draft-ietf-ccamp-sdhsonet-control-01.txt   draft-ietf-ccamp-sdhsonet-control-02.txt 
CCAMP G. Bernstein (Ciena)
Internet Draft E. Mannie (KPNQwest) CCAMP Working Group G. Bernstein (Grotto Networking)
Internet Draft E. Mannie (InterAir Link)
Document: <draft-ietf-ccamp-sdhsonet- V. Sharma (Metanoia, Inc.) Document: <draft-ietf-ccamp-sdhsonet- V. Sharma (Metanoia, Inc.)
control-01.txt> control-02.txt>
Category: Informational Category: Informational
Expires November 2002 May 2002 Expires August 2003 February 2003
Framework for GMPLS-based Control of SDH/SONET Networks Framework for GMPLS-based Control of SDH/SONET Networks
<draft-ietf-ccamp-sdhsonet-control-01.txt> <draft-ietf-ccamp-sdhsonet-control-02.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [1]. all provisions of Section 10 of RFC2026 [1].
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Internet-Drafts are draft documents valid for a maximum of Drafts. Internet-Drafts are draft documents valid for a maximum of
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needed in transport path computation and network operations, needed in transport path computation and network operations,
together with the extensions to MPLS label distribution protocols together with the extensions to MPLS label distribution protocols
needed for the provisioning of transport circuits. New capabilities needed for the provisioning of transport circuits. New capabilities
that an MPLS control plane would bring to SONET/SDH networks, such that an MPLS control plane would bring to SONET/SDH networks, such
as new restoration methods and multi-layer circuit establishment, as new restoration methods and multi-layer circuit establishment,
are also discussed. are also discussed.
2. Conventions used in this document 2. Conventions used in this document
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC-2119 [2]. this document are to be interpreted as described in RFC-2119 [2].
3. Introduction 3. Introduction
The CCAMP Working Group of the IETF is currently working on The CCAMP Working Group of the IETF is currently working on
extending MPLS [3] protocols to support multiple network layers and extending MPLS [3] protocols to support multiple network layers and
new services. This extended MPLS, which was initially known as new services. This extended MPLS, which was initially known as
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3.1. MPLS Overview 3.1. MPLS Overview
A major advantage of the MPLS architecture [3] for use as a general A major advantage of the MPLS architecture [3] for use as a general
network control plane is its clear separation between the forwarding network control plane is its clear separation between the forwarding
(or data) plane, the signaling (or connection control) plane, and (or data) plane, the signaling (or connection control) plane, and
the routing (or topology discovery/resource status) plane. This the routing (or topology discovery/resource status) plane. This
allows the work on MPLS extensions to focus on the forwarding and allows the work on MPLS extensions to focus on the forwarding and
signaling planes, while allowing well-known IP routing protocols to signaling planes, while allowing well-known IP routing protocols to
be reused in the routing plane. This clear separation also allows be reused in the routing plane. This clear separation also allows
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for MPLS to be used to control networks that do not have a packet- for MPLS to be used to control networks that do not have a packet-
based forwarding plane. based forwarding plane.
An MPLS network consists of MPLS nodes called Label Switch Routers An MPLS network consists of MPLS nodes called Label Switch Routers
(LSRs) connected via circuits called Label Switched Paths (LSPs). An (LSRs) connected via circuits called Label Switched Paths (LSPs). An
LSP is unidirectional and could be of several different types such LSP is unidirectional and could be of several different types such
as point-to-point, point-to-multipoint, and multipoint-to-point. as point-to-point, point-to-multipoint, and multipoint-to-point.
Border LSRs in an MPLS network act either as ingress or egress LSRs Border LSRs in an MPLS network act either as ingress or egress LSRs
depending on the direction of the traffic being forwarded. depending on the direction of the traffic being forwarded.
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appropriate forwarding, such as normal IP forwarding. We will see appropriate forwarding, such as normal IP forwarding. We will see
that for a SONET/SDH network these operations do not occur in quite that for a SONET/SDH network these operations do not occur in quite
the same way. the same way.
3.2. SDH/SONET Overview 3.2. SDH/SONET Overview
There are currently two different multiplexing technologies in use There are currently two different multiplexing technologies in use
in optical networks: wavelength division multiplexing (WDM) and time in optical networks: wavelength division multiplexing (WDM) and time
division multiplexing (TDM). This work focuses on TDM technology. division multiplexing (TDM). This work focuses on TDM technology.
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SDH and SONET are two TDM standards widely used by operators to SDH and SONET are two TDM standards widely used by operators to
transport and multiplex different tributary signals over optical transport and multiplex different tributary signals over optical
links, thus creating a multiplexing structure, which we call the links, thus creating a multiplexing structure, which we call the
SDH/SONET multiplex. SDH, which was developed by the ETSI and later SDH/SONET multiplex. SDH, which was developed by the ETSI and later
standardized by the ITU-T [4], is now used worldwide, while SONET, standardized by the ITU-T [4], is now used worldwide, while SONET,
which was standardized by the ANSI [5], is mainly used in the US. which was standardized by the ANSI [5], is mainly used in the US.
However, these two standards have several similarities, and to some However, these two standards have several similarities, and to some
extent SONET can be viewed as a subset of SDH. Internetworking extent SONET can be viewed as a subset of SDH. Internetworking
between the two is possible using gateways. between the two is possible using gateways.
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xN x1 xN x1
STM-N<----AUG<----AU-4<--VC4<------------------------------C-4 E4 STM-N<----AUG<----AU-4<--VC4<------------------------------C-4 E4
^ ^ ^ ^
Ix3 Ix3 Ix3 Ix3
I I x1 I I x1
I -----TUG-3<----TU-3<---VC-3<---I I -----TUG-3<----TU-3<---VC-3<---I
I ^ C-3 DS3/E3 I ^ C-3 DS3/E3
-------AU-3<---VC-3<-- I ---------------------I -------AU-3<---VC-3<-- I ---------------------I
^ I ^ I
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Ix7 Ix7 Ix7 Ix7
I I x1 I I x1
-----TUG-2<---TU-2<---VC-2<---C-2 DS2/T2 -----TUG-2<---TU-2<---VC-2<---C-2 DS2/T2
^ ^ ^ ^
I I x3 I I x3
I I----TU-12<---VC-12<--C-12 E1 I I----TU-12<---VC-12<--C-12 E1
I I
I x4 I x4
I-------TU-11<---VC-11<--C-11 DS1/T1 I-------TU-11<---VC-11<--C-11 DS1/T1
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be re-aligned via a pointer, i.e. a VC-x in the case of SDH and a be re-aligned via a pointer, i.e. a VC-x in the case of SDH and a
SPE in the case of SONET. SPE in the case of SONET.
