CCAMP Working Group S. Belotti, Ed.
Internet-Draft P. Grandi
Intended status: Informational Alcatel-Lucent
Expires: March 24, 2012 D. Ceccarelli, Ed.
D. Caviglia
Ericsson
F. Zhang
D. Li
Huawei Technologies
September 21, 2011
Information model for G.709 Optical Transport Networks (OTN)
draft-ietf-ccamp-otn-g709-info-model-01
Abstract
The recent revision of ITU-T recommendation G.709 [G.709-v3] has
introduced new fixed and flexible ODU containers in Optical Transport
Networks (OTNs), enabling optimized support for an increasingly
abundant service mix.
This document provides a model of information needed by the routing
and signaling process in OTNs to support Generalized Multiprotocol
Label Switching (GMPLS) control of all currently defined ODU
containers.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 24, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. OSPF-TE requirements overview . . . . . . . . . . . . . . . . 4
3. RSVP-TE requirements overview . . . . . . . . . . . . . . . . 5
4. G.709 Digital Layer Info Model for Routing and Signaling . . . 5
4.1. Tributary Slot Granularity . . . . . . . . . . . . . . . . 8
4.1.1. Fall-back procedure . . . . . . . . . . . . . . . . . 10
4.2. Tributary Port Number . . . . . . . . . . . . . . . . . . 11
4.3. Signal type . . . . . . . . . . . . . . . . . . . . . . . 11
4.4. Bit rate and tolerance . . . . . . . . . . . . . . . . . . 13
4.5. Unreserved Resources . . . . . . . . . . . . . . . . . . . 13
4.6. Maximum LSP Bandwidth . . . . . . . . . . . . . . . . . . 13
4.7. Distinction between terminating and switching
capability . . . . . . . . . . . . . . . . . . . . . . . . 14
4.8. Priority Support . . . . . . . . . . . . . . . . . . . . . 16
4.9. Multi-stage multiplexing . . . . . . . . . . . . . . . . . 16
4.10. Generalized Label . . . . . . . . . . . . . . . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
GMPLS[RFC3945] extends MPLS to include Layer-2 Switching (L2SC),
Time-Division Multiplexing (e.g., SONET/SDH, PDH, and OTN),
Wavelength (OCh, Lambdas) Switching and Spatial Switching (e.g.,
incoming port or fiber to outgoing port or fiber).
The establishment of LSPs that span only interfaces recognizing
packet/cell boundaries is defined in [RFC3036, RFC3212, RFC3209].
[RFC3471] presents a functional description of the extensions to
Multi-Protocol Label Switching (MPLS) signaling required to support
GMPLS. ReSource reserVation Protocol-Traffic Engineering (RSVP-TE)
-specific formats,mechanisms and technology specific details are
defined in [RFC3473].
From a routing perspective, Open Shortest Path First-Traffic
Engineering (OSPF-TE) generates Link State Advertisements (LSAs)
carrying application-specific information and floods them to other
nodes as defined in [RFC5250]. Three types of opaque LSA are
defined, i.e. type 9 - link-local flooding scope, type 10 - area-
local flooding scope, type 11 - AS flooding scope.
Type 10 LSAs are composed of a standard LSA header and a payload
including one top-level TLV and possible several nested sub-TLVs.
[RFC3630] defines two top-level TLVs: Router Address TLV and Link
TLV; and nine possible sub-TLVs for the Link TLV, used to carry link
related TE information. The Link type sub-TLVs are enhanced by
[RFC4203] in order to support GMPLS networks and related specific
link information. In GMPLS networks each node generates TE LSAs to
advertise its TE information and capabilities (link-specific or node-
specific)through the network. The TE information carried in the LSAs
are collected by the other nodes of the network and stored into their
local Traffic Engineering Databases (TED).
In a GMPLS enabled G.709 Optical Transport Networks (OTN), routing
and signaling are fundamental in order to allow automatic calculation
and establishment of routes for ODUk LSPs. The recent revision of
ITU-T Recommendation G.709 [G709-V3] has introduced new fixed and
flexible ODU containers that augment those specified in foundation
OTN. As a result, it is necessary to provide OSPF-TE and RSVP-TE
extensions to allow GMPLS control of all currently defined ODU
containers.
This document provides the information model needed by the routing
and signaling processses in OTNs to allow GMPLS control of all
currently defined ODU containers.
