Network Working Group Fatai Zhang
Internet Draft Huawei
Category: Standards Track Guoying Zhang
CATR
Sergio Belotti
Alcatel-Lucent
D. Ceccarelli
Ericsson
Khuzema Pithewan
Infinera
Expires: January 8, 2012 July 8, 2011
Generalized Multi-Protocol Label Switching (GMPLS) Signaling
Extensions for the evolving G.709 Optical Transport Networks Control
draft-zhang-ccamp-gmpls-evolving-g709-08.txt
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Abstract
Recent progress in ITU-T Recommendation G.709 standardization has
introduced new ODU containers (ODU0, ODU4, ODU2e and ODUflex) and
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enhanced Optical Transport Networking (OTN) flexibility. Several
recent documents have proposed ways to modify GMPLS signaling
protocols to support these new OTN features.
It is important that a single solution is developed for use in GMPLS
signaling and routing protocols. This solution must support ODUk
multiplexing capabilities, address all of the new features, be
acceptable to all equipment vendors, and be extensible considering
continued OTN evolution.
This document describes the extensions to the Generalized Multi-
Protocol Label Switching (GMPLS) signaling to control the evolving
Optical Transport Networks (OTN) addressing ODUk multiplexing and new
features including ODU0, ODU4, ODU2e and ODUflex.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Table of Contents
1. Introduction .................................................. 3
2. Terminology ................................................... 4
3. GMPLS Extensions for the Evolving G.709 - Overview ............ 4
3.1. Requirements for supporting services over hierarchical OTN
network ....................................................... 5
4. Extensions for Traffic Parameters for the Evolving G.709 ...... 8
4.1. Usage of ODUflex(CBR) Traffic Parameter .................. 9
4.2. Example of ODUflex(CBR) Traffic Parameter ............... 10
5. Generalized Label ............................................ 11
5.1. New definition of Single-stage ODUk Generalized Label ... 11
5.1.1. Examples ........................................... 14
5.1.2. Label Distribution Procedure ....................... 16
5.1.2.1. Notification on Label Error ................... 17
5.1.3. Supporting Virtual Concatenation and Multiplication. 17
5.1.4. Supporting Multiplexing Hierarchy .................. 18
5.1.5. Supporting One-hop Multiplexing Hierarchy via Single
Session ................................................... 19
5.1.5.1. Multiplexing Hierarchy and Solution Alternatives19
5.1.5.2. Multi Stage Label Format ...................... 19
5.1.5.3. Label format for NVC or Multiplier > 1 ........ 20
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5.1.5.4. Usage of Multi-stage Label in Multi Stage Muxing21
5.2. New definition of Multi-stage ODUk Generalized Label .... 22
5.2.1. Multi-stage Label .................................. 23
5.2.2. Label format for NVC or Multiplier > 1 ............. 24
5.2.3. Usage of Multi-stage Label ......................... 24
5.2.4. Label Distribution Rules ........................... 26
5.2.5. Examples ........................................... 27
5.3. Control Plane Backward Compatibility Considerations ..... 29
6. Security Considerations ...................................... 30
7. IANA Considerations .......................................... 30
8. References ................................................... 31
8.1. Normative References .................................... 31
8.2. Informative References .................................. 32
9. Authors' Addresses ........................................... 33
Acknowledgment .................................................. 35
1. Introduction
Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] extends
MPLS to include Layer-2 Switching (L2SC), Time-Division Multiplex
(e.g., SONET/SDH, PDH, and ODU), Wavelength (OCh, Lambdas) Switching,
and Spatial Switching (e.g., incoming port or fiber to outgoing port
or fiber). [RFC3471] presents a functional description of the
extensions to Multi-Protocol Label Switching (MPLS) signaling
required to support Generalized MPLS. RSVP-TE-specific formats and
mechanisms and technology specific details are defined in [RFC3473].
With the evolution and deployment of G.709 technology, it is
necessary that appropriate enhanced control technology support be
provided for G.709. [RFC4328] describes the control technology
details that are specific to foundation G.709 Optical Transport
Networks (OTN), as specified in the ITU-T Recommendation G.709 [G709-
V1], for ODUk deployments without multiplexing.
In addition to increasing need to support ODUk multiplexing, the
evolution of OTN has introduced additional containers and new
flexibility. For example, ODU0, ODU2e, ODU4 containers and ODUflex
are developed in [G709-V3].
In addition, the following issues require consideration:
- Support for hitless adjustment of ODUflex, which is to be
specified in ITU-T G.hao.
- Support for Tributary Port Number. The Tributary Port Number
has to be negotiated on each link for flexible assignment of
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tributary ports to tributary slots in case of LO-ODU over HO-
ODU (e.g., ODU2 into ODU3).
Therefore, it is clear that [RFC4328] has to be updated or superceded
in order to support ODUk multiplexing, as well as other ODU
enhancements introduced by evolution of OTN standards.
This document updates [RFC4328] extending the G.709 ODUk traffic
parameters and also presents a new OTN label format which is very
flexible and scalable.
2. 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].
3. GMPLS Extensions for the Evolving G.709 - Overview
New features for the evolving OTN, for example, new ODU0, ODU2e, ODU4
and ODUflex containers are specified in [G709-V3]. The corresponding
new signal types are summarized below:
- Optical Channel Transport Unit (OTUk):
. OTU4
- Optical Channel Data Unit (ODUk):
. ODU0
. ODU2e
. ODU4
. ODUflex
A new Tributary Slot (TS) granularity (i.e., 1.25 Gbps) is also
described in [G709-V3]. Thus, there are now two TS granularities for
the foundation OTN ODU1, ODU2 and ODU3 containers. The TS granularity
at 2.5 Gbps is used on legacy interfaces while the new 1.25 Gbps will
be used for the new interfaces.
In addition to the support of ODUk mapping into OTUk (k = 1, 2, 3, 4),
the evolving OTN [G.709-V3] encompasses the multiplexing of ODUj (j =
0, 1, 2, 2e, 3, flex) into an ODUk (k > j), as described in Section
3.1.2 of [OTN-frwk].
Virtual Concatenation (VCAT) of OPUk (OPUk-Xv, k = 1/2/3, X = 1...256)
are also supported by [OTN-V3]. Note that VCAT of OPU0 / OPU2e / OPU4
/ OPUflex are not supported per [OTN-V3].
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[RFC4328] describes GMPLS signaling extensions to support the control
for G.709 Optical Transport Networks (OTN) [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. Moreover, it 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.
This document extends the G.709 traffic parameters described in
[RFC4328] and presents a new OTN label format which is very flexible
and scalable. Additionally, procedures about Tributary Port Number
assignment through control plane are also provided in this document.
3.1. Requirements for supporting services over hierarchical OTN network
[Editor's Note] The section 3.1 about requirements will be moved to
the framework document after discussion.
