Request for Comments: 4606 Perceval
Obsoletes: 3946 D. Papadimitriou
Category: Standards Track Alcatel
August 2006
Generalized Multi-Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and
Synchronous Digital Hierarchy (SDH) Control
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution cof this memo is
unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document provides minor clarification to RFC 3946.
This document is a companion to the Generalized Multi-protocol Label
Switching (GMPLS) signaling. It defines the Synchronous Optical
Network (SONET)/Synchronous Digital Hierarchy (SDH) technology-
specific information needed when GMPLS signaling is used.
Table of Contents
1. Introduction ....................................................2
2. SONET and SDH Traffic Parameters ................................3
2.1. SONET/SDH Traffic Parameters ...............................3
2.2. RSVP-TE Details ............................................9
2.3. CR-LDP Details ............................................10
3. SONET and SDH Labels ...........................................11
4. Acknowledgements ...............................................16
5. Security Considerations ........................................16
6. IANA Considerations ............................................16
Contributors ......................................................17
Appendix 1. Signal Type Values Extension for VC-3 .................20
Annex 1. Examples .................................................20
Normative References ..............................................23
1. Introduction
As described in [RFC3945], Generalized MPLS (GMPLS) extends MPLS from
supporting packet (Packet Switching Capable, or PSC) interfaces and
switching to include support of four new classes of interfaces and
switching: Layer-2 Switch Capable (L2SC), Time-Division Multiplex
(TDM), Lambda Switch Capable (LSC) and Fiber-Switch Capable (FSC). A
functional description of the extensions to MPLS signaling needed to
support the new classes of interfaces and switching is provided in
[RFC3471]. [RFC3473] describes RSVP-TE-specific formats and
mechanisms needed to support all five classes of interfaces, and CR-
LDP extensions can be found in [RFC3472].
This document presents details that are specific to Synchronous
Optical Network (SONET)/Synchronous Digital Hierarchy (SDH). Per
[RFC3471], SONET/SDH-specific parameters are carried in the signaling
protocol in traffic parameter specific objects.
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].
Moreover, the reader is assumed to be familiar with the terminology
in American National Standards Institute (ANSI) [T1.105] and ITU-T
[G.707], as well as with that in [RFC3471], [RFC3472], and [RFC3473].
The following abbreviations are used in this document:
DCC: Data Communications Channel.
LOVC: Lower-Order Virtual Container
HOVC: Higher-Order Virtual Container
MS: Multiplex Section.
MSOH: Multiplex Section overhead.
POH: Path overhead.
RS: Regenerator Section.
RSOH: Regenerator Section overhead.
SDH: Synchronous digital hierarchy.
SOH: Section overhead.
SONET: Synchronous Optical Network.
SPE: Synchronous Payload Envelope.
STM(-N): Synchronous Transport Module (-N) (SDH).
STS(-N): Synchronous Transport Signal-Level N (SONET).
VC-n: Virtual Container-n (SDH).
VTn: Virtual Tributary-n (SONET).
2. SONET and SDH Traffic Parameters
This section defines the GMPLS traffic parameters for SONET/SDH. The
protocol-specific formats, for the SONET/SDH-specific RSVP-TE objects
and CR-LDP TLVs, are described in Sections 2.2 and 2.3, respectively.
These traffic parameters specify a base set of capabilities for SONET
ANSI [T1.105] and SDH ITU-T [G.707], such as concatenation and
transparency. Other documents may further enhance this set of
capabilities in the future. For instance, signaling for SDH over PDH
ITU-T G.832 or sub-STM-0 ITU-T G.708 interfaces could be defined.
The traffic parameters defined hereafter (see Section 2.1) MUST be
used when the label is encoded as SUKLM as defined in this memo (see
Section 3). They MUST also be used when requesting one of Section/RS
or Line/MS overhead transparent STS-1/STM-0, STS-3*N/STM-N (N=1, 4,
16, 64, 256) signals.
