Network Working Group D. Papadimitriou, Ed.

Network Working Group D. Papadimitriou, Ed.
Request for Comments: 4652 Alcatel
Category: Informational L.Ong
Ciena
J. Sadler
Tellabs
S. Shew
Nortel
D. Ward
Cisco
October 2006

Evaluation of Existing Routing Protocols against
Automatic Switched Optical Network (ASON) Routing Requirements

Status of This Memo

This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2006).

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 Synchronous Optical Network/Synchronous Digital Hierarchy
(SONET/SDH) and Optical Transport Networks (OTNs).

This document provides an evaluation of the IETF Routing Protocols
against the routing requirements for an Automatically Switched
Optical Network (ASON) as defined by ITU-T.

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1. Introduction

Certain capabilities are needed to support the ITU-T Automatically
Switched Optical Network (ASON) control plane architecture as defined
in [G.8080].

[RFC4258] details the routing requirements for the GMPLS routing
suite of protocols to support the capabilities and functionality of
ASON control planes identified in [G.7715] and in [G.7715.1]. The
ASON routing architecture provides for a conceptual reference
architecture, with definition of functional components and common
information elements to enable end-to-end routing in the case of
protocol heterogeneity and to facilitate management of ASON networks.
This description is only conceptual: no physical partitioning of
these functions is implied.

However, [RFC4258] does not address GMPLS routing protocol
applicability or capabilities. This document evaluates the IETF
Routing Protocols against the requirements identified in [RFC4258].
The result of this evaluation is detailed in Section 5. Close
examination of applicability scenarios and the result of the
evaluation of these scenarios are provided in Section 6.

ASON (Routing) terminology sections are provided in Appendices A and
B.

2. 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 expected to be familiar with the terminology introduced
in [RFC4258].

3. Contributors

This document is the result of the CCAMP Working Group ASON Routing
Solution design team's joint effort.

Dimitri Papadimitriou (Alcatel, Team Leader and Editor)
EMail: [email protected]
Chris Hopps (Cisco)
EMail: [email protected]
Lyndon Ong (Ciena Corporation)
EMail: [email protected]
Jonathan Sadler (Tellabs)
EMail: [email protected]

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Stephen Shew (Nortel Networks)
EMail: [email protected]
Dave Ward (Cisco)
EMail: [email protected]

4. Requirements: Overview

The following functionality is expected from GMPLS routing protocols
to instantiate the ASON hierarchical routing architecture realization
(see [G.7715] and [G.7715.1]):

- Routing Areas (RAs) shall be uniquely identifiable within a
carrier's network, each having a unique RA Identifier (RA ID)
within the carrier's network.

- Within a RA (one level), the routing protocol shall support
dissemination of hierarchical routing information (including
summarized routing information for other levels) in support of an
architecture of multiple hierarchical levels of RAs; the number of
hierarchical RA levels to be supported by a routing protocol is
implementation specific.

- The routing protocol shall support routing information based on a
common set of information elements as defined in [G.7715] and
[G.7715.1], divided between attributes pertaining to links and
abstract nodes (each representing either a sub-network or simply a
node). [G.7715] recognizes that the manner in which the routing
information is represented and exchanged will vary with the routing
protocol used.

- The routing protocol shall converge such that the distributed
Routing DataBases (RDB) become synchronized after a period of time.

To support dissemination of hierarchical routing information, the
routing protocol must deliver:

- Processing of routing information exchanged between adjacent levels
of the hierarchy (i.e., Level N+1 and N), including reachability
and (upon policy decision) summarized topology information.

- Self-consistent information at the receiving level resulting from
any transformation (filter, summarize, etc.) and forwarding of
information from one Routing Controller (RC) to RC(s) at different
levels when multiple RCs are bound to a single RA.

- A mechanism to prevent re-introduction of information propagated
into the Level N RA's RC back to the adjacent level RA's RC from
which this information has been initially received.

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Note: The number of hierarchical levels to be supported is routing
protocol specific and reflects a containment relationship.

Reachability information may be advertised either as a set of UNI
Transport Resource address prefixes, or as a set of associated
Subnetwork Point Pool (SNPP) link IDs/SNPP link ID prefixes, assigned
and selected consistently in their applicability scope. The formats
of the control plane identifiers in a protocol realization are
implementation specific. Use of a routing protocol within a RA
should not restrict the choice of routing protocols for use in other
RAs (child or parent).

