CCAMP Working Group E. Mannie (KPNQwest)
Internet Draft D. Papadimitriou (Alcatel)
Expiration Date: December 2002
June 2002
GMPLS Extensions to OSPF and IS-IS for SONET/SDH Network Control
draft-mannie-ccamp-gmpls-sonet-sdh-ospf-isis-01.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [1].
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Abstract
This document introduces some of the extensions required in existing
IGP routing protocols to support sub-sequent signalling for
dynamically established SONET/SDH circuits using GMPLS-based control
plane architecture [GMPLS-ARCH]. In particular, it specifies the
GMPLS routing extensions to OSPF and IS-IS routing protocols for
SONET/SDH networks using [GMPLS-RTG] as guideline.
The current document is based on the Traffic Engineering (TE)
extensions defined in [OSPF-TE] and [ISIS-TE]. It supports link
bundling (aka TE Links) as defined in [MPLS-BDL]. This document
proposes several new sub-TLVs for SONET/SDH network control which
complement those proposed in [GMPLS-OSPF] and [GMPLS-ISIS]. The
proposed encoding does not preclude any further integration in these
documents that the current one intends to complement.
1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT","SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119.
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2. Introduction
This document is based on Traffic Engineering (TE) extensions
defined in [OSPF-TE] and [ISIS-TE]. [GMPLS-OSPF] and [GMPLS-ISIS]
have extended these attributes in the GMPLS context.
The proposed approach also uses the notion of Link Bundling as
defined in [MPLS-BDL]. A set of data bearing links between two
adjacent GMPLS nodes (or simply nodes) is defined as a TE Link and
identified by a TE Link ID. The set of data bearing links belonging
to a given TE Link must have the same TE metric, the same set of
Resource Classes and the same set of Switching Capabilities and can
be advertised as a single TE Link. Such TE Links are also referred
to as link bundles and their individual data bearing link (or simply
links) as component links. Moreover, there is no longer a one-to-one
association between a regular routing adjacency and a TE Link (see
[MPLS-HIER]).
In order to enable distributed SONET/SDH network control, the IGP TE
routing protocol has to enable the exchange of two different sets of
TE Attributes. On one hand, a set that describes the TE Link
capabilities of the SONET/SDH nodeÆs interfaces, independently of
their usage. On the other hand, a set that describes the resources
(i.e. the SONET/SDH signals) usage on each TE Link.
The first set can be defined as being driven by less frequent
updates (since TE Link capabilities changes are not expected to be
frequent) while the second would follow update interval values as
the ones used for any other TE Link attribute. Therefore, when this
frequency is very low the corresponding TE Link capabilities are
considered as static and by opposition, the TE Link resources usage
as dynamic.
When using OSPF, GMPLS TE links can be advertised using Opaque LSAs
(Link State Advertisements) of Type 10. The Traffic Engineering (TE)
LSA, whose area flooding scope is specified [RFC-2370], has one top-
level Type/Length/Value (TLV) triplet and one or more nested sub-
TLVs for extensibility. Per [OSPF-TE], the following top-level TLVs
are defined (1) Router Address (referred to as the Node TLV) and (2)
TE Link TLV. When using IS-IS, GMPLS TE links are advertised using
LS PDUs. TE Attributes TLVs are defined as sub-TLV for the Extended
IS Reachability TLV (TLV 22) (see [ISIS-TE] and [GMPLS-ISIS]).
Thus, here we propose to extend the current sub-TLV set of the TE
Link TLV and Extended IS Reachability TLV, respectively. The sub-
TLVs describing the capabilities of SONET/SDH TE Links are
separately defined for LOVC/VT and HOVC/STS SPE; these are:
- LS-MC TLV : TE Link SONET/SDH Multiplexing Capability TLV
- LS-CC TLV : TE Link SONET/SDH Concatenation Capability TLV
- LS-TC TLV : TE Link SONET/SDH Transparency Capability TLV
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The sub-TLV describing the dynamic status of the SONET/SDH TE Link
components is:
- LS-UT-TLV : TE Link SONET/SDH (number of) Unallocated Timeslot TLV
Note: the proposed sub-TLVs can also complement the Interface
Switching Capability Descriptor sub-TLV of the TE Link TLV and
Extended IS Reachability TLV (see [GMPLS-OSPF] and [GMPLS-ISIS],
respectively) when the Switching Capability field value refers to
TDM.
