- All Implemented Interfaces:
- PCEPElement
public class InterLayer
extends PCEPObject
3.1. INTER-LAYER Object
The INTER-LAYER object is optional and can be used in PCReq and PCRep
messages.
In a PCReq message, the INTER-LAYER object indicates whether inter-
layer path computation is allowed, the type of path to be computed,
and whether triggered signaling (hierarchical LSPs per [RFC4206] or
stitched LSPs per [RFC5150] depending on physical network
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technologies) is allowed. When the INTER-LAYER object is absent from
a PCReq message, the receiving PCE MUST process as though inter-layer
path computation had been explicitly disallowed (I-bit set to zero -
see below).
In a PCRep message, the INTER-LAYER object indicates whether inter-
layer path computation has been performed, the type of path that has
been computed, and whether triggered signaling is used.
When a PCReq message includes more than one request, an INTER-LAYER
object is used per request. When a PCRep message includes more than
one path per request that is responded to, an INTER-LAYER object is
used per path.
INTER-LAYER Object-Class is to be assigned by IANA (recommended
value=18)
INTER-LAYER Object-Type is to be assigned by IANA (recommended
value=1)
The format of the INTER-LAYER object body is 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |T|M|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I flag (1 bit): The I flag is used by a PCC in a PCReq message to
indicate to a PCE whether an inter-layer path is allowed. When the I
flag is set (one), the PCE MAY perform inter-layer path computation
and return an inter-layer path. When the flag is clear (zero), the
path that is returned MUST NOT be an inter-layer path.
The I flag is used by a PCE in a PCRep message to indicate to a PCC
whether the path returned is an inter-layer path. When the I flag is
set (one), the path is an inter-layer path. When it is clear (zero),
the path is contained within a single layer either because inter-
layer path computation was not performed or because a mono-layer path
(without any virtual TE link and without any loose hop that spans the
lower-layer network) was found notwithstanding the use of inter-layer
path computation.
M flag (1 bit): The M flag is used by a PCC in a PCReq message to
indicate to a PCE whether mono-layer path or multi-layer path is
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requested. When the M flag is set (one), multi-layer path is
requested. When it is clear (zero), mono-layer path is requested.
The M flag is used by a PCE in a PCRep message to indicate to a PCC
whether mono-layer path or multi-layer path is returned. When M flag
is set (one), multi-layer path is returned. When M flag is set (zero),
mono-layer path is returned.
If the I flag is clear (zero), the M flag has no meaning and MUST be
ignored.
[PCE-INTER-LAYER-REQ] describes two sub-options for mono-layer path.
- A mono-layer path that is specified by strict hops. The path may
include virtual TE links.
- A mono-layer path that includes loose hops that span the lower-
layer network.
The choice of this sub-option can be specified by the use of O flag
in the RP object specified in [RFC5440].
T flag (1 bit): The T flag is used by a PCC in a PCReq message to
indicate to a PCE whether triggered signaling is allowed. When the T
flag is set (one), triggered signaling is allowed. When it is clear
(zero), triggered signaling is not allowed.
The T flag is used by a PCE in a PCRep message to indicate to a PCC
whether triggered signaling is required to support the returned path.
When the T flag is set (one), triggered signaling is required. When
it is clear (zero), triggered signaling is not required.
Note that triggered signaling is used to support hierarchical
[RFC4206] or stitched [RFC5150] LSPs according to the physical
attributes of the network layers.
If the I flag is clear (zero), the T flag has no meaning and MUST be
ignored.
Note that the I flag and M flag differ in the following ways. - When
the I flag is clear (zero), virtual TE links must not be used in path
computation. In addition, loose hops that span the lower-layer
network must not be specified. Only regular TE links from the same
layer may be used.
- When the I flag is set (one), the M flag is clear (zero), and the T
flag is set (one), virtual TE links are allowed in path computation.
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In addition, when the O flag of the RP object is set, loose hops that
span the lower-layer network may be specified. This will initiate
lower-layer LSP setup, thus inter-layer path is setup even though the
path computation result from a PCE to a PCC include hops from the
same layer only.
- However, when the I flag is set (one), the M flag is clear (zero),
and the T flag is clear (zero), since triggered signaling is not
allowed, virtual TE links must not be used in path computation. In
addition, loose hops that span the lower-layer network must not be
specified. Therefore, this is equivalent to the I flag being clear
(zero).
Reserved bits of the INTER-LAYER object SHOULD be transmitted as zero
and SHOULD be ignored on receipt. A PCE that forwards a path
computation request to other PCEs SHOULD preserve the settings of
reserved bits in the PCReq messages it sends and in the PCRep
messages it forwards to PCCs.
- Author:
- ogondio