TEAS Working Group Zafar Ali
Internet Draft George Swallow
Intended status: Standard Track Clarence Filsfils
Expires: January 5, 2016 Cisco Systems
Luyuan Fang
Microsoft
Kenji Kumaki
KDDI Corporation
Ruediger Kunze
Deutsche Telekom AG
Daniele Ceccarelli
Ericsson
Xian Zhang
Huawei
July 6, 2015
Resource ReserVation Protocol-Traffic Engineering (RSVP-TE)
Extension for Signaling Objective Function and Metric Bound
draft-ali-teas-rc-objective-function-metric-bound-00.txt
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Abstract
In particular networks such as those used by financial
institutions, network performance criteria such as latency are
becoming critical to data path selection. However cost is still an
important consideration. This leads to a situation where path
calculation involves multiple metrics and more complex objective
functions.
When using GMPLS control plane, there are many scenarios in which a
node may need to request a remote node to perform path computation
or expansion, like for example multi-domain LSP setup, Generalized
Multi-Protocol Label Switching (GMPLS) User-Network Interface (UNI)
or simply the utilization of a loose ERO in intra domain signaling.
In such cases, the node requesting the setup of an LSP needs to
convey the required objective function to the remote node, to
enable it to perform route computation in the desired fashion.
Similarly, there are cases where the ingress node needs to indicate
a TE metric bound for a loose segment that is expanded by a remote
node.
This document defines extensions to the RSVP-TE Protocol to allow
an ingress node to request the required objective function for the
route computation, as well as a metric bound to influence route
computation decisions at a remote node(s).
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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
[RFC2119].
Table of Contents
Copyright Notice..................................................1
1. Introduction...................................................3
2. RSVP-TE signaling extensions...................................4
2.1. Objective Function (OF) Subobject......................4
2.1.1. Minimum TE Metric Cost Path Objective Function....6
2.1.2. Minimum IGP Metric Cost Path Objective Function...6
2.1.3. Minimum Latency Path Objective Function...........6
2.1.4. Minimum Latency Variation Path Objective Function.7
2.2. Metric subobject.......................................7
2.3. Processing Rules for the OF Subobjects.................8
2.4. Processing Rules for the Metric subobject..............9
3. Security Considerations.......................................11
4. IANA Considerations...........................................11
5. Acknowledgments...............................................12
6. References....................................................12
6.1. Normative References..................................12
6.2. Informative References................................13
1. Introduction
As noted in [OSPF-TE-METRIC] and [ISIS-TE-METRIC], in certain
networks such as financial information networks, performance
criteria such as latency are becoming critical to data path
selection along with other metrics. Such networks may require
selection of a path that minimizes end-to-end latency. Or a path
may need to be found that minimizes some other TE metric(s),
while subject to a latency bound. In summary, there is a
requirement to find end-to-end paths with different optimization
criteria while subjected to a metric bound.
When the entire route for an LSP is computed at the ingress node,
this requirement can be met by a local decision at that node.
However, there are scenarios where partial or full route
computations are performed by remote nodes. The scenarios include
(but are not limited to):
. LSPs with loose hops in the Explicit Route Object (ERO),
including intra-domain LSPs.
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. GMPLS-UNI where route computation may be performed by the
UNI-Network (server) node [RFC 4208];
. Multi domain LSP setup with per domain path computation;
In these scenarios, there is a need for the ingress node to
convey the optimization criteria (e.g., IGP cost, TE cost, hop
counts, latency, etc.) to be used for the path computation to the
node performing route computation or expansion. Similarly, there
is a need for the ingress node to indicate a TE metric bound for
the loose segment being expanded by a remote node.
This draft defines mechanisms for the RSVP-TE protocol allowing
an ingress node to indicate in a Path request the desired
objective function along with any associated TE metric bound(s).
The nodes performing route expansion use this information to
find the "best" candidate route.
2. RSVP-TE signaling extensions
This section defines RSVP-TE signaling extensions required to
address the above-mentioned requirements. Two new ERO subobject
types, Objective Function (OF) and Metric, are defined. Their
purpose is as follows.
. OF subobject conveys a set of one or more specific
optimization criteria that needs be followed in expanding
route of a TE-LSP in MultiProtocol Label Switching (MPLS) and
GMPLS networks.
. Metric Bound subobject indicates the bound on the path metric
that needs to be observed for the loose segment to be
considered as acceptable by the ingress node.
