One document matched: draft-dimitri-ccamp-gmpls-ason-routing-sol-01.txt
Differences from draft-dimitri-ccamp-gmpls-ason-routing-sol-00.txt
CCAMP Working Group Dimitri Papadimitriou
Internet Draft (Alcatel)
Category: Standard
Expiration Date: August 2006 March 2006
Link State Routing Protocols Extensions for ASON Routing
draft-dimitri-ccamp-gmpls-ason-routing-sol-01.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2006). All Rights Reserved.
Abstract
The Generalized MPLS (GMPLS) suite of protocols has been defined to
control different switching technologies as well as different
applications. These include support for requesting TDM connections
including SONET/SDH and Optical Transport Networks (OTNs).
This document provides the extensions of the IETF Link State Routing
Protocols to meet the routing requirements for an Automatically
Switched Optical Network (ASON) as defined by ITU-T.
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1. Conventions used in this document
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].
The reader is assumed to be familiar with the terminology and
requirements developed in [ASON-RR] and the evaluation outcomes
detailed in [ASON-EVAL].
2. Introduction
There are certain capabilities that are needed to support the ITU-T
Automatically Switched Optical Network (ASON) control plane
architecture as defined in [G.8080]. [ASON-RR] details the routing
requirements for the GMPLS suite of routing protocols to support the
capabilities and functionality of ASON control planes identified in
[G.7715] and in [G.7715.1].
[ASON-EVAL] evaluates the IETF Link State Routing Protocols against
the requirements identified in [ASON-RR]. Candidate routing protocols
are IGP (OSPFv2 and IS-IS).
ASON (Routing) terminology sections are provided in Appendix 1 and 2.
3. Reachability
3.1 OSPFv2
In order to advertise blocks of reachable address prefixes a
summarization mechanism is introduced that complements the
techniques described in [OSPF-NODE].
This extension takes the form of a network mask (a 32-bit number
indicating the range of IP addresses residing on a single IP
network/subnet). The set of local addresses are carried in an OSPF
TE LSA node attribute TLV (a specific sub-TLV is defined per address
family, e.g., IPv4 and IPv6).
The proposed solution is to advertise the local address prefixes of
a router as new sub-TLVs of the (OSPFv2 TE LSA) Node Attribute top
level TLV (of Type TBD). This document defines the following sub-
TLVs:
- Node IPv4 Local Prefix sub-TLV: Type 3 - Length: variable
- Node IPv6 Local Prefix sub-TLV: Type 4 - Length: variable
3.1.1 Node IPv4 local prefix sub-TLV
The node IPv4 local prefix sub-TLV has a type of 3 and contains one
or more local IPv4 prefixes. It has the following format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . .
. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The length is set to 8 * n where n is the number of local prefixes
included in the sub-TLV.
Network mask: A 32-bit number indicating the IPv4 address mask
for the advertised destination prefix.
Each <Network mask, IPv4 Address> pair listed as part of this sub-
TLV represents a reachable destination prefix hosted by the
advertising Router ID.
The local addresses that can be learned from TE LSAs i.e. router
address and TE interface addresses SHOULD not be advertised in the
node IPv4 local prefix sub-TLV.
3.1.2 Node IPv6 local prefix sub-TLV
The node IPv6 local prefix sub-TLV has a type of 4 and contains one
or more local IPv6 prefixes. IPv6 Prefix Representation uses RFC
2740 Section A.4.1. It 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PrefixLength | PrefixOptions | (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Address Prefix 1 |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . .
. . .
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. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PrefixLength | PrefixOptions | (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Address Prefix n |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PrefixLength: length in bits of the prefix.
PrefixOptions: 8-bit field describing various capabilities
associated with the prefix (see [RFC2740] Section A.4.2).
Address Prefix: encoding of the prefix itself as an even multiple of
32-bit words, padding with zero bits as necessary.
The Length is set to Sum[n][4 + #32-bit words/4] where n is the
number of local prefixes included in the sub-TLV.
The local addresses that can be learned from TE LSAs i.e. router
address and TE interface addresses SHOULD not be advertised in the
node IPv6 local prefix sub-TLV.