An STM-N/STS-N signal is formed from N x STM-1/STS-1 signals via An STM-N/STS-N signal is formed from N x STM-1/STS-1 signals via
byte interleaving. The VCs/SPEs in the N interleaved frames are byte interleaving. The VCs/SPEs in the N interleaved frames are
independent and float according to their own clocking. To transport independent and float according to their own clocking. To transport
tributary signals in excess of the basic STM-1/STS-1 signal rates, tributary signals in excess of the basic STM-1/STS-1 signal rates,
the VCs/SPEs can be concatenated, i.e., glued together. In this case the VCs/SPEs can be concatenated, i.e., glued together. In this case
their relationship with respect to each other is fixed in time and their relationship with respect to each other is fixed in time and
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hence this relieves, when possible, an end system of any inverse hence this relieves, when possible, an end system of any inverse
multiplexing bonding processes. Different types of concatenations multiplexing bonding processes. Different types of concatenations
are defined in SDH/SONET. are defined in SDH/SONET.
For example, standard SONET concatenation allows the concatenation For example, standard SONET concatenation allows the concatenation
of M x STS-1 signals within an STS-N signal with M <= N, and M = 3, of M x STS-1 signals within an STS-N signal with M <= N, and M = 3,
12, 48, 192,...). The SPEs of these M x STS-1s can be concatenated 12, 48, 192,...). The SPEs of these M x STS-1s can be concatenated
to form an STS-Mc. The STS-Mc notation is short hand for describing to form an STS-Mc. The STS-Mc notation is short hand for describing
an STS-M signal whose SPEs have been concatenated. an STS-M signal whose SPEs have been concatenated.
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client is in a different time zone than the operator's main office. client is in a different time zone than the operator's main office.
This first-time connection time is frequently accounted for in the This first-time connection time is frequently accounted for in the
overall establishment time. overall establishment time.
3.3.3. Planning Tool Operation 3.3.3. Planning Tool Operation
Another portion of the time is consumed by planning tools that run Another portion of the time is consumed by planning tools that run
simulations using heuristic algorithms to find an optimized simulations using heuristic algorithms to find an optimized
placement for the required circuits. These planning tools can placement for the required circuits. These planning tools can
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require a significant running time, sometimes on the order of days. require a significant running time, sometimes on the order of days.
These simulations are, in general, executed for a set of demands for These simulations are, in general, executed for a set of demands for
circuits, i.e., a batch mode, to improve the optimality of network circuits, i.e., a batch mode, to improve the optimality of network
resource usage and other parameters. Today, we do not really have a resource usage and other parameters. Today, we do not really have a
means to reduce this simulation time. On the contrary, to support means to reduce this simulation time. On the contrary, to support
fast, on-line, circuit establishment, this phase may be invoked more fast, on-line, circuit establishment, this phase may be invoked more
frequently, i.e., we will not "batch up" as many connection frequently, i.e., we will not "batch up" as many connection
requests before we plan out the corresponding circuits. This means requests before we plan out the corresponding circuits. This means
that the network may need to be re-optimized periodically, implying that the network may need to be re-optimized periodically, implying
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networks does not preclude either model, although MPLS is itself a networks does not preclude either model, although MPLS is itself a
distributed technology. distributed technology.
The basic tradeoff between the centralized and distributed The basic tradeoff between the centralized and distributed
approaches is that of complexity of the network elements versus that approaches is that of complexity of the network elements versus that
of the network management system (NMS). Since adding functionality of the network management system (NMS). Since adding functionality
to existing SDH/SONET network elements may not be possible, a to existing SDH/SONET network elements may not be possible, a
centralized approach may be needed in some cases. The main issue centralized approach may be needed in some cases. The main issue
facing centralized control via an NMS is one of scalability. For facing centralized control via an NMS is one of scalability. For
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instance, this approach may be limited in the number of network instance, this approach may be limited in the number of network
elements that can be managed (e.g., one thousand). It is, therefore, elements that can be managed (e.g., one thousand). It is, therefore,
quite common for operators to deploy several NMSÆs in parallel at quite common for operators to deploy several NMSÆs in parallel at
the Network Management Layer, each managing a different zone. In the Network Management Layer, each managing a different zone. In
that case, however, a Service Management Layer must be built on the that case, however, a Service Management Layer must be built on the
top of several individual NMSÆs to take care of end-to-end on-demand top of several individual NMSÆs to take care of end-to-end on-demand
services. On the other hand, in a complex and/or dense network, services. On the other hand, in a complex and/or dense network,
restoration could be faster with a distributed approach than with a restoration could be faster with a distributed approach than with a
centralized approach. centralized approach.
Let's now look at how the major control plane functional components Let's now look at how the major control plane functional components
are handled via the centralized and distributed approaches: are handled via the centralized and distributed approaches:
3.4.1. Topology Discovery and Resource Dissemination 3.4.1. Topology Discovery and Resource Dissemination
Currently NMS's maintain a consistent view of all the networking Currently NMS's maintain a consistent view of all the networking
layers under their purview. This can include the physical topology, layers under their purview. This can include the physical topology,
such as information about fibers and ducts. Since most of this such as information about fibers and ducts. Since most of this
information is entered manually, it remains error prone. information is entered manually, it remains error prone.
A link state GMPLS routing protocol, on the other hand, could A link state GMPLS routing protocol, on the other hand, could perform
perform automatic topology discovery and dissemination the topology automatic topology discovery and dissemination the topology as well as
as well as resource status. This information would be available to resource status. This information would be available to all nodes in
all nodes in the network, and hence also the NMS. Hence one can the network, and hence also the NMS. Hence one can look at a continuum
look at a continuum of functionality between manually provisioned of functionality between manually provisioned topology information (of
topology information (of which there will always be some) and fully which there will always be some) and fully automated discovery and
automated discovery and dissemination as in a link state protocol. dissemination as in a link state protocol. Note that, unlike the IP
Note that, unlike the IP datagram case, a link state routing datagram case, a link state routing protocol applied to the SDH/SONET
protocol applied to the SDH/SONET network does not have any service network does not have any service impacting implications. This is
impacting implications. This is because in the SDH/SONET case, the because in the SDH/SONET case, the circuit is source-routed (so there
circuit is source-routed (so there can be no loops), and no traffic can be no loops), and no traffic is transmitted until a circuit has
is transmitted until a circuit has been established, and an been established, and an acknowledgement received at the source.
acknowledgement received at the source.
