One document matched: draft-ietf-ccamp-rsvp-te-domain-subobjects-02.xml
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<rfc ipr="trust200902" category="exp" docName="draft-ietf-ccamp-rsvp-te-domain-subobjects-02" obsoletes="" updates="" submissionType="IETF" xml:lang="en">
<front>
<title abbrev="DOMAIN SUBOBJ">Domain Subobjects for Resource
ReserVation Protocol - Traffic Engineering (RSVP-TE)</title>
<author initials="D" surname="Dhody" fullname="Dhruv Dhody">
<organization>Huawei Technologies</organization>
<address>
<postal>
<street>Leela Palace</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560008</code>
<country>INDIA</country>
</postal>
<email>dhruv.ietf@gmail.com</email>
</address>
</author>
<author initials="U" surname="Palle" fullname="Udayasree Palle">
<organization>Huawei Technologies</organization>
<address>
<postal>
<street>Leela Palace</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560008</code>
<country>INDIA</country>
</postal>
<email>udayasree.palle@huawei.com</email>
</address>
</author>
<author initials="V" surname="Kondreddy" fullname="Venugopal Reddy Kondreddy">
<organization>Huawei Technologies</organization>
<address>
<postal>
<street>Leela Palace</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560008</code>
<country>INDIA</country>
</postal>
<email>venugopalreddyk@huawei.com</email>
</address>
</author>
<author initials="R" surname="Casellas" fullname="Ramon Casellas">
<organization>CTTC</organization>
<address>
<postal>
<street>Av. Carl Friedrich Gauss n7</street>
<city>Castelldefels</city>
<region>Barcelona </region>
<code>08860</code>
<country>SPAIN</country>
</postal>
<email>ramon.casellas@cttc.es </email>
</address>
</author>
<date month="July" year="2014" />
<area>Routing</area>
<workgroup>CCAMP Working Group</workgroup>
<abstract>
<t>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. </t>
<t>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.</t>
</abstract>
</front>
<middle>
<section title="Introduction" toc="default">
<t>The RSVP-TE specification <xref target="RFC3209"/> and the GMPLS extensions
to RSVP-TE <xref target="RFC3473"/> allow abstract nodes and resources to be
explicitly included in a path setup using the Explicit Route Object (ERO). </t>
<t>Further Exclude Routes extensions <xref target="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. </t>
<t><xref target="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. </t>
<t>This document extends the notion of abstract nodes by adding new subobjects
for IGP Areas and 4-byte AS numbers (as per <xref target="RFC6793"/>). These
subobjects MAY be included in Explicit Route Object (ERO), Exclude Route Object
(XRO) or Explicit Exclusion Route Subobject (EXRS).</t>
<t>In case of per-domain path computation <xref target="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 <xref target="SEC_E"/>.</t>
<t>Further, the domain
identifier may simply act as delimiter to specify where the domain boundary
starts and ends.</t>
<t>This is a companion document to Path Computation Element Protocol (PCEP)
extensions for the domain sequence <xref target="PCE-DOMAIN"/>. </t>
<section title="Requirements Language" toc="default">
<t>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 <xref target="RFC2119"/>.</t>
</section>
</section>
<section title="Terminology" toc="default">
<t>The following terminology is used in this document.</t>
<t>
<list style="hanging">
<t hangText="AS:">Autonomous System.</t>
<t hangText="Domain:">As per <xref target="RFC4655"/>, any collection
of network elements within a common sphere of address management or path
computational responsibility. Examples of domains include Interior
Gateway Protocol (IGP) areas and Autonomous Systems (ASs).</t>
<t hangText="ERO:">Explicit Route Object</t>
<t hangText="EXRS:">Explicit Exclusion Route Subobject</t>
<t hangText="IGP:">Interior Gateway Protocol. Either of the two routing
protocols, Open Shortest Path First (OSPF) or Intermediate System to
Intermediate System (IS-IS).</t>
<t hangText="IS-IS:">Intermediate System to Intermediate System.</t>
<t hangText="OSPF:">Open Shortest Path First.</t>
<t hangText="PCE:">Path Computation Element. An entity (component,
application, or network node) that is capable of computing a network
path or route based on a network graph and applying computational
constraints.</t>
<t hangText="PCEP:">Path Computation Element Protocol.</t>
<t hangText="RSVP:">Resource Reservation Protocol</t>
<t hangText="TE LSP:">Traffic Engineering Label Switched Path.</t>