The scope of the Metric and OF subobjects is the node performing
the expansion for loose ERO and the subsequent ERO subobject that
identifies an abstract node. The following subsection provides
the details.
2.1. Objective Function (OF) Subobject
A new ERO subobject type Objective Function (OF) is defined in
order for the ingress node to indicate the required objective
function on a loose hop. The ERO subobject type OF is optional.
It MAY be carried within an ERO object of RSVP-TE Path message
and its scope is limited to the node performing the expansion
for loose ERO and the subsequent ERO subobject that identifies
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an abstract node. For more details please refer to the
Processing Rules for the OF Subobjects section.
The OF subobject 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | OF Code | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields of OF subobject are defined as follows:
L bit: The L bit MUST be set to represent a loose hop in the
explicit route.
Type: The Type is to be assigned by IANA (suggested value:
66).
Length: The Length contains the total length of the subobject
in bytes, including the Type field, the Length field. The Length
of the subobject is 4.
OF Code (8 bits): The identifier of the objective function.
The following OF code values are suggested. These values are to
be assigned by IANA.
* OF code value 0 is reserved.
* OF code value 1 (to be assigned by IANA) is for Minimum TE
Metric Cost Path (MTMCP) OF defined in this document. See
definition of MTCP OF in the following.
* OF code value 2 (to be assigned by IANA) is for Minimum
Interior Gateway Protocol (IGP) Metric Cost Path (MIMCP) OF
defined in the following.
* OF code value 3 (to be assigned by IANA) is for Minimum
Load Path (MLP) OF as defined in RFC5541.
* OF code value 4 (to be assigned by IANA) is for Maximum
Residual Bandwidth Path (MBP) OF as defined in RFC5541.
* OF code value 5 (to be assigned by IANA) is for Minimize
Aggregate Bandwidth Consumption (MBC) OF as defined in RFC5541.
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* OF code value 6 (to be assigned by IANA) is for Minimize
the Load of the most loaded Link (MLL) OF as defined in RFC5541.
- OF code value 7 is skipped (to keep the objective function
code values consistent between [RFC5541] and this draft.
* OF code value 8 (to be assigned by IANA) is for Minimum
Latency Path (MLP) OF defined in this document. See definition
of MLP OF in the following.
* OF code value 9 (to be assigned by IANA) is for Minimum
Latency Variation Path (MLVP) OF defined in this document. See
definition of MLVP OF in the following.
Other objective functions may be defined in future.
Reserved (8 bits): This field MUST be set to zero on
transmission and MUST be ignored on receipt.
2.1.1. Minimum TE Metric Cost Path Objective Function
Minimum TE Metric Cost Path (MTMCP) OF is defined as an
Objective Function where a path is computed such that the sum of
the TE metric of the links along the path is minimized. In the
context of loose hop expansion, the ERO expanding node MUST try
to find a route such that the sum of the TE metric of the links
along the route is minimized.
2.1.2. Minimum IGP Metric Cost Path Objective Function
Minimum IGP Metric Cost Path (MIMCP) OF is defined as an
Objective Function where a path is computed such that the sum of
the IGP metric of the links along the path is minimized. In the
context of loose hop expansion, the ERO expanding node MUST try
to find a route such that the sum of the IGP metric of the links
along the route is minimized.
2.1.3. Minimum Latency Path Objective Function
Minimum Latency Path (MLP) OF is defined as an Objective
Function where a path is computed such that latency of the path
is minimized. In the context of loose hop expansion, the ERO
expanding node MUST try to find a route such that overall
latency of the loose hop is minimized.
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2.1.4. Minimum Latency Variation Path Objective Function
Minimum Latency Variation Path (MLVP) OF is defined as an
Objective Function where a path is computed such that latency
variation in the path is minimized. In the context of loose hop
expansion, the ERO expanding node MUST try to find a route such
that overall latency variation of the loose hop is minimized.
2.2. Metric Bound subobject
The ERO subobject type Metric Bound (MB) is optional. It MAY be
carried within an ERO object of RSVP-TE Path message and its
scope is limited to the node performing the expansion for loose
ERO and the subsequent ERO subobject that identifies an abstract
node. It is possible to identify different Metric Bound
subobjects for different loose hops of the ERO to be expanded.
For more details please refer to the Processing Rules for the
Metric Bound Subobjects section.
This subobject 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length |metric-type|B| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| metric-bound |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields of the Metric subobject are defined as follows:
L bit: 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 the explicit route.