1.[R1] Support signaling mechanism to instantiate ODUj service layer
on an ODUk link via single stage muxing.
An ODUj LSP could involve zero (j=k) or one stage (j<k)
multiplexing on a given ODUk link. Here both Control-plane and
Data-plane entities are created for the ODUj service layer. ODUk
link could be a point-to-point OTUk link or an H-LSP. This is the
most foundational and important requirement the control plane
should support.
2.[R2] Support signaling mechanism to instantiate ODUj LSP involving
one or more intermediate ODU layers (either pre-existing or not)
which cross multiple ODUk links.
| |
|<-------------- ODU0 Connection --------------->|
| | | |
| |<----- ODU2 Connection ----->| |
| | | |
+--+ +--+ +--+ +--+ +--+ +--+
|N1+------+N2+======+N3+======+N4+======+N5+------+N6|
+--+ ODU3 +--+ ODU3 +--+ ODU4 +--+ ODU3 +--+ ODU3 +--+
link link link link link
Figure 1 - Requirement 2
Figure 1 shows an example where the ODU0 LSP is multiplexed into an
intermediate ODU2, which crosses three ODU links between N2 and N5.
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There are two typical scenarios requesting two or more stage
multiplexing crossing multiple ODUk links:
- Tunnel scenario: Assume that N3 and N4 in figure 1 are legacy
nodes which don't support ODU0 or ODUflex cross-connection. In
order to create ODU0 or ODUflex service between N1 and N6, an
intermediate ODU2 connection can be created between N2 and N5.
Then, the ODU0 or ODUflex can be multiplexed into this ODU2
connection. In this case, N3 and N4 only need to perform ODU2
cross-connection and are not aware of ODU0 or ODUflex service
inside.
- Carrier-in-carrier scenario: Assume that N2, N3, N4 and N5 in
figure 1 belong to carrier A, while N1 and N6 belong to carrier
B. Carrier B may lease an ODU2 pipe between N2 and N5, which is
pre-provisioned by carrier A, to carry LO ODU services between
N1 and N6.
More specifically, this requirement can be further divided into two
items:
[R2.1] Support signaling mechanism to trigger the creation of one
or more intermediate ODU layers over multiple ODUk links based on
the ODUj LSP creation request.
[R2.2] Support signaling mechanism to instantiate ODUj service
layer on multiple ODUk links where one or more intermediate ODU
layers may be pre-existing.
3.[R3] Support signaling mechanism to instantiate ODUj LSP involving
one or more intermediate ODU layers (either pre-existing or not) on
one hop ODUk link.
More specifically, this requirement can be further divided into two
items:
[R3.1] Support signaling mechanism to instantiate one or more
intermediate layers on one hop ODUk link in order to support the
ODUj service layer.
An ODUj LSP could involve two or more stage multiplexing on a given
ODUk link. These intermediate layers may be implicitly created as a
part of ODUj service LSP creation. In this case, both control plane
and data plane entities will be created for the ODUj service layer.
However, intermediate ODU layer(s) (implicitly created) will have
data plane representation only.
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[R3.2] Support signaling mechanism to instantiate ODUj service
layer on an ODUk link where one or more intermediate ODU layers may
be pre-existing.
An ODUj LSP could involve two or more stage multiplexing on a given
ODUk link. These intermediate layers may be pre-existing as a
result of another LSP creation on the same ODU hierarchy or
explicitly configured through management interface.
4.[R4] Support controllable and manageable capability for the
intermediate ODU layers which cross one or more hops of ODUk links
and which is used for carrying ODUj services.
Once the intermediate ODU layers are created by control plane (may
be triggered by the ODUj service or by management plane), they
should be under the control of control plane or management plane.
The following typical scenarios should be considered:
- The control/management plane should have the capability to
reroute the intermediate ODU layers to recover all the contained
ODUj layer services to improve the recovery performance after
network failure occurs in the intermediate ODU layers.
- The control/management plane should have the capability to
delete an empty intermediate ODU connection (i.e., without any
ODUj service inside it) to release the bandwidth resource of
ODUk link. For example, the management plane may request the
control plane to delete an empty intermediate ODU2 in an ODU4
link so that the ODU4 link has enough bandwidth resource to
carry a new ODU3 service.
5.[R5] Support signaling mechanism where ODUj service LSP creation
may involve varying mux hierarchies on each hop.
An end-to-end ODUj service LSP creation may involve zero or more
stage ODU multiplexing on every hop in the path. Basically, the
scenarios discussed in R1 to R3 could be associated with any of the
hops involved.
6.[R6] Support signaling mechanism for egress control of OTN
interfaces.
An egress interface of an ODUj LSP could involve single or multiple
stage multiplexing. Egress Label sub-object defined in [RFC-4003]
must be used to signal hierarchical multiplexing information
pertaining to the egress interface of the LSP.
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4. Extensions for Traffic Parameters for the Evolving G.709
The traffic parameters for G.709 are defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Tolerance | NMC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NVC | Multiplier (MT) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bit_Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Signal Type should be extended to cover the new Signal Type
introduced by the evolving OTN. The new Signal Type is extended as
follows:
Value Type
----- ----
0 Not significant
1 ODU1 (i.e., 2.5 Gbps)
2 ODU2 (i.e., 10 Gbps)
3 ODU3 (i.e., 40 Gbps)
4 ODU4 (i.e., 100 Gbps)
5 Reserved (for future use)
6 OCh at 2.5 Gbps
7 OCh at 10 Gbps
8 OCh at 40 Gbps
9 OCh at 100 Gbps
10 ODU0 (i.e., 1.25 Gbps)
11 ODU2e (i.e., 10Gbps for FC1200 and GE LAN)
12~19 Reserved (for future use)
20 ODUflex(CBR) (i.e., 1.25*N Gbps)
21 ODUflex(GFP-F), resizable (i.e., 1.25*N Gbps)
22 ODUflex(GFP-F), non resizable (i.e., 1.25*N Gbps)
23~255 Reserved (for future use)
In case of ODUflex(CBR), the Bit_Rate and Tolerance fields are used
together to represent the actual bandwidth of ODUflex, where:
- The Bit_Rate field indicates the nominal bit rate of ODUflex(CBR)
encoded as a 32-bit IEEE single-precision floating-point number
(referring to [RFC4506] and [IEEE]).
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- The Tolerance field indicates the bit rate tolerance (part per
million, ppm) of the ODUflex(CBR) encoded as an unsigned integer,
which is bounded in 0~100ppm.
For example, for an ODUflex(CBR) service with Bit_Rate = 2.5Gbps and
Tolerance = 100ppm, the actual bandwidth of the ODUflex is:
2.5Gbps * (1 - 100ppm) ~ 2.5Gbps * (1 + 100ppm)
In case of other ODUk signal types, the Bit_Rate and Tolerance fields
are not necessary and MUST be filled with 0.