3.4.2. Path Computation (Route Determination) 3.4.2. Path Computation (Route Determination)
In the SDH/SONET case, unlike the IP datagram case, there is no need In the SDH/SONET case, unlike the IP datagram case, there is no need
for network elements to all perform the same path calculation [9]. for network elements to all perform the same path calculation [9].
In addition, path determination is an area for vendors to provide a In addition, path determination is an area for vendors to provide a
potentially significant value addition in terms of network potentially significant value addition in terms of network
efficiency, reliability, and service differentiation. In this sense, efficiency, reliability, and service differentiation. In this sense,
a centralized approach to path computation may be easier to operate a centralized approach to path computation may be easier to operate
and upgrade. For example, new features such as new types of path and upgrade. For example, new features such as new types of path
diversity or new optimization algorithms can be introduced with a diversity or new optimization algorithms can be introduced with a
simple NMS software upgrade. On the other hand, updating switches simple NMS software upgrade. On the other hand, updating switches
with new path computation software is a more complicated task. In with new path computation software is a more complicated task. In
addition, many of the algorithms can be fairly computationally addition, many of the algorithms can be fairly computationally
intensive and may be completely unsuitable for the embedded intensive and may be completely unsuitable for the embedded
processing environment available on most switches. In restoration processing environment available on most switches. In restoration
scenarios, the ability to perform a reasonably sophisticated level scenarios, the ability to perform a reasonably sophisticated level
of path computation on the network element can be particularly of path computation on the network element can be particularly
useful for restoring traffic during major network faults. useful for restoring traffic during major network faults.
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3.4.3. Connection Establishment (provisioning) 3.4.3. Connection Establishment (provisioning)
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The actual setting up of circuits, i.e., a coupled collection of The actual setting up of circuits, i.e., a coupled collection of
cross connects across a network, can be done either via the NMS cross connects across a network, can be done either via the NMS
setting up individual cross connects or via a "soft permanent LSP" setting up individual cross connects or via a "soft permanent LSP"
(SPLSP) type approach. In the SPLSP approach, the NMS may just kick (SPLSP) type approach. In the SPLSP approach, the NMS may just kick
off the connection at the "ingress" switch with GMPLS signaling off the connection at the "ingress" switch with GMPLS signaling
setting up the connection from that point onward. Connection setting up the connection from that point onward. Connection
establishment is the trickiest part to distribute, however, since establishment is the trickiest part to distribute, however, since
errors in the connection setup/tear down process are service errors in the connection setup/tear down process are service
impacting. impacting.
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Suitable for very dynamic For less dynamic demands Suitable for very dynamic For less dynamic demands
demands (longer lived) demands (longer lived)
Probably faster to restore, Probably slower to restore,but Probably faster to restore, Probably slower to restore,but
but more difficult to have could effect reliable but more difficult to have could effect reliable
reliable restoration. restoration. reliable restoration. restoration.
High scalability Limited scalability: #nodes, High scalability Limited scalability: #nodes,
(hierarchical) links, circuits, messages (hierarchical) links, circuits, messages
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Planning (optimization) Planning is a background Planning (optimization) Planning is a background
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harder to achieve centralized activity harder to achieve centralized activity
Easier future integration Easier future integration
with other control plane with other control plane
layers layers
Table 1. Qualitative comparison between centralized and distributed Table 1. Qualitative comparison between centralized and distributed
approaches. approaches.
3.5. Why SDH/SONET will not Disappear Tomorrow 3.5. Why SDH/SONET will not Disappear Tomorrow
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directly over a wavelength. A framing or encapsulation is always directly over a wavelength. A framing or encapsulation is always
required to delimit IP datagrams. The Total Length field of an IP required to delimit IP datagrams. The Total Length field of an IP
header cannot be trusted to find the start of a new datagram, since header cannot be trusted to find the start of a new datagram, since
it could be corrupted and would result in a loss of synchronization. it could be corrupted and would result in a loss of synchronization.
The typical framing used today for IP over DWDM is defined in The typical framing used today for IP over DWDM is defined in
RFC1619/RFC2615 and known as POS (Packet Over SONET/SDH), i.e., IP RFC1619/RFC2615 and known as POS (Packet Over SONET/SDH), i.e., IP
over PPP (in HDLC-like format) over SDH/SONET. SDH and SONET are over PPP (in HDLC-like format) over SDH/SONET. SDH and SONET are
actually efficient encapsulations for IP. For instance, with an actually efficient encapsulations for IP. For instance, with an
average IP datagram length of 350 octets, an IP over GBE average IP datagram length of 350 octets, an IP over GBE
encapsulation using an 8B/10B encoding results in 28% overhead, an encapsulation using an 8B/10B encoding results in 28% overhead, an
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IP/ATM/SDH encapsulation results in 22% overhead and an IP/PPP/SDH IP/ATM/SDH encapsulation results in 22% overhead and an IP/PPP/SDH
encapsulation results in only 6% overhead. (New simplified encapsulation results in only 6% overhead. (New simplified
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encapsulations could reduce this overhead to as low as 3%, but the encapsulations could reduce this overhead to as low as 3%, but the
gain is not huge compared to SDH and SONET, which have other gain is not huge compared to SDH and SONET, which have other
benefits as well.) benefits as well.)
Any encapsulation of IP over WDM should at least provide error Any encapsulation of IP over WDM should at least provide error
monitoring capabilities (to detect signal degradation), error monitoring capabilities (to detect signal degradation), error
correction capabilities, such as FEC (Forward Error Correction) that correction capabilities, such as FEC (Forward Error Correction) that
are particularly needed for ultra long haul transmission, sufficient are particularly needed for ultra long haul transmission, sufficient
timing information, to allow robust synchronization (that is, to timing information, to allow robust synchronization (that is, to
detect the beginning of a packet), and capacity to transport detect the beginning of a packet), and capacity to transport
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that contains them, namely the STS-1, VT-6, VT-3, VT-2 and VT-1.5. that contains them, namely the STS-1, VT-6, VT-3, VT-2 and VT-1.5.
The STS-1 SPE corresponds to a VC-3, a VT-6 SPE corresponds to a VC- The STS-1 SPE corresponds to a VC-3, a VT-6 SPE corresponds to a VC-
2, a VT-2 SPE corresponds to a VC-12, and a VT-1.5 SPE corresponds 2, a VT-2 SPE corresponds to a VC-12, and a VT-1.5 SPE corresponds
to a VC-11. The SONET VT-3 SPE has no correspondence in SDH, however to a VC-11. The SONET VT-3 SPE has no correspondence in SDH, however
SDH's VC-4 corresponds to SONET's STS-3c SPE. SDH's VC-4 corresponds to SONET's STS-3c SPE.