OSPF-TE and RSVP-tE requirements are defined in [OTN-FWK], while
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protocol extensions are defined in [OTN-OSPF] and [OTN-RSVP].
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. OSPF-TE requirements overview
[OTN-FWK] provides a set of functional routing requirements
summarized below :
- Support for link multiplexing capability advertisement: The
routing protocol has to be able to carry information regarding the
capability of an OTU link to support different type of ODUs
- Support of any ODUk and ODUflex: The routing protocol must be
capable of carrying the required link bandwidth information for
performing accurate route computation for any of the fixed rate
ODUs as well as ODUflex.
- Support for differentiation between switching and terminating
capacity
- Support for the client server mappings as required by
[G.7715.1]. The list of different mappings methods is reported in
[G.709-v3]. Since different methods exist for how the same client
layer is mapped into a server layer, this needs to be captured in
order to avoid the set-up of connections that fail due to
incompatible mappings.
- Support different priorities for resource reservation. How many
priorities levels should be supported depends on operator
policies. Therefore, the routing protocol should be capable of
supporting either no priorities or up to 8 priority levels as
defined in [RFC4202].
- Support link bundling of component links at the same line rate
and with same muxing hierarchy.
- Support for Tributary Slot Granularity (TSG) advertisement.
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3. RSVP-TE requirements overview
[OTN-FWK] also provides a set of functional signaling requirements
summarized below :
- Support for LSP setup of new ODUk/ODUflex containers with
related mapping and multiplexing capabilities
- Support for LSP setup using different Tributary Slot granularity
- Support for Tributary Port Number allocation and negoziation
- Support for constraint signaling
- Support for TSG signaling
4. G.709 Digital Layer Info Model for Routing and Signaling
The digital OTN layered structure is comprised of digital path layer
networks (ODU) and digital section layer networks (OTU). An OTU
section layer supports one ODU path layer as client and provides
monitoring capability for the OCh. An ODU path layer may transport a
heterogeneous assembly of ODU clients. Some types of ODUs (i.e.,
ODU1, ODU2, ODU3, ODU4) may assume either a client or server role
within the context of a particular networking domain. ITU-T G.872
recommendation provides two tables defining mapping and multiplexing
capabilities of OTNs, which are reproduced below.
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+--------------------+--------------------+
| ODU client | OTU server |
+--------------------+--------------------+
| ODU 0 | - |
+--------------------+--------------------+
| ODU 1 | OTU 1 |
+--------------------+--------------------+
| ODU 2 | OTU 2 |
+--------------------+--------------------+
| ODU 2e | - |
+--------------------+--------------------+
| ODU 3 | OTU 3 |
+--------------------+--------------------+
| ODU 4 | OTU 4 |
+--------------------+--------------------+
| ODU flex | - |
+--------------------+--------------------+
Figure 1: OTN mapping capability
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+=================================+=========================+
| ODU client | ODU server |
+---------------------------------+-------------------------+
| 1,25 Gbps client | |
+---------------------------------+ ODU 0 |
| - | |
+=================================+=========================+
| 2,5 Gbps client | |
+---------------------------------+ ODU 1 |
| ODU 0 | |
+=================================+=========================+
| 10 Gbps client | |
+---------------------------------+ ODU 2 |
| ODU0,ODU1,ODUflex | |
+=================================+=========================+
| 10,3125 Gbps client | |
+---------------------------------+ ODU 2e |
| - | |
+=================================+=========================+
| 40 Gbps client | |
+---------------------------------+ ODU 3 |
| ODU0,ODU1,ODU2,ODU2e,ODUflex | |
+=================================+=========================+
| 100 Gbps client | |
+---------------------------------+ ODU 4 |
|ODU0,ODU1,ODU2,ODU2e,ODU3,ODUflex| |
+=================================+=========================+
|CBR clients from greater than | |
|2.5 Gbit/s to 100 Gbit/s: or | |
|GFP-F mapped packet clients from | ODUflex |
|1.25 Gbit/s to 100 Gbit/s. | |
+---------------------------------+ |
| - | |
+=================================+=========================+
Figure 2: OTN multiplexing capability
How an ODUk connection service is transported within an operator
network is governed by operator policy. For example, the ODUk
connection service might be transported over an ODUk path over an
OTUk section, with the path and section being at the same rate as
that of the connection service (see Table 1). In this case, an
entire lambda of capacity is consumed in transporting the ODUk
connection service. On the other hand, the operator might exploit
different multiplexing capabilities in the network to improve
infrastructure efficiencies within any given networking domain. In
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this case, ODUk multiplexing may be performed prior to transport over
various rate ODU servers (as per Table 2) over associated OTU
sections.
