Route
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... allow abstract nodes and resources to be explicitly included in a
path setup, using the Explicit Route Object (ERO).
...
... This may be because loose hops or abstract nodes need to be prevented
from selecting a route through a specific resource. This is a
special case of distributed path calculation in the network.
...
... network.
For example, route exclusion could be used in the case where two
non-overlapping Label Switched Paths (LSPs ...
... Label Switched Paths (LSPs) are required. In this
case, one option might be to set up one path and collect its route
using route recording, and then to exclude the routers ...
... case, one option might be to set up one path and collect its route
using route recording, and then to exclude the routers on that first
path from the setup for the second path. Another option might be to
...
... path. This set of abstract nodes is referred to as the Exclude
Route list.
2. Exclusion of certain abstract nodes ...
... nodes present in an ERO. Such specific
exclusions are referred to as Explicit Exclusion Route.
To convey these constructs within the signaling protocol ...
...
- A new RSVP-TE object is introduced to convey the Exclude Route
list. This object is the EXCLUDE_ROUTE object (XRO ...
... RSVP-TE object is introduced to convey the Exclude Route
list. This object is the EXCLUDE_ROUTE object (XRO).
...
... the existing ERO. A new ERO subobject type the Explicit Exclusion
Route Subobject (EXRS) is introduced to indicate an exclusion
between a pair of included abstract nodes ...
... This document does not assume or preclude any other usage for this
subobject. This subobject might also be appropriate for use within
an Explicit Route object (ERO) or Record Route object (RRO ...
... an Explicit Route object (ERO) or Record Route object (RRO), but this
is outside the scope of this document.
...
...
This document does not preclude a route exclusion from listing
arbitrary nodes or network elements ...
... explicitly avoided. For instance, it may be necessary to signal only
the SRLGs (or Shared Risk Link Groups) to avoid. That is, the route
exclusion is not intended to define the actual route by listing all
...
... Shared Risk Link Groups) to avoid. That is, the route
exclusion is not intended to define the actual route by listing all
of the choices to exclude at each hop, but rather to constrain the
normal route selection ...
... route by listing all
of the choices to exclude at each hop, but rather to constrain the
normal route selection process where loose hops or abstract nodes are
to be expanded by listing certain elements ...
... XRO is not needed from BC2 onwards.
In general, consideration SHOULD be given (as with explicit route) to
the size of signaled data and the impact on the signaling protocol.
...
... This document does not assume or preclude any other usage for this
subobject. This subobject might also be appropriate for use within
Explicit Route object (ERO) or Record Route object (RRO ...
... Explicit Route object (ERO) or Record Route object (RRO), but this is
outside the scope of this document.
...
... L bit is an attribute of the subobject. The L bit is set
if the subobject represents a loose hop in the explicit route.
If the bit is not set, the subobject represents a strict hop in
...
... If the bit is not set, the subobject represents a strict hop in
the explicit route.
For exclusions (as used by XRO ...
... Exclude Route List ...
...
The exclude route identifies a list of abstract nodes that should not
be traversed along the path of the LSP ...
... be traversed along the path of the LSP being established. It is
RECOMMENDED that the size of the exclude route list be limited to a
value local to the node originating the exclude route ...
... EXCLUDE_ROUTE Object (XRO) ...
... Abstract nodes to be excluded from the path are specified via the
EXCLUDE_ROUTE object (XRO).
...
... XRO).
Currently, one C_Type is defined, Type 1 EXCLUDE_ROUTE. The
EXCLUDE_ROUTE object has the following format:
...
... Currently, one C_Type is defined, Type 1 EXCLUDE_ROUTE. The
EXCLUDE_ROUTE object has the following format:
Class ...
... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The contents of an EXCLUDE_ROUTE object are a series of variable-
length data items called subobjects. This specification adapts ERO
...
... RFC3473], and [RFC3477] for use
in route exclusions. The SRLG subobject as defined in Section 2 of
this document has not been defined before. The SRLG ...
... this document has not been defined before. The SRLG subobject is
defined here for use with route exclusions.
The following subobject types are supported.
...
... this document.
The concept of loose or strict hops has no meaning in route
exclusion. The L bit, defined for ERO ...
...
The exclude route list is encoded as a series of subobjects contained
in an EXCLUDE_ROUTE object. Each subobject identifies an abstract
...