3.2 IS-IS
A similar mechanism does not exist for IS-IS as the Extended IP
Reachability TLV [RFC3784] focuses on IP reachable end-points
(terminating points), as its name indicates.
For this purpose, a new Extended TE Reachability TLV (Type TBD) is
defined as follows
7 octets of system Id and pseudonode number
1 octet of length of sub-TLVs
0-246 octets of sub-TLVs,
where each sub-TLV consists of a sequence of
1 octet of sub-type
1 octet of length of the value field of the sub-TLV
0-244 octets of value
Each sub-TLV (Type TBD) is either an IPv4 TE Reachability sub-TLV or
an IPv6 TE Reachability sub-TLV.
3.2.1 IPv4 TE Reachability sub-TLV
The "IPv4 TE Reachability" sub-TLV describes TE reachability through
the specification of a routing prefix, a bit to indicate if the
prefix is being advertised down from a higher level, and optionally
the existence of sub-TLVs to allow for later extension. The
following illustrates encoding of the Value field of this sub-TLV
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Reserved | Prefix Len| Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 6 bits of prefix length can have the values 0-32 and indicate
the number of significant bits in the prefix. The prefix is encoded
in the minimal number of octets for the given number of significant
bits. The remaining bits of prefix are transmitted as zero and
ignored upon receipt.
The U bit is described in Section 6.2.
3.2.2 IPv6 TE Reachability sub-TLV
The "IPv6 TE Reachability" sub-TLV describes TE reachability through
the specification of a routing prefix, a bit to indicate if the
prefix is being advertised down from a higher level, and optionally
the existence of sub-TLVs to allow for later extension. The
following illustrates encoding of the Value field of this sub-TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Reserved | Prefix Len | Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Prefix ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix ... |
+-+-+-+-+-+-+-+-+
The 8 bits of prefix length can have the values 0-128 and indicate
the number of significant bits in the prefix. Only the required
number of octets of prefix are present. This number can be computed
from the prefix length octet as follows:
prefix octets = integer of ((prefix length + 7) / 8)
The U bit is described in Section 6.2.
4. Link Attribute
4.1 Local Adaptation
The Local Adaptation is defined as TE link attribute (i.e. sub-TLV)
that describes the cross/inter-layer relationships.
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The Interface Switching Capability Descriptor (ISCD) TE Attribute
[RFC4202] identifies the ability of the TE link to support cross-
connection to another link within the same layer and the ability to
use a locally terminated connection that belongs to one layer as a
data link for another layer (adaptation capability). However, the
information associated to the ability to terminate connections
within that layer (referred to as the termination capability) is
embedded with the adaptation capability.
For instance, a link between two optical cross-connects will contain
at least one ISCD attribute describing LSC switching capability.
Whereas a link between an optical cross-connect and an IP/MPLS LSR
will contain at least two ISCD attributes: one for the description
of the LSC termination capability and one for the PSC adaptation
capability.
Note that per [RFC4202], an interface may have more than one ISCD
sub-TLV. Hence, the corresponding advertisements should not result
in any compatibility issue.
4.1.2 OSPFv2
In OSPFv2, the Interface Switching Capability Descriptor is a sub-
TLV (of type TBA) of the Link TLV (of type 2) [RFC4203].
The adaptation and termination capabilities are advertised using two
separate ISCD sub-TLVs within the same top-level link TLV.
4.1.2 IS-IS
In IS-IS, the Interface Adaptation Capability Descriptor is a sub-
TLV (of type TBA) of the Extended IS Reachability TLV (of type 22)
[RFC4205].
The adaptation and termination capabilities are advertised using two
separate ISCD sub-TLVs within the same Extended IS Reachability TLV.
4.2 Technology Specific Bandwidth Accounting
GMPLS Routing defines an Interface Switching Capability Descriptor
(ISCD) that delivers among others the information about the
(maximum/minimum) bandwidth per priority an LSP can make use of.
In the ASON context, accounting on per timeslot basis using 32-bit
tuples of the form <signal_type (8 bits); number of unallocated
timeslots (24 bits)> may optionally be incorporated in the
technology specific field of the ISCD TE link attribute when the
switching capability field is set to TDM value. When included,
format and encoding MUST follow the rules defined in [RFC4202].