In addition, it is possible to concatenate some of the structures In addition, it is possible to concatenate some of the structures
that contain these elements to build larger elements. For instance, that contain these elements to build larger elements. For instance,
SDH allows the concatenation of X contiguous AU-4s to build a VC-4- SDH allows the concatenation of X contiguous AU-4s to build a VC-4-
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Xc and of m contiguous TU-2s to build a VC-2-mc. In that case, a VC- Xc and of m contiguous TU-2s to build a VC-2-mc. In that case, a VC-
4-Xc or a VC-2-mc can be switched and controlled by MPLS. Note that 4-Xc or a VC-2-mc can be switched and controlled by MPLS. Note that
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SDH also defines virtual (non-contiguous) concatenation of TU- 2s, SDH also defines virtual (non-contiguous) concatenation of TU- 2s,
but in that case each constituent VC-2 is switched individually. but in that case each constituent VC-2 is switched individually.
4.2. SDH/SONET LSR and LSP Terminology 4.2. SDH/SONET LSR and LSP Terminology
Let a SDH or SONET Terminal Multiplexer (TM), Add-Drop Multiplexer Let a SDH or SONET Terminal Multiplexer (TM), Add-Drop Multiplexer
(ADM) or cross-connect (i.e. a switch) be called an SDH/SONET LSR. A (ADM) or cross-connect (i.e. a switch) be called an SDH/SONET LSR. A
SDH/SONET path or circuit between two SDH/SONET LSRs now becomes a SDH/SONET path or circuit between two SDH/SONET LSRs now becomes a
GMPLS LSP. An SDH/SONET LSP is a logical connection between the GMPLS LSP. An SDH/SONET LSP is a logical connection between the
point at which a tributary signal (client layer) is adapted into its point at which a tributary signal (client layer) is adapted into its
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protected versus being routed over those that are not ring protected protected versus being routed over those that are not ring protected
(differentiation based on reliability), the type of protection on a (differentiation based on reliability), the type of protection on a
SDH/SONET line would be an important topological parameter that SDH/SONET line would be an important topological parameter that
would have to be distributed via the link state routing protocol. would have to be distributed via the link state routing protocol.
(ii) Information that is only needed between two "adjacent" switches (ii) Information that is only needed between two "adjacent" switches
for the purposes of connection establishment is appropriate for for the purposes of connection establishment is appropriate for
distribution via one of the label distribution protocols. In fact, distribution via one of the label distribution protocols. In fact,
this information can be thought of as the "virtual" label. For this information can be thought of as the "virtual" label. For
example, in SONET networks, when distributing information to example, in SONET networks, when distributing information to
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switches concerning an end-to-end STS-1 path traversing a network, switches concerning an end-to-end STS-1 path traversing a network,
it is critical that adjacent switches agree on the multiplex entry it is critical that adjacent switches agree on the multiplex entry
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used by this STS-1 (but this information is only of local used by this STS-1 (but this information is only of local
significance between those two switches). Hence, the multiplex entry significance between those two switches). Hence, the multiplex entry
number in this case can be used as a virtual label. Note that the number in this case can be used as a virtual label. Note that the
label is virtual, in that it is not appended to the payload in any label is virtual, in that it is not appended to the payload in any
way, but it is still a label in the sense that it uniquely way, but it is still a label in the sense that it uniquely
identifies the signal locally on the link between the two switches. identifies the signal locally on the link between the two switches.
(iii) Information that all switches in the path need to know about a (iii) Information that all switches in the path need to know about a
circuit will also be distributed via the label distribution circuit will also be distributed via the label distribution
protocol. Examples of such information include bandwidth, priority, protocol. Examples of such information include bandwidth, priority,
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compare and contrast this situation with the datagram routing case compare and contrast this situation with the datagram routing case
[15]. In the case of routing datagrams, all routes on all nodes [15]. In the case of routing datagrams, all routes on all nodes
must be calculated exactly the same to avoid loops and "black must be calculated exactly the same to avoid loops and "black
holes". In circuit switching, this is not the case since routes are holes". In circuit switching, this is not the case since routes are
established per circuit and are fixed for that circuit. Hence, established per circuit and are fixed for that circuit. Hence,
unlike the datagram case, routing is not service impacting in the unlike the datagram case, routing is not service impacting in the
circuit switched case. This is helpful, because, to accommodate the circuit switched case. This is helpful, because, to accommodate the
optical layer, routing protocols need to be supplemented with new optical layer, routing protocols need to be supplemented with new
information, much more than the datagram case. This information is information, much more than the datagram case. This information is
also likely to be used in different ways for implementing different also likely to be used in different ways for implementing different
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GMPLS based Control of SDH/SONET May 2002
user services. Due to the increase in information transferred in user services. Due to the increase in information transferred in
the routing protocol, it may be useful to separate the relatively the routing protocol, it may be useful to separate the relatively
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GMPLS based Control of SDH/SONET February 2003
static parameters concerning a link from those that may be subject static parameters concerning a link from those that may be subject
to frequent changes. The current GMPLS routing extensions to frequent changes. The current GMPLS routing extensions
[12],[13],[14] do not make such a separation, however. [12],[13],[14] do not make such a separation, however.
6.1. Switching Capabilities 6.1. Switching Capabilities
The main switching capabilities that characterize a SONET/SDH end The main switching capabilities that characterize a SONET/SDH end
system and thus need to be advertised via the link state routing system and thus need to be advertised via the link state routing
protocol are: the switching granularity, supported forms of protocol are: the switching granularity, supported forms of
concatenation, and the level of transparency. concatenation, and the level of transparency.
skipping to change at line 776 skipping to change at line 777
VC-12s. In order to cover the needs of all manufacturers and VC-12s. In order to cover the needs of all manufacturers and
operators, GMPLS signaling [6],[7],[8] covers both higher order and operators, GMPLS signaling [6],[7],[8] covers both higher order and
lower order signals. lower order signals.