As ASON does not restrict the control plane architecture choice,
either a co-located architecture or a physically separated
architecture may be used. A collection of links and nodes, such as a
sub-network or RA, must be able to represent itself to the wider
network as a single logical entity with only its external links
visible to the topology database.

5. Evaluation

This section evaluates support of existing IETF routing protocols
with respect to the requirements summarized from [RFC4258] in Section
4. Candidate routing protocols are Interior Gateway Protocol (IGP)
(OSPF and Intermediate System to Intermediate System (IS-IS)) and
BGP. The latter is not addressed in the current version of this
document. BGP is not considered a candidate protocol mainly because
of the following reasons:

- Non-support of TE information exchange. Each BGP router advertises
only its path to each destination in its vector for loop avoidance,
with no costs or hop counts; each BGP router knows little about
network topology.

- BGP can only advertise routes that are eligible for use (local RIB)
or routing loops can occur; there is one best route per prefix, and
that is the route that is advertised.

- BGP is not widely deployed in optical equipment and networks.

5.1. Terminology and Identification

- Pi is a physical (bearer/data/transport plane) node.

- Li is a logical control plane entity that is associated to a single
data plane (abstract) node. The Li is identified by the TE
Router_ID. The latter is a control plane identifier defined as
follows:

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[RFC3630]: Router_Address (top level) TLV of the Type 1 TE LSA
[RFC3784]: Traffic Engineering Router ID TLV (Type 134)

Note: This document does not define what the TE Router ID is. This
document simply states the use of the TE Router ID to identify Li.
[RFC3630] and [RFC3784] provide the definitions.

- 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

[RFC2328]: Router ID (32-bit)
[RFC1195]: IS-IS System ID (48-bit)

The Router_ID, which is represented by Ri and which corresponds to
the RC_ID [RFC4258], does not enter into the identification of the
logical entities representing the data plane resources such as
links. The Routing DataBase (RDB) is associated to the Ri. Note
that, in the ASON context, an arrangement consisting of multiple
Ris announcing routing information related to a single Li is under
evaluation.

Aside from the Li/Pi mappings, these identifiers are not assumed to
be in a particular entity relationship except that the Ri may have
multiple Lis in its scope. The relationship between Ri and Li is
simple at any moment in time: an Li may be advertised by only one Ri
at any time. However, an Ri may advertise a set of one or more Lis.
Thus, the routing protocol MUST be able to advertise multiple TE
Router IDs (see Section 5.7).

Note: Si is a control plane signaling function associated with one or
more Lis. This document does not assume any specific constraint on
the relationship between Si and Li. This document does not discuss
issues of control plane accessibility for the signaling function, and
it makes no assumptions about how control plane accessibility to the
Si is achieved.

5.2. RA Identification

G.7715.1 notes some necessary characteristics for RA identifiers,
e.g., that they may provide scope for the Ri, and that they must be
provisioned to be unique within an administrative domain. The RA ID
format itself is allowed to be derived from any global address space.
Provisioning of RA IDs for uniqueness is outside the scope of this
document.

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Under these conditions, GMPLS link state routing protocols provide
the capability for RA Identification without further modification.

5.3. Routing Information Exchange

In this section, the focus is on routing information exchange Ri
entities (through routing adjacencies) within a single hierarchical
level. Routing information mapping between levels require specific
processing (see Section 5.5).

The control plane does not transport Pi identifiers, as these are
data plane addresses for which the Li/Pi mapping is kept (link)
local; see, for instance the transport LMP document [RFC4394] where
such an exchange is described. Example: The transport plane
identifier is the Pi (the identifier assigned to the physical
element) that could be, for instance, "666B.F999.AF10.222C", whereas
the control plane identifier is the Li (the identifier assigned by
the control plane), which could be, for instance, "192.0.2.1".

The control plane exchanges the control plane identifier information,
but not the transport plane identifier information (i.e., not
"666B.F999.AF10.222C", but only "192.0.2.1"). The mapping Li/Pi is
kept local. So, when the Si receives a control plane message
requesting the use of "192.0.2.1", Si knows locally that this
information refers to the data plane entity identified by the
transport plane identifier "666B.F999.AF10.222C".

Note also that the Li and Pi addressing spaces may be identical.

The control plane carries:

1) its view of the data plane link end-points and other link
connection end-points.

2) the identifiers scoped by the Lis, i.e., referred to as an
associated IPv4/IPv6 addressing space. Note that these
identifiers may be either bundled TE link addresses or component
link addresses.