<t hangText="XRO:">Exclude Route Object</t>
</list>
</t>
</section>
<section title="Subobjects for Domains" toc="default">
<section title="Domains" toc="default">
<t><xref target="RFC4726"/> and <xref target="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.</t>
<t>As per <xref target="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.</t>
<t>The sub-objects MAY appear in RSVP-TE, notably in - </t>
<t>
<list style="symbols">
<t>Explicit Route Object (ERO): As per <xref target="RFC3209"/>, an explicit
route is a particular path in the network topology including abstract nodes
(domains). </t>
<t>Exclude Route Object (XRO): As per <xref target="RFC4874"/>, an exclude
route identifies a list of abstract nodes (domains) that should not be
traversed along the path of the LSP being established. </t>
<t>Explicit Exclusion Route Subobject (EXRS): As per <xref target="RFC4874"/>,
used to specify exclusion of certain abstract nodes between a specific pair
of nodes. EXRS are a subobject carried inside the ERO. These subobjects are
used to specify the domains that must be excluded between two abstract nodes.</t>
</list>
</t>
</section>
<section title="Explicit Route Object (ERO)'s Subobjects" toc="default">
<t>As stated in <xref target="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. </t>
<t>Some subobjects are defined in <xref target="RFC3209"/>, <xref target="RFC3473"/>,
<xref target="RFC3477"/>, <xref target="RFC4874"/> and <xref target="RFC5553"/> but
new subobjects related to domains are needed.</t>
<t>The following subobject types are used in ERO.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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
]]></artwork>
</figure>
</t>
<t>This document extends the above list to support 4-Byte AS numbers and IGP Areas.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Type Subobject
TBD Autonomous system number (4 Byte)
TBD OSPF Area id
TBD ISIS Area id
]]></artwork>
</figure>
</t>
<section title="Autonomous system" toc="default" anchor="sec_ero_as">
<t><xref target="RFC3209"/> already defines 2-Byte AS number.</t>
<t>To support 4-Byte AS numbers as per <xref target="RFC6793"/>, the following subobject is defined: </t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>
<list style="hanging">
<t hangText="L:">The L bit is an attribute of the subobject as defined in
<xref target="RFC3209"/>.</t>
<t hangText="Type:">(TBA by IANA) indicating a 4-Byte AS Number.</t>
<t hangText="Length:">8 (Total length of the subobject in bytes).</t>
<t hangText="Reserved:">Zero at transmission, ignored at receipt.</t>
<t hangText="AS-ID:">The 4-Byte AS Number. Note that if 2-Byte AS numbers
are in use, the low order bits (16 through 31) should be used and the
high order bits (0 through 15) should be set to zero. </t>
</list>
</t>
</section>
<section title="IGP Area" toc="default" anchor="sec_ero_area">
<t>Since the length and format of Area-id is different for OSPF and ISIS,
the following two subobjects are defined: </t>
<t>For OSPF, the area-id is a 32 bit number. The subobject is encoded
as follows: </t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>
<list style="hanging">
<t hangText="L:">The L bit is an attribute of the subobject as defined
in <xref target="RFC3209"/>.</t>
<t hangText="Type:">(TBA by IANA) indicating a 4-Byte OSPF Area ID.</t>
<t hangText="Length:">8 (Total length of the subobject in bytes).</t>
<t hangText="Reserved:">Zero at transmission, ignored at receipt.</t>
<t hangText="OSPF Area Id:">The 4-Byte OSPF Area ID.</t>
</list>
</t>
<t>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
<xref target="ISO10589"/>. The subobject is encoded as follows:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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 //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>
<list style="hanging">
<t hangText="L:">The L bit is an attribute of the subobject as
defined in <xref target="RFC3209"/>.</t>
<t hangText="Type:">(TBA by IANA) indicating IS-IS Area ID.</t>
<t hangText="Length:">Variable. As per <xref target="RFC3209"/>,
the total length of the subobject in bytes, including the L, Type
and Length fields. The Length MUST be at least 4, and MUST be a
multiple of 4.</t>
<t hangText="Area-Len:">Variable (Length of the actual (non-padded)
IS-IS Area Identifier in octets; Valid values are from 2 to 11
inclusive). </t>
<t hangText="Reserved:">Zero at transmission, ignored at receipt.</t>
<t hangText="IS-IS Area Id:">The variable-length IS-IS area identifier.