6.1.2. Signal Concatenation Capabilities 6.1.2. Signal Concatenation Capabilities
As stated in the SONET/SDH overview, to transport tributary signals As stated in the SONET/SDH overview, to transport tributary signals
with rates in excess of the basic STM-1/STS-1 signal, the VCs/SPEs with rates in excess of the basic STM-1/STS-1 signal, the VCs/SPEs
can be concatenated, i.e., glued together. Different types of can be concatenated, i.e., glued together. Different types of
concatenations are defined: contiguous standard concatenation, concatenations are defined: contiguous standard concatenation,
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GMPLS based Control of SDH/SONET May 2002
arbitrary concatenation, and virtual concatenation with different arbitrary concatenation, and virtual concatenation with different
rules concerning their size, placement, and binding. rules concerning their size, placement, and binding.
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GMPLS based Control of SDH/SONET February 2003
Standard SONET concatenation allows the concatenation of M x STS-1 Standard SONET concatenation allows the concatenation of M x STS-1
signals within an STS-N signal with M <= N, and M = 3, 12, 48, 192, signals within an STS-N signal with M <= N, and M = 3, 12, 48, 192,
...). The SPEs of these M x STS-1s can be concatenated to form an ...). The SPEs of these M x STS-1s can be concatenated to form an
STS-Mc. The STS-Mc notation is short hand for describing an STS-M STS-Mc. The STS-Mc notation is short hand for describing an STS-M
signal whose SPEs have been concatenated. The multiplexing signal whose SPEs have been concatenated. The multiplexing
procedures for SDH and SONET are given in references [4] and [5], procedures for SDH and SONET are given in references [4] and [5],
respectively. Constraints are imposed on the size of STS-Mc signals, respectively. Constraints are imposed on the size of STS-Mc signals,
i.e., they must be a multiple of 3, and on their starting location i.e., they must be a multiple of 3, and on their starting location
and interleaving. and interleaving.
skipping to change at line 833 skipping to change at line 833
implement with SONET/SDH signals rather than packets. Since virtual implement with SONET/SDH signals rather than packets. Since virtual
concatenation is provided by end systems, it is compatible with concatenation is provided by end systems, it is compatible with
existing SONET/SDH networks. Virtual concatenation is defined for existing SONET/SDH networks. Virtual concatenation is defined for
both higher order signals and low order signals. Table 3 shows the both higher order signals and low order signals. Table 3 shows the
nomenclature and capacity for several lower-order virtually nomenclature and capacity for several lower-order virtually
concatenated signals contained within different higher-order concatenated signals contained within different higher-order
signals. signals.
Table 3 Capacity of Virtually Concatenated VTn-Xv (9/G.707) Table 3 Capacity of Virtually Concatenated VTn-Xv (9/G.707)
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GMPLS based Control of SDH/SONET May 2002
Carried In X Capacity In steps Carried In X Capacity In steps
of of
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GMPLS based Control of SDH/SONET February 2003
VT1.5/ STS-1/VC-3 1 to 28 1600kbit/s to 1600kbit/s VT1.5/ STS-1/VC-3 1 to 28 1600kbit/s to 1600kbit/s
VC-11-Xv 44800kbit/s VC-11-Xv 44800kbit/s
VT2/ STS-1/VC-3 1 to 21 2176kbit/s to 2176kbit/s VT2/ STS-1/VC-3 1 to 21 2176kbit/s to 2176kbit/s
VC-12-Xv 45696kbit/s VC-12-Xv 45696kbit/s
VT1.5/ STS-3c/VC-4 1 to 64 1600kbit/s to 1600kbit/s VT1.5/ STS-3c/VC-4 1 to 64 1600kbit/s to 1600kbit/s
VC-11-Xv 102400kbit/s VC-11-Xv 102400kbit/s
VT2/ STS-3c/VC-4 1 to 63 2176kbit/s to 2176kbit/s VT2/ STS-3c/VC-4 1 to 63 2176kbit/s to 2176kbit/s
skipping to change at line 888 skipping to change at line 888
viewed as a constraint, since some multiplexers and switches may not viewed as a constraint, since some multiplexers and switches may not
switch with as fine a granularity as others. Table 4 summarizes the switch with as fine a granularity as others. Table 4 summarizes the
levels of SONET/SDH transparency. levels of SONET/SDH transparency.
Table 4. SONET/SDH transparency types and their properties. Table 4. SONET/SDH transparency types and their properties.
Transparency Type Comments Transparency Type Comments
Path Layer (or Line Standard higher order SONET path Path Layer (or Line Standard higher order SONET path
Terminating) switching. Line overhead is terminated Terminating) switching. Line overhead is terminated
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or modified. or modified.
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Line Level (or Section Preserves line overhead and switches Line Level (or Section Preserves line overhead and switches
Terminating) the entire line multiplex as a whole. Terminating) the entire line multiplex as a whole.
Section overhead is terminated or Section overhead is terminated or
modified. modified.
Section layer Preserves all section overhead, Section layer Preserves all section overhead,
Basically does not touch any of the Basically does not touch any of the
SONET/SDH bits. SONET/SDH bits.
6.2. Protection 6.2. Protection
skipping to change at line 945 skipping to change at line 944
1:1 Yes Dedicated protection. 1:1 Yes Dedicated protection.
1:N Yes One Protection line shared 1:N Yes One Protection line shared
by N working lines by N working lines
4F-BLSR (4 Yes Dedicated protection, with 4F-BLSR (4 Yes Dedicated protection, with
fiber bi- alternative ring path. fiber bi- alternative ring path.
directional directional
line switched line switched
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GMPLS based Control of SDH/SONET May 2002
ring) ring)
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2F-BLSR (2 Yes Dedicated protection, with 2F-BLSR (2 Yes Dedicated protection, with
fiber bi- alternative ring path fiber bi- alternative ring path
directional directional
line switched line switched
ring) ring)
UPSR (uni- No Dedicated protection via UPSR (uni- No Dedicated protection via
directional alternative ring path. directional alternative ring path.
path switched Typically used in access path switched Typically used in access
ring) networks. ring) networks.
skipping to change at line 999 skipping to change at line 997
number between working and protection lines number between working and protection lines
Protection line Used to indicate if the line is a Protection line Used to indicate if the line is a
number protection line. number protection line.
Extra Traffic Yes or No Extra Traffic Yes or No
Supported Supported
Layer If this protection parameter is specific to Layer If this protection parameter is specific to
SONET then this parameter is unneeded, SONET then this parameter is unneeded,
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otherwise it would indicate the signal otherwise it would indicate the signal
layer that the protection is applied. layer that the protection is applied.
