSR1 corresponding to
IPv6 Prefix-LSPs application once a session is established mainly IPv6 Prefix-LSPs application once a session is established mainly for
for exchanging state for IPv4. The similar scenario also applies exchanging state for IPv4. The similar scenario also applies when
when advertising IPv4 Prefix-LSPs state on a session meant for IPv6. advertising IPv4 Prefix-LSPs state on a session meant for IPv6. The
The SAC capability and its procedures defined in this document can SAC capability and its procedures defined in this document can help
help to avoid such unnecessary state advertisement. to avoid such unnecessary state advertisement.
Consider IP dual-stack environment where LSR2 is enabled for Prefix- Consider IP dual-stack environment where LSR2 is enabled for Prefix-
LSPs application for both IPv4 and IPv6, but LSR1 is enabled for (or LSPs application for both IPv4 and IPv6, but LSR1 is enabled for (or
interested in) only IPv4 Prefix-LSPs. To avoid receiving unwanted interested in) only IPv4 Prefix-LSPs. To avoid receiving unwanted
state advertisement for IPv6 Prefix-LSPs application from LSR2, LSR1 state advertisement for IPv6 Prefix-LSPs application from LSR2, LSR1
can send SAC capability with element for IPv6 Prefix-LSPs with D bit can send SAC capability with element for IPv6 Prefix-LSPs with D bit
set to 1 in the Initialization message towards LSR2 at the time of set to 1 in the Initialization message towards LSR2 at the time of
session establishment. Upon receipt of this capability, LSR2 will session establishment. Upon receipt of this capability, LSR2 will
disable all IPv6 label binding advertisement towards LSR1. If IPv6 disable all IPv6 label binding advertisement towards LSR1. If IPv6
Prefix-LSPs application is later enabled on LSR1, LSR1 can update Prefix-LSPs application is later enabled on LSR1, LSR1 can update the
the capability by sending SAC capability in a Capability message capability by sending SAC capability in a Capability message towards
towards LSR2 to enable this application dynamically. LSR2 to enable this application dynamically.
6. Security Considerations 7. Security Considerations
The proposal introduced in this document does not introduce any new The proposal introduced in this document does not introduce any new
security considerations beyond that already apply to the base LDP security considerations beyond that already apply to the base LDP
specification [RFC5036] and [RFC5920]. specification [RFC5036] and [RFC5920].
7. IANA Considerations 8. IANA Considerations
This document defines a new LDP capability parameter TLV. IANA is This document defines a new LDP capability parameter TLV. IANA is
requested to assign the lowest available value after 0x0500 from requested to assign the lowest available value after 0x0500 from "TLV
"TLV Type Name Space" in the "Label Distribution Protocol (LDP) Type Name Space" in the "Label Distribution Protocol (LDP)
Parameters" registry as the new code point for the new LDP Parameters" registry as the new code point for the new LDP capability
capability TLV code point. TLV code point.
+-----+---------------------+---------------+-----------------------+ +-----+---------------------+---------------+-----------------------+
|Value| Description | Reference |Notes/Registration Date| |Value| Description | Reference |Notes/Registration Date|
+-----+---------------------+---------------+-----------------------+ +-----+---------------------+---------------+-----------------------+
| TBA | State Advertisement | This document | | | TBA | State Advertisement | This document | |
| | Control Capability | | | | | Control Capability | | |
+-----+---------------------+---------------+-----------------------+ +-----+---------------------+---------------+-----------------------+
8. References 9. References
8.1. Normative References 9.1 Normative References
[RFC5036] L. Andersson, I. Minei, and B. Thomas, "LDP [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Specification", RFC 5036, September 2007. Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5561] B. Thomas, K. Raza, S. Aggarwal, R. Aggarwal, and JL. Le [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
Roux, "LDP Capabilities", RFC 5561, July 2009. "LDP Specification", RFC 5036, October 2007,
<http://www.rfc-editor.org/info/rfc5036>.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
Requirement Levels", BCP 14, RFC2119, March 1997. Le Roux, "LDP Capabilities", RFC 5561, July 2009,
<http://www.rfc-editor.org/info/rfc5561>.