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The purpose is purely informative: there is no mandatory processing
or topology/traffic-engineering significance associated to this
information.
4.2.1 OSPFv2
In OSPF, the Interface Switching Capability Descriptor is a sub-TLV
(of type 15) of the Link TLV (of type 2).
4.2.2 IS-IS
In IS-IS, the Interface Switching Capability Descriptor is a sub-TLV
(of type 21) of the Extended IS Reachability TLV (of type 22).
5. Routing Information Scope
The Ri is a logical control plane entity that is associated to a
control plane "router". The latter is the source for topology
information that it generates and shares with other control plane
"routers". The Ri is identified by the (advertising) Router_ID. The
routing protocol MUST support a single Ri advertising on behalf of
more than one Li. Each Li is identified by a unique TE Router ID.
5.1 Link Advertisement (Local and Remote TE Router ID sub-TLV)
A Router_ID (Ri) advertising on behalf multiple TE Router_ID (Li's)
creates a 1:N relationship between the Router_ID and the TE
Router_ID. As the link local and link remote (unnumbered) ID
association is not unique per node (per Li unicity), the
advertisement needs to indicate the remote Lj value and rely on the
initial discovery process to retrieve the [Li;Lj] relationship. In
brief, as unnumbered links have their ID defined on per Li bases,
the remote Lj needs to be identified to scope the link remote ID to
the local Li. Therefore, the routing protocol MUST be able to
disambiguate the advertised TE links so that they can be associated
with the correct TE Router ID.
5.1.1 OSPFv2
For this purpose, a new sub-TLV of the (OSPFv2 TE LSA) top level
Link TLV is introduced that defines the local and the remote
TE_Router_ID.
The type of this sub-TLV is 17, and length is eight octets. The
value field of this sub-TLV contains four octets of Local TE Router
Identifier followed by four octets of Remote TE Router Identifier.
The value of the Remote TE Router Identifier SHOULD NOT be set to 0.
The format of this sub-TLV is the following:
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
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 17 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV is optional and SHOULD only be included as part of the
top level Link TLV if the Router_ID is advertising on behalf of more
than one TE_Router_ID. In any other case, this sub-TLV SHOULD be
omitted.
Note: The Link ID sub-TLV that identifies the other end of the link
(i.e. Router ID of the neighbor for point-to-point links) MUST
appear exactly once per Link TLV.
5.1.2 IS-IS
For this purpose, a new sub-TLV of the Extended IS Reachability TLV
(Type 22, RFC 3784) is introduced that defines the local and the
remote TE_Router_ID.
The type of this sub-TLV is TBD, and length is eight octets. The
value field of this sub-TLV contains four octets of Local TE Router
Identifier followed by four octets of Remote TE Router Identifier.
The value of the Remote TE Router Identifier SHOULD NOT be set to 0.
The format of the value field of this sub-TLV is the following:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV is optional and SHOULD only be included as part of the
Extended IS Reachability TLV if the RC is advertising on behalf of
more than one TE_Router_ID. In any other case, this sub-TLV SHOULD
be omitted.
5.2 Reachability Advertisement (Local TE Router ID sub-TLV)
When the Router_ID advertises on behalf of multiple TE Router_IDs,
the routing protocol MUST be able to associate the advertised
reachability information with the correct TE Router ID.
5.2.1 OSPFv2
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For this purpose, a new sub-TLV of the (OSPFv2 TE LSA) top level
Node Attribute TLV is introduced. This TLV associates the local
prefixes (sub-TLV 3 and 4, see above) to a given TE Router_ID.
The type of this sub-TLV is 5, and length is four octets. The value
field of this sub-TLV contains four octets of Local TE Router
Identifier [RFC3630].
The format of this sub-TLV is the following:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV is optional and SHOULD only be included as part of the
Node Attribute TLV if the Router_ID is advertising on behalf of more
than one TE_Router_ID. In any other case, this sub-TLV SHOULD be
omitted.
5.2.2 IS-IS
For this purpose, a new sub-TLV of the newly defined Extended TE
Reachability TLV is introduced that defines the local TE_Router_ID.
The type of this sub-TLV is TBD, and length is four octets. The
value field of this sub-TLV contains four octets of Local TE Router
Identifier [RFC3784].