3) when using OSPF or ISIS as the IGP in support of traffic
engineering, [RFC3477] RECOMMENDS that the Li value (referred to
the "LSR Router ID") be set to the TE Router ID value.

Therefore, OSPF and IS-IS carry sufficient node identification
information without further modification.

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5.3.1. Link Attributes

[RFC4258] provides a list of link attributes and characteristics that
need to be advertised by a routing protocol. All TE link attributes
and characteristics are currently handled by OSPF and IS-IS (see
Table 1) with the exception of Local Adaptation support. Indeed,
GMPLS routing does not currently consider the use of dedicated TE
link attribute(s) to describe the cross/inter-layer relationships.

In addition, the representation of bandwidth requires further
consideration. GMPLS Routing defines an Interface Switching
Capability Descriptor (ISCD) that delivers information about the
(maximum/ minimum) bandwidth per priority of which an LSP can make
use. This information is usually used in combination with the
Unreserved Bandwidth sub-TLV that provides the amount of bandwidth
not yet reserved on a TE link.

In the ASON context, other bandwidth accounting representations are
possible, e.g., in terms of a set of tuples <signal_type; number of
unallocated timeslots>. The latter representation may also require
definition of additional signal types (from those defined in
[RFC3946]) to represent support of contiguously concatenated signals,
i.e., STS-(3xN)c SPE / VC-4-Nc, N = 4, 16, 64, 256.

However, the method proposed in [RFC4202] is the most straightforward
without requiring any bandwidth accounting change from an LSR
perspective (in particular, when the ISCD sub-TLV information is
combined with the information provided by the Unreserved Bandwidth
sub-TLV).

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Link Characteristics GMPLS OSPF
----------------------- ----------
Local SNPP link ID Link-local part of the TE link identifier
sub-TLV [RFC4203]
Remote SNPP link ID Link remote part of the TE link identifier
sub-TLV [RFC4203]
Signal Type Technology specific part of the Interface
Switching Capability Descriptor sub-TLV
[RFC4203]
Link Weight TE metric sub-TLV [RFC3630]
Resource Class Administrative Group sub-TLV [RFC3630]
Local Connection Types Switching Capability field part of the
Interface Switching Capability Descriptor
sub-TLV [RFC4203]
Link Capacity Unreserved bandwidth sub-TLV [RFC3630]
Max LSP Bandwidth part of the Interface
Switching Capability Descriptor sub-TLV
[RFC4203]
Link Availability Link Protection sub-TLV [RFC4203]
Diversity Support SRLG sub-TLV [RFC4203]
Local Adaptation support See above

Table 1. TE link attributes in GMPLS OSPF-TE

Link Characteristics GMPLS IS-IS
----------------------- -----------
Local SNPP link ID Link-local part of the TE link identifier
sub-TLV [RFC4205]
Remote SNPP link ID Link-remote part of the TE link identifier
sub-TLV [RFC4205]
Signal Type Technology specific part of the Interface
Switching Capability Descriptor sub-TLV
[RFC4205]
Link Weight TE Default metric [RFC3784]
Resource Class Administrative Group sub-TLV [RFC3784]
Local Connection Types Switching Capability field part of the
Interface Switching Capability Descriptor
sub-TLV [RFC4205]
Link Capacity Unreserved bandwidth sub-TLV [RFC3784]
Max LSP Bandwidth part of the Interface
Switching Capability Descriptor sub-TLV
[RFC4205]
Link Availability Link Protection sub-TLV [RFC4205]
Diversity Support SRLG sub-TLV [RFC4205]
Local Adaptation support See above

Table 2. TE link attributes in GMPLS IS-IS-TE

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Note: Link Attributes represent layer resource capabilities and
their utilization i.e. the IGP should be able to advertise these
attributes on a per-layer basis.

5.3.2. Node Attributes

Node attributes are the "Logical Node ID" (described in Section 5.1)
and the reachability information described in Section 5.3.3.

5.3.3. Reachability Information

Advertisement of reachability can be achieved using the techniques
described in [OSPF-NODE], where 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). However,
[OSPF-NODE] is restricted to advertisement of Host addresses and not
prefixes, and therefore it requires enhancement (see below). Thus,
in order to advertise blocks of reachable address prefixes a
summarization mechanism is additionally required. This mechanism may
take the form of a prefix length (which indicates the number of
significant bits in the prefix) or a network mask.