From the perspective of multiplexing relationships, a given ODUk may
play different roles as it traverses various networking domains.
As detailed in [OTN-FWK], client ODUk connection services can be
transported over:
o Case A) one or more wavelength sub-networks connected by optical
links or
o Case B) one or more ODU links (having sub-lambda and/or lambda
bandwidth granularity)
o Case C) a mix of ODU links and wavelength sub-networks.
This document considers the TE information needed for ODU path
computation and parameters needed to be signaled for LSP setup.
The following sections list and analyze each type of data that needs
to be advertised and signaled in order to support path computation
and LSP setup.
4.1. Tributary Slot Granularity
ITU-T recommendations define two types of TS but each link can only
support a single type at a given time. The rules to be followed when
selecting the TS to be used are:
- If both ends of a link can support both 2.5Gbps TS and 1.25Gbps
TS, then the link will work with 1.25Gbps TS.
- If one end can support the 1.25Gbps TS, and another end the
2.5Gbps TS, the link will work with 2.5Gbps TS.
The tributary slot type information is one of the parameters needed
to correctly configure physical interfaces. When setting up and HO-
ODUk/OTUk LSP or an H-LSP/FA, the penultimate node of the path might
need to choose among interfaces supporting 1,25 Gbps or 2,5 Gbps.
The choice depends on the type of client signal (e.g. an ODU0 can
only be supported by 1.25Gbps TSG) and this information needs to be
carried in the signaling messages.
In order to carry the tributary slot granularity information, an
object that can be examinded by the penultimate hop and terminated
just by the end nodes of the path is needed. The utilization of the
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label is not the correct choice as it can be changed hop by hop. One
possible solution is the G-PID field of the GENERALIZED LABEL REQUEST
Object. The following table shows the different mapping
possibilities depending on the TSG types. The client types are shown
in the left column, while the different OPUk server and related TSGs
are listed in the top row.
+------------------------------------------------+
| 2.5G TS || 1.25G TS |
| OPU2 | OPU3 || OPU1 | OPU2 | OPU3 | OPU4 |
+-------+------------------------------------------------+
| | - | - || AMP | GMP | GMP | GMP |
| ODU0 | | || PT=20 | PT=21 | PT=21 | PT=21 |
+-------+------------------------------------------------+
| | AMP | AMP || - | AMP | AMP | GMP |
| ODU1 | PT=20 | PT=20 || | PT=21 | PT=21 | PT=21 |
+-------+------------------------------------------------+
| | - | AMP || - | - | AMP | GMP |
| ODU2 | | PT=20 || | | PT=21 | PT=21 |
+-------+------------------------------------------------+
| | - | - || - | - | GMP | GMP |
| ODU2e | | || | | PT=21 | PT=21 |
+-------+------------------------------------------------+
| | - | - || - | - | - | GMP |
| ODU3 | | || | | | PT=21 |
+-------+------------------------------------------------+
| | - | - || - | GMP | GMP | GMP |
| ODUfl | | || | PT=21 | PT=21 | PT=21 |
+-------+------------------------------------------------+
Figure 3: ODUj into OPUk mapping types
The G-PID value defined in [RFC 4328] is associated to the mapping
with 2.5Gbps TSG type (G-PID = 47). A new G-PID value has to be
defined (TBA by IANA) in order to cover the mapping on 1.25Gbps TSG
type.
The G-PID information is not enough to have a complete choice since
the penultimate hop node has to distinguish between interfaces with
the same TSG (e.g. 1.25Gbps) whether the interface is able to support
the right hierarchy, i.e. it is possible to have two interfaces both
at 1.25 TSG but only one is supporting ODU0.
A dedicated optional object should to be defined in order to carry
the multiplexing hierarchy and have a more precise choice capability.
In this way, when the penultimate node receives the GENERALIZED LABEL
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REQUEST Object, the G-PID value together with the ODU bandwdith
included into the Traffic Parameters Object allow desuming the
correct TSG value.