8.2. Informative References 9.2 Informative References
[RFC5918] R. Asati, I. Minei, and B. Thomas, "Label Distribution [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
Protocol Typed Wildcard FEC", RFC 5918, August 2010. G. Heron, "Pseudowire Setup and Maintenance Using the
Label Distribution Protocol (LDP)", RFC 4447, April 2006,
<http://www.rfc-editor.org/info/rfc4447>.
[RFC4447] L. Martini, E. Rosen, El-Aawar, T. Smith, and G. Heron, [RFC4762] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private
"Pseudowire Setup and Maintenance using the Label LAN Service (VPLS) Using Label Distribution Protocol (LDP)
Distribution Protocol", RFC 4447, April 2006. Signaling", RFC 4762, January 2007, <http://www.rfc-
editor.org/info/rfc4762>.
[RFC4762] M. Lasserre, and V. Kompella, "Virtual Private LAN Service [RFC5918] Asati, R., Minei, I., and B. Thomas, "Label Distribution
(VPLS) Using Label Distribution Protocol (LDP) Signaling", Protocol (LDP) 'Typed Wildcard' Forward Equivalence Class
RFC 4762, January 2007. (FEC)", RFC 5918, August 2010, <http://www.rfc-
editor.org/info/rfc5918>.
[P2MP-PW] Martini, L. et. al, "Signaling Root-Initiated Point-to- [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Multipoint Pseudowires using LDP", draft-ietf-pwe3-p2mp-pw- Networks", RFC 5920, July 2010, <http://www.rfc-
04.txt, Work in Progress, March 2012. editor.org/info/rfc5920>.
[ICCP] L. Martini, S. Salam, A. Sajassi, and S. Matsushima, [RFC6388] Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B.
"Inter-Chassis Communication Protocol for L2VPN PE Thomas, "Label Distribution Protocol Extensions for Point-
Redundancy", draft-ietf-pwe3-iccp-16.txt, Work in to-Multipoint and Multipoint-to-Multipoint Label Switched
Progress, March 2014. Paths", RFC 6388, November 2011, <http://www.rfc-
editor.org/info/rfc6388>.
[RFC6388] I. Minei, I. Wijnands, K. Kompella, and B. Thomas, "LDP [RFC7275] Martini, L., Salam, S., Sajassi, A., Bocci, M.,
Extensions for P2MP and MP2MP LSPs", RFC 6388, November Matsushima, S., and T. Nadeau, "Inter-Chassis
2011. Communication Protocol for Layer 2 Virtual Private Network
(L2VPN) Provider Edge (PE) Redundancy", RFC 7275, June
2014, <http://www.rfc-editor.org/info/rfc7275>.
[RFC5920] L. Fang, et al., "Security Framework for MPLS and GMPLS [P2MP-PW] Martini, L. et. al, "Signaling Root-Initiated Point-to-
Networks", RFC 5920, July 2010. Multipoint Pseudowires using LDP", draft-ietf-pwe3-p2mp-
pw-04.txt, Work in Progress, March 2012.
9. Acknowledgments [RLFA] Bryant, S., Filsfils, C., Previdi, S., Shand, M., So, N.,
"Remote LFA FRR", draft-ietf-rtgwg-remote-lfa-08, Work in
Progress, September 2014.
The authors would like to thank Eric Rosen for his valuable input 10. Acknowledgments
and comments. We also acknowledge Karthik Subramanian and IJsbrand
Wijnands for bringing up mLDP use case.
This document was prepared using 2-Word-v2.0.template.dot. The authors would like to thank Eric Rosen and Alexander Vainshtein
for their review and valuable comments. We also acknowledge Karthik
Subramanian and IJsbrand Wijnands for bringing up mLDP use case.
Authors' Addresses Authors' Addresses
Kamran Raza Kamran Raza
Cisco Systems, Inc., Cisco Systems, Inc.,
2000 Innovation Drive, 2000 Innovation Drive,
Ottawa, ON K2K-3E8, Canada. Ottawa, ON K2K-3E8, Canada.
E-mail: skraza@cisco.com E-mail: skraza@cisco.com
Sami Boutros Sami Boutros
Cisco Systems, Inc. Cisco Systems, Inc.
3750 Cisco Way, 3750 Cisco Way,
San Jose, CA 95134, USA. San Jose, CA 95134, USA.
E-mail: sboutros@cisco.com E-mail: sboutros@cisco.com
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