The traffic parameters and label encoding defined in [RFC3471],
Section 3.2, MUST be used for fully transparent STS-1/STM-0,
STS-3*N/STM-N (N=1, 4, 16, 64, 256) signal requests. A fully
transparent signal is one for which all overhead is left unmodified
by intermediate nodes; i.e., when all defined Transparency (T) bits
would be set if the traffic parameters defined in Section 2.1 were
used.
2.1. SONET/SDH Traffic Parameters
The traffic parameters for SONET/SDH are organized 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 | RCC | NCC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NVC | Multiplier (MT) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transparency (T) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Profile (P) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Annex 1 lists examples of SONET and SDH signal coding.
o) Signal Type (ST): 8 bits
This field indicates the type of Elementary Signal that constitutes
the requested Label Switched Path (LSP). Several transforms can be
applied successively on the Elementary Signal to build the Final
Signal actually being requested for the LSP.
Each transform application is optional and must be ignored if zero,
except the Multiplier (MT), which cannot be zero and is ignored if
equal to one.
Transforms must be applied strictly in the following order:
- First, contiguous concatenation (by using the RCC and NCC fields)
can be optionally applied on the Elementary Signal, resulting in a
contiguously concatenated signal.
- Second, virtual concatenation (by using the NVC field) can be
optionally applied on the Elementary Signal, resulting in a
virtually concatenated signal.
- Third, some transparency (by using the Transparency field) can be
optionally specified when a frame is requested as signal rather
than an SPE- or VC-based signal.
- Fourth, a multiplication (by using the Multiplier field) can be
optionally applied directly on the Elementary Signal, on the
contiguously concatenated signal obtained from the first phase, on
the virtually concatenated signal obtained from the second phase,
or on these signals combined with some transparency.
Permitted Signal Type values for SONET/SDH are
Value Type (Elementary Signal)
----- ------------------------
1 VT1.5 SPE / VC-11
2 VT2 SPE / VC-12
3 VT3 SPE
4 VT6 SPE / VC-2
5 STS-1 SPE / VC-3
6 STS-3c SPE / VC-4
7 STS-1 / STM-0 (only when transparency is requested)
8 STS-3 / STM-1 (only when transparency is requested)
9 STS-12 / STM-4 (only when transparency is requested)
10 STS-48 / STM-16 (only when transparency is requested)
11 STS-192 / STM-64 (only when transparency is requested)
12 STS-768 / STM-256 (only when transparency is requested)
A dedicated signal type is assigned to a SONET STS-3c SPE instead of
being coded as a contiguous concatenation of three STS-1 SPEs. This
is done in order to provide easy interworking between SONET and SDH
signaling.
Appendix 1 adds one signal type (optional) to the above values.
o) Requested Contiguous Concatenation (RCC): 8 bits
This field is used to request the optional SONET/SDH contiguous
concatenation of the Elementary Signal.
This field is a vector of flags. Each flag indicates the support of
a particular type of contiguous concatenation. Several flags can be
set at the same time to indicate a choice.
These flags allow an upstream node to indicate to a downstream node
the different types of contiguous concatenation that it supports.
However, the downstream node decides which one to use according to
its own rules.
A downstream node receiving simultaneously more than one flag chooses
a particular type of contiguous concatenation, if any is supported,
and according to criteria that are out of this document’s scope. A
downstream node that doesn’t support any of the concatenation types
indicated by the field must refuse the LSP request. In particular,
it must refuse the LSP request if it doesn’t support contiguous
concatenation at all.
When several flags have been set, the upstream node retrieves the
(single) type of contiguous concatenation the downstream node has
selected by looking at the position indicated by the first label and
the number of labels as returned by the downstream node (see also
Section 3).
The entire field is set to zero to indicate that no contiguous
concatenation is requested at all (default value). A non-zero field
indicates that some contiguous concatenation is requested.
The following flag is defined:
Flag 1 (bit 1): Standard contiguous concatenation.