A similar mechanism does not exist for IS-IS. Moreover, the Extended
IP Reachability TLV [RFC3784] focuses on IP reachable end-points
(terminating points), as its name indicates.

5.4. Routing Information Abstraction

G.7715.1 describes both static and dynamic methods for abstraction of
routing information for advertisement at a different level of the
routing hierarchy. However, the information that is advertised
continues to be in the form of link and node advertisements
consistent with the link state routing protocol used at that level.
Hence, no specific capabilities need to be added to the routing
protocol beyond the ability to locally identify when routing
information originates outside of a particular RA.

The methods used for abstraction of routing information are outside
the scope of GMPLS routing protocols.

5.5. Dissemination of Routing Information in Support of Multiple
Hierarchal Levels of RAs

G.7715.1 does not define specific mechanisms to support multiple
hierarchical levels of RAs beyond the ability to support abstraction
as discussed above. However, if RCs bound to adjacent levels of the
RA hierarchy are allowed to redistribute routing information in both

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directions between adjacent levels of the hierarchy without any
additional mechanisms, they would not be able to determine looping of
routing information.

To prevent this looping of routing information between levels, IS-IS
[RFC1195] allows only advertising routing information upward in the
level hierarchy and disallows the advertising of routing information
downward in the hierarchy. [RFC2966] defines the up/down bit to
allow advertising downward in the hierarchy the "IP Internal
Reachability Information" TLV (Type 128) and "IP External
Reachability Information" TLV (Type 130). [RFC3784] extends its
applicability for the "Extended IP Reachability" TLV (Type 135).
Using this mechanism, the up/down bit is set to 0 when routing
information is first injected into IS-IS. If routing information is
advertised from a higher level to a lower level, the up/down bit is
set to 1, indicating that it has traveled down the hierarchy.
Routing information that has the up/down bit set to 1 may only be
advertised down the hierarchy, i.e., to lower levels. This mechanism
applies independently of the number of levels. However, this
mechanism does not apply to the "Extended IS Reachability" TLV (Type
22) used to propagate the summarized topology (see Section 5.3),
traffic engineering information as listed in Table 1, as well as
reachability information (see Section 5.3.3).

OSPFv2 [RFC2328] prevents inter-area routes (which are learned from
area 0) from being passed back to area 0. However, GMPLS makes use
of Type 10 (area-local scope) LSAs to propagate TE information
[RFC3630], [RFC4202]. Type 10 Opaque LSAs are not flooded beyond the
borders of their associated area. It is therefore necessary to have
a means by which Type 10 Opaque LSA may carry the information that a
particular piece of routing information has been learned from a
higher-level RC when propagated to a lower-level RC. Any downward RC
from this level, which receives an LSA with this information would
omit the information in this LSA and thus not re-introduce this
information back into a higher-level RC.

5.6. Routing Protocol Convergence

Link state protocols have been designed to propagate detected
topological changes (such as interface failures and link attributes
modification). The convergence period is short and involves a
minimum of routing information exchange.

Therefore, existing routing protocol convergence involves mechanisms
that are sufficient for ASON applications.

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5.7. Routing Information Scoping

The routing protocol MUST support a single Ri advertising on behalf
of more than one Li. Since each Li is identified by a unique TE
Router ID, the routing protocol MUST be able to advertise multiple TE
Router IDs. That is, for [RFC3630], multiple Router Addresses and
for [RFC3784] multiple Traffic Engineering Router Ids.

The Link sub-TLV that is currently part of the top level Link TLV
associates the link to the Router_ID. However, having the Ri
advertising on behalf of multiple Lis creates the following issue, as
there is no longer a 1:1 relationship between the Router_ID and the
TE Router_ID, but a 1:N relationship is possible (see Section 5.1).
As the link-local and link-remote (unnumbered) ID association may not
be unique per abstract 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(s). 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.

Moreover, when the Ri advertises on behalf multiple Lis, the routing
protocol MUST be able to disambiguate the advertised reachability
information (see Section 5.3.3) so that it can be associated with the
correct TE Router ID.

6. Evaluation Scenarios

The evaluation scenarios are the following; they are respectively
referred to as cases 1, 2, 3, and 4.

In Figure 1, below,

- R3 represents an LSR with all components collocated.
- R2 shows how the "router" component may be disjoint from the node.
- R1 shows how a single "router" may manage multiple nodes.