Please note that use of MB subobject is also applicable to
strict hops, e.g., in selecting a component link within a
heterogeneous bundled TE link.
Type: The Type is to be assigned by IANA (suggested value:
67).
Length: The Length is 8.
Metric-type (6 bits): Specifies the metric type associated
with the bound. The following values are currently defined:
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* T=1: cumulative IGP cost
* T=2: cumulative TE cost
* T=3: Hop Count
* T=4: Cumulative Latency
* T=5: Cumulative Latency Variation
B bit: Best-effort bit. When the best-effort (B) bit is set,
it means that the ingress node allows loose hop expansion
that does not meeting the MB requirement. When the best-
effort (B) bit is not set, it means that the MB MUST be
observed.
Reserved (9 bits): This field MUST be set to zero on
transmission and MUST be ignored on receipt.
Metric-bound (32 bits): The metric-bound indicates an upper
metric bound for the loose hop. The metric bound is encoded
in 32 bits using IEEE floating point format as defined in
[IEEE.754.1985]). When it indicates a time value (i.e.
Latency or Latency Variation) it is expressed in
milliseconds.
2.3. Processing rules
2.3.1. Processing Rules for the OF Subobjects
A single OF subobjects SHOULD be used between a pair of abstract
nodes in ERO. Same OF SHOULD be identified for each hop
expansion.
The basic processing rules of an ERO are not altered. Please
refer to [RFC3209] for details.
The scope of the OF subobject is the previous ERO subobject that
identifies an abstract node, and the subsequent ERO subobject
that identifies an abstract node. Multiple OF subobjects MAY be
present between any pair of abstract nodes. However, only first
OF subobject is analyzed and others are ignored.
The following conditions SHOULD result in Path Error with error
code "Routing Problem" and error subcode "Bad EXPLICIT_ROUTE
object":
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. If the first OF subobject is not preceded by an ERO subobject
identifying the next hop.
. If the OF subobject follows an ERO subobject identifying the
next hop that does not have the L-bit set.
If the processing node does not understand the OF subobject, it
SHOULD send a PathErr with the error code "Routing Error" and
error value of "Bad Explicit Route Object" toward the sender
[RFC3209].
If the processing node understands the OF subobject and the ERO
passes the above mentioned sanity check and any other sanity
checks associated with other ERO subobjects local to the node,
the node takes the following actions:
. If the node supports the requested OF, the node expands the
loose hop using the requested OF as optimization criterion for
computing the route to the next abstract node. After
processing, the OF subobjects are removed from the ERO. The
rest of the steps for the loose ERO processing follow
procedures outlined in [RFC3209].
. If the node understands the OF subobject but does not support
the requested OF, it SHOULD send a Path Error with error code
"Routing Problem" and a new error subcode "Unsupported
Objective Function". The error subcode "Unsupported Objective
Function" for Path Error code "Routing Problem" is to be
assigned by IANA.
. If the OF is supported but policy does not permit applying
it, the processing node SHOULD send a Path Error with error
code "Policy control failure" (value 2) and subcode "objective
function not allowed". The error subcode "objective function
not allowed" for Path Error code "Policy control failure" is
to be assigned by IANA.
2.3.2. Processing Rules for the MB subobject
Multiple Metric Bound subobjects MAY be indicated for each hop
to be expanded and MUST be placed after each abstract node
subobject. Different Metric Bounds MAY be identified for each
hop expansion.
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The basic processing rules of an ERO are not altered. Please
refer to [RFC3209] for details.
The scope of the MB subobject is between the previous ERO
subobject that identifies an abstract node, and the subsequent
ERO subobject that identifies an abstract node. Multiple MB
subobjects may be present between any pair of abstract nodes.
If the processing node does not understand the MB subobject, it
SHOULD send a PathErr with the error code "Routing Error" and
error value of "Bad Explicit Route Object" toward the sender
[RFC3209].
If the processing node understands the MB subobject and the ERO
passes the above mentioned sanity check and any other sanity
checks associated with other ERO subobjects local to the node,
the node takes the following actions:
. For all the MB subobject(s), the node expands the ERO such
that the requested metric bound(s) are met for the route
between the two abstract nodes in the ERO. After processing,
the Metric subobjects are removed from the ERO. The rest of
the steps for the ERO processing follow procedure outlined in
[RFC3209].