Flag 1 indicates that the standard SONET/SDH contiguous
concatenation, as defined in [T1.105]/[G.707], is supported. Note
that bit 1 is the low-order bit. Other flags are reserved for
extensions; if not used, they must be set to zero when sent and
should be ignored when received.
See note 1 in the section on the NCC about the SONET contiguous
concatenation of STS-1 SPEs when the number of components is a
multiple of three.
o) Number of Contiguous Components (NCC): 16 bits
This field indicates the number of identical SONET SPEs/SDH VCs
(i.e., Elementary Signal) that are requested to be concatenated, as
specified in the RCC field.
Note 1: When a SONET STS-Nc SPE with N=3*X is requested, the
Elementary Signal to be used must always be an STS-3c_SPE signal
type, and the value of NCC must always be equal to X. This allows
facilitating the interworking between SONET and SDH. In particular,
it means that the contiguous concatenation of three STS-1 SPEs cannot
be requested, as according to this specification this type of signal
must be coded using the STS-3c SPE signal type.
Note 2: When a transparent STS-N/STM-N signal is requested that is
limited to a single contiguously concatenated STS-Nc_SPE/VC-4-Nc, the
signal type must be STS-N/STM-N, RCC with flag 1, NCC set to 1.
The NCC value must be consistent with the type of contiguous
concatenation being requested in the RCC field. In particular, this
field is irrelevant if no contiguous concatenation is requested (RCC
= 0). In that case, it must be set to zero when sent and should be
ignored when received. A RCC value different from 0 implies a number
of contiguous components greater than or equal to 1.
Note 3: Following these rules, when a VC-4 signal is requested, the
RCC and the NCC values SHOULD be set to 0, whereas for an STS-3c SPE
signal, the RCC and the NCC values SHOULD be set 1. However, if
local conditions allow, since the setting of the RCC and NCC values
is locally driven, the requesting upstream node MAY set the RCC and
NCC values to either SDH or SONET settings without impacting the
function. Moreover, the downstream node SHOULD accept the requested
values if local conditions allow. If these values cannot be
supported, the receiver downstream node SHOULD generate a
PathErr/NOTIFICATION message (see Sections 2.2 and 2.3,
respectively).
o) Number of Virtual Components (NVC): 16 bits
This field indicates the number of signals that are requested to be
virtually concatenated. These signals are all of the same type by
definition. They are Elementary Signal SPEs/VCs for which signal
types are defined in this document; i.e., VT1.5_SPE/VC-11,
VT2_SPE/VC-12, VT3_SPE, VT6_SPE/VC-2, STS-1_SPE/VC-3, or
STS-3c_SPE/VC-4.
This field is set to 0 (default value) to indicate that no virtual
concatenation is requested.
o) Multiplier (MT): 16 bits
This field indicates the number of identical signals that are
requested for the LSP; i.e., that form the Final Signal. These
signals can be identical Elementary Signals, identical contiguously
concatenated signals, or identical virtually concatenated signals.
Note that all of these signals thus belong to the same LSP.
The distinction between the components of multiple virtually
concatenated signals is done via the order of the labels that are
specified in the signaling. The first set of labels must describe
the first component (set of individual signals belonging to the first
virtual concatenated signal), the second set must describe the second
component (set of individual signals belonging to the second virtual
concatenated signal), and so on.
This field is set to one (default value) to indicate that exactly one
instance of a signal is being requested. Intermediate and egress
nodes MUST verify that the node itself and the interfaces on which
the LSP will be established can support the requested multiplier
value. If the requested values cannot be supported, the receiver
node MUST generate a PathErr/NOTIFICATION message (see Sections 2.2
and 2.3, respectively).
Zero is an invalid value. If a zero is received, the node MUST
generate a PathErr/NOTIFICATION message (see Sections 2.2 and 2.3,
respectively).