As an example it is possible to consider the setup of an ODU3 path
that is going to carry an ODU0. In this case it is needed the
support of 1,25 GBps TS. The information related to the TSG is
carried via the G-PID and node C, having two different interfaces
toward D with different TSG, can choose the right one as depicted in
the following figure.
ODU0
________________________________________
| |
+--------+ +--------+ +--------+ +--------+
| | | | | | 1.25 | |
| Node | | Node | | Node +------+ Node |
| A +------+ B +------+ C | ODU3 | D |
| | ODU3 | | ODU3 | +------+ |
+--------+ 1.25 +--------+ 1.25 +--------+ 2.5 +--------+
Figure 4: TSG in signaling
The TSG information is needed also in the routing protocol as the
ingress node (A in the previous example) needs to know if the
interfaces between C and D can support the required TSG. In case
they cannot, A will compute an alternate path from itself to D.
In a multi-stage multiplexing environment any layer can have a
different TSG structure, e.g. in a multiplexing hierarchy like
ODU0->ODU2->ODU3, the ODU3 can be structured at TSG=2.5 in order to
support an ODU2 connection, but this ODU2 connection can be a tunnel
for ODU0, and hence structured with 1.25 TSG. Therefore any
multiplexing level has to advertise his TSG capabilities in order to
allow a correct path computation by the end nodes (both of the ODUk
trail and of the H-LSP/FA).
4.1.1. Fall-back procedure
SG15 ITU-T G.798 recommendation describes the so called PT=21-to-
PT=20 interworking process that explains how two equipments with
interfaces with different PayloadType, and hence different TS
granularity (1.25Gbps vs. 2.5Gbps), can be coordinated so to permit
the equipment with 1.25 TS granularity to adapt his TS allocation
accordingly to the different TS granularity (2.5Gbps) of a neighbour.
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Therefore, in order to let the NE change TS granularity accordingly
to the nieghbour requirements, the AUTOpayloadtype needs to be set.
When both the neighbors (link or trail) have been configured as
structured, the payload type received in the overhead is compared to
the transmitted PT. If they are different and the transmitted PT=21,
the node must fallback to PT=20. In this case the fall-back process
makes the system self consistent and the only reason for signaling
the TS granularity is to provide the correct label (i.e. label for
PT=21 has twice the TS number of PT=20). On the other side, if the
AUTOpayloadtype is not configured, the RSVP-TE consequent actions in
case of TS mismatch need to be defined.
4.2. Tributary Port Number
[RFC4328] supports only the deprecated auto-MSI mode which assumes
that the Tributary Port Number is automatically assigned in the
transmit direction and not checked in the receive direction.
As described in [G709-V3] and [G798-V3], the OPUk overhead in an OTUk
frame contains n (n = the total number of TSs of the ODUk) MSI
(Multiplex Structure Identifier) bytes (in the form of multi-frame),
each of which is used to indicate the association between tributary
port number and tributary slot of the ODUk.
The association between TPN and TS has to be configured by the
control plane and checked by the data plane on each side of the link.
(Please refer to [OTN-FWK] for further details). As a consequence,
the RSVP-TE signaling needs to be extended to support the TPN
assignment function.
4.3. Signal type
From a routing perspetive, [RFC 4203] allows advertising foundation
G.709 (single TS type) without the capability of providing precise
information about bandwidth specific allocation. For example, in
case of link bundling, dividing the unreserved bandwidth by the MAX
LSP bandwidth it is not possible to know the exact number of LSPs at
MAX LSP bandwidth size that can be set up. (see example fig. 3)
The lack of spatial allocation heavily impacts the restoration
process, because the lack of information of free resources highly
increases the number of crank-backs affecting network convergence
time.
Moreover actual tools provided by OSPF-TE only allow advertising
signal types with fixed bandwidth and implicit hierarchy (e.g. SDH/
SONET networks) or variable bandwidth with no hierarchy (e.g. packet
switching networks) but do not provide the means for advertising
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networks with mixed approach (e.g. ODUflex CBR and ODUflex packet).