The format of the value field of this sub-TLV is the following:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV is optional and SHOULD only be included as part of the
Extended TE Reachability TLV if the RC is advertising on behalf of
more than one TE_Router_ID. In any other case, this sub-TLV SHOULD
be omitted.
6. Routing Information Dissemination
6.1 OSPFv2
RC disseminates downward/upward the hierarchy by re-originating this
routing information as Opaque TE LSA (Opaque Type 1) of LS Type 10.
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The information that MAY be exchanged between adjacent levels
includes the Router_Address, Link and Node_Attribute top level TLV.
The Opaque TE LSA re-origination is governed as follows:
- If the target interface is associated to the same area than the
one associated with the receiving interface, the Opaque LSA MUST
NOT be re-originated out that interface.
- If a match is found between the Advertising Router ID in the
received Opaque TE LSA and one of the Router ID belonging to the
area of the target interface, the Opaque LSA MUST NOT be re-
originated out that interface.
- If these two conditions are met the Opaque TE LSA MAY be re-
originated.
The re-originated content MAY be transformed e.g. filtered, as long
as the resulting routing information is consistent. In particular,
when than one RC are bound to adjacent levels and both allowed to
redistribute routing information it is expected that these
transformation are performed in consistent manner. Definition of
these policy mechanisms is outside the scope of this document.
In practice, and in order to avoid scalability and processing
overhead, routing information re-distributed downward/upward the
hierarchy is expected to include reachability information (see
Section 3.1) and upon strict policy control link topology
information.
6.1.1 Discovery and Selection
In order to discover RCs that are capable to disseminate routing
information upward the routing hierarchy, the following Capability
Descriptor bit [OSPF-TE-CAP] are defined:
- U bit: when set, this flag indicates that the RC is capable to
disseminate routing information upward the adjacent level.
In case of multiple supporting RCs, the RC with the highest Router
ID SHOULD be selected. More precisely, the RC with the highest
Router ID among the RCs having set the U bit SHOULD be selected as
the RC for upward dissemination of routing information. It is
expected that other RCs will not participate in the upward
dissemination of routing information as long as the opaque LSA
information corresponding to the highest Router ID RC does not reach
MaxAge.
Note that alternatively if this information cannot be discovered
automatically, it MUST be manually configured.
The same mechanism is used for selecting the RC taking in charge
dissemination of routing information downward the hierarchy with the
restriction that the RC selection process needs to take into account
that an upper level may be adjacent to one or more lower levels. For
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this purpose a specific TLV indexing the (lower) area ID to which
the RC's are capable to disseminate routing information is needed.
OSPF Associated Area ID TLV format carried in the OSPF router
information LSA [OSPF-CAP] is defined. This TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Associated Area ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (16 bits): identifies the TLV type
Length (16 bits): length of the value field in octets
Value (32 bits): Associated Area ID whose value space is the Area ID
as defined in [RFC2328].
Note that this information MUST be present when the D bit is set. To
discover RCs that are capable to disseminate routing information
downward the routing hierarchy, the following Capability Descriptor
bit [OSPF-TE-CAP] is defined, that MUST be advertised together with
the OSPF Area ID TLV:
- D bit: when set, this flag indicates that the RC is capable to
disseminate routing information downward the adjacent level.
In case of multiple supporting RCs for the same Associated Area ID,
the RC with the highest Router ID SHOULD be selected. More
precisely, the RC with the highest Router ID among the RCs having
set the D bit SHOULD be selected as the RC for downward
dissemination of routing information. It is expected that other RCs
for the same Associated Area ID will not participate in the downward
dissemination of routing information as long as the opaque LSA
information corresponding to the highest Router ID RC does not reach
MaxAge.
Note that alternatively if this information cannot be discovered
automatically, it MUST be manually configured.
The OSPF Router information opaque LSA (opaque type of 4, opaque ID
of 0) and its content in particular, the Router Informational
Capabilities TLV [OSPF-CAP] and TE Node Capability Descriptor TLV
[OSPF-TE-CAP] MUST NOT be re-originated.