Note 1: When a transparent STS-N/STM-N signal is requested that is
limited to a single contiguously concatenated STS-Nc-SPE/VC-4-Nc, the
multiplier field MUST be equal to 1 (only valid value).
o) Transparency (T): 32 bits
This field is a vector of flags that indicates the type of
transparency being requested. Several flags can be combined to
provide different types of transparency. Not all combinations are
necessarily valid. The default value for this field is zero, i.e.,
no transparency is requested.
Transparency, as defined from the point of view of this signaling
specification, is only applicable to the fields in the SONET/SDH
frame overheads. In the SONET case, these are the fields in the
Section Overhead (SOH) and the Line Overhead (LOH). In the SDH case,
these are the fields in the Regenerator Section Overhead (RSOH), the
Multiplex Section overhead (MSOH), and the pointer fields between the
two. With SONET, the pointer fields are part of the LOH.
Note also that transparency is only applicable when the following
signal types are used: STS-1/STM-0, STS-3/STM-1, STS-12/STM-4,
STS-48/STM-16, STS-192/STM-64, and STS-768/STM-256. At least one
transparency type must be specified when such a signal type is
requested.
Transparency indicates precisely which fields in these overheads must
be delivered unmodified at the other end of the LSP. An ingress
Label Switching Router (LSR) requesting transparency will pass these
overhead fields that must be delivered to the egress LSR without any
change. From the ingress and egress LSRs point of views, these
fields must be seen as being unmodified.
Transparency is applied not at the interfaces with the initiating and
terminating LSRs but only between intermediate LSRs. The
transparency field is used to request an LSP that supports the
requested transparency type; it may also be used to set up the
transparency process to be applied at each intermediate LSR.
The different transparency flags are as follows:
Flag 1 (bit 1): Section/Regenerator Section layer
Flag 2 (bit 2): Line/Multiplex Section layer
where bit 1 is the low-order bit. Other flags are reserved; they
should be set to zero when sent and ignored when received. A flag is
set to one to indicate that the corresponding transparency is
requested.
Intermediate and egress nodes MUST verify that the node itself and
the interfaces on which the LSP will be established can support the
requested transparency. If the requested flags cannot be supported,
the receiver node MUST generate a PathErr/NOTIFICATION message (see
Sections 2.2 and 2.3, respectively).
Section/Regenerator Section layer transparency means that the entire
frames must be delivered unmodified. This implies that pointers
cannot be adjusted. When Section/Regenerator Section layer
transparency is used all other flags MUST be ignored.
Line/Multiplex Section layer transparency means that the LOH/MSOH
must be delivered unmodified. This implies that pointers cannot be
adjusted.
o) Profile (P): 32 bits
This field is intended to indicate particular capabilities that must
be supported for the LSP; for example, monitoring capabilities.
No standard profile is currently defined, and this field SHOULD be
set to zero when transmitted and ignored when received.
In the future, TLV-based extensions may be created.
2.2. RSVP-TE Details
For RSVP-TE, the SONET/SDH traffic parameters are carried in the
SONET/SDH SENDER_TSPEC and FLOWSPEC objects. The same format is used
both for the SENDER_TSPEC object and for FLOWSPEC objects. The
content of the objects is defined above, in Section 2.1. The objects
have the following class and type for SONET ANSI T1.105 and SDH ITU-T
G.707:
SONET/SDH SENDER_TSPEC object: Class = 12, C-Type = 4
SONET/SDH FLOWSPEC object: Class = 9, C-Type = 4
There is no Adspec associated with the SONET/SDH SENDER_TSPEC.
Either the Adspec is omitted, or an int-serv Adspec with the Default
General Characterization Parameters and Guaranteed Service fragment
is used; see [RFC2210].
For a particular sender in a session, the contents of the FLOWSPEC
object received in a Resv message SHOULD be identical to the contents
of the SENDER_TSPEC object received in the corresponding Path
message. If the objects do not match, a ResvErr message with a
"Traffic Control Error/Bad Flowspec value" error SHOULD be generated.