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------------------- -------
|R1 | |R2 |
| | | | ------
| L1 L2 L3 | | L4 | |R3 |
| : : : | | : | | |
| : : : | | : | | L5 |
Control ---+-----+-----+--- ---+--- | : |
Plane : : : : | : |
----------------+-----+-----+-----------+-------+---+--+-
Data : : : : | : |
Plane -- : -- -- | -- |
----|P1|--------|P3|--------|P4|------+-|P5|-+-
-- \ : / -- -- | -- |
\ -- / | |
|P2| ------
--

Figure 1. Evaluation Cases 1, 2, and 3

Case 1 as represented refers either to direct links between edges or
to "logical links" as shown in Figure 2 (or any combination of them).

------ ------
| | | |
| L1 | | L2 |
| : | | : |
| : R1| | : R2|
Control Plane --+--- --+---
Elements : :
------------------+-----------------------------+------------------
Data Plane : :
Elements : :
----+-----------------------------+-----
| : : |
| --- --- --- |
| | |----------| P |----------| | |
---+--| | --- | |---+---
| | | | | |
| | P1|-------------------------| P2| |
| --- --- |
----------------------------------------

Figure 2. Case 1 with Logical Links

Another case (referred to as Case 4) is constituted by the Abstract
Node as represented in Figure 3. There is no internal structure
associated (externally) to the abstract node.

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--------------
|R4 |
| |
| L6 |
| : |
| ...... |
---:------:---
Control Plane : :
+------+------+------+
Data Plane : :
---:------:---
|P8 : : |
| -- -- |
--+-|P |----|P |-+--
| -- -- |
--------------

Figure 3. Case 4: Abstract Node

Note: the "signaling function" referred to as Si, i.e., the control
plane entity that processes the signaling messages, is not
represented in these figures.

7. Summary of Necessary Additions to OSPF and IS-IS

The following sections summarize the additions to be provided to OSPF
and IS-IS in support of ASON routing.

7.1. OSPFv2

Reachability Extend Node Attribute sub-TLVs to support address
prefixes (see Section 5.3.3).

Link Attributes Representation of cross/inter-layer relationships
in link top-level link TLV (see Section 5.3.1).

Optionally, provide for per-signal-type bandwidth
accounting (see Section 5.3.1).

Scoping TE link advertisements to allow for retrieving
their respective local-remote TE Router_ID
relationship(s) (see Section 5.7).

Prefixes part of the reachability advertisement
(using Node Attribute top-level TLV) needs to be
associated to its respective local TE Router_ID
(see Section 5.7).

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Hierarchy Provide a mechanism by which Type 10 Opaque LSA may
carry the information that a particular piece of
routing information has been learned from a
higher-level RC when propagated to a lower-level RC
(so as not to re-introduce this information into a
higher-level RC).

7.2. IS-IS

Reachability Provide for reachability advertisement (in the form
of reachable TE prefixes).

Link Attributes Representation of cross/inter-layer relationships
in Extended IS Reachability TLV (see Section
5.3.1).

Optionally, provide for per-signal-type bandwidth
accounting (see Section 5.3.1).

Scoping Extended IS Reachability TLVs to allow for
retrieving their respective local-remote TE
Router_ID relationship(s) (see Section 5.7).

Prefixes part of the reachability advertisement
needs to be associated to its respective local TE
Router_ID (see Section 5.7).

Hierarchy Extend the up/down bit mechanisms to propagate the
summarized topology (see Section 5.3) and traffic
engineering information as listed in Table 1, as
well as reachability information (see Section
5.3.3).

8. Security Considerations

The introduction of a dynamic control plane to an ASON network
exposes it to additional security risks that may have been controlled
or limited by the use of management plane solutions. The routing
protocols play a part in the control plane and may be attacked so
that they become unstable or provide incorrect information for use in
path computation or by the signaling protocols.

Nevertheless, there is no reason why the control plane components
cannot be secured, and the security mechanisms developed for the
routing protocol and used within the Internet are equally applicable
within an ASON context.

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[RFC4258] describes the requirements for security of routing
protocols for the Automatically Switched Optical Network. Reference
is made to [M.3016], which lays out the overall security objectives
of confidentiality, integrity, and accountability. These are well
discussed for the Internet routing protocols in [THREATS].

A detailed discussion of routing threats and mechanisms that are
currently deployed in operational networks to counter these threats
is found in [OPSECPRACTICES]. A detailed listing of the device
capabilities that can be used to support these practices can be found
in [RFC3871].

9. Acknowledgements

The authors would like to thank Adrian Farrel for having initiated
the proposal of an ASON Routing Solution Design Team and the ITU-T
SG15/Q14 for their careful review and input.