6.1.2 Loop prevention
When more than one RC are bound to adjacent levels of the hierarchy,
configured and selected to redistribute upward and downward the
routing information, a specific mechanism is required to avoid
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looping/re-introduction of routing information back to the upper
level. In all other cases, the procedure described in this section
is optional.
When these conditions are met, it is necessary to have a mean by
which an RC receiving an Opaque TE LSA re-originated downward by an
RC associated to the same area omits to re-originate back the
content of this LSA upward into the (same) upper level.
Thus we need some way of filtering the downward/onward re-originated
Opaque TE LSA.
For opaque LSAs including the Router Address TLV, if the Router
address has been already installed into the TEDB, the LSA should not
be re-originated since this address belongs to a router part of the
target area.
For opaque LSAs including the Link TLV, if the Link ID has been
already installed into the TEDB, the LSA should not be re-originated
since the corresponding router ID belongs to a router part of the
target area.
For opaque LSAs including the Node Attribute TLV, if one of the
included prefixes has been already installed into the TEDB, the LSA
should not be re-originated with that prefix since the corresponding
reachable end-points belonging to a router part of the target area.
If no prefix remains, the LSA SHOULD not be re-originated.
6.2. IS-IS
6.2.1 Discovery and Selection
In order to discover RCs that are capable to disseminate routing
information upward the routing hierarchy, the following Capability
Descriptor bit [ISIS-TE-CAP] are defined:
- U bit: when set, this flag indicates that the RC is capable to
disseminate routing information upward the adjacent level.
In case of multiple supporting RCs, the RC with the highest Router
ID [ISIS-CAP] SHOULD be selected. More precisely, the RC with the
highest Router ID among the RCs having set the U bit SHOULD be
selected as the RC for upward dissemination of routing information.
It is expected that other RCs will not participate in the upward
dissemination of routing information as long as the routing
information corresponding to the highest Router ID RC is not
withdrawn.
Note that alternatively if this information cannot be discovered
automatically, it MUST be manually configured.
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The same mechanism is used for selecting the RC taking in charge
dissemination of routing information downward the hierarchy with the
restriction that the RC selection process needs to take into account
that an upper level may be adjacent to one or more lower levels. For
this purpose a specific TLV indexing the (lower) ISIS area ID to
which the RC's are capable to disseminate routing information is
needed.
To discover RCs that are capable to disseminate routing information
downward the routing hierarchy, the following Capability Descriptor
bit [ISIS-TE-CAP] is defined:
- D bit: when set, this flag indicates that the RC is capable to
disseminate routing information downward the adjacent level.
In case of multiple supporting RCs for the same ISIS Area ID, the RC
with the highest Router ID SHOULD be selected. More precisely, the
RC with the highest Router ID among the RCs having set the D bit
SHOULD be selected as the RC for downward dissemination of routing
information. It is expected that other RCs for the same Area ID will
not participate in the downward dissemination of routing information
as long as the routing information corresponding to the highest
Router ID RC is not withdrawn.
Note that alternatively if this information cannot be discovered
automatically, it MUST be manually configured.
The ISIS Router Capability TLV [ISIS-CAP] and its content in
particular MUST NOT be redistributed between adjacent levels.
6.2.2 Loop prevention
As described in [RFC3784], to prevent this looping of TE reachable
prefixes between levels, an up/down bit (U bit) is defined in the
newly defined extended TE reachability TLV.
The up/down bit MUST be set to 0 when a prefix is first injected
into IS-IS. If a prefix is advertised from a higher level to a
lower level (e.g. level 2 to level 1), the bit MUST be set to 1,
indicating that the prefix has traveled down the hierarchy. Prefixes
that have the up/down bit set to 1 may only be advertised down the
hierarchy, i.e. to lower levels.
For the extended IS reachability TLV, the same re-origination rules
as described in Section 6.1.2 applies.