The usage of the NMC, NVC and Multiplier (MT) fields are the same as
[RFC4328].
4.1. Usage of ODUflex(CBR) Traffic Parameter
In case of ODUflex(CBR), the information of Bit_Rate and Tolerance in
the ODUflex traffic parameter is used to determine the total number
of tributary slots N in the HO ODUk link to be reserved. Here:
N = Ceiling of
ODUflex(CBR) nominal bit rate * (1 + ODUflex(CBR) bit rate tolerance)
---------------------------------------------------------------------
ODTUk.ts nominal bit rate * (1 - HO OPUk bit rate tolerance)
Therefore, a node receiving a Path message containing ODUflex(CBR)
traffic parameter can allocate precise number of tributary slots and
set up the cross-connection for the ODUflex service.
Table 1 below shows the actual bandwidth of the tributary slot of
ODUk (in Gbps), referring to [G709-V3].
Table 1 - Actual TS bandwidth of ODUk
ODUk Minimum Nominal Maximum
-------------------------------------------------------
ODU2 1.249 384 632 1.249 409 620 1.249 434 608
ODU3 1.254 678 635 1.254 703 729 1.254 728 823
ODU4 1.301 683 217 1.301 709 251 1.301 735 285
Note that:
Minimum bandwidth of ODUTk.ts =
ODTUk.ts nominal bit rate * (1 - HO OPUk bit rate tolerance)
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Maximum bandwidth of ODTUk.ts =
ODTUk.ts nominal bit rate * (1 + HO OPUk bit rate tolerance)
Where: HO OPUk bit rate tolerance = 20ppm
For different ODUk, the bandwidths of the tributary slot are
different, and so the total number of tributary slots to be reserved
for the ODUflex(CBR) may not be the same on different HO ODUk links.
This is why the traffic parameter should bring the actual bandwidth
information other than the NMC field.
4.2. Example of ODUflex(CBR) Traffic Parameter
This section gives an example to illustrate the usage of ODUflex(CBR)
traffic parameter.
As shown in Figure 2, assume there is an ODUflex(CBR) service
requesting a bandwidth of (2.5Gbps, +/-100ppm) from node A to node C.
In other words, the ODUflex traffic parameter indicates that Signal
Type is 33 (ODUflex(CBR)), Bit_Rate is 2.5Gbps and Tolerance is
100ppm.
+-----+ +---------+ +-----+
| +-------------+ +-----+ +-------------+ |
| +=============+\| ODU |/+=============+ |
| +=============+/| flex+-+=============+ |
| +-------------+ | |\+=============+ |
| +-------------+ +-----+ +-------------+ |
| | | | | |
| | ....... | | ....... | |
| A +-------------+ B +-------------+ C |
+-----+ HO ODU4 +---------+ HO ODU2 +-----+
=========: TS occupied by ODUflex
---------: free TS
Figure 2 - Example of ODUflex(CBR) Traffic Parameter
- On the HO ODU4 link between node A and B:
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The maximum bandwidth of the ODUflex equals 2.5Gbps * (1 +
100ppm), and the minimum bandwidth of the tributary slot of ODU4
equals 1.301 683 217Gbps, so the total number of tributary slots
N1 to be reserved on this link is:
N1 = ceiling (2.5Gbps * (1 + 100ppm) / 1.301 683 217) = 2
- On the HO ODU2 link between node B and C:
The maximum bandwidth of the ODUflex equals 2.5Gbps * (1 +
100ppm), and the minimum bandwidth of the tributary slot of ODU2
equals 1.249 384 632Gbps, so the total number of tributary slots
N2 to be reserved on this link is:
N2 = ceiling (2.5Gbps * (1 + 100ppm) / 1.249 384 632) = 3
5. Generalized Label
[RFC3471] has defined the Generalized Label which extends the
traditional label by allowing the representation of not only labels
which travel in-band with associated data packets, but also labels
which identify time-slots, wavelengths, or space division multiplexed
positions. The format of the corresponding RSVP-TE Generalized Label
object is defined in the Section 2.3 of [RFC3473].
However, for different technologies, we usually need use specific
label rather than the Generalized Label. For example, the label
format described in [RFC4606] could be used for SDH/SONET, the label
format in [RFC4328] for G.709.
[RFC 6107] defines using hierarchical LSP for MLN. The H-LSPs can be
setup manually or dynamically (induced FAs) for multi-stage
multiplexing scenarios. Service creation in hierarchical OTN network
can be achieved in following 2 ways.
5.1. New definition of Single-stage ODUk Generalized Label
In order to be compatible with new types of ODU signal and new types
of tributary slot, the following new ODUk label format is defined:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ODUj |OD(T)Uk| T | Reserved | TPN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bit Map ......... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ODUj and OD(T)Uk (4 bits respectively): indicate that LO ODUj is
multiplexed into HO ODUk(k>j), or LO ODUj is mapped into OTUk (j=k).
ODUj field Signal type
---------- -----------
0 LO ODU0
1 LO ODU1
2 LO ODU2
3 LO ODU3
4 LO ODU4
5 LO ODU2e
6 LO ODUflex
7-15 Reserved (for future use)
OD(T)Uk field Signal type
------------- -----------
0 Reserved (for future use)
1 HO ODU1 / OTU1
2 HO ODU2 / OTU2
3 HO ODU3 / OTU3
4 HO ODU4 / OTU4
5-15 Reserved (for future use)
T (2 bits): indicates the type of tributary slot of HO ODUk when LO
ODUj is multiplexed into the HO ODUk (j<k). Currently, two types of
tributary slot are defined in [G709-V3], the 1.25Gbps tributary slot
and the 2.5Gbps tributary slot.
T field TS type
------- -------
0 1.25Gbps TS granularity
1 2.5Gbps TS granularity
2-3 Reserved (for future use)
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In case of LO ODUj mapped into OTUk (j=k), this field is not
necessary and should be ignored.
TPN (16 bits): indicates the Tributary Port Number (TPN) for the
assigned Tributary Slot(s).
- In case of LO ODUj multiplexed into HO ODU1/ODU2/ODU3, only the
lower 6 bits of TPN field is significant and the other bits of
TPN MUST be set to 0.
- In case of LO ODUj multiplexed into HO ODU4, only the lower 7
bits of TPN field is significant and the other bits of TPN MUST
be set to 0.
- In case of ODUj mapped into OTUk (j=k), the TPN is not needed
and this field MUST be set to 0.
As per [G709-V3], The TPN is used to allow for correct demultiplexing
in the data plane. When an LO ODUj is multiplexed into HO ODUk
occupying one or more TSs, a new TPN value is configured at the two
end of the HO ODUk link and is put into the related MSI byte(s) in
the OPUk overhead at the (traffic) ingress end of the link, so that
the other end of the link can learn which TS(s) is/are used by the LO
ODUj in the data plane.