10. References

10.1. Normative References

[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP
and dual environments", RFC 1195, December 1990.

[RFC2966] Li, T., Przygienda, T., and H. Smit, "Domain-wide
Prefix Distribution with Two-Level IS-IS", RFC
2966, October 2000.

[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April
1998.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered
Links in Resource ReSerVation Protocol - Traffic
Engineering (RSVP-TE)", RFC 3477, January 2003.

[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic
Engineering (TE) Extensions to OSPF Version 2", RFC
3630, September 2003.

[RFC3784] Smit, H. and T. Li, "Intermediate System to
Intermediate System (IS-IS) Extensions for Traffic
Engineering (TE)", RFC 3784, June 2004.

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[RFC3871] Jones, G., Ed., "Operational Security Requirements
for Large Internet Service Provider (ISP) IP
Network Infrastructure", RFC 3871, September 2004.

[RFC3946] Mannie, E. and D. Papadimitriou, "Generalized
Multi-Protocol Label Switching (GMPLS) Extensions
for Synchronous Optical Network (SONET) and
Synchronous Digital Hierarchy (SDH) Control", RFC
3946, October 2004.

[RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
Extensions in Support of Generalized Multi-Protocol
Label Switching (GMPLS)", RFC 4202, October 2005.

[RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF
Extensions in Support of Generalized Multi-Protocol
Label Switching (GMPLS)", RFC 4203, October 2005.

[RFC4205] Kompella, K., Ed., and Y. Rekhter, Ed.,
"Intermediate System to Intermediate System (IS-IS)
Extensions in Support of Generalized Multi-Protocol
Label Switching (GMPLS)", RFC 4205, October 2005.

[RFC4258] Brungard, D., "Requirements for Generalized Multi-
Protocol Label Switching (GMPLS) Routing for the
Automatically Switched Optical Network (ASON)", RFC
4258, November 2005.

10.2. Informative References

[RFC4394] Fedyk, D., Aboul-Magd, O., Brungard, D., Lang, J.,
and D. Papadimitriou, "A Transport Network View of
the Link Management Protocol (LMP)", RFC 4394,
February 2006.

[OPSECPRACTICES] Kaeo, M., "Operational Security Current Practices",
Work in Progress, July 2006.

[OSPF-NODE] Aggarwal, R. and K. Kompella, "Advertising a
Router's Local Addresses in OSPF TE Extensions",
Work in Progress, June 2006.

[THREATS] Barbir, A., Murphy, S., and Y. Yang, "Generic
Threats to Routing Protocols", RFC 4593, October
2006.

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For information on the availability of ITU Documents, please see
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)",
June 2006.

[M.3016] ITU-T Rec. M.3016.0, "Security for the Management
Plane: Overview", May 2005.

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Appendix A. ASON Terminology

This document makes use of the following terms:

Administrative domain (see Recommendation G.805): For the purposes of
[G.7715.1], an administrative domain represents the extent of
resources that 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" that
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 that are grouped to meet
organizational requirements according to geography, technology,
policy, or other structure, and for a number of functional areas such
as fault, configuration, accounting, performance, and 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.

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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
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.

Appendix B. ASON Routing Terminology

This document makes use of the following terms:

Routing Area (RA): An 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], an 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. An RA
may contain smaller RAs inter-connected by links. The limit of
subdivision results in an 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 that may additionally
contain information that is configured. The RDB may contain routing
information for more than one Routing Area (RA).

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Routing Components: ASON routing architecture functions. These
functions can be classified as being 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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Authors' Addresses

Dimitri Papadimitriou, Ed.
Alcatel
Francis Wellensplein 1,
B-2018 Antwerpen, Belgium
Phone: +32 3 2408491
EMail: [email protected]

Lyndon Ong
Ciena Corporation
PO Box 308
Cupertino, CA 95015 , USA
Phone: +1 408 705 2978
EMail: [email protected]

Jonathan Sadler
Tellabs
1415 W. Diehl Rd
Naperville, IL 60563
EMail: [email protected]

Stephen Shew
Nortel Networks
3500 Carling Ave.
Ottawa, Ontario, CANADA K2H 8E9
Phone: +1 613 7632462
EMail: [email protected]

Dave Ward
Cisco Systems
170 W. Tasman Dr.
San Jose, CA 95134 USA
Phone: +1-408-526-4000
EMail: [email protected]

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