... The exclude route list is encoded as a series of subobjects contained
in an EXCLUDE_ROUTE object. Each subobject identifies an abstract
node in the exclude route ...
... EXCLUDE_ROUTE object. Each subobject identifies an abstract
node in the exclude route list.
Each abstract node ...
... SRLG.
The Explicit Route and routing processing is unchanged from the
description in [RFC3209 ...
... error value
of "Local node in Exclude Route".
2. Each subobject MUST be consistent. If a subobject is not
...
...
4. When choosing a next hop or expanding an explicit route to include
additional subobjects, a node:
...
... equals or is a member of any abstract node that is specified in
the EXCLUDE_ROUTE object with the L-flag set to "exclude". The
number of introduced explicit nodes or abstract nodes ...
... Routing
Problem" and error value of "Route blocked by Exclude Route".
Note that the subobjects in the XRO ...
... receiving this error
code/value combination MAY reduce the complexity of the XRO or route
around the node that rejected the XRO ...
... extensions to ERO processing described above. This approach is
chosen to allow route exclusion to traverse parts of the network that
are not capable of parsing or handling the new function. Note that
...
... are not capable of parsing or handling the new function. Note that
Record Route may be used to allow computing nodes to observe
violations of route ...
... Route may be used to allow computing nodes to observe
violations of route exclusion and attempt to re-route the LSP
...
... Explicit Exclusion Route ...
... should not be used on the path between two inclusive abstract nodes
or resources in the explicit route.
...
... Explicit Exclusion Route Subobject (EXRS) ...
...
A new ERO subobject type is defined. The Explicit Exclusion Route
Subobject (EXRS) has type 33. Although the EXRS is an ERO ...
... error code "Routing Error" and error
value "Bad EXPLICIT_ROUTE object" with the EXPLICIT_ROUTE object
included, truncated (on the left) to the offending EXRS ...
... Routing Error" and error
value "Bad EXPLICIT_ROUTE object" with the EXPLICIT_ROUTE object
included, truncated (on the left) to the offending EXRS.
...
... error code/value combination MAY reduce
the complexity of the EXRS or route around the node that rejected the
EXRS ...
... Note that any security concerns that exist with explicit routes
should be considered with regard to route exclusions. For example,
some administrative boundaries may consider explicit routes to be
...
... EXRS)
The Explicit Exclusion Route subobject (EXRS) is defined in Section
4.1, "Explicit Exclusion Route Subobject ...
... Explicit Exclusion Route subobject (EXRS) is defined in Section
4.1, "Explicit Exclusion Route Subobject (EXRS)". This subobject may
be present in the Explicit Route Object ...
... Explicit Exclusion Route Subobject (EXRS)". This subobject may
be present in the Explicit Route Object, but not in the Route Record
Object or in the new EXCLUDE_ROUTE object, and it should not be
...
... EXRS)". This subobject may
be present in the Explicit Route Object, but not in the Route Record
Object or in the new EXCLUDE_ROUTE object, and it should not be
listed among the subobjects for those objects.
...
... be present in the Explicit Route Object, but not in the Route Record
Object or in the new EXCLUDE_ROUTE object, and it should not be
listed among the subobjects for those objects.
...
...
A new class number has been added for EXCLUDE_ROUTE object (XRO) as
defined in Section 3.1, "EXCLUDE_ROUTE Object ...
... Class-Num of type 11bbbbbb
Value: 232
Defined CType: 1 (EXCLUDE_ROUTE)
Subobjects 1, 2, 4, and 32 are as defined for Explicit Route Object ...
... ROUTE)
Subobjects 1, 2, 4, and 32 are as defined for Explicit Route Object.
An additional subobject has been registered as requested in Section
8.1, "New ERO ...
... Autonomous system number [RFC3209]
33 Explicit Exclusion Route subobject (EXRS) [RFC4874prop]
...
... Routing Problem' (24).
64 = Unsupported Exclude Route Subobject Type
65 = Inconsistent Subobject
66 = Local Node ...
... 65 = Inconsistent Subobject
66 = Local Node in Exclude Route
67 = Route Blocked by Exclude Route ...
... This document reuses text from [RFC3209] for the description of
EXCLUDE_ROUTE.
The authors would like to express their thanks to Lou Berger, Steffen
...