7. OSPFv2 Extensions
7.1 Compatibility
Extensions specified in this document are associated to the
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OSPFv2 TE LSA:
o) Router Address top level TLV (Type 1):
- no additional sub-TLV
o) Link top level TLV (Type 2):
- Local and Remote TE Router ID sub-TLV: optional sub-TLV for
scoping link attributes per TE_Router ID
o) Node Attribute top level TLV (Type TBD):
- Node IPv4 Local Prefix sub-TLVs: optional sub-TLV for IPv4
reachability advertisement
- Node IPv6 Local Prefix sub-TLVs: optional sub-TLV for IPv6
reachability advertisement
- Local TE Router ID sub-TLV: optional sub-TLV for scoping
reachability per TE_Router ID
OSPFv2 RI LSA:
o) Routing information dissemination
- U and D bit in Capability Descriptor TLV [OSPF-TE-CAP]
- Associated Area ID TLV in the OSPF Routing Information LSA
[OSPF-CAP]
7.2 Scalability
o) Routing information exchange upward/downward the hierarchy
between adjacent areas SHOULD by default be limited to reachability.
In addition, several transformation such as prefix aggregation are
recommended when allowing decreasing the amount of information re-
originated by a given RC without impacting consistency.
o) Routing information exchange upward/downward the hierarchy when
involving TE attributes MUST be under strict policy control. Pacing
and min/max thresholds for triggered updates are strongly
recommended.
8. IS-IS Extensions and Compatibility
TBD
9. Acknowledgements
The authors would like to thank Alan Davey and Adrian Farrel for
their useful comments and suggestions.
10. References
11.1 Normative References
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draft-dimitri-ccamp-gmpls-ason-routing-sol-01.txt February 2006
[OSPF-NODE] R.Aggarwal, and K.Kompella, "Advertising a Router's
Local Addresses in OSPF TE Extensions," Internet Draft,
(work in progress), draft-ietf-ospf-te-node-addr-
02.txt, March 2005.
[RFC2026] S.Bradner, "The Internet Standards Process --
Revision 3", BCP 9, RFC 2026, October 1996.
[RFC2328] J.Moy, "OSPF Version 2", RFC 2328, April 1998.
[RFC2740] R.Coltun et al. "OSPF for IPv6", RFC 2740, December
1999.
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3477] K.Kompella et al. "Signalling Unnumbered Links in
Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, January 2003.
[RFC3630] D.Katz et al. "Traffic Engineering (TE) Extensions to
OSPF Version 2", RFC 3630, September 2003.
[RFC3667] S.Bradner, "IETF Rights in Contributions", BCP 78,
RFC 3667, February 2004.
[RFC3668] S.Bradner, Ed., "Intellectual Property Rights in IETF
Technology", BCP 79, RFC 3668, February 2004.
[RFC3784] H.Smit and T.Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE),"
RFC 3784, June 2004.
[RFC3946] E.Mannie, and D.Papadimitriou, (Editors) et al.,
"Generalized Multi-Protocol Label Switching Extensions
for SONET and SDH Control," RFC 3946, October 2004.
[RFC4202] Kompella, K. (Editor) et al., "Routing Extensions in
Support of Generalized MPLS," RFC 4202, October 2005.
8.2 Informative References
[ASON-EVAL] C.Hopps et al. "Evaluation of existing Routing Protocols
against ASON Routing Requirements", Work in progress,
draft-ietf-ccamp-gmpls-ason-routing-eval-02.txt, October
2005.
[ASON-RR] D.Brungard et al. "Requirements for Generalized MPLS
(GMPLS) Routing for Automatically Switched Optical
Network (ASON)," RFC 4258, November 2005.
For information on the availability of ITU Documents, please see
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draft-dimitri-ccamp-gmpls-ason-routing-sol-01.txt February 2006
http://www.itu.int
[G.7715] ITU-T Rec. G.7715/Y.1306, "Architecture and
Requirements for the Automatically Switched Optical
Network (ASON)," June 2002.
[G.7715.1] ITU-T Draft Rec. G.7715.1/Y.1706.1, "ASON Routing
Architecture and Requirements for Link State Protocols,"
November 2003.
[G.8080] ITU-T Rec. G.8080/Y.1304, "Architecture for the
Automatically Switched Optical Network (ASON),"
November 2001 (and Revision, January 2003).
