Network Working Group A. Zamfir
Internet Draft Z. Ali
Intended status: Experimental Cisco Systems
Expires: October 26, 2011 D. Papadimitriou
Alcatel-Lucent
April 27, 2011
Component Link Recording and Resource Control for TE Links
draft-ietf-mpls-explicit-resource-control-bundle-10.txt
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Abstract
Record Route is a useful administrative tool that has been used
extensively by the service providers. However, when TE links are
bundled, identification of label resource in Record Route object
(RRO) is not sufficient to determine the component link within a TE
link that is being used by a given LSP. In other words, when link
bundling is used, resource recording requires mechanisms to specify
the component link identifier, along with the TE link identifier and
Label. As it is not possible to record component link in the RRO,
this document defines the extensions to RSVP-TE [RFC3209] and
[RFC3473] to specify component link identifiers for resource
recording purposes.
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This document also defines the Explicit Route object (ERO)
counterpart of the RRO extension. The ERO extensions are needed to
perform explicit label/resource control over bundled TE link.
Hence, this document defines the extensions to RSVP-TE [RFC3209]
and [RFC3473] to specify component link identifiers for explicit
resource control and recording over TE link bundles.
Table of Contents
1. Introduction................................................3
Conventions used in this document..............................4
2. Terminology.................................................4
3. LSP Resource Recording......................................4
3.1. Component Interface Identifier RRO Subobject...........5
3.2. Processing of Component Interface ID RRO Subobject.....6
4. Signaling Component Interface Identifier in ERO.............7
4.1. Component Interface ID ERO Subobject...................7
4.2. Processing of Component Interface ID ERO Subobject.....8
5. Backward Compatibility.....................................10
6. Security Considerations....................................10
7. IANA Considerations........................................10
8. References.................................................11
8.1. Normative References..................................11
9. Acknowledgments............................................12
10. Copyright.................................................13
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1. Introduction
In GMPLS networks [RFC3945] where unbundled (being either Packet-
Switching Capable, Layer2-Switching Capable, Time Division
Multiplexing or Lambda-Switching Capable) Traffic Engineering (TE)
Links are used, one of the types of resources that an LSP originator
could control and record are the component links used by non-
neighboring nodes on the LSP path. The resource control and
recording is done by the use of the EXPLICIT_ROUTE object (ERO) and
RECORD_ROUTE object (RRO), respectively.
Link Bundling, introduced in [RFC4201], is used to improve routing
scalability by reducing the amount of TE related information that
need to be flooded and handled by IGP in a TE network. This is
accomplished by aggregating and abstracting the TE Link components.
In some cases the component link selection/recording within a TE
link is left as a local decision (ERO and RRO contains only TE
links). However there are cases when it is desirable for a non-local
(e.g., LSP head-end) node to make this selection. The use of such
information has found since so far three main applications (while
not excluding others unknown at the time of writing): diagnostic,
association of component specific attributes for which the bundled
information is too coarse (e.g., Shared Risk Link Groups) and thus
blocking SRLG-disjoint LSP establishment, allocation of labels at
network edges, and notification in case of failures. The latter is
useful when a single TE link interconnects two parts of the network.
In case one of its components fails notifying a complete TE link
failure leaves the network disconnected. In either case, it is
required to know which component link within a bundled TE link has
been used for a given LSP. For these cases, the TE Link and the
Label currently specified in the ERO/RRO are not enough and the
component link needs to be specified along with the label. In the
case of bi-directional Label Switched Paths (LSP) both upstream
and downstream information may be specified. Therefore, explicit
resource control and recording over a bundled TE link also requires
ability to specify a component link within the TE link.
Another important assumption of this document is that the identifier
space used for component link identification are unique for a given
node (following [RFC4201]). The reason stems as follows: most
experimental developments started with TE links composed by a single
component link and then only bundling was added by grouping them.
Component links where thus identified such that they could mimic the
behavior of TE link processing. This also justifies the experimental
status of this document.
This document defines extensions to and describes the use of RSVP-TE
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[RFC3209], [RFC3471], [RFC3473] to specify the component link
identifier for resource recording and explicit resource control over
TE link bundles. Specifically, in this document, component interface
identifier RRO and ERO subobjects are defined to complement their
Label RRO and ERO counterparts. Furthermore, procedures for
processing component interface identifier RRO and ERO subobjects and
how they can co-exist with the Label RRO and ERO subobjects are
specified.
Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC 2119 significance.
In this document, the characters ">>" preceding an indented line(s)
indicates a compliance requirement statement using the key words
listed above. This convention aids reviewers in quickly identifying
or finding the explicit compliance requirements of this RFC.