Intermediate and egress nodes MUST verify that the node itself and
the interfaces on which the LSP will be established can support the
requested Signal Type, RCC, NCC, NVC and Multiplier (as defined in
Section 2.1). If the requested value(s) can not be supported, the
receiver node MUST generate a PathErr message with a "Traffic Control
Error/ Service unsupported" indication (see [RFC2205]).
In addition, if the MT field is received with a zero value, the node
MUST generate a PathErr message with a "Traffic Control Error/Bad
Tspec value" indication (see [RFC2205]).
Intermediate nodes MUST also verify that the node itself and the
interfaces on which the LSP will be established can support the
requested Transparency (as defined in Section 2.1). If the requested
value(s) cannot be supported, the receiver node MUST generate a
PathErr message with a "Traffic Control Error/Service unsupported"
indication (see [RFC2205]).
2.3. CR-LDP Details
For CR-LDP, the SONET/SDH traffic parameters are carried in the
SONET/SDH Traffic Parameters TLV. The content of the TLV is defined
above, in Section 2.1. The header of the TLV has the following
format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The type field for the SONET/SDH Traffic Parameters TLV is 0x0838.
Intermediate and egress nodes MUST verify that the node itself and
the interfaces on which the LSP will be established can support the
requested Signal Type, RCC, NCC, NVC, and Multiplier (as defined in
Section 2.1). If the requested value(s) cannot be supported, the
receiver node MUST generate a NOTIFICATION message with a "Resource
Unavailable" status code (see [RFC3212]).
In addition, if the MT field is received with a zero value, the node
MUST generate a NOTIFICATION message with a "Resource Unavailable"
status code (see [RFC3212]).
Intermediate nodes MUST also verify that the node itself and the
interfaces on which the LSP will be established can support the
requested Transparency (as defined in Section 2.1). If the requested
value(s) cannot be supported, the receiver node MUST generate a
NOTIFICATION message with a "Resource Unavailable" status code (see
[RFC3212]).
3. SONET and SDH Labels
SONET and SDH each define a multiplexing structure. Both structures
are trees whose roots are, respectively, an STS-N or an STM-N and
whose leaves are the signals that can be transported via the time-
slots and switched between time-slots within an ingress port and
time-slots within an egress port; i.e., a VTx SPE, an STS-x SPE, or a
VC-x. A SONET/SDH label will identify the exact position (i.e.,
first time-slot) of a particular VTx SPE, STS-x SPE, or VC-x signal
in a multiplexing structure. SONET and SDH labels are carried in the
Generalized Label per [RFC3473] and [RFC3472].
Note that by time-slots we mean the time-slots as they appear
logically and sequentially in the multiplex, not as they appear after
any possible interleaving.
These multiplexing structures will be used as naming trees to create
unique multiplex entry names or labels. The same format of label is
used for SONET and SDH. As explained in [RFC3471], a label does not
identify the "class" to which the label belongs. This is implicitly
determined by the link on which the label is used.
In case of signal concatenation or multiplication, a list of labels
can appear in the Label field of a Generalized Label.
In case of contiguous concatenation, only one label appears in the
Label field. This unique label is encoded as a single 32-bit label
value (as defined in this section) of the Generalized Label object
(Class-Num = 16, C-Type = 2)/TLV (0x0825). This label identifies the
lowest time-slot occupied by the contiguously concatenated signal.
By lowest time-slot, we mean the one having the lowest label (value)
when compared as an integer value; i.e., the time-slot occupied by
the first component signal of the concatenated signal encountered
descending the tree.
In case of virtual concatenation, the explicit ordered list of all
labels in the concatenation is given. This ordered list of labels is
encoded as a sequence of 32-bit label values (as defined in this
section) of the Generalized Label object (Class-Num = 16, C-Type =
2)/TLV (0x0825). Each label indicates the first time-slot occupied
by a component of the virtually concatenated signal. The order of