Padded with trailing zeroes to a four-byte boundary.</t>
</list>
</t>
</section>
<section title="Mode of Operation" toc="default">
<t>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). </t>
<t>All the rules of processing (for example Next Hop Selection, L bit
processing, unrecognized subobjects etc) are as per the
<xref target="RFC3209"/>. </t>
</section>
</section>
<section title="Exclude Route Object (XRO)'s Subobjects" toc="default">
<t>As stated in <xref target="RFC4874"/>, the exclude route identifies
a list of abstract nodes that should not be traversed along the path
of the LSP being established. </t>
<t>Some subobjects are defined in <xref target="RFC3209"/>,
<xref target="RFC3477"/>, <xref target="RFC4874"/> and
<xref target="RFC6001"/> but new subobjects related to
domains are needed.</t>
<t>The following subobject types are used in XRO.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Type Subobject
1 IPv4 prefix
2 IPv6 prefix
3 Label
4 Unnumbered Interface ID
32 Autonomous system number (2 Byte)
34 SRLG
]]></artwork>
</figure>
</t>
<t>This document extends the above list to support
4-Byte AS numbers and IGP Areas.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Type Subobject
TBD Autonomous system number (4 Byte)
TBD OSPF Area id
TBD ISIS Area id
]]></artwork>
</figure>
</t>
<section title="Autonomous system" toc="default">
<t><xref target="RFC3209"/> and <xref target="RFC4874"/> already
define a 2-Byte AS number.</t>
<t>To support 4-Byte AS numbers as per <xref target="RFC6793"/>,
a subobject is with the same format as defined in
<xref target="sec_ero_as"/> with following difference:</t>
<t>The meaning of the L bit (similar to <xref target="RFC4874"/>).</t>
<t>
<list style="hanging">
<t hangText="0:">indicates that the abstract node (AS) specified
MUST be excluded.</t>
<t hangText="1:">indicates that the abstract node (AS) specified
SHOULD be avoided.</t>
</list>
</t>
</section>
<section title="IGP Area" toc="default">
<t>Since the length and format of Area-id is different for OSPF
and ISIS, the following two subobjects are defined: </t>
<t>For OSPF, the area-id is a 32 bit number.
Subobjects for OSPF and IS-IS are of the
same format as defined in
<xref target="sec_ero_area"/> with following difference:
</t>
<t>The meaning of the L bit (similar to <xref target="RFC4874"/>).</t>
<t>
<list style="hanging">
<t hangText="0:">indicates that the abstract node (OSPF or IS-IS Area)
specified MUST be excluded.</t>
<t hangText="1:">indicates that the abstract node (OSPF or IS-IS Area)
specified SHOULD be avoided.</t>
</list>
</t>
</section>
<section title="Mode of Operation" toc="default">
<t>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). </t>
<t>All the rules of processing are as per the <xref target="RFC4874"/>. </t>
</section>
</section>
<section title="Explicit Exclusion Route Subobject" toc="default">
<t>As per <xref target="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.</t>
<t>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.</t>
<t>All the rules of processing are as per the <xref target="RFC4874"/>. </t>
</section>
</section>
<section title="Interaction with Path Computation Element (PCE)" toc="default">
<t>The domain subobjects to be used in Path Computation Element
Protocol (PCEP) are referred to in <xref target="PCE-DOMAIN"/>. Note that the
new domain subobjects follow the principle that subobjects used in
PCEP <xref target="RFC5440"/> are identical to the subobjects used in RSVP-TE and
thus are interchangeable between PCEP and RSVP-TE.</t>
</section>
<section title="IANA Considerations" toc="default">
<section title="New Subobjects" toc="default">
<t>IANA registry: RSVP PARAMETERS</t>
<t>Subsection: Class Names, Class Numbers, and Class Types</t>
<t>IANA is requested to add further subobjects to the existing entry for:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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.]