3. Additional Considerations
Between two adjacent nodes, several links having the same Traffic
Engineering (TE) capabilities (i.e. same TE metric, same set of
Resource Class and same Switching capability) can be advertised as a
single TE Link, such TE links are referred to as link bundles. The
individual links (or data bearing links) belonging to a given bundle
are referred to as component links. Also there is no longer a one-
to-one association between a regular routing adjacency and a TE
link.
The result is that each component of a TE Link may have the same
SONET/SDH multiplexing and concatenation capabilities as defined
later in this document. The two corresponding TLVs (LS-MC and LS-CC)
are specified once, but apply to each component of the TE Link.
Thus, no per component information or identification is required for
these TLVs. The TE Link SONET/SDH Unallocated Timeslot TLV defined
in Section 5 gives the total number of unallocated components (i.e.
timeslots) included in a given TE Link.
Combined with the Link Property Correlation (see [LMP]) of data
links into TE Links (also referred to as link bundling) this
capability helps in removing the potential problem of flooding huge
amount routing information. For instance, with a group of 10 fibers
and 40 wavelengths per fiber, each of them supporting an STM-64,
there are potentially 76800 VC-3 timeslots that can be allocated
into the corresponding TE Link and that have therefore to be
advertised to all nodes in the same routing domain. The most
efficient way to proceed on a per-TE Link basis is to advertise the
number of unallocated timeslots, such that after the initial
advertisement, each node within a given routing area is aware of
total capacity per TE Link (see Section 5.1).
Despite being bundled, the usage of each component link in a TE Link
may differ completely. For example, in a TE Link comprising two
components the first component could be structured in VC-4-4c while
the second component could be structured in VC-3s. Likewise, each
STM-i of an STM-N (N > 1) could also be structured differently from
the others.
Therefore, for given TE Link it is not sufficient to simply
represent the total number of timeslots (i.e. the bandwidth) that
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are (un)allocated. It is also essential to know the corresponding
signal types. This because in an allocated component does not only
consume a timeslot at a given position in the multiplex, it also
imposes some restrictions on the future allocations that can be made
from the free portion of the SONET/SDH multiplex. This imposes a
specific Concatenation Capability rules as described in Section 4.2.
The knowledge of the signal types that can be carried in an STS-
(3*N)/STM-N (for High Order, HO) or an STS-1/STM-0 (for Low Order,
LO) and supported by the TE links are needed for path computation
purposes. When computing an explicit route, a node considers the
Interface Switching Capability descriptor subùTLV (see [GMPLS-RTG])
and the LS-MC sub-TLV to ensure that the path (a) has the capability
to carry the requested signal and (b) that it has sufficient
available bandwidth (i.e. enough timeslot within the SONET/SDH
multiplex on each interface) to carry the requested signal.
4. TE Link Capabilities
There are two SONET/SDH TE Link capabilities to be advertised in the
routing protocols: the multiplexing capabilities and the
concatenation capability.
4.1 TE Link Multiplexing Capability
The types of signals that are supported by the TE Links of SONET/SDH
node constitute an important information with respect to the
SONET/SDH network capability. Therefore this information is to be
advertised via IGP TE routing protocol extensions.
The purpose of the TE Link multiplexing capability is to succinctly
describe the types of SONET/SDH signals that can be multiplexed by a
TE Link for explicit route computation purposes. For example,
depending on how it is structured, an OC-48/STM-16 link may be able
to multiplex a variety of signal types.
4.1.1 Structure of SONET/SDH Multiplexing Capabilities
GMPLS-based control of SONET/SDH networks enables the control of
multiplex structures at a finer level of granularity than both STM-
N/STS-(3xN) with N = 1, 4, 16, 64, 256 and STM-0/STS-1. These
multiplexing structures are defined in [T1.105] and [G.707].
4.1.2 TE Link SONET/SDH Multiplexing Capability TLV (LS-MC)
The Link SONET/SDH Multiplexing Capability (LS-MC) TLV describes the
multiplexing capabilities of either a low-order link (i.e. a single
STS-1/STM-0), or a high-order link (i.e. a single STS-(3*N)/STM-N (N
= 1, 4, 16, 64, 256). It indicates precisely the types of elementary
signal that can be multiplexed by this link. Both low order and high
order instances of this TLV can be used simultaneously (for reasons
outside of the scope of this document).