2. Terminology
o) TE Link: Unless specified otherwise, it refers to a bundled
Traffic Engineering link as defined in [RFC4201]. Furthermore, the
terms TE Link and bundled TE Link are used interchangeably in this
document.
o) Component (interface) link: refers (locally) to a link that is
part of a bundled TE link as described in RFC4201.
o) Component Interface Identifier: Refers to an ID used to uniquely
identify a Component Interface. on a bundled link a combination of
<component link identifier, label> is sufficient to unambiguously
identify the appropriate resources used by an LSP. The IDs used for
component link identification are unique for a given node [RFC4201].
3. LSP Resource Recording
LSP Resource Recording refers to the ability to record the resources
used by an LSP.
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The procedure for unbundled numbered TE links is described in
[RFC3209] and for unbundled unnumbered TE links in [RFC3477]. For
the purpose of recording LSP resources used over bundled TE Links,
the Component Interface Identifier RRO sub-object is introduced.
3.1. Component Interface Identifier RRO subobject
A new subobject of the Record Route object (RRO) is used to record
component interface identifier of a (bundled) TE Link. This
subobject 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length |U| Reserved (must be zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IPv4, IPv6 or unnumbered Component Interface Identifier //
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L: 1 bit
This bit must be set to 0.
Type
Type 10 (TBD): Component Interface identifier IPv4
Type 11 (TBD): Component Interface identifier IPv6
Type 12 (TBD): Component Interface identifier Unnumbered
Length
Component Link Record. & Resource Control for TE Link Bundles
The Length contains the total length of the subobject in
bytes, including the Type and Length fields. The Length is
8 bytes for the Component Interface identifier IPv4 and
Component Interface identifier Unnumbered types. For
Component Interface identifier IPv6 type of sub-object, the
length field is 20 bytes.
U: 1 bit
This bit indicates the direction of the component interface.
It is set to 0 for the downstream interface.
It is set to 1 for the upstream interface and is only used for
bi-directional LSPs.
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3.2. Processing of Component Interface identifier RRO Subobject
If a node desires component link recording, the "Component Link
Recording desired" flag (value TBD) should be set in the
LSP_ATTRIBUTES object, object that is defined in [RFC5420].
Setting of "Component Link Recording desired" flag is independent of
the Label Recording flag in SESSION_ATTRIBUTE object as specified in
[RFC3209]. Nevertheless, the following combinations are valid:
1) If both Label and Component Link flags are clear, then neither
Labels nor Component Links are recorded.
2) If Label Recording flag is set and Component Link flag is
clear, then only Label Recording is performed as defined in
[RFC3209].
3) If Label Recording flag is clear and Component Link flag is
set, then Component Link Recording is performed as defined in
this document.
4) If both Label Recording and Component Link flags are set, then
Label Recording is performed as defined in [RFC3209] and also
Component Link recording is performed as defined in this
document.
In most cases, a node initiates recording for a given LSP by adding
the RRO to the Path message. If the node desires Component Link
recording and if the outgoing TE link is bundled, then the initial
RRO contains the Component Link identifier (numbered or unnumbered)
as selected by the sender. As well, the Component Link Recording
desired flag is set in the LSP_ATTRIBUTE object. If the node also
desires label recording, it sets the Label_Recording flag in the
SESSION_ATTRIBUTE object.
When a Path message with the "Component Link Recording desired" flag
set is received by an intermediate node, if a new Path message is to
be sent for a downstream bundled TE link, the node adds a new
Component Link subobject to the RECORD_ROUTE object (RRO) and
appends the resulting RRO to the Path message before transmission.
Note also that, unlike Labels, Component Link identifiers are always
known on receipt of the Path message.
When the destination node of an RSVP session receives a Path message
with an RRO and the "Component Link Recording desired" flag set,
this indicates that the sender node needs TE route as well as
component link recording. The destination node initiates the RRO
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process by adding an RRO to Resv messages. The processing mirrors
that of the Path messages. The Component Interface Record subobject
is pushed onto the RECORD_ROUTE object (RRO) prior to pushing on the
node"s IP address. A node MUST NOT push on a Component Interface
Record subobject without also pushing on the IP address or
unnumbered Interface Id subobject that identifies the TE Link.
When component interfaces are recorded for unidirectional LSPs, the
downstream interface is the one identified by the Component
Interface subobject. For bi-directional LSPs, component interface
RRO subobjects for both downstream and upstream interfaces MUST be
included.