For example, advertising ODU0 as MIN LSP bandwidth and ODU4 as MAX
LSP bandwidth it is not possible to state whether the advertised link
supports ODU4 and ODUflex or ODU4, ODU3, ODU2, ODU1, ODU0 and
ODUflex. Such ambiguity is not present in SDH networks where the
hierarchy is implicit and flexible containers like ODUFlex do not
exist. The issue could be resolved by declaring 1 ISCD for each
signal type actually supported by the link.
Supposing for example to have an equivalent ODU2 unreserved bandwidth
in a TE-link (with bundling capability) distributed on 4 ODU1, it
would be advertised via the ISCD in this way:
MAX LSP Bw: ODU1
MIN LSP Bw: ODU1
- Maximum Reservable Bandwidth (of the bundle) set to ODU2
- Unreserved Bandwidth (of the bundle) set to ODU2
Moreover with the current IETF solutions, ([RFC4202], [RFC4203]) as
soon as no bandwidth is available for a certain signal type it is not
advertised into the related ISCD, losing also the related capability
until bandwidth is freed.
In conclusion, the OSPF-TE extensions defined in [RFC4203] require a
different ISCD per signal type in order to advertise each supported
container. This motivates attempting to look for a more optimized
solution, without proliferations of the number of ISCD advertised.
The OSPF LSA is required to stay within a single IP PDU;
fragmentation is not allowed. In a conforming Ethernet environment,
this limits the LSA to 1432 bytes (Packet_MTU (1500 Bytes) -
IP_Header (20 bytes) - OSPF_Header (28 bytes) - LSA_Header (20
bytes)).
With respect to link bundling, the utilization of the ISCD as it is,
would not allow precise advertising of spatial bandwidth allocation
information unless using only one component link per TE link.
On the other hand, from a singaling point of view, [RFC4328]
describes GMPLS signaling extensions to support the control for G.709
OTNs [G709-V1]. However,[RFC4328] needs to be updated because it
does not provide the means to signal all the new signal types and
related mapping and multiplexing functionalities.
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4.4. Bit rate and tolerance
In the current traffic parameters signaling, bit rate and tolerance
are implicitly defined by the signal type. ODUflex CBR and Packet
can have variable bit rates and tolerances (please refer to [OTN-FWK]
table 2); it is thus needed to upgrade the signaling traffic
patameters so to specify requested bit rates and tolerance values
during LSP setup.
4.5. Unreserved Resources
Unreserved resources need to be advertised per priority and per
signal type in order to allow the correct functioning of the
restoration process. [RFC4203] only allows advertising unreserved
resources per priority, this leads not to know how many LSPs of a
specific signal type can be restored. As example it is possible to
consider the scenario depicted in the following figure.
+------+ component link 1 +------+
| +------------------+ |
| | component link 2 | |
| N1 +------------------+ N2 |
| | component link 3 | |
| +------------------+ |
+------+ +---+--+
Figure 5: Concurrent path computation
Suppose to have a TE link comprising 3 ODU3 component links with
32TSs available on the first one, 24TSs on the second, 24TSs on the
third and supporting ODU2 and ODU3 signal types. The node would
advertise a TE link unreserved bandwidth equal to 80 TSs and a MAX
LSP bandwidth equal to 32 TSs. In case of restoration the network
could try to restore 2 ODU3 (64TSs) in such TE-link while only a
single ODU3 can be set up and a crank-back would be originated. In
more complex network scenarios the number of crank-backs can be much
higher.
4.6. Maximum LSP Bandwidth
Maximum LSP bandwidth is currently advertised in the common part of
the ISCD and advertised per priority, while in OTN networks it is
only required for ODUflex advertising. This leads to a significant
waste of bits inside each LSA.
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4.7. Distinction between terminating and switching capability
The capability advertised by an interface needs further distinction
in order to separate termination and switching capabilities. Due to
internal constraints and/or limitations, the type of signal being
advertised by an interface could be just switched (i.e. forwarded to
switching matrix without multiplexing/demultiplexing actions), just
terminated (demuxed) or both of them. The following figures help
explainig the switching and terminating capabilities.