According to [G709-V3], the rules of TPN assignment should be as the
following tables:
Table 2 - TPN Assignment Rules (2.5Gbps TS granularity)
+-------+-------+----+----------------------------------------------+
|HO ODUk|LO ODUj|TPN | TPN Assignment Rules |
+-------+-------+----+----------------------------------------------+
| ODU2 | ODU1 |1~4 |Fixed, = TS# occupied by ODU1 |
+-------+-------+----+----------------------------------------------+
| | ODU1 |1~16|Fixed, = TS# occupied by ODU1 |
| ODU3 +-------+----+----------------------------------------------+
| | ODU2 |1~4 |Flexible, != other existing LO ODU2s' TPNs |
+-------+-------+----+----------------------------------------------+
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Table 3 - TPN Assignment Rules (1.25Gbps TS granularity)
+-------+-------+----+----------------------------------------------+
|HO ODUk|LO ODUj|TPN | TPN Assignment Rules |
+-------+-------+----+----------------------------------------------+
| ODU1 | ODU0 |1~2 |Fixed, = TS# occupied by ODU0 |
+-------+-------+----+----------------------------------------------+
| | ODU1 |1~4 |Flexible, != other existing LO ODU1s' TPNs |
| ODU2 +-------+----+----------------------------------------------+
| |ODU0 & |1~8 |Flexible, != other existing LO ODU0s and |
| |ODUflex| |ODUflexes' TPNs |
+-------+-------+----+----------------------------------------------+
| | ODU1 |1~16|Flexible, != other existing LO ODU1s' TPNs |
| +-------+----+----------------------------------------------+
| | ODU2 |1~4 |Flexible, != other existing LO ODU2s' TPNs |
| ODU3 +-------+----+----------------------------------------------+
| |ODU0 & | |Flexible, != other existing LO ODU0s and |
| |ODU2e &|1~32|ODU2es and ODUflexes' TPNs |
| |ODUflex| | |
+-------+-------+----+----------------------------------------------+
| ODU4 |Any ODU|1~80|Flexible, != ANY other existing LO ODUs' TPNs |
+-------+-------+----+----------------------------------------------+
Note that in the case of "Flexible", the value of TPN is not relevant
to the TS number as per [G709-V3].
Bit Map (variable): indicates which tributary slots in HO ODUk that
the LO ODUj will be multiplexed into. The sequence of the Bit Map is
consistent with the sequence of the tributary slots in HO ODUk. Each
bit in the bit map represents the corresponding tributary slot in HO
ODUk with a value of 1 or 0 indicating whether the tributary slot
will be used by LO ODUj or not.
The size of the bit map equals to the total number of the tributary
slots of HO ODUk, which is deduced by the ODU(T)k and T fields.
In case of an ODUk mapped into OTUk, it's no need to indicate which
tributary slots will be used, so the size of Bit Map is 0.
Padded bits are added behind the Bit Map to make the whole label a
multiple of four bytes if necessary. Padded bit MUST be set to 0 and
MUST be ignored.
5.1.1. Examples
The following examples are given in order to illustrate the label
format described in the previous sections of this document.
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(1) ODUk into OTUk mapping:
In such conditions, the downstream node along an LSP returns a label
indicating that the ODU1 (ODU2 or ODU3 or ODU4) is directly mapped
into the corresponding OTU1 (OTU2 or OTU3 or ODU4). The following
example label indicates an ODU1 mapped into OTU1.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|0 0 0 1|0 0| Reserved | All 0s |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2) ODUj into ODUk multiplexing:
In such conditions, this label indicates that an ODUj is multiplexed
into several tributary slots of OPUk and then mapped into OTUk. Some
instances are shown as follow:
- ODU0 into ODU2 Multiplexing:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0|0 0 1 0|0 0| Reserved | TPN = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 0 0 0 0 0 0| Padded Bits (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This above label indicates an ODU0 multiplexed into the second
tributary slot of ODU2, wherein the type of the tributary slot is
1.25Gbps, and the TPN value is 2.
- ODU1 into ODU2 Multiplexing with 1.25Gbps TS granularity:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|0 0 1 0|0 0| Reserved | TPN = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 0 1 0 0 0 0| Padded Bits (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This above label indicates an ODU1 multiplexed into the 2nd and the
4th tributary slot of ODU2, wherein the type of the tributary slot is
1.25Gbps, and the TPN value is 1.
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- ODU2 into ODU3 Multiplexing with 2.5Gbps TS granularity:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0|0 0 1 1|0 1| Reserved | TPN = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0| Padded Bits (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This above label indicates an ODU2 multiplexed into the 2nd, 3rd, 5th
and 7th tributary slot of ODU3, wherein the type of the tributary
slot is 2.5Gbps, and the TPN value is 1.
5.1.2. Label Distribution Procedure
This document does not change the existing label distribution
procedures [RFC4328] for GMPLS except that the new ODUk label should
be processed as follows.
When a node receives a generalized label request for setting up an
ODUj LSP from its upstream neighbor node, the node should generate an
ODU label according to the signal type of the requested LSP and the
free resources (i.e., free tributary slots of ODUk) that will be
reserved for the LSP, and send the label to its upstream neighbor
node.
In case of ODUj to ODUk multiplexing, the node should firstly
determine the size of the Bit Map field according to the signal type
and the tributary slot type of ODUk, and then set the bits to 1 in
the Bit Map field corresponding to the reserved tributary slots. The
node should also assign a valid TPN, which does not collided with
other TPN value used by existing LO ODU connections in the selected
HO ODU link, and configure the expected multiplex structure
identifier (ExMSI) using this TPN. Then, the assigned TPN is filled
into the label.
In case of ODUk to OTUk mapping, the node only needs to fill the ODUj
and the ODUk fields with corresponding values in the label. Other
bits are reserved and MUST be set to 0.
When receiving an ODU label from its downstream neighbor node, the
node should learn which ODU signal type is multiplexed or mapped into
which ODU signal type by analyzing the ODUj and the ODUk fields.
In case of ODUj to ODUk multiplexing, the node should firstly
determine the size of the Bit Map field according to the signal type
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and the tributary slot type of ODUk, and then obtain which tributary
slots in ODUk are reserved by its downstream neighbor node according
to the position of the bits that are set to 1 in the Bit Map field,
so that the node can multiplex the ODUj into the reserved tributary
slots of ODUk after the LSP is established. The node should also get
the TPN value assigned by its downstream neighbor node from the label,
and fill the TPN into the related MSI byte(s) in the OPUk overhead in
the data plane, so that the downstream neighbor node can check
whether the TPN received from the data plane is consistent with the
ExMSI and determine whether there is any mismatch defect.