4. Signaling Component Interface Identifier in ERO
4.1. Component Interface Identifier ERO subobject
A new oPTIoNAL subobject of the EXPLICIT_ROUTE object (ERO) is used
to specify component interface identifier of a bundled TE Link.
This Component Interface Identifier subobject 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length |U| Reserved (MUST be zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IPv4, IPv6 or unnumbered Component Interface Identifier //
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L: 1 bit
This bit must be set to 0.
Type
Type 10 (TBD): Component Interface identifier IPv4
Type 11 (TBD): Component Interface identifier IPv6
Type 12 (TBD): Component Interface identifier Unnumbered
Length
The Length contains the total length of the subobject in
bytes, including the Type and Length fields. The Length is
8 bytes for the Component Interface identifier types: IPv4
and Component Interface identifier Unnumbered. For Component
Interface identifier IPv6 type of sub-object, the length field
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is 20 bytes.
U: 1 bit
This bit indicates the direction of the component interface.
It is 0 for the downstream interface. It is set to 1 for the
upstream interface and is only used for bi-directional LSPs.
4.2. Processing of Component Interface Identifier ERO Subobject
The Component Interface Identifier ERO subobject follows a subobject
containing the IP address, or the link identifier [RFC3477],
associated with the TE link on which it is to be used. It is used to
identify the component of a bundled TE Link.
The following SHOULD result in "Bad EXPLICIT_ROUTE object" error
being sent upstream by a node processing an ERO that contains the
Component Interface ID sub-object:
o) The first component interface identifier subobject is not
preceded by a sub-object containing an IPv4 or IPv6 address, or
an interface identifier [RFC3477], associated with a TE link.
o) The Component Interface Identifier ERO subobject follows a
subobject that has the L-bit set.
o) on unidirectional LSP setup, there is a Component Interface
Identifier ERO subobject with the U-bit set.
o) Two Component Interface Identifier ERO subobjects with the same
U-bit values exist.
If a node implements the component interface identifier subobject,
it MUST check if it represents a component interface in the bundled
TE Link specified in the preceding subobject that contains the
IPv4/IPv6 address or interface identifier of the TE Link. If the
content of the component interface identifier subobject does not
match a component interface in the TE link, a "Bad EXPLICIT_ROUTE
object" error SHOULD be reported as "Routing Problem" (error code
24).
If U-bit of the subobject being examined is cleared (0) and the
upstream interface specified in this subobject is acceptable, then
the value of the upstream component interface is translated locally
in the TLV of the IF_ID RSVP_HOP object [RFC3471]. The local
decision normally used to select the upstream component link is
bypassed except for local translation into the outgoing interface
identifier from the received incoming remote interface identifier.
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If this interface is not acceptable, a "Bad EXPLICIT_ROUTE object"
error SHOULD be reported as "Routing Problem" (error code 24).
If the U-bit of the subobject being examined is set (1), then the
value represents the component interface to be used for upstream
traffic associated with the bidirectional LSP. Again, if this
interface is not acceptable or if the request is not one for a
bidirectional LSP, then a "Bad EXPLICIT_ROUTE object" error SHOULD
be reported as "Routing Problem" (error code 24). otherwise, the
component interface IP address/ identifier is copied into a TLV sub-
object as part of the IF_ID RSVP_HOP object. The local decision
normally used to select the upstream component link is bypassed
except for local translation into the outgoing interface identifier
from the received incoming remote interface identifier.
The IF_ID RSVP_HOP object constructed as above MUST be included in
the corresponding outgoing Path message.
Note that, associated with a TE Link sub-object in the ERO, either
the (remote) upstream component interface or the (remote) downstream
component interface or both may be specified. As specified in
[RFC4201] there is no relationship between the TE Link type
(numbered or unnumbered) and the Link type of any one of its
components.
The Component Interface Identifier ERO subobject is optional.
Similarly, presence of the Label ERO sub-objects is not mandatory
[RFC3471], [RFC3473]. Furthermore, component interface identifier
ERO subobject and Label ERO subobject may be included in the ERO
independently of each other. one of the following alternatives
applies:
o) When both sub-objects are absent, a node may select any
appropriate component link within the TE link and any label on
the selected component link.
o) When the Label subobject is only present for a bundled link, then
the selection of the component link within the bundle is a local
decision and the node may select any appropriate component link,
which can assume the label specified in the Label ERO.
o) When only the component interface identifier ERO subobject is
present, a node MUST select the component interface specified in
the ERO and may select any appropriate label value at the
specified component link.
o) When both component interface identifier ERO subobject and Label
ERO subobject are present, the node MUST select the locally
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corresponding component link and the specified label value on
that component link. When present, both subobjects may appear in
any relative order to each other but they MUST appear after the
TE Link subobject that they refer to.