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In IS-IS, this TLV is a sub-TLV of the Extended IS Reachability TLV
(TLV 22) with Type TBD. In OSPF, this TLV is a sub-TLV of the Link
TLV, with type TBD. The length of this TLV is four octets. The
Multiplexing Capability Flag (MC-Flag) field defined as a vector of
flags is coded over one octet.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MC Flag | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OSPF SONET/SDH TE Link Multiplex Capability TLV
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MC Flag | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IS-IS SONET/SDH TE Link Multiplex Capability TLV
The MC Flag field indicates the capability of a link to multiplex a
given signal into the higher order signal in the SONET/SDH multiplex
tree.
This flag is a vector of bits defined separately for both High Order
(HO) and for Low Order (LO) SONET/SDH signals. A bit value of 1
indicates that the multiplexing capability is supported while a bit
value of 0 indicates that the multiplexing capability is not
supported. Bit 1 is the lowest order bit of the flag field.
The MC-Flag for SDH High Order VC (HOVC) is:
- Bit 1 : VC-3 in AUG-1
- Bit 2 : AUG-1 in AUG-4
- Bit 3 : AUG-4 in AUG-16
- Bit 4 : AUG-16 in AUG-64
- Bit 5 : AUG-64 in AUG-256
- Bit 6 : TUG-3 in AUG-1 (via VC-4)
- Bit 7 : Reserved
- Bit 8 : Reserved
For instance, a value of HOVC MC-Flag can take the following values:
- 0b00111111 (0x3f): indicates a full SDH HO multiplexing capability
- 0b00011110 (0x1e): indicates that the lowest multiplexing
capability is AUG-1 (with C4->VC4->AU4->AUG1)
- 0b00000111 (0x05): indicates a full AUG-4 (within an STM-4)
multiplexing capability
Similarly, the MC-Flag for SDH Low Order VC (LOVC) is:
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- Bit 1 : VC-11 in TUG-2
- Bit 2 : VC-12 in TUG-2
- Bit 3 : Reserved
- Bit 4 : VC-2 in TUG-2
- Bit 5 : TUG-2 in TUG-3
- Bit 6 : TUG-2 in VC-3
- Bit 7 : Reserved
- Bit 8 : Reserved
For instance, a value of LOVC MC-Flag can take the following values:
- 0b00100010 (0x22): indicates that VC-12 can only be multiplexed in
VC-3 (through TUG-2).
- 0b00101000 (0x28): indicates that VC-2 can only be multiplexed in
VC-3 (through TUG-2).
Note: A binary value of 0b0..0 when advertised indicates no SDH
multiplexing capability at all. Therefore referring to VC-4-Nc in
AUG-N/STM-N capable interfaces only.
The MC Flag for SONET high order STS SPE is:
- Bit 1 : STS-1 in STSG-3
- Bit 2 : STSG-3 in STSG-12
- Bit 3 : STSG-12 in STSG-48
- Bit 4 : STSG-48 in STSG-192
- Bit 5 : STSG-192 in STSG-768
- Bit 6 to 8 : reserved
Similarly, the MC Flag for SONET low order VT SPE is:
- Bit 1 : VT-1.5 SPE in VT Group
- Bit 2 : VT-2 SPE in VT Group
- Bit 3 : VT-3 SPE in VT Group
- Bit 4 : VT-6 SPE in VT Group
- Bit 5 : VT-Group in STS-1 SPE
- Bit 6 to 8 : reserved
Note: A binary value of 0b0...0 when advertised indicates no SONET
multiplexing capability at all. Therefore referring to STS3-Mc in
STS-N (with N = 3xM) capable interfaces only.
4.2 TE Link Concatenation Capability
Contiguous and Virtual concatenation of Low Order (LO) and High
Order (HO) SONET and SDH signals are respectively defined in
[T1.105] and [G.707].
Note: Some equipmentÆs have limitations on the number of signal that
can be concatenated. In that case, it may not possible to use a
complete range of signals for contiguous (or even virtual)
concatenation. It might also be that some of the supported
contiguous and virtual concatenation capabilities are precluded or
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discarded for reasons outside of the scope of this specification.
Therefore, we propose an alternate way of representing the
concatenation capabilities of a link by listing explicitly all of
the levels of contiguous and virtual concatenation being supported.
4.2.1 SDH TE Link Concatenation Capability TLV (LS-CC)
The SDH TE Link Concatenation Capability TLV describes the SONET/SDH
concatenation capabilities on a link.