In case of ODUk to OTUk mapping, the size of Bit Map field is 0 and
no additional procedure is needed.
Note that the procedures of other label related objects (e.g.,
Upstream Label, Label Set) are similar as described above.
Note also that the TPN in the label_ERO may not be assigned (i.e.,
TPN field = 0) if the TPN is requested to be assigned locally.
5.1.2.1. Notification on Label Error
When receiving an ODUk label from the neighbor node, the node should
check the integrity of the label. An error message containing an
"Unacceptable label value" indication ([RFC3209]) should be sent if
one of the following cases occurs:
- The ODUj field does not match with the Traffic Parameters;
- The OD(T)Uk field does not match with the type of the selected
link;
- The selected link only supports 2.5Gbps TS granularity while the T
field in the label indicates the 1.25Gbps TS granularity;
- The label includes an invalid TPN value that breaks the TPN
assignment rules;
- Not enough bits of Bit Map, or Bit Map with non-zero padding bits;
- The reserved resources (i.e., the number of "1" in the Bit Map
field) do not match with the Traffic Parameters.
5.1.3. Supporting Virtual Concatenation and Multiplication
As per [VCAT], the VCGs can be created using Co-Signaled style or
Multiple LSPs style.
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In case of Co-Signaled style, the explicit ordered list of all labels
reflects the order of VCG members, which is similar to [RFC4328]. In
case of multiplexed virtually concatenated signals (NVC > 1), the
first label indicates the components of the first virtually
concatenated signal; the second label indicates the components of the
second virtually concatenated signal; and so on. In case of
multiplication of multiplexed virtually concatenated signals (MT > 1),
the first label indicates the components of the first multiplexed
virtually concatenated signal; the second label indicates components
of the second multiplexed virtually concatenated signal; and so on.
In case of Multiple LSPs style, multiple control plane LSPs are
created with a single VCG and the VCAT Call can be used to associate
the control plane LSPs. The procedures are similar to section 6 of
[VCAT].
5.1.4. Supporting Multiplexing Hierarchy
As described in [OTN-FRWK], one ODUj connection can be nested into
another ODUk (j<k) connection, which forms the multiplexing hierarchy
in the ODU layer. This is useful if there are some intermediate nodes
in the network which only support ODUk but not ODUj switching.
For example, in Figure 3, assume that N3 is a legacy node which only
supports [G709-V1] and does not support ODU0 switching. If an ODU0
connection between N1 and N5 is required, then we can create an ODU2
connection between N2 and N4 (or ODU1 / ODU3 connection, depending on
policies and the capabilities of the two ends of the connection), and
nest the ODU0 into the ODU2 connection. In this way, N3 only needs to
perform ODU2 switching and does not need to be aware of the inner
ODU0.
| |
|<------------------- ODU0 Connection -------------------->|
| | | |
| |<---- ODU2 Connection ----->| |
| | | |
+----+ +----+ +----+ +----+ +----+
| N1 +---------+ N2 +=========+ N3 +=========+ N4 +---------+ N5 |
+----+ +----+ +----+ +----+ +----+
ODU3 link ODU3 link ODU3 link ODU3 link
Figure 3 - Example of multiplexing hierarchy
The control plane signaling should support the provisioning of
hierarchical multiplexing. Two methods are provided below (taking
Figure 3 as example):
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- The outer ODU2 connection is created in advance based on network
planning, which is treated as a Forwarding Adjacency (FA). Then
the inner ODU0 can be created using the resource of the ODU2 FA.
In this case, the outer ODU2 and inner ODU0 connections are
created separately, and the normal ODU connection creation
procedure described in this document can be used.
- Using the multi-layer network signaling described in [RFC4206],
[RFC6107] and [RFC6001] (including related modifications, if
needed). That is, when the signaling message for ODUO connection
arrives at N2, a new RSVP session between N2 and N4 is triggered
to create the ODU2 connection. This ODU2 connection is treated as
an FA after it is created. And then the signaling procedure for
the ODU0 connection can be continued using the resource of the
ODU2 FA.
5.1.5. Supporting One-hop Multiplexing Hierarchy via Single Session
5.1.5.1. Multiplexing Hierarchy and Solution Alternatives
In order to support instantiating ODUj LSP involving one or more
intermediate ODU layers on an ODUk link (i.e., the scenario described
in Requirement 3 of Section 3.1), there are two approaches to achieve
the objective. The existing approach is the hierarchical LSP (H-LSP)
approach described in Section 5.5, and another one is to use the
multi-stage label approach.
For the multi-stage label approach, the whole multiplexing structure
on the ODUk link (i.e., ODUj service multiplexed into one or more
intermediate ODU layers and then multiplexed into ODUk link) is
included in the signaling message which is used for creating the ODUj
service. After receiving the message, both ends of the ODUk link will
construct the multi-stage multiplexing in the data plane. In this way,
creation of intermediate ODU layers is treated as part of creation of
the ODUj service, without any intermediate ODU FA on the ODUk link.
Note that the ODUk link can either be mapped to an OTUk link directly,
or be a multi-hop FA created in advance crossing multiple OTU links
(using H-LSP mechanism).
5.1.5.2. Multi Stage Label Format
In this document, a new optional object named MULTI-STAGE LABEL
Object is introduced to indicate how the intermediate ODU layers are
multiplexed into ODUk link in the one-hop multi-stage multiplexing
scenario. The format of this object is shown below (The Class-Num and
the C-Type of this new object are TBD):
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num=TBD | C-Type=TBD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num MUX Stages| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tributary Slot Info (Stage-2) |
| (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tributary Slot Info (Stage-n) |
| (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Num MUX Stages: This field indicates the number of multiplexing
stages specified by the label.
Tributary Slot Info: This field has the same format as the ODUk label
format described in Section 5.1. In the case of n-step multiplexing
(e.g., ODUj into ODUi1 into ODUi2 ... into ODUi(n-1) into ODUk
multiplexing), The Tributary Slot Info (Stage-2) indicates how ODUi1
is multiplexed into ODUi2; the Tributary Slot Info (Stage-3)
indicates how ODUi2 is multiplexed into ODUi3 ... and the Tributary
Slot Info (Stage-n) indicates how ODUi(n-1) is multiplexed into the
ODUk link. Note that how ODUj is multiplexed into ODUi1 is indicated
by the generalized label and is not included in this object.
Note that the MULTI-STAGE LABEL Object is not necessary and must not
be included in the signaling message in case the signaling message
is used for creating only one ODU layer connection via single stage
muxing. One example is to instantiate ODUj service on an ODUk link
via single stage muxing. Another example is to use H-LSP mechanism to
instantiate ODUj service involving one or more intermediate ODU FAs,
where multiple RSVP sessions will be created separately, each of
which is used to create one ODU-FA layer connection In such cases,
the generalized label is used without the multi-stage label, as
described in Section 5.