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An open issue concerning protection is the extent of information An open issue concerning protection is the extent of information
regarding protection that must be disseminated. The contents of regarding protection that must be disseminated. The contents of
Table 6 represent one extreme while a simple enumerated list of: Table 6 represent one extreme while a simple enumerated list of:
Extra-Traffic/Protection line, Unprotected, Shared (1:N)/Working Extra-Traffic/Protection line, Unprotected, Shared (1:N)/Working
line, Dedicated (1:1, 1+1)/Working Line, Enhanced (Ring) /Working line, Dedicated (1:1, 1+1)/Working Line, Enhanced (Ring) /Working
Line, represents the other. Line, represents the other.
There is also a potential implication for link bundling [16], that There is also a potential implication for link bundling [16], that
is, for each link, the routing protocol could advertise whether that is, for each link, the routing protocol could advertise whether that
link is a working or protection link and possibly some parameters link is a working or protection link and possibly some parameters
skipping to change at line 1055 skipping to change at line 1052
information is updated, the percentage of connection establishments information is updated, the percentage of connection establishments
that are unsuccessful on their first attempt due to the granularity that are unsuccessful on their first attempt due to the granularity
of the advertised information, and the extent to which network of the advertised information, and the extent to which network
resources can be optimized. There are different levels of resources can be optimized. There are different levels of
summarization that are being considered today for the available summarization that are being considered today for the available
capacity information. At one extreme, all signals that are allocated capacity information. At one extreme, all signals that are allocated
on an interface could be advertised, while at the other extreme, a on an interface could be advertised, while at the other extreme, a
single aggregated value of the available bandwidth per link could be single aggregated value of the available bandwidth per link could be
advertised. advertised.
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Consider first the relatively simple structure of SONET and its most Consider first the relatively simple structure of SONET and its most
common current and planned usage. DS1s and DS3s are the signals most common current and planned usage. DS1s and DS3s are the signals most
often carried within a SONET STS-1. Either a single DS3 occupies often carried within a SONET STS-1. Either a single DS3 occupies
the STS-1 or up to 28 DS1s (4 each within the 7 VT groups) are the STS-1 or up to 28 DS1s (4 each within the 7 VT groups) are
carried within the STS-1. With a reasonable VT1.5 placement carried within the STS-1. With a reasonable VT1.5 placement
algorithm within each node it may be possible to just report on algorithm within each node it may be possible to just report on
aggregate bandwidth usage in terms of number of whole STS-1s aggregate bandwidth usage in terms of number of whole STS-1s
(dedicated to DS3s) used and the number of STS-1s dedicated to (dedicated to DS3s) used and the number of STS-1s dedicated to
carrying DS1s allocated for this purpose. This way a network carrying DS1s allocated for this purpose. This way a network
skipping to change at line 1110 skipping to change at line 1107
the paths that would be selected in response to a request to set up the paths that would be selected in response to a request to set up
a batch of connections between a set of endpoints in order to a batch of connections between a set of endpoints in order to
optimize network link utilization. One can think of this along the optimize network link utilization. One can think of this along the
lines of global or local optimization of the network in time. lines of global or local optimization of the network in time.
Due to the complexity of some of the connection routing algorithms Due to the complexity of some of the connection routing algorithms
(high dimensionality, non-linear integer programming problems) and (high dimensionality, non-linear integer programming problems) and
various criteria by which one may optimize a network, it may not be various criteria by which one may optimize a network, it may not be
possible or desirable to run these algorithms on network nodes. possible or desirable to run these algorithms on network nodes.
However, it may still be desirable to have some basic path However, it may still be desirable to have some basic path
computation ability running on the network nodes, particularly for
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computation ability running on the network nodes, particularly for
use during restoration situations. Such an approach is in line with use during restoration situations. Such an approach is in line with
the use of MPLS for traffic engineering, but is much different than the use of MPLS for traffic engineering, but is much different than
typical OSPF or IS-IS usage where all nodes must run the same typical OSPF or IS-IS usage where all nodes must run the same
routing algorithm. routing algorithm.
7. LSP Provisioning/Signaling for SDH/SONET 7. LSP Provisioning/Signaling for SDH/SONET
Traditionally, end-to-end circuit connections in SDH/SONET networks Traditionally, end-to-end circuit connections in SDH/SONET networks
have been set up via network management systems (NMSs), which issue have been set up via network management systems (NMSs), which issue
commands (usually under the control of a human operator) to the commands (usually under the control of a human operator) to the
various network elements involved in the circuit, via an equipment various network elements involved in the circuit, via an equipment
vendor's element management system (EMS). Very little multi-vendor vendor's element management system (EMS). Very little multi-vendor
interoperability has been achieved via management systems. Hence, interoperability has been achieved via management systems. Hence, end-
end-to-end circuits in a multi-vendor environment typically require to-end circuits in a multi-vendor environment typically require the
the use of multiple management systems and the infamous use of multiple management systems and the infamous configuration via
configuration via "yellow sticky notes". As discussed in Section 2, "yellow sticky notes". As discussed in Section 2, a common signaling
a common signaling protocol, such as RSVP with TE extensions or CR- protocol, such as RSVP with TE extensions or CR- LDP appropriately
LDP appropriately extended for circuit switching applications, could extended for circuit switching applications, could therefore help to
therefore help to solve these interoperability problems. In this solve these interoperability problems. In this section, we examine the
section, we examine the various components involved in the automated various components involved in the automated provisioning of SONET/SDH
provisioning of SONET/SDH LSPs. LSPs.
7.1.1. What do we Label in SDH/SONET? Frames or Circuits? 7.1.1. What do we Label in SDH/SONET? Frames or Circuits?
MPLS was initially introduced to control asynchronous technologies MPLS was initially introduced to control asynchronous technologies
like IP, where a label was attached to each individual block of like IP, where a label was attached to each individual block of
data, such as an IP packet or a Frame Relay frame. SONET and SDH, data, such as an IP packet or a Frame Relay frame. SONET and SDH,
however, are synchronous technologies that define a multiplexing however, are synchronous technologies that define a multiplexing
structure (see Section 3), which we referred to as the SDH (or structure (see Section 3), which we referred to as the SDH (or
SONET) multiplex. This multiplex involves a hierarchy of signals, SONET) multiplex. This multiplex involves a hierarchy of signals,
lower order signals embedded within successive higher order ones lower order signals embedded within successive higher order ones
skipping to change at line 1167 skipping to change at line 1164
For instance, the payload of an SDH STM-1 frame does not fully For instance, the payload of an SDH STM-1 frame does not fully
contain a complete unit of user data. In fact, the user data is contain a complete unit of user data. In fact, the user data is
contained in a virtual container (VC) that is allowed to float over contained in a virtual container (VC) that is allowed to float over
two contiguous frames for synchronization purposes. A pointer in the two contiguous frames for synchronization purposes. A pointer in the
Section Overhead (SOH) indicates the beginning of the VC in the Section Overhead (SOH) indicates the beginning of the VC in the
payload. Thus, frames are now inter-related, since each consecutive payload. Thus, frames are now inter-related, since each consecutive
pair may share a common virtual container. From the point of view of pair may share a common virtual container. From the point of view of
GMPLS, therefore, it is not the successive frames that are treated GMPLS, therefore, it is not the successive frames that are treated
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GMPLS based Control of SDH/SONET May 2002 GMPLS based Control of SDH/SONET February 2003
independently or labeled, but rather the entire user signal. An independently or labeled, but rather the entire user signal. An
identical argument applies to SONET. identical argument applies to SONET.