9. Author's Addresses
Dimitri Papadimitriou (Alcatel)
Francis Wellensplein 1,
B-2018 Antwerpen, Belgium
Phone: +32 3 2408491
EMail: dimitri.papadimitriou@alcatel.be
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Appendix 1: ASON Terminology
This document makes use of the following terms:
Administrative domain: (see Recommendation G.805) for the purposes of
[G7715.1] an administrative domain represents the extent of resources
which belong to a single player such as a network operator, a service
provider, or an end-user. Administrative domains of different players
do not overlap amongst themselves.
Control plane: performs the call control and connection control
functions. Through signaling, the control plane sets up and releases
connections, and may restore a connection in case of a failure.
(Control) Domain: represents a collection of (control) entities that
are grouped for a particular purpose. The control plane is subdivided
into domains matching administrative domains. Within an
administrative domain, further subdivisions of the control plane are
recursively applied. A routing control domain is an abstract entity
that hides the details of the RC distribution.
External NNI (E-NNI): interfaces are located between protocol
controllers between control domains.
Internal NNI (I-NNI): interfaces are located between protocol
controllers within control domains.
Link: (see Recommendation G.805) a "topological component" which
describes a fixed relationship between a "subnetwork" or "access
group" and another "subnetwork" or "access group". Links are not
limited to being provided by a single server trail.
Management plane: performs management functions for the Transport
Plane, the control plane and the system as a whole. It also provides
coordination between all the planes. The following management
functional areas are performed in the management plane: performance,
fault, configuration, accounting and security management
Management domain: (see Recommendation G.805) a management domain
defines a collection of managed objects which are grouped to meet
organizational requirements according to geography, technology,
policy or other structure, and for a number of functional areas such
as configuration, security, (FCAPS), for the purpose of providing
control in a consistent manner. Management domains can be disjoint,
contained or overlapping. As such the resources within an
administrative domain can be distributed into several possible
overlapping management domains. The same resource can therefore
belong to several management domains simultaneously, but a management
domain shall not cross the border of an administrative domain.
Subnetwork Point (SNP): The SNP is a control plane abstraction that
represents an actual or potential transport plane resource. SNPs (in
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different subnetwork partitions) may represent the same transport
resource. A one-to-one correspondence should not be assumed.
Subnetwork Point Pool (SNPP): A set of SNPs that are grouped together
for the purposes of routing.
Termination Connection Point (TCP): A TCP represents the output of a
Trail Termination function or the input to a Trail Termination Sink
function.
Transport plane: provides bi-directional or unidirectional transfer
of user information, from one location to another. It can also
provide transfer of some control and network management information.
The Transport Plane is layered; it is equivalent to the Transport
Network defined in G.805 Recommendation.
User Network Interface (UNI): interfaces are located between protocol
controllers between a user and a control domain. Note: there is no
routing function associated with a UNI reference point.
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Appendix 2: ASON Routing Terminology
This document makes use of the following terms:
Routing Area (RA): a RA represents a partition of the data plane and
its identifier is used within the control plane as the representation
of this partition. Per [G.8080] a RA is defined by a set of sub-
networks, the links that interconnect them, and the interfaces
representing the ends of the links exiting that RA. A RA may contain
smaller RAs inter-connected by links. The limit of subdivision
results in a RA that contains two sub-networks interconnected by a
single link.
Routing Database (RDB): repository for the local topology, network
topology, reachability, and other routing information that is updated
as part of the routing information exchange and may additionally
contain information that is configured. The RDB may contain routing
information for more than one Routing Area (RA).
Routing Components: ASON routing architecture functions. These
functions can be classified as protocol independent (Link Resource
Manager or LRM, Routing Controller or RC) and protocol specific
(Protocol Controller or PC).
Routing Controller (RC): handles (abstract) information needed for
routing and the routing information exchange with peering RCs by
operating on the RDB. The RC has access to a view of the RDB. The RC
is protocol independent.
Note: Since the RDB may contain routing information pertaining to
multiple RAs (and possibly to multiple layer networks), the RCs
accessing the RDB may share the routing information.
Link Resource Manager (LRM): supplies all the relevant component and
TE link information to the RC. It informs the RC about any state
changes of the link resources it controls.
Protocol Controller (PC): handles protocol specific message exchanges
according to the reference point over which the information is
exchanged (e.g. E-NNI, I-NNI), and internal exchanges with the RC.
The PC function is protocol dependent.
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