5.1.5.3. Label format for NVC or Multiplier > 1
For NVC or Multiplier field value > 1, the multi-stage label format
defined in Section 6.2 needs to be repeated NVC/multiplier times.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multi-stage Label Instance #1 |
| (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multi-stage Label Instance #n |
| (n = NVC/Multiplier) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1.5.4. Usage of Multi-stage Label in Multi Stage Muxing
When an ODUj LSP is requested where one or more intermediate ODU
layers are involved on an ODUk link, the multi-stage label together
with the generalized label can be used to indicate the multi-stage
multiplexing structure. The generalized label, as described in
Section 5, is used to indicate how the ODUj service is multiplexed
into the first intermediate ODU layer and the multi-stage label is
used to indicate how the intermediate ODU layers are multiplexed into
the ODUk link.
Take Figure 4 as an example. Assume on an OTU3 Link, a restrictive
MUX hierarchy is supported on the associated interfaces. In order to
switch ODU1 on this Link, ODU3 and ODU2 need to be terminated on the
same span as the OTU3 link.
ODU1 ODU0
\ /
ODU2
|
---------- ODU3 ----------
| | | | |
| Node | OTU3 | Node |
| |-----------------------------| |
| A | | B |
| | | |
---------- ----------
|<----- OTU3 TE-Link ------>|
Figure 4 - Multi-stage Label on OTUk Link
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In this example, the generalized label is used to indicate how the
ODU1 service is multiplexed into the intermediate ODU2, the
procedures are the same as described in Section 5. An example
generalized label is shown below, assuming that the ODU1 is
multiplexed into the 2nd and the 4th tributary slot of ODU2, wherein
the type of the tributary slot is 1.25Gbps, and the TPN value is 1:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|0 0 1 0|0 0| Reserved | TPN = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 0 1 0 0 0 0| Padded Bits (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
At the same time, the MULTI-STAGE LABEL Object is also included in
the signaling message, which is used to indicate how the intermediate
ODU2 is multiplexed into the ODU3. An example multi-stage label is
shown below, assuming that the ODU2 is multiplexed into the 2nd, 3rd,
5th and 7th tributary slot of ODU3, wherein the type of the tributary
slot is 2.5Gbps, and the TPN value is 1:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUX-Stages=2 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0|0 0 1 1|0 1| Reserved | TPN = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0| Padded Bits (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2. New definition of Multi-stage ODUk Generalized Label
Multi-stage label is a composite label, which can carry timeslot
information for one or more ODU layers.
ODUk-------------------ODUj-------------------ODUh
TS/TPN for stage-1 TS/TPN for stage-2
Figure 5 - Multi-stage Label
In an OTN network, path of an LSP could be going through links that
support restrictive hierarchy. Multi-stage Label is needed when
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Service ODU layer requires termination of more than one HO-ODUs on a
given OTU/ODU Link.
Multi stage label allows implicit creation of intermediate ODU layers
for supporting the instantiation of service ODU layer on a given hop,
thus eliminating the need for one hop H-LSPs pertaining to
intermediate ODU layers.
If higher order ODU layers spans more than one hop due to switching
restrictions, H-LSP needs to be used in tandem with multi-stage Label
to facilitate end to end service creation.
5.2.1. Multi-stage Label
A multi-stage label includes TS and TPN information for all the
stages of a multi-stage multiplexing hierarchy.
The format of a multi-stage label is explained below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num MUX Stages| OD(T)Uk (ST) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tributary Slot Info (Stage-1) |
| (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tributary Slot Info (Stage-n) |
| (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Num MUX Stages:
This field indicates the number of multiplexing stages specified by
the label.
OD(T)Uk:
This field encodes the signal type of HO OD(T)Uk container.
Tributary Slot Info:
Tributary Slot Information for a single stage is encoded as follows.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ODUj (ST) | T | Length | Tributary Port Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Bit Map (4-byte boundary aligned) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ODUj:
This field indicates the signal type of a LO-ODU being multiplexed
into its immediate HO-ODU.
Length:
This field indicates the number of valid Bits in the Bit Map
excluding the filler bits.
T & Tributary Port Number & Bit Map: See section 5.1.
5.2.2. Label format for NVC or Multiplier > 1
For NVC or Multiplier field value > 1, the label format defined in
section 5 needs to be repeated NVC/multiplier times.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Instance #1 |
| (Variable Length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Instance #n |
| (n = NVC/Multiplier) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2.3. Usage of Multi-stage Label
Multi-stage Label is needed when switching of an ODU Layer requires
termination of more than one HO-ODUs on a given OTU/ODU Link. This
eliminates the need for creating H-LSPs whose span matches its parent
TE-Link.
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Example-1:
Assume on an OTU3 Link, a restrictive MUX hierarchy (as shown in
figure 6) is supported on the associated interfaces. In order to
switch ODU1 on this Link, ODU3 and ODU2 need to be terminated on the
same span as the OTU3 link. If multi-stage Label is not supported, H-
LSP need to be created for ODU3 and ODU2 layers (or just ODU2 layer
at the minimum) in order to support ODU1 LSP. Creation of ODU3 and
ODU2 H-LSP on top of OTU3 Link on the same span is not really
required as bandwidth management for all ODU layers can still be
managed on the OTU3 Link itself.
Multi-stage Label helps in implicit creation of ODU3 and ODU2 layers
as part of ODU1 LSP setup and thus eliminates the need for the
creation of the H-LSP on every hop.
ODU0
|
ODU1 ODU0
\ /
ODU2
|
---------- ODU3 ----------
| | | | |
| Node | OTU3 | Node |
| |-----------------------------| |
| A | | B |
| | | |
---------- ----------
|<----- OTU3 TE-Link ------->|
Label Format:
Stage-1: ODU3<-ODU2/TPN/Trib Slots
Stage-2: ODU2<-ODU1/TPN/Trib Slots
Figure 6 - Multi-stage Label on OTUk Link
Example-2:
Assume on an ODU3 H-LSP (B-C-D), signaling of ODU1 LSP requires
termination of ODU2. Multi-stage Label helps in implicit creation of
ODU2 layer as part of ODU1 LSP setup (A-B-D-E).
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ODU1 ODU1
| |
ODU2 ODU2
| |
ODU3 ODU3
| |
OTU3 OTU3
/ \
------ -----/ ------ \------ ------
| | | | | | | | | |
|Node| |Node| |Node| |Node| |Node|
| |--------| |--------| |--------| |--------| |
| A | | B | | C | | D | | E |
| | | | | | | | | |
------ ------ ------ ------ ------
|<-OTU2->| |<-OTU3->| |<-OTU3->| |<-OTU2->|
| |
|<-----ODU3 H-LSP----->|
Figure 7 - Multi-stage Label on ODUk Link
Note: Multi-stage Label is NOT intended to facilitate the creation of
H-LSP or Hierarchical LSP. It is basically used to eliminate the need
for H-LSP in some obvious scenarios.