In IS-IS, this TLV is a sub-TLV of the Extended IS Reachability TLV
with type TBD. In OSPF, this TLV is a sub-TLV of the Link TLV, with
type TBD. The corresponding encoding and values are defined for Low
Order and High Order VCs. If no concatenation is supported on a TE
Link, this TLV should not be advertised.
1. Low Order VC (LOVC) Concatenation
LOVC Concatenation includes:
- Contiguous concatenation of X VC-2s (VC-2-Xc, X = 1,...,7)
- Virtual concatenation of X VC-2/12/11s (VC-m-Xv, m = 11,12,2)
as defined in the following table:
Signal Carried in X interval
--------------------------------------------------
VC-11-Xv VC-3 1 to 28
VC-12-Xv VC-3 1 to 21
VC-2-Xv VC-3 1 to 7
VC-11-Xv VC-4 1 to 64
VC-12-Xv VC-4 1 to 63
VC-2-Xv VC-4 1 to 21
The SDH LOVC TE Link Concatenation Capability 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// . . . //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OSPF SDH LOVC TE Link Concatenation Capability TLV
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 | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// . . . //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IS-IS SDH LOVC TE Link Concatenation Capability TLV
Signal Type (8 bits):
The Signal Type field values are defined in [GMPLS-SONET-SDH].
CT û Concatenation Type (4 bits):
The CT field is defined as a 4-bit vector of flags indicating
the supported concatenation type(s):
Bit 1: Contiguous Concatenation
Bit 2: Virtual Concatenation
Bit 3: Concatenation Conversion (see ITU-T G.783)
Bit 4: Reserved
Reserved (4 bits):
The Reserved field bits must be set to zero when sent and
should be ignored when received.
LT û List Type (4 bits):
The LT field indicates the type of the list; the following
values are defined (the values to which they refer must be
mutually disjoint):
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0 Inclusive list
1 Exclusive list
2 Inclusive range (one or more Minimum/Maximum pairs)
3 Exclusive range (one or more Minimum/Maximum pairs)
Values ranging from 4 to 15 are reserved.
List Length (12 bits):
The List Length indicates the number of NCC elements included
within the sub-list. Zero is an invalid value.
NCC - Number of Concatenated Components (16 bits):
The NCC field indicates the supported number of low order VCÆs
with respect to the Signal Type and the CT values. For SDH
LOVCs, the number of VC-mÆs values MUST refer to one or more of
the following values (as defined in the Signal Type field): VC-
11, VC-12 and/or VC-2.
When the LT field value equals 2 or 3, at least one pair of
LOVCÆs numbers (i.e. two NCC fields) must be included in the
list. The first value indicates the minimum number of LOVCÆs
and the second one the maximum number of LOVCÆs supported (or
not supported, respectively) with the selected concatenation
type (CT).
2. High Order VC (HOVC) Concatenation:
HOVC Concatenation includes:
- Contiguous concatenation of X VC-4s (VC-4-Xc, X = 4,16,64,256)
- Virtual concatenation of X VC-3/4s (VC-3/4-Xv, X = 1,...,256)
The SDH HOVC TE Link Concatenation Capability 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// . . . //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OSPF SDH HOVC TE Link SDH Concatenation Capability TLV
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 | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// . . . //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | CT | Res. | LT | List Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NCC | . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IS-IS SDH HOVC TE Link SDH Concatenation Capability TLV
Signal Type (8 bits): see above.
CT û Concatenation Type (4 bits): see above.
Reserved (4 bits): see above.
LT û List Type (4 bits): see above.
List Length (12 bits): see above.
NCC - Number of Concatenated Components (16 bits):
The NCC field indicates the supported number of high order VCÆs
with respect to the Signal Type (i.e. VC-3 and/or VC-4) and the
CT values.
When the LT field value equals 2 or 3, at least one pair of
HOVCÆs numbers (i.e. two NCC fields) must be included in the
list. The first value indicates the minimum number of HOVCÆs
and the second one the maximum number of HOVCÆs supported (or
not supported, respectively) with the selected concatenation
type (CT).
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4.2.2 SONET TE Link Concatenation Capability TLV (LS-CC)
Using the STS-1 SPE and STS-3c SPE equivalence to a VC-3 and a VC-4,
respectively, the above High Order Concatenation Capability TLV
applies. Notice that in SONET, contiguous concatenation is
applicable to STS-3c SPE signals, resulting in STS-(3*X)c SPE
signals with X = 4, 16, 64, 256. For low order signal, only virtual
concatenation of X VTn SPEs (VTn-Xv SPE, n = 1.5,2,3,6) must be
considered since low order contiguous concatenation is not defined
in ANSI [T1.105].