. If the node understands the MB subobject but cannot find a
route to the next abstract node such that the requested metric
bound(s) can be satisfied and the best-effort (B) bit is not
set, it SHOULD send a Path Error with error code "Routing
Problem" and a new error subcode "No route available toward
destination with the requested metric bounds". The error
subcode "No route available toward destination with the
requested metric bounds" for Path Error code "Routing Problem"
is to be assigned by IANA (See IANA section for details).
. If the node understands the Metric subobject but cannot find
a route to the next abstract node such that the requested
metric bound(s) can be satisfied and the best-effort (B) bit
is set, it SHOULD send a Path Error message with error code
"Notify Error" and a new error subcode "Route not matching the
requested metric bounds" is to be assigned by IANA (See IANA
section for details).
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. The ERO expanding node SHOULD respect the Metric Bound
constraints in realizing any segment recovery procedure to
change the route of the segment expanded by the said node. If
best-effort (B) bit is set and the new recovery segment
violates the Metric Bound constraints, the ERO expanding
SHOULD send a Path Error message with error code "Notify
Error" and a new error subcode "Route not matching the
requested metric bounds" is to be assigned by IANA (See IANA
section for details).
3. Security Considerations
This document does not introduce any additional security issues
above those identified in [RFC5920], [RFC2205], [RFC3209], and
[RFC3473].
4. IANA Considerations
4.1. ERO Subobject
This document adds the following two new subobject of the
existing entry for ERO (20, EXPLICIT_ROUTE):
Value Description
----- ------------
TBA (suggest value: 66) Objective Function (OF) subobject
TBA (suggest value: 67) Metric subobject
These subobject may be present in the Explicit Route Object, but
not in the Route Record Object.
OF Code values carried in OF subobject requires an IANA entry
with suggested values as defined in section 2.1.
4.2. New RSVP error sub-code
For Error Code = 24 "Routing Problem" (see [RFC2205]) the
following sub-code is defined.
Sub-code Value
-------- -----
No route available toward destination To be assigned by IANA.
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with the requested metric bounds Suggested Value: TBA.
For Error Code = 25 "Notify Error" (see [RFC2205]) the following
sub-code is defined.
Sub-code Value
-------- -----
Route not matching the requested To be assigned by IANA.
metric bounds Suggested Value: TBA.
5. Acknowledgments
Authors would like to thank Matt Hartley, Ori Gerstel, Gabriele
Maria Galimberti, and Walid Wakim for their review comments.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
V., and G. Swallow, "RSVP-TE: Extensions to RSVP for
LSP Tunnels", RFC 3209, December 2001.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, January 2003.
[IEEE.754.1985] IEEE Standard 754, "Standard for Binary
Floating-Point Arithmetic", August 1985.
[RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS)
User-Network Interface (UNI): Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Support for the
Overlay Model", RFC 4208, October 2005.
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6.2. Informative References
[RFC2209] Braden, R. and L. Zhang, "Resource ReSerVation
Protocol (RSVP) -- Version 1 Message Processing
Rules", RFC 2209, September 1997.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
Computation Element (PCE) Communication Protocol
(PCEP)", RFC 5440, March 2009.
[RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541, June 2009.
[ID-SERVICE-AWARE] D. Dhody, V. Manral, Z. Ali, G. Swallow, K.
Kumaki, " Extensions to the Path Computation Element
Communication Protocol (PCEP) to compute service aware
Label Switched Path (LSP)", draft-ietf-pce-pcep-
service-aware, work in progress.
[OSPF-TE-METRIC] S. Giacalone, D. Ward, J. Drake, A. Atlas, S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", draft-ietf-ospf-te-metric-extensions,
work in progress.
[ISIS-TE-METRIC] S. Previdi, S. Giacalone, D. Ward, J. Drake, A.
Atlas, C. Filsfils, "IS-IS Traffic Engineering (TE)
Metric Extensions", draft-previdi-isis-te-metric-
extensions, work in progress.
Authors' Addresses
Zafar Ali
Cisco Systems.
Email: zali@cisco.com
George Swallow
Cisco Systems.
swallow@cisco.com
Clarence Filsfils
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Cisco Systems.
cfilsfil@cisco.com
Luyuan Fang
Microsoft
lufang@microsoft.com
Kenji Kumaki
KDDI Corporation
Email: ke-kumaki@kddi.com
Rudiger Kunze
Deutsche Telekom AG
Ruediger.Kunze@telekom.de
Daniele Ceccarelli
Ericsson
Email: daniele.ceccarelli@ericsson.com
Xian Zhang
Huawei Technologies
Email: zhang.xian@huawei.com
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