MATRIX LINE INTERFACE
+-----------------+ +-----------------+
| +-------+ | ODU2 | |
----->| ODU-2 |----|----------|--------\ |
| +-------+ | | +----+ |
| | | \__/ |
| | | \/ |
| +-------+ | ODU3 | | ODU3 |
----->| ODU-3 |----|----------|------\ | |
| +-------+ | | \ | |
| | | \| |
| | | +----+ |
| | | \__/ |
| | | \/ |
| | | ---------> OTU-3
+-----------------+ +-----------------+
Figure 6: Switching and Terminating capabilities
The figure in the example shows a line interface able to:
- Multiplex an ODU2 coming from the switching matrix into and ODU3
and map it into an OTU3
- Map an ODU3 coming from the switching matrix into an OTU3
In this case the interface bandwidth advertised is ODU2 with
switching capability and ODU3 with both switching and terminating
capabilities.
This piece of information needs to be advertised together with the
related unreserved bandwidth and signal type. As a consequence
signaling must have the possibility to setup an LSP allowing the
local selection of resources consistent with the limitations
considered during the path computation.
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In figures 6 and 7 there are two examples of the need of termination/
switching capability differentiation. In both examples all nodes are
supposed to support single-stage capability. The figure 6 addresses
a scenario in which a failure on link B-C forces node A to calculate
another ODU2 LSP path carrying ODU0 service along the nodes B-E-D.
Being D a single stage capable node, it is able to extract ODU0
service only from ODU2 interface. Node A has to know that from E to
D exists an available OTU2 link from which node D can extract the
ODU0 service. This information is required in order to avoid that
the OTU3 link is considered in the path computation.
ODU0 transparently transported
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| ODU2 LSP Carrying ODU0 service |
| |'''''''''''''''''''''''''''''''''''''''''''| |
| | | |
| +----++ OTU2 +-----+ OTU2 +-----+ OTU2 ++----+ |
ODU0 | | Link | | Link | | Link | | ODU0
---->| A |_________| B |_________| C |_________| D |---->
| | | | | | | |
+-----+ +--+--+ +-----+ ++--+-+
| | |
OTU3| | |
Link| +-----+__________________| |
| | | OTU3 Link |
|____| E | |
| |_____________________|
+-----+ OTU2 Link
Figure 7: Switching and Terminating capabilities - Example 1
Figure 7 addresses the scenario in which the restoration of the ODU2
LSP (ABCD) is required. The two bundled component links between B
and E could be used, but the ODU2 over the OTU2 component link can
only be terminated and not switched. This implies that it cannot be
used to restore the ODU2 LSP (ABCD). However such ODU2 unreserved
bandwidth must be advertised since it can be used for a different
ODU2 LSP terminating on E, e.g. (FBE). Node A has to know that the
ODU2 capability on the OTU2 link can only be terminated and that the
restoration of (ABCD) can only be performed using the ODU2 bandwidth
available on the OTU3 link.
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ODU0 transparently transported
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| ODU2 LSP Carrying ODU0 service |
| |'''''''''''''''''''''''''''''''''''''''''''| |
| | | |
| +----++ OTU2 +-----+ OTU2 +-----+ OTU2 ++----+ |
ODU0 | | Link | | Link | | Link | | ODU0
---->| A |_________| B |_________| C |_________| D |---->
| | | | | | | |
+-----+ ++-+-++ +-----+ +--+--+
| | | |
OTU2| | | |
+-----+ Link| | | OTU3 +-----+ |
| | | | | Link | | |
| F |_______| | |___________| E |___________|
| | |_____________| | OTU2 Link
+-----+ OTU2 Link +-----+
Figure 8: Switching and Terminating capabilities - Example 2
4.8. Priority Support
The IETF foresees that up to eight priorities must be supported and
that all of them have to be advertised independently on the number of
priorities supported by the implementation. Considering that the
advertisement of all the different supported signal types will
originate large LSAs, it is advised to advertise only the information
related to the really supported priorities.
4.9. Multi-stage multiplexing
With reference to the [OTN-FWK], introduction of multi-stage
multiplexing implies the advertisement of cascaded adaptation
capabilities together with the matrix access constraints. The
structure defined by IETF for the advertisement of adaptation
capabilities is ISCD/IACD as in [RFC4202] and [RFC5339].
Modifications to ISCD/IACD, if needed, have to be addressed in the
releted encoding documents.
With respect to the routing, please note that in case of multi stage
muxing hierarchy (e.g. ODU1->ODU2->ODU3), not only the ODUk/OTUk
bandwidth (ODU3) and service layer bandwidth (ODU1) are needed, but
also the intermediate one (ODU2). This is a typical case of spatial
allocation problem.