After processing, the component interface identifier subobjects are
removed from the ERO.
Inferred from above, the interface subobject should never be the
first subobject in a newly received message. If the component
interface subobject is the first subobject in a received ERO, then
it SHOULD be treated as a "Bad strict node" error.
Note: Information to construct the Component Interface ERO subobject
MAY come from the same mean used to populate the label ERO
subobject. Procedures by which an LSR at the head-end of an LSP
obtains the information needed to construct the Component Interface
subobject are outside the scope of this document.
5. Backward Compatibility
The extensions specified in this document do not affect the
processing of the RRO, ERO at nodes that do not support them. A node
that does not support the Component Interface RRO subobject but that
does support Label subobject SHOULD only insert the Label subobject
in the RRO as per [RFC3471] and [RFC3473].
A node that receives an ERO that contains a Component Link ID
subobject SHOULD send "Bad EXPLICIT_ROUTE object" if it does not
implement this subobject.
Per [RFC3209], Section 4.4.5, a non-compliant node that receives an
RRO that contains Component Interface Identifier sub-objects should
ignore and pass them on. This limits the full applicability of if
nodes traversed by the LSP are compliant with the proposed
extensions.
6. Security Considerations
An implementation of the extensions described in this document does
exposes the component interface identifiers to other nodes in the
network. If this is considered confidential information the
mechanisms described in [RFC5920] should be considered.
7. IANA Considerations
This document introduces the following RSVP protocol elements:
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o) Component Interface Identifier RRO subobject of the RECORD_ROUTE
object (RRO):
. IANA registry: RSVP PARAMETERS
. Registry Name: Class Names, Class Numbers, and Class Types
. Reference: [RFC3936]
. Following subobjects have been added to the existing entry for:
21 RECORD_ROUTE
. Type 10 (TBD): Component Interface identifier IPv4
. Type 11 (TBD): Component Interface identifier IPv6
. Type 12 (TBD): Component Interface identifier Unnumbered
o) Component Interface Identifier subobject of the EXPLICIT_ROUTE
object (ERO).
. IANA registry: RSVP PARAMETERS
. Registry Name: Class Names, Class Numbers, and Class Types
. Reference: [RFC3936]
. Following subobjects have been added to the existing entry for:
20 EXPLICIT_ROUTE
. Type 10 (TBD): Component Interface identifier IPv4
. Type 11 (TBD): Component Interface identifier IPv6
. Type 12 (TBD): Component Interface identifier Unnumbered
o) A new "Component Link Recording desired" flag (value TBD)
of the LSP_ATTRIBUTES object [RFC5420]:
. Bit Flag: 0x80
. Name: Local Component Link Recording desired
8. References
8.1. Normative References
[RFC2205] R.Braden, et al., "Resource ReSerVation Protocol (RSVP)
Version 1, Functional Specification", RFC 2205,
September 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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Component Link Recording & Resource Control for TE Links April 27, 2011
[RFC2234] Crocker, D. and overell, P. (Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
[RFC3209] D.Awduche, et al., "Extensions to RSVP for LSP Tunnels",
RFC 3209, December 2001.
[RFC3471] L.Berger, et al., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC3473] L.Berger, et al., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
3473, January 2003.
[RFC3477] K.Kompella, et al., "Signaling Unnumbered Links in
Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, January 2003.
[RFC3945] E.Mannie, et al., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC4201] K.Kompella, et al., "Link Bundling in MPLS Traffic
Engineering", RFC 4201, January 2003.
[RFC5420] A.Farrel, et al., "Encoding of Attributes for
Multiprotocol Label Switching (MPLS) Label Switched Path
(LSP) Establishment Using Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE)", RFC 5420.
[RFC5920] L.Fang, "Security Framework for MPLS and GMPLS Networks",
RFC 5920, July 2010.
9. Acknowledgments
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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10. Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions
Relating to IETF Documents (http://trustee.ietf.org/license-info)
in effect on the date of publication of this document. Please
review these documents carefully, as they describe your rights and
restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License
text as described in Section 4.e of the Trust Legal Provisions and
are provided without warranty as described in the Simplified BSD
License.
Authors Addresses
Anca Zamfir
Cisco Systems Inc.
Email: ancaz@cisco.com
Zafar Ali
Cisco systems Inc.
Email: zali@cisco.com
Dimitri Papadimitriou
Alcatel-Lucent Bell
Email: dimitri.papadimitriou@alcatel-lucent.com
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