5.2.4. Label Distribution Rules
This document does not change the existing label distribution
procedures defined in [RFC4328] except that the new ODU label should
be processed as follows.
A. Sending Side
When Generalized Label Request is received on given node for setting
up an ODU LSP from its upstream neighbor, it reserves the bandwidth
required for the ODU Layer being switched and also the terminating
HO-ODUs layers involved. It sends upstream label and suggested label
(if applicable) to the downstream node and downstream label via PATH
Message and downstream label to the upstream node via RESV Message.
Note that Label can also be explicitly specified by source node.
The encoding of Generalized Label is as follows:
Case-1: ODUk mapping into OTUk
Number of MUX stages = 0
Tributary Slot information is not included.
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Case-2: ODUj mux into ODUk
Number of MUX Stages = 1.
Stage-1: Length = <number of TSs on ODUk>.
TPN = <specified as per Section 5>
TS BitMap = <TSs reserved for ODUj are set to 1>
Case-3 ODUh mux into ODUj into ODUk
Number of MUX Stages = 2.
Stage-1: Length = <number of TSs on ODUk>.
TPN = <specified as per Section 5>
TS BitMap = <TSs reserved for ODUj are set to 1>
Stage-2: Length = <number of TSs on ODUj>.
TPN = <specified as per Section 5>
TS BitMap = <TSs reserved for ODUh are set to 1>
B. Receiving Side
The decoding of the Generalized Label is as follows:
Case-1: ODUk mapping into OTUk
For ODUk to OTUk mapping, the Tributary Slot Information is not
expected.
Case-2: ODUj mux into ODUk
For ODUj to ODUk multiplexing, one MUX stage Label is expected.
The node extracts the Bit Map field in Tributary Slot Info using the
Length field. The position of Bit in the Bitmap interpreted as the
Tributary Slot Number. The value stored in the bit indicates if it is
reserved for the ODUj.
Case-3: ODUh mux into ODUj into ODUk
For ODUh mux into ODUj into ODUk, two MUX stage Label is expected.
Each stage is further decoded as explained in case-2 above.
5.2.5. Examples
Example-1: ODUj LSP over OTUk Links
Consider the network topology shown in the Figure 8 below:
+-----+ +-----+ +-----+ +-----+
| OTN | | OTN | | OTN | | OTN |
| SW |<-OTU2 Link->| SW |<-OTU3 Link->| SW |<-OTU2 Link->| SW |
| A | | B | | C | | D |
+-----+ +-----+ +-----+ +-----+
Figure 8 - OTN Signaling Example
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Assumptions:
(1) ODU2 links between OTN-Switches A & B and C & D support 1.25Gbps
TS Granularity.
(2) ODU3 link between OTN-Switches B & C supports TS Granularity of
2.5Gbps only. Hence, ODU0 switching on this link is possible only
through ODU3-ODU2-ODU0 or ODU3-ODU1-ODU0 multiplexing hierarchies.
G.709 Traffic Parameters and Generalized Label for ODU0 LSP from node
A to D is captured below:
A. G.709 Traffic Parameters
Signal Type = ODU0
NMC/Tolerance = 0 // NMC is not used.
NVC = 0
Multiplier (MT) = 1
Bit_Rate = 0
B. Generalized Label Format:
+=============+==============+==============+==============+
| | A to B | B to C | C to D |
+=============+==============+==============+==============+
| # of Stages | 1 | 2 | 1 |
+-------------+--------------+--------------+--------------+
| Stage-1 | ODU2<--ODU0 | ODU3<--ODU2 | ODU2<--ODU0 |
| | TSG = 1.25G | TSG = 2.5G | TSG = 1.25G |
| | #TSs = 8 | #TSs = 16 | #TSs = 8 |
| | TPN = <1..8> | TPN = <1..4> | TPN = <1..8> |
| | BMap = 4bytes| BMap = 4bytes| BMap = 4bytes|
+-------------+--------------+--------------+--------------+
| Stage-2 | N/A | ODU2<--ODU0 | N/A |
| | | TSG = 1.25G | |
| | | #TSs = 8 | |
| | | TPN = <1..8> | |
| | | BMap = 4bytes| |
+-------------+--------------+--------------+--------------+
Example 2: ODUj LSP over ODUk H-LSP
Refer to Figure 7. The G.709 Traffic Parameters and Generalized Label
for ODU1 LSP from Node A to E are captured below:
A. G.709 Traffic Parameters:
Signal Type = ODU1
NMC/Tolerance = 0 // NMC is not used.
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NVC = 0
Multiplier (MT) = 1
Bit_Rate = 0
B. Generalized Label Format:
+=============+==============+==============+==============+
| | A to B | B to D | D to E |
+=============+==============+==============+==============+
| # of Stages | 1 | 2 | 1 |
+-------------+--------------+--------------+--------------+
| Stage-1 | ODU2<--ODU1 | ODU3<--ODU2 | ODU2<--ODU1 |
| | TSG = 1.25G | TSG = 2.5G | TSG = 1.25G |
| | #TSs = 8 | #TSs = 16 | #TSs = 8 |
| | TPN = <1..4> | TPN = <1..4> | TPN = <1..4> |
| | BMap = 4bytes| BMap = 4bytes| BMap = 4bytes|
+-------------+--------------+--------------+--------------+
| Stage-2 | N/A | ODU2<--ODU1 | N/A |
| | | TSG = 1.25G | |
| | | #TSs = 8 | |
| | | TPN = <1..4> | |
| | | BMap = 4bytes| |
+-------------+--------------+--------------+--------------+
5.3. Control Plane Backward Compatibility Considerations
Since the [RFC4328] has been deployed in the network for the nodes
that support [G709-V1] (herein we call them "legacy nodes"), backward
compatibility SHOULD be taken into consideration when the new nodes
(i.e., nodes that support [G709-V3]) and the legacy nodes are
interworking.
For backward compatibility consideration, the new node SHOULD have
the ability to generate and parse legacy labels.
o For the legacy node, it always generates and sends legacy label to
its upstream node, no matter the upstream node is new or legacy,
as described in [RFC4328].
o For the new node, it will generate and send legacy label if its
upstream node is a legacy one, and generate and send new label if
its upstream node is a new one.
One backwards compatibility example is shown in Figure 9:
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Path Path Path Path
+-----+ ----> +-----+ ----> +------+ ----> +------+ ----> +-----+
| | | | | | | | | |
| A +-------+ B +-------+ C +-------+ D +-------+ E |
| new | | new | |legacy| |legacy| | new |
+-----+ <---- +-----+ <---- +------+ <---- +------+ <---- +-----+
Resv Resv Resv Resv
(new label) (legacy label) (legacy label) (legacy label)
Figure 9 - Backwards compatibility example
As described above, for backward compatibility considerations, it is
necessary for a new node to know whether the neighbor node is new or
legacy.