Suppose in this scenario to have the following advertisement:
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Hierarchy: ODU1->ODU2->ODU3
Number of ODU1==5
The number of ODU1 suggests that it is possible to have an ODU2 FA,
but it depends on the spatial allocation of such ODU1s.
It is possible that 2 links are bundled together and 3
ODU1->ODU2->ODU3 are available on a component link and 2 on the other
one, in such a case no ODU2 FA could be set up. The advertisement of
the ODU2 is needed because in case of ODU1 spatial allocation (3+2),
the ODU2 available bandwidth would be 0 (no ODU2 FA can be created),
while in case of ODU1 spatial allocation (4+1) the ODU2 available
bandwidth would be 1 (1 ODU2 FA can be created).
4.10. Generalized Label
The ODUk label format defined in [RFC4328] could be updated to
support new signal types defined in [G709-V3] but would hardly be
further enhanced to support possible new signal types.
Furthermore such label format may have scalability issues due to the
high number of labels needed when signaling large LSPs. For example,
when an ODU3 is mapped into an ODU4 with 1.25G tributary slots, it
would require the utilization of thirty-one labels (31*4*8=992 bits)
to be allocated while an ODUflex into an ODU4 may need up to eighty
labels (80*4*8=2560 bits).
A new flexible and scalable ODUk label format needs to be defined.
5. Security Considerations
TBD
6. IANA Considerations
TBD
7. Contributors
Jonathan Sadler, Tellabs
EMail: jonathan.sadler@tellabs.com
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John Drake, Juniper
EMail: jdrake@juniper.net
8. Acknowledgements
The authors would like to thank Eve Varma and Sergio Lanzone for
their precious collaboration and review.
9. References
9.1. Normative References
[HIER-BIS]
K.Shiomoto, A.Farrel, "Procedure for Dynamically Signaled
Hierarchical Label Switched Paths", work in
progress draft-ietf-lsp-hierarchy-bis-08, February 2010.
[OTN-OSPF]
D.Ceccarelli,D.Caviglia,F.Zhang,D.Li,Y.Xu,P.Grandi,S.Belot
ti, "Traffic Engineering Extensions to OSPF for
Generalized MPLS (GMPLS) Control of Evolutive G.709 OTN
Networks", work in
progress draft-ceccarelli-ccamp-gmpls-ospf-g709-03, August
2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005.
[RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support
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of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4203, October 2005.
[RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC 4328, January 2006.
[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
OSPF Opaque LSA Option", RFC 5250, July 2008.
[RFC5339] Le Roux, JL. and D. Papadimitriou, "Evaluation of Existing
GMPLS Protocols against Multi-Layer and Multi-Region
Networks (MLN/MRN)", RFC 5339, September 2008.
9.2. Informative References
[G.709-v1]
ITU-T, "Interface for the Optical Transport Network
(OTN)", G.709 Recommendation (and Amendment 1),
February 2001.
[G.709-v2]
ITU-T, "Interface for the Optical Transport Network
(OTN)", G.709 Recommendation (and Amendment 1),
March 2003.
[G.709-v3]
ITU-T, "Rec G.709, version 3", approved by ITU-T on
December 2009.
[G.872-am2]
ITU-T, "Amendment 2 of G.872 Architecture of optical
transport networks for consent", consented by ITU-T on
June 2010.
[OTN-FWK] F.Zhang, D.Li, H.Li, S.Belotti, "Framework for GMPLS and
PCE Control of G.709 Optical Transport Networks", work in
progress draft-ietf-ccamp-gmpls-g709-framework-00, April
2010.
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Authors' Addresses
Sergio Belotti (editor)
Alcatel-Lucent
Via Trento, 30
Vimercate
Italy
Email: sergio.belotti@alcatel-lucent.com
Pietro Vittorio Grandi
Alcatel-Lucent
Via Trento, 30
Vimercate
Italy
Email: pietro_vittorio.grandi@alcatel-lucent.com
Daniele Ceccarelli (editor)
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: daniele.ceccarelli@ericsson.com
Diego Caviglia
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: diego.caviglia@ericsson.com
Fatai Zhang
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Shenzhen 518129 P.R.China Bantian, Longgang District
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
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Dan Li
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Shenzhen 518129 P.R.China Bantian, Longgang District
Phone: +86-755-28973237
Email: danli@huawei.com
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