| CCAMP Working Group | D. Dhody |
| Internet-Draft | U. Palle |
| Intended status: Experimental | V. Kondreddy |
| Expires: January 2, 2015 | Huawei Technologies |
| R. Casellas | |
| CTTC | |
| July 1, 2014 |
Domain Subobjects for Resource ReserVation Protocol - Traffic Engineering (RSVP-TE)
draft-ietf-ccamp-rsvp-te-domain-subobjects-02
The Resource ReserVation Protocol - Traffic Engineering (RSVP-TE) specification and the Generalized Multiprotocol Label Switching (GMPLS) extensions to RSVP-TE allow abstract nodes and resources to be explicitly included in a path setup. Further Exclude Routes extensions to RSVP-TE allow abstract nodes and resources to be explicitly excluded in a path setup.
This document specifies new subobjects to include or exclude domains during path setup where domain is a collection of network elements within a common sphere of address management or path computational responsibility (such as an Interior Gateway Protocol (IGP) area or an Autonomous System (AS)). Note that the use of AS as an abstract node representing domain is already defined in existing RSVP-TE specefications, albeit with a 2-Byte AS number.
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The RSVP-TE specification [RFC3209] and the GMPLS extensions to RSVP-TE [RFC3473] allow abstract nodes and resources to be explicitly included in a path setup using the Explicit Route Object (ERO).
Further Exclude Routes extensions [RFC4874] allow abstract nodes or resources to be excluded from the whole path using the Exclude Route object (XRO). To exclude certain abstract nodes or resources between a specific pair of abstract nodes present in an ERO, a Explicit Exclusion Route Subobject (EXRS) is used.
[RFC3209] already describes the notion of abstract nodes, where an abstract node is a group of nodes whose internal topology is opaque to the ingress node of the Label Switched Path (LSP). It further defines a subobject for AS, but with a 2-Byte AS number only.
This document extends the notion of abstract nodes by adding new subobjects for IGP Areas and 4-byte AS numbers (as per [RFC6793]). These subobjects MAY be included in Explicit Route Object (ERO), Exclude Route Object (XRO) or Explicit Exclusion Route Subobject (EXRS).
In case of per-domain path computation [RFC5152], where the full path of an inter-domain TE LSP cannot be or is not determined at the ingress node, and signaling message may use domain identifiers. The use of these new subobjects is illustrated in Appendix A.
Further, the domain identifier may simply act as delimiter to specify where the domain boundary starts and ends.
This is a companion document to Path Computation Element Protocol (PCEP) extensions for the domain sequence [PCE-DOMAIN].
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 [RFC2119].
The following terminology is used in this document.
[RFC4726] and [RFC4655] define domain as a separate administrative or geographic environment within the network. A domain may be further defined as a zone of routing or computational ability. Under these definitions a domain might be categorized as an AS or an IGP area.
As per [RFC3209], an abstract node is a group of nodes whose internal topology is opaque to the ingress node of the LSP. Using this concept of abstraction, an explicitly routed LSP can be specified as a sequence of IP prefixes or a sequence of Autonomous Systems. In this document we extend the notion to include IGP area and 4-Byte AS number.
The sub-objects MAY appear in RSVP-TE, notably in -
As stated in [RFC3209], an explicit route is a particular path in the network topology. In addition to the ability to identify specific nodes along the path, an explicit route can identify a group of nodes (abstract nodes) that must be traversed along the path.
Some subobjects are defined in [RFC3209], [RFC3473], [RFC3477], [RFC4874] and [RFC5553] but new subobjects related to domains are needed.
The following subobject types are used in ERO.
Type Subobject
1 IPv4 prefix
2 IPv6 prefix
3 Label
4 Unnumbered Interface ID
32 Autonomous system number (2 Byte)
33 Explicit Exclusion (EXRS)
34 SRLG
64 IPv4 Path Key
65 IPv6 Path Key
This document extends the above list to support 4-Byte AS numbers and IGP Areas.