]]></artwork>
</figure>
</t>
</section>
</section>
<section title="Security Considerations" toc="default">
<t>Security considerations for MPLS-TE and GMPLS signaling are
covered in <xref target="RFC3209"/> and <xref target="RFC3473"/>.
This document does not introduce any new messages or any
substantive new processing, and so those security
considerations continue to apply. </t>
<t>The route exclusion security consideration are covered in
<xref target="RFC4874"/> and continue to apply. </t>
</section>
<section title="Acknowledgments" toc="default">
<t>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.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119.xml" ?>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.3209.xml" ?>
<?rfc include="reference.RFC.3473.xml" ?>
<?rfc include="reference.RFC.3477.xml" ?>
<?rfc include="reference.RFC.4655.xml" ?>
<?rfc include="reference.RFC.4726.xml" ?>
<?rfc include="reference.RFC.4874.xml" ?>
<?rfc include="reference.RFC.5152.xml" ?>
<?rfc include="reference.RFC.5440.xml" ?>
<?rfc include="reference.RFC.5553.xml" ?>
<?rfc include="reference.RFC.6001.xml" ?>
<?rfc include="reference.RFC.6793.xml" ?>
<!--PCE-DOMAIN-->
<reference anchor="PCE-DOMAIN">
<front>
<title>Standard Representation Of Domain Sequence. (draft-ietf-pce-pcep-domain-sequence)</title>
<author initials="D" surname="Dhody" fullname="Dhody D">
<organization />
</author>
<author initials="U" surname="Palle" fullname="Palle U">
<organization />
</author>
<author initials="R" surname="Casellas" fullname="Casellas R">
<organization />
</author>
<date month="July" year="2014" />
</front>
</reference>
<!--ISO-->
<reference anchor="ISO10589">
<front>
<title>
Intermediate system to Intermediate system routing information
exchange protocol for use in conjunction with the Protocol for
providing the Connectionless-mode Network Service (ISO
8473)
</title>
<author fullname="ISO">
<organization >ISO</organization>
</author>
<date month="" year="1992"/>
</front>
<seriesInfo name="ISO/IEC" value="10589:2002"/>
</reference>
</references>
<section title="Examples" toc="default" anchor="SEC_E">
<t>These examples are for illustration purposes only, to show
how the new subobjects may be encoded.</t>
<section title="Inter-Area LSP Path Setup" toc="default">
<t>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. </t>
<t>
<figure title="Domain Corresponding to IGP Area" anchor="fig1" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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)
]]></artwork>
</figure>
</t>
<t>As per <xref target="fig1"/>, the signaling at Ingress MAY be - </t>
<t>ERO:(A1, ABF1, Area B, Area C, Egress); or </t>
<t>ERO:(A1, ABF1, AS 100, Area B, AS 100, Area C, Egress). </t>
<t>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
<xref target="RFC3209"/>. </t>
</section>
<section title="Inter-AS LSP Path Setup" toc="default">
<section title="Example 1" toc="default">
<t>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. </t>
<t>
<figure title="Domain Corresponding to AS" anchor="fig2" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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)
]]></artwork>
</figure>
</t>
<t>As per <xref target="fig2"/>, the signaling at Ingress MAY be - </t>
<t>ERO:(A1, A2, AS B, AS C, Egress); or </t>
<t>ERO:(A1, A2, AS B, Area 0, AS C, Area 0, Egress). </t>
<t>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
<xref target="RFC3209"/>.</t>
<t>Note that to get a domain disjoint path, the ingress may also
signal the backup path with -</t>
<t>XRO:(AS B)</t>
</section>
<section title="Example 2" toc="default">
<t>As shown in <xref target="fig3"/>, where AS 200 is made up of
multiple areas, the signaling MAY include both AS and Area subobject
to uniquely identify a domain.</t>
<t>
<figure title="Domain Corresponding to AS and Area" anchor="fig3" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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
]]></artwork>
</figure>
</t>
<t>As per <xref target="fig3"/>, the signaling at Ingress MAY be - </t>
<t>ERO:(X1, AS 200, Area D, Area B, Area C, Egress). </t>
<t>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 <xref target="RFC3209"/> with
respect to subobjects. </t>
</section>
</section>
</section>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 16:23:57 |