One optional method is manual configuration. But it is recommended to
use LMP to discover the capability of the neighbor node automatically,
as described in [OTN-LMP].
When performing the HO ODU link capability negotiation:
o If the neighbor node only support the 2.5Gbps TS and only support
ODU1/ODU2/ODU3, the neighbor node should be treated as a legacy
node.
o If the neighbor node can support the 1.25Gbps TS, or can support
other LO ODU types defined in [G709-V3]), the neighbor node should
be treated as new node.
o If the neighbor node returns a LinkSummaryNack message including
an ERROR_CODE indicating nonsupport of HO ODU link capability
negotiation, the neighbor node should be treated as a legacy node.
6. Security Considerations
This document introduces no new security considerations to the
existing GMPLS signaling protocols. Referring to [RFC3473], further
details of the specific security measures are provided. Additionally,
[GMPLS-SEC] provides an overview of security vulnerabilities and
protection mechanisms for the GMPLS control plane.
7. IANA Considerations
- G.709 SENDER_TSPEC and FLOWSPEC objects:
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The traffic parameters, which are carried in the G.709
SENDER_TSPEC and FLOWSPEC objects, do not require any new object
class and type based on [RFC4328]:
o G.709 SENDER_TSPEC Object: Class = 12, C-Type = 5 [RFC4328]
o G.709 FLOWSPEC Object: Class = 9, C-Type = 5 [RFC4328]
- Generalized Label Object:
The new defined ODU label (session 5) is a kind of generalized
label. Therefore, the Class-Num and C-Type of the ODU label is
the same as that of generalized label described in [RFC3473],
i.e., Class-Num = 16, C-Type = 2.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4328] D. Papadimitriou, Ed. "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC 4328, Jan 2006.
[RFC3209] D. Awduche et al, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC3209, December 2001.
[RFC3471] Berger, L., Editor, "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC3473] L. Berger, Ed., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture", RFC 3945, October 2004.
[VCAT] G. Bernstein et al, "Operating Virtual Concatenation (VCAT)
and the Link Capacity Adjustment Scheme (LCAS) with
Generalized Multi-Protocol Label Switching (GMPLS)", draft-
ietf-ccamp-gmpls-vcat-lcas-13.txt, May 4, 2011.
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[RFC4206] K. Kompella, Y. Rekhter, Ed., " Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC6107] K. Shiomoto, A. Farrel, "Procedures for Dynamically
Signaled Hierarchical Label Switched Paths", RFC6107,
February 2011.
[RFC6001] Dimitri Papadimitriou et al, "Generalized Multi-Protocol
Label Switching (GMPLS) Protocol Extensions for Multi-Layer
and Multi-Region Networks (MLN/MRN)", RFC6001, February 21,
2010.
[OTN-frwk] Fatai Zhang et al, "Framework for GMPLS and PCE Control of
G.709 Optical Transport Networks", draft-ietf-ccamp-gmpls-
g709-framework-04.txt, March 11, 2011.
[OTN-info] S. Belotti et al, "Information model for G.709 Optical
Transport Networks (OTN)", draft-ietf-ccamp-otn-g709-info-
model-00.txt, April 18, 2011.
[OTN-LMP] Fatai Zhang, Ed., "Link Management Protocol (LMP)
extensions for G.709 Optical Transport Networks", draft-
zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt, April 6, 2011.
[G709-V3] ITU-T, "Interfaces for the Optical Transport Network (OTN)
", G.709/Y.1331, December 2009.
8.2. Informative References
[G709-V1] ITU-T, "Interface for the Optical Transport Network (OTN),"
G.709 Recommendation (and Amendment 1), February 2001
(November 2001).
[G709-V2] ITU-T, "Interface for the Optical Transport Network (OTN),"
G.709 Recommendation, March 2003.
[G798-V2] ITU-T, "Characteristics of optical transport network
hierarchy equipment functional blocks", G.798, December
2006.
[G798-V3] ITU-T, "Characteristics of optical transport network
hierarchy equipment functional blocks", G.798v3, consented
June 2010.
[RFC4506] M. Eisler, Ed., "XDR: External Data Representation
Standard", RFC 4506, May 2006.
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[IEEE] "IEEE Standard for Binary Floating-Point Arithmetic",
ANSI/IEEE Standard 754-1985, Institute of Electrical and
Electronics Engineers, August 1985.
[GMPLS-SEC] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", Work in Progress, October 2009.
9. Authors' Addresses
Fatai Zhang
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
Guoying Zhang
China Academy of Telecommunication Research of MII
11 Yue Tan Nan Jie Beijing, P.R.China
Phone: +86-10-68094272
Email: zhangguoying@mail.ritt.com.cn
Sergio Belotti
Alcatel-Lucent
Optics CTO
Via Trento 30 20059 Vimercate (Milano) Italy
+39 039 6863033
Email: sergio.belotti@alcatel-lucent.it
Daniele Ceccarelli
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: daniele.ceccarelli@ericsson.com
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Khuzema Pithewan
Infinera Corporation
169, Java Drive
Sunnyvale, CA-94089, USA
Email: kpithewan@infinera.com
Yi Lin
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28972914
Email: yi.lin@huawei.com
Yunbin Xu
China Academy of Telecommunication Research of MII
11 Yue Tan Nan Jie Beijing, P.R.China
Phone: +86-10-68094134
Email: xuyunbin@mail.ritt.com.cn
Pietro Grandi
Alcatel-Lucent
Optics CTO
Via Trento 30 20059 Vimercate (Milano) Italy
+39 039 6864930
Email: pietro_vittorio.grandi@alcatel-lucent.it
Diego Caviglia
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: diego.caviglia@ericsson.com
Mohit Misra
Infinera Corporation
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169, Java Drive
Sunnyvale, CA-94089, USA
Email: mmisra@infinera.com
Rajan Rao
Infinera Corporation
169, Java Drive
Sunnyvale, CA-94089, USA
Email: rrao@infinera.com
Ashok Kunjidhapatham
Infinera Corporation
169, Java Drive
Sunnyvale, CA-94089, USA
Email: akunjidhapatham@infinera.com
Biao Lu
Infinera Corporation
169, Java Drive
Sunnyvale, CA-94089, USA
Email: blu@infinera.com
Lyndon Ong
Ciena
PO Box 308, Cupertino, CA 95015, USA
EMail: lyong@ciena.com
Igor Bryskin
Adva Optical
EMail: IBryskin@advaoptical.com
Acknowledgment
The authors would like to thank Jonathan Sadler and John E Drake for
their useful comments to the document.
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