Type Subobject
TBD Autonomous system number (4 Byte)
TBD OSPF Area id
TBD ISIS Area id
[RFC3209] already defines 2-Byte AS number.
To support 4-Byte AS numbers as per [RFC6793], the following subobject is defined:
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 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AS-ID (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Since the length and format of Area-id is different for OSPF and ISIS, the following two subobjects are defined:
For OSPF, the area-id is a 32 bit number. The subobject is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OSPF Area Id (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For IS-IS, the area-id is of variable length and thus the length of the subobject is variable. The Area-id is as described in IS-IS by ISO standard [ISO10589]. The subobject is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Type | Length | Area-Len | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // IS-IS Area ID // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The new subobjects to support 4-Byte AS and IGP (OSPF / ISIS) Area MAY also be used in the ERO to specify an abstract node (a group of nodes whose internal topology is opaque to the ingress node of the LSP).
All the rules of processing (for example Next Hop Selection, L bit processing, unrecognized subobjects etc) are as per the [RFC3209].
As stated in [RFC4874], the exclude route identifies a list of abstract nodes that should not be traversed along the path of the LSP being established.
Some subobjects are defined in [RFC3209], [RFC3477], [RFC4874] and [RFC6001] but new subobjects related to domains are needed.
The following subobject types are used in XRO.
Type Subobject
1 IPv4 prefix
2 IPv6 prefix
3 Label
4 Unnumbered Interface ID
32 Autonomous system number (2 Byte)
34 SRLG
This document extends the above list to support 4-Byte AS numbers and IGP Areas.
Type Subobject
TBD Autonomous system number (4 Byte)
TBD OSPF Area id
TBD ISIS Area id
[RFC3209] and [RFC4874] already define a 2-Byte AS number.
To support 4-Byte AS numbers as per [RFC6793], a subobject is with the same format as defined in Section 3.2.1 with following difference:
The meaning of the L bit (similar to [RFC4874]).
Since the length and format of Area-id is different for OSPF and ISIS, the following two subobjects are defined:
For OSPF, the area-id is a 32 bit number. Subobjects for OSPF and IS-IS are of the same format as defined in Section 3.2.2 with following difference:
The meaning of the L bit (similar to [RFC4874]).
The new subobjects to support 4-Byte AS and IGP (OSPF / ISIS) Area MAY also be used in the XRO to specify exclusion of an abstract node (a group of nodes whose internal topology is opaque to the ingress node of the LSP).
All the rules of processing are as per the [RFC4874].
As per [RFC4874], the Explicit Exclusion Route defines abstract nodes or resources that must not or should not be used on the path between two inclusive abstract nodes or resources in the explicit route. EXRS is an ERO subobject that contains one or more subobjects of its own, called EXRS subobjects.
The EXRS subobject may carry any of the subobjects defined for XRO, thus the new subobjects to support 4-Byte AS and IGP (OSPF / ISIS) Area MAY also be used in the EXRS. The meanings of the fields of the new XRO subobjects are unchanged when the subobjects are included in an EXRS, except that scope of the exclusion is limited to the single hop between the previous and subsequent elements in the ERO.
All the rules of processing are as per the [RFC4874].
The domain subobjects to be used in Path Computation Element Protocol (PCEP) are referred to in [PCE-DOMAIN]. Note that the new domain subobjects follow the principle that subobjects used in PCEP [RFC5440] are identical to the subobjects used in RSVP-TE and thus are interchangeable between PCEP and RSVP-TE.
IANA registry: RSVP PARAMETERS
Subsection: Class Names, Class Numbers, and Class Types
IANA is requested to add further subobjects to the existing entry for:
20 EXPLICIT_ROUTE
232 EXCLUDE_ROUTE
Subobject Type Reference
TBA 4-Byte AS number [This I.D.]