Observe also that the GMPLS signaling used to control the SDH/SONET Observe also that the GMPLS signaling used to control the SDH/SONET
multiplex must honor its hierarchy. In other words, the SDH/SONET multiplex must honor its hierarchy. In other words, the SDH/SONET
layer should not be viewed as homogeneous and flat, because this layer should not be viewed as homogeneous and flat, because this
would limit the scope of the services that SDH/SONET can provide. would limit the scope of the services that SDH/SONET can provide.
Instead, GMPLS tunnels should be used to dynamically and Instead, GMPLS tunnels should be used to dynamically and
hierarchically control the SDH/SONET multiplex. For example, one hierarchically control the SDH/SONET multiplex. For example, one
skipping to change at line 1224 skipping to change at line 1221
difficult to match a label with the corresponding signal, since , as difficult to match a label with the corresponding signal, since , as
we saw in Section 7.1.1, the label is not coded in the SDH/SONET we saw in Section 7.1.1, the label is not coded in the SDH/SONET
overhead of the signal. overhead of the signal.
Another way is to use the well-defined and finite structure of the Another way is to use the well-defined and finite structure of the
SDH/SONET multiplexing tree to devise a signal numbering scheme that SDH/SONET multiplexing tree to devise a signal numbering scheme that
makes use of the multiplex as a naming tree, and assigns each makes use of the multiplex as a naming tree, and assigns each
multiplex entry a unique associated value. This allows the unique multiplex entry a unique associated value. This allows the unique
identification of each multiplex entry (signal) in terms of its type identification of each multiplex entry (signal) in terms of its type
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GMPLS based Control of SDH/SONET May 2002 GMPLS based Control of SDH/SONET February 2003
and position in the multiplex tree. By using this multiplex entry and position in the multiplex tree. By using this multiplex entry
value itself as the label, we automatically add SDH/SONET semantics value itself as the label, we automatically add SDH/SONET semantics
to the label! Thus, simply by examining the label, one can now to the label! Thus, simply by examining the label, one can now
directly deduce the signal that it represents, as well as its directly deduce the signal that it represents, as well as its
position in the SDH/SONET multiplex. We refer to this as position in the SDH/SONET multiplex. We refer to this as
multiplex-based labeling. This is the idea that was incorporated in multiplex-based labeling. This is the idea that was incorporated in
the GMPLS signaling specifications for SDH/SONET [17]. the GMPLS signaling specifications for SDH/SONET [17].
7.3. Signaling Elements 7.3. Signaling Elements
skipping to change at line 1279 skipping to change at line 1276
We began with a brief overview of MPLS and SDH/SONET networks, We began with a brief overview of MPLS and SDH/SONET networks,
discussing current circuit establishment in TDM networks, and discussing current circuit establishment in TDM networks, and
arguing why SDH/SONET technologies will not be "outdated" in the arguing why SDH/SONET technologies will not be "outdated" in the
foreseeable future. Next, we looked at MPLS applied to SDH/SONET foreseeable future. Next, we looked at MPLS applied to SDH/SONET
networks, where we considered why such an application makes sense, networks, where we considered why such an application makes sense,
and reviewed some MPLS terminology as applied to TDM networks. We and reviewed some MPLS terminology as applied to TDM networks. We
considered the two main areas of application of MPLS methods to TDM considered the two main areas of application of MPLS methods to TDM
networks, namely routing and signaling. We reviewed in detail the networks, namely routing and signaling. We reviewed in detail the
switching capabilities of TDM equipment, and the requirement to switching capabilities of TDM equipment, and the requirement to
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GMPLS based Control of SDH/SONET May 2002 GMPLS based Control of SDH/SONET February 2003
learn about the protection capabilities of underlying links, and how learn about the protection capabilities of underlying links, and how
these influence the available capacity advertisement in TDM these influence the available capacity advertisement in TDM
networks. We focused briefly on path computation methods, pointing networks. We focused briefly on path computation methods, pointing
out that these were not subject to standardization. We then examined out that these were not subject to standardization. We then examined
optical path provisioning or signaling, considering the issue of optical path provisioning or signaling, considering the issue of
what constitutes an appropriate label for TDM circuits and how this what constitutes an appropriate label for TDM circuits and how this
label should be structured, and we focused on the importance of label should be structured, and we focused on the importance of
hierarchical label allocation in a TDM network. Finally, we reviewed hierarchical label allocation in a TDM network. Finally, we reviewed
the signaling elements involved when setting up an optical TDM the signaling elements involved when setting up an optical TDM
skipping to change at line 1311 skipping to change at line 1308
We acknowledge all the participants of the MPLS and CCAMP WGs, whose We acknowledge all the participants of the MPLS and CCAMP WGs, whose
constant enquiry about GMPLS issues in TDM networks motivated the constant enquiry about GMPLS issues in TDM networks motivated the
writing of this document, and whose questions helped shape its writing of this document, and whose questions helped shape its
contents. Also, thanks to Kireeti Kompella for his careful reading contents. Also, thanks to Kireeti Kompella for his careful reading
of the last version of this draft, and for his helpful comments and of the last version of this draft, and for his helpful comments and
feedback. feedback.
11.Author's Addresses 11.Author's Addresses
Greg Bernstein Greg Bernstein
Ciena Corporation Grotto Networking
10480 Ridgeview Court
Cupertino, CA 94014
Phone: +1 510 573-2237 Phone: +1 510 573-2237
E-mail: greg@ciena.com E-mail: greg@ciena.com
Eric Mannie Eric Mannie
KPNQwest InterAir Link
Terhulpsesteenweg 6A
1560 Hoeilaart - Belgium Phone: +32 2 790 34 25
Phone: +32 2 658 56 52 E-mail: eric_mannie@hotmail.com
Mobile: +32 496 58 56 52
Fax: +32 2 658 51 18
E-mail: eric.mannie@kpnqwest.com
Vishal Sharma Vishal Sharma
Metanoia, Inc. Metanoia, Inc.