In IS-IS, this TLV is a sub-TLV of the Extended IS Reachability TLV
with type TBD. In OSPF, this TLV is a sub-TLV of the Link TLV, with
type TBD. The corresponding encoding and values are defined for Low
Order and High Order VCs.
1. Low order VT SPEs concatenation:
- Virtual concatenation of X VTnÆs SPE (VTn-Xv SPE, n = 1.5,2,3,
6) as defined in the following table:
Signal Carried in X interval
--------------------------------------------------
VT1.5-Xv SPE STS-1 1 to 28
VT2-Xv SPE STS-1 1 to 21
VT3-Xv SPE STS-1 1 to 14
VT6-Xv SPE STS-1 1 to 7
VT1.5-Xv SPE STS-3c 1 to 64
VT2-Xv SPE STS-3c 1 to 63
VT3-Xv SPE STS-3c 1 to 42
VT6-Xv SPE STS-3c 1 to 21
The OSPF/ISIS encoding for the Low Order SONET TE Link
Concatenation Capability TLV is identical to the one defined for
SDH LOVC Concatenation.
2. High order STS SPEs concatenation:
- Contiguous concatenation of X STS-3c SPEs (STS-(3*X)c with X =
4,16,64,256)
- Virtual concatenation of X STS-1/STS-3c SPEs (STS-1-Xv/STS-3c-
Xv with X = 1,...,256)
The OSPF and ISIS encoding for the High Order SONET TE Link
Concatenation Capability TLV is identical to the one defined for
SDH HOVC Concatenation.
4.2.3 SONET/SDH TE Link Transparency Capability (LS-TC TLV)
This TLV is defined as a vector of flags that indicates the type of
transparency supported by each of the component of a given TE Link.
Several flags can be combined to provide different types of
transparency while any combination is not necessarily valid. By
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default, the supported transparency on a TE Link is defined as the
Path Overhead (POH) transparency; therefore the LS-TC TLV should not
be sent for a TE Link only supporting POH transparency.
Note that when the LS-TC TLV is advertised, the Signal Type(s)
field(s) in the LS-UT TLV (see Section 5) MUST take at least one of
the following values (see [GMPLS-SONET-SDH]): STM-0/STS-1, STM-
1/STS-3, STM-4/STS-12, STM-16/STS-48, STM-64/STS-192, and STM-
256/STS-768. Equivalently, at least one transparency type must be
specified when advertising such Signal Type(s) in the LS-UT TLV.
In IS-IS, the LS-TC TLV is a sub-TLV of the Extended IS Reachability
TLV (TLV 22) with Type TBD. In OSPF, this TLV is a sub-TLV of the
Link TLV, with type TBD. The length of this TLV is four octets. It
includes the Transparency field defined as a 32-bit vector of flags.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transparency (T) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OSPF SONET/SDH TE Link Transparency Capability TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transparency (T) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IS-IS SONET/SDH TE Link Transparency Capability TLV
The different transparency flags are the following:
Flag 1 (bit 1): Section/Regenerator Section layer
Flag 2 (bit 2): Line/Multiplex Section layer
Where bit 1 is the low order bit. Others flags are reserved, they
should be set to zero when sent, and should be ignored when
received. A flag is set to one to indicate that the corresponding
transparency is supported on the corresponding TE Link.
We refer to [GMPLS-SONET-SDH-EXT] for an extended set of
transparency flags beyond the standard transparencies defined in
ANSI [T1.105] and ITU-T [G.707].
5. Dynamic Allocation
This section defines the dynamic capabilities of a link that should
be advertised by OSPF/IS-IS. The most important dynamic link
capability that needs to be advertised concerns the link resources
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usage. In the SONET/SDH context, this information can be represented
by the number of unallocated (free) timeslots per signal type and
per link.
5.1 Link SONET/SDH Unallocated Timeslot (LS-UT) TLV
The Link SONET/SDH Unallocated Timeslot TLV specifies the number of
identical unallocated timeslots per TE Link. As such, the initial
value(s) of this TLV indicates the total capacity in terms of number
of timeslot per TE Link.