TBA OSPF Area ID [This I.D.]
TBA IS-IS Area ID [This I.D.]
Security considerations for MPLS-TE and GMPLS signaling are covered in [RFC3209] and [RFC3473]. This document does not introduce any new messages or any substantive new processing, and so those security considerations continue to apply.
The route exclusion security consideration are covered in [RFC4874] and continue to apply.
We would like to thank Adrian Farrel, Lou Berger, George Swallow, Chirag Shah, Reeja Paul Sandeep Boina and Avantika for their useful comments and suggestions.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
These examples are for illustration purposes only, to show how the new subobjects may be encoded.
In an inter-area LSP path setup where the ingress and the egress belong to different IGP areas within the same AS, the domain subobjects MAY be represented using an ordered list of IGP area subobjects in an ERO.
D2 Area D
|
|
D1
|
|
********BD1******
* | *
* | * Area C
Area A * | *
* | *
Ingress------A1-----ABF1------B1------BC1------C1------Egress
/ * | *
/ * | *
/ * Area | B *
F1 * | *
/ ********BE1******
/ |
/ |
F2 E1
|
Area F |
E2 Area E
* All IGP Area in one AS (AS 100)
Figure 1: Domain Corresponding to IGP Area
As per Figure 1, the signaling at Ingress MAY be -
ERO:(A1, ABF1, Area B, Area C, Egress); or
ERO:(A1, ABF1, AS 100, Area B, AS 100, Area C, Egress).
The AS subobject is optional and it MAY be skipped. An RSVP-TE implementation should be able to understand both notations and there is no change in the processing rules as mentioned in [RFC3209].
In an inter-AS LSP path setup where the ingress and the egress belong to different AS, the domain subobjects MAY be represented using an ordered list of AS subobjects in an ERO.
AS A AS E AS C
<-------------> <----------> <------------->
A4----------E1---E2---E3---------C4
/ / \
/ / \
/ / AS B \
/ / <----------> \
Ingress------A1---A2------B1---B2---B3------C1---C2------Egress
\ / /
\ / /
\ / /
\ / /
A3----------D1---D2---D3---------C3
<---------->
AS D
* All AS have one area (area 0)
Figure 2: Domain Corresponding to AS
As per Figure 2, the signaling at Ingress MAY be -
ERO:(A1, A2, AS B, AS C, Egress); or
ERO:(A1, A2, AS B, Area 0, AS C, Area 0, Egress).
Each AS has a single IGP area (area 0), Area subobject is optional and it MAY be skipped as AS is enough to uniquely identify a domain. An RSVP-TE implementation should be able to understand both notations and there is no change in the processing rules as mentioned in [RFC3209].
Note that to get a domain disjoint path, the ingress may also signal the backup path with -
XRO:(AS B)
As shown in Figure 3, where AS 200 is made up of multiple areas, the signaling MAY include both AS and Area subobject to uniquely identify a domain.
Ingress *
| *
| *
X1 *
| \ *
| * \
|* \
* | \ Inter-AS
AS 100 * | \ Link
* | \
* | \
* | \
| D2 Area D
AS 200 | |
| |
Inter | D1
-AS | |
Link | |
A3 ********BD1******
| * | *
| * | * Area C
| Area A * | *
| * | *
A2------A1------AB1------B1------BC1------C1------Egress
* | *
* | *
* | *
* Area | B *
********BE1******
|
|
E1
|
|
E2 Area E
Figure 3: Domain Corresponding to AS and Area
As per Figure 3, the signaling at Ingress MAY be -
ERO:(X1, AS 200, Area D, Area B, Area C, Egress).
The combination of both an AS and an Area uniquely identifies a domain, note that an Area domain identifier always belongs to the previous AS that appears before it or, if no AS subobjects are present, it is assumed to be the current AS. Also note that there are no changes in the processing rules as mentioned in [RFC3209] with respect to subobjects.