305 Elan Village Lane, Unit 121 1600 Villa Street, Unit 352
San Jose, CA 95134 Mountain View, CA 94041
Phone: +1 408 955 0910
Phone: +1 650 386 6723
Email: v.sharma@ieee.org Email: v.sharma@ieee.org
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GMPLS based Control of SDH/SONET May 2002 GMPLS based Control of SDH/SONET February 2003
Full Copyright Statement Full Copyright Statement
"Copyright (C) The Internet Society (date). All Rights Reserved. "Copyright (C) The Internet Society (date). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published or assist in its implmentation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this are included on all such copies and derivative works. However, this
skipping to change at line 1370 skipping to change at line 1364
[3] Rosen, E., Viswanathan, A., and Callon, R., "Multiprotocol Label [3] Rosen, E., Viswanathan, A., and Callon, R., "Multiprotocol Label
Switching Architecture", RFC 3031, January 2001. Switching Architecture", RFC 3031, January 2001.
[4] G.707, Network Node Interface for the Synchronous Digital [4] G.707, Network Node Interface for the Synchronous Digital
Hierarchy (SDH), International Telecommunication Union, 03/96. Hierarchy (SDH), International Telecommunication Union, 03/96.
[5] Synchronous Optical Network (SONET) Basic Description including [5] Synchronous Optical Network (SONET) Basic Description including
Multiplex Structure, Rates, and Formats, ANSI T1.105-1995. Multiplex Structure, Rates, and Formats, ANSI T1.105-1995.
[6] Berger, L. (Editor), "Generalized MPLS - - Signaling Functional [6] Berger, L. (Editor), "Generalized MPLS - - Signaling Functional
Description," Internet Draft, Work in Progress, draft-ietf-mpls- Description," RFC 3472, January 2003.
generalized-signaling-08.txt, April 2002.
[7] Berger, L. (Editor), "Generalized MPLS Signaling - - RSVP-TE [7] Berger, L. (Editor), "Generalized MPLS Signaling - - RSVP-TE
Extensions," Internet Draft, Work in Progress, draft-ietf-mpls- Extensions," RFC 3473, January 2003.
generalized-rsvp-te-07.txt, April 2002.
[8] Berger, L. (Editor), "Generalized MPLS Signaling - - CR-LDP [8] Berger, L. (Editor), "Generalized MPLS Signaling - - CR-LDP
Extensions," Internet Draft, Work in Progress, draft-ietf-mpls- Extensions," RFC 3473, January 2003.
generalized-cr-ldp-06.txt, April 2002.
[9] Bernstein, G., Yates, J., Saha, D., "IP-Centric Control and [9] Bernstein, G., Yates, J., Saha, D., "IP-Centric Control and
Management of Optical Transport Networks," IEEE Communications Management of Optical Transport Networks," IEEE Communications
Mag., Vol. 40, Issue 10, October 2000. Mag., Vol. 40, Issue 10, October 2000.
Bernstein, Mannie, Sharma Informational- Expires August 2002 25
GMPLS based Control of SDH/SONET May 2002
[10] ANSI T1.105.01-1995, Synchronous Optical Network (SONET) [10] ANSI T1.105.01-1995, Synchronous Optical Network (SONET)
Automatic Protection Switching, American National Standards Automatic Protection Switching, American National Standards
Institute. Institute.
Bernstein, Mannie, Sharma Expires August 2003 25
GMPLS based Control of SDH/SONET February 2003
[11] G.841, Types and Characteristics of SDH Network Protection [11] G.841, Types and Characteristics of SDH Network Protection
Architectures, ITU-T, 07/95. Architectures, ITU-T, 07/95.
[12] Kompella, K., et al, "Routing Extensions in Support of [12] Kompella, K., et al, "Routing Extensions in Support of
Generalize MPLS, " Internet Draft, Work-in-Progress, draft-ietf- Generalize MPLS, " Internet Draft, Work-in-Progress, draft-ietf-
ccamp-gmpls-routing-04.txt, April 2002. ccamp-gmpls-routing-05.txt, August 2002.
[13] Kompella, K., et al, "OSPF Extensions in Support of Generalize [13] Kompella, K., et al, "OSPF Extensions in Support of Generalize
MPLS," Internet Draft, Work-in-Progress, draft-ietf-ccamp-ospf- MPLS," Internet Draft, Work-in-Progress, draft-ietf-ccamp-ospf-
extensions-07.txt, May 2002. extensions-09.txt, December 2002.
[14] Kompella, K., et al, "IS-IS Extensions in Support of Generalize [14] Kompella, K., et al, "IS-IS Extensions in Support of Generalize
MPLS," Internet Draft, Work-in-Progress, draft-ietf-isis-gmpls- MPLS," Internet Draft, Work-in-Progress, draft-ietf-isis-gmpls-
extensions-12.txt, May 2002. extensions-16.txt, August 2002.
[15] Bernstein, G., Sharma, V., Ong, L., ææInter-domain Optical [15] Bernstein, G., Sharma, V., Ong, L., ææInter-domain Optical
Routing,ÆÆ OSA J. of Optical Networking, vol. 1, no. 2, pp. 80-92. Routing,ÆÆ OSA J. of Optical Networking, vol. 1, no. 2, pp. 80-92.
[16] Kompella, K., Rekhter, Y., and Berger, L., "Link Bundling in [16] Kompella, K., Rekhter, Y., and Berger, L., "Link Bundling in
MPLS Traffic Engineering", Internet Draft, Work-in-Progress, MPLS Traffic Engineering", Internet Draft, Work-in-Progress,
draft-kompella-mpls-bundle-05.txt, Feb. 2001. draft-ietf-mpls-bundle-04.txt, July 2002.
[17] Mannie, E. (Editor), "GMPLS Extensions for SONET and SDH [17] Mannie, E. (Editor), "GMPLS Extensions for SONET and SDH
Control", Internet Draft, Work-in-Progress, draft-ietf-ccamp- Control", Internet Draft, Work-in-Progress, draft-ietf-ccamp-
gmpls-sonet-sdh-04.txt, April 2002. gmpls-sonet-sdh-07.txt, October 2002.
Bernstein, Mannie, Sharma Informational- Expires August 2002 26 Bernstein, Mannie, Sharma Expires August 2003 26
 End of changes. 

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