In IS-IS, this TLV is a sub-TLV of the Extended IS Reachability TLV
with type TBD. In OSPF, this TLV is a sub-TLV of the Link TLV, with
type TBD. The length is n*4 octets. The value is the number of
unallocated (free) timeslot in the TE Link, and is coded in 4
octets. The Signal Type field values are defined in [GMPLS-SONET-
SDH].
Typically, a given LS-UT TLV will be advertised by including Signal
Type(s) of the same order since one expects (as it is mostly the
case in legacy networks) separated routing instances between Low
Order and High Order VC transport layers.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length = n*4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Number of Unallocated Timeslots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Number of Unallocated Timeslots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// . . . //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OSPF Link SONET/SDH Unallocated Timeslot TLV
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 | Number of Unallocated Timeslots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Number of Unallocated Timeslots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// . . . //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IS-IS Link SONET/SDH Unallocated Timeslot TLV
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For instance, if a TE Link is constituted by 40 STM-64, each of them
decomposed in VC-4, initially the value of the Number of Unallocated
Timeslots field of this TLV is 40 x 64. Thus, 2560 VC-4 signals are
supported, and, if required, 2560 instances of exactly the same
signal can be allocated.
When two Number of Unallocated Timeslots fields with the same Signal
Type value are advertised, the second one indicates the number of
contiguous block of unallocated timeslots. Thus, when advertised
initially the corresponding value equal 1.
6 Security Considerations
This document does not introduce additional considerations to [OSPF-
TE] and [ISIS-TE].
7. References
[G.707] ITU-T Recommendation G.707, ôNetwork Node Interface for
the Synchronous Digital Hierarchyö, April 2000.
[GMPLS-ARCH] E.Mannie (Editor) et al., ôGeneralized MPLS (GMPLS)
Architecture,ö Internet Draft, Work in Progress, draft-
ietf-ccamp-gmpls-architecture-02.txt, February 2002.
[GMPLS-ISIS] K.Kompella et al, ôIS-IS Extensions in Support of
Generalized MPLS,ö Internet Draft, Work in Progress,
draft-ietf-isis-gmpls-extensions-13.txt, June 2002.
[GMPLS-OSPF] K.Kompella et al., ôOSPF Extensions in Support
of Generalized MPLS,ö Internet Draft, Work in Progress,
draft-ietf-ccamp-ospf-gmpls-extensions-07.txt, April
2002.
[GMPLS-RTG] K.Kompella et al., ôRouting Extensions in Support of
Generalized MPLS,ö Internet Draft, Work in Progress,
draft-ietf-ccamp-gmpls-routing-04.txt, April 2002.
[GMPLS-SONET-SDH] E.Mannie and D.Papadimitriou (Editors) et al.,
"GMPLS extensions for SONET and SDH control", Internet
Draft, Work in progress, draft-ietf-ccamp-gmpls-sonet-
sdh-05.txt, May 2002.
[ISIS-TE] H.Smith and T.Li, ôISIS Extensions for Traffic
Engineeringö, draft-ietf-isis-traffic-04.txt, Internet
Draft, Work in Progress, June 2001.
[MPLS-BDL] K.Kompella et al., ôLink Bundling in MPLS Traffic
Engineering,ö Internet Draft, Work in Progress, draft-
ietf-mpls-bundle-03.txt, May 2002.
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[MPLS-HIER] K.Kompella and Y.Rekhter, ôLSP Hierarchy with
Generalized MPLS TEö, Internet Draft, Work in progress,
draft-ietf-mpls-lsp-hierarchy-06.txt, May 2002.
[OSPF-TE] D.Katz, D.Yeung and K.Kompella, ôTraffic Engineering
Extensions to OSPFö, draft-katz-yeung-ospf-traffic-
06.txt, Internet Draft, Work in Progress, October 2001.
[RFC-2370] R.Coltun, RFC 2370, Standard Track, "The OSPF Opaque
LSA Option", July 1998.
[T1.105] American National Standards Institute, ôSynchronous
Optical Network - Payload Mappingsö, ANSI T1.105, 2001.
8. Author's Addresses
Eric Mannie (KPNQwest) Dimitri Papadimitriou (Alcatel)
Terhulpsesteenweg, 6A Francis Wellesplein 1,
1560 Hoeilaart, Belgium B-2018 Antwerpen, Belgium
Phone:+32 2 658-5652 Phone:+32 3 240-8491
Email: eric.mannie@ebone.com Email:dimitri.papadimitriou@alcatel.be
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