Networking Working Group JP. Vasseur, Ed.
Internet-Draft Cisco Systems, Inc
Intended status: Standards Track JL. Le Roux
Expires: July 24, 2009 France Telecom
Y. Ikejiri
NTT Communications Corporation
January 20, 2009
A set of monitoring tools for Path Computation Element based
Architecture
draft-ietf-pce-monitoring-04.txt
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Abstract
A Path Computation Element (PCE) based architecture has been
specified for the computation of Traffic Engineering (TE) Label
Switched Paths (LSPs) in Multiprotocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) networks in the context of single or
multiple domains (where a domain refers to a collection of network
elements within a common sphere of address management or path
computational responsibility such as IGP areas and Autonomous
Systems). Path Computation Clients (PCCs) send computation requests
to PCEs, and these may forward the requests to and cooperate with
other PCEs forming a "path computation chain". In PCE-based
environments, it is thus critical to monitor the state of the path
computation chain for troubleshooting and performance monitoring
purposes: liveness of each element (PCE) involved in the PCE chain,
detection of potential resource contention states and statistics in
term of path computation times are examples of such metrics of
interest. This document specifies procedures and extensions to the
Path Computation Element Protocol (PCEP) in order to gather such
information.
Requirements Language
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].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Path Computation Monitoring messages . . . . . . . . . . . . . 5
3.1. Path Computation Monitoring Request message (PCMonReq) . . 6
3.2. Path Monitoring Reply message (PCMonRep) . . . . . . . . . 9
4. Path Computation Monitoring Objects . . . . . . . . . . . . . 11
4.1. MONITORING Object . . . . . . . . . . . . . . . . . . . . 12
4.2. PCE-ID Object . . . . . . . . . . . . . . . . . . . . . . 14
4.3. PROC-TIME Object . . . . . . . . . . . . . . . . . . . . . 14
4.4. CONGESTION Object . . . . . . . . . . . . . . . . . . . . 16
5. Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 17
7. Manageability Considerations . . . . . . . . . . . . . . . . . 19
7.1. Control of Function and Policy . . . . . . . . . . . . . . 19
7.2. Information and Data Models . . . . . . . . . . . . . . . 19
7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 20
7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 20
7.5. Requirements On Other Protocols . . . . . . . . . . . . . 20
7.6. Impact On Network Operations . . . . . . . . . . . . . . . 20
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
8.1. New PCEP Message . . . . . . . . . . . . . . . . . . . . . 20
8.2. New PCEP Objects . . . . . . . . . . . . . . . . . . . . . 20
8.3. New Error-Type and Error-Values . . . . . . . . . . . . . 21
8.4. MONITORING Object Flag Field . . . . . . . . . . . . . . . 21
8.5. PROC-TIME Object Flag Field . . . . . . . . . . . . . . . 22
8.6. CONGESTION Object Flag field . . . . . . . . . . . . . . . 22
9. Security Considerations . . . . . . . . . . . . . . . . . . . 23
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
11.1. Normative References . . . . . . . . . . . . . . . . . . . 23
11.2. Informative References . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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1. Introduction
The Path Computation Element (PCE) based architecture has been
specified in [RFC4655] for the computation of Traffic Engineering
(TE) Label Switched Paths (LSPs) in Multiprotocol Label Switching
(MPLS) and Generalized MPLS (GMPLS) networks in the context of single
or multiple domains where a domain refers to a collection of network
elements within a common sphere of address management or path
computational responsibility such as IGP areas and Autonomous
Systems.
Path Computation Clients (PCCs) send computation requests to PCEs,
and these may forward the requests to and cooperate with other PCEs
forming a "path computation chain". In PCE-based environments, it is
critical to monitor the state of the path computation chain for
troubeshooting and performance monitoring purposes: liveness of each
element (PCE) involved in the PCE chain, detection of potential
resource contention states and statistics in term of path computation
times are examples of such metrics of interest. This document
specifies procedures and extensions to the Path Computation Element
Protocol (PCEP) ([I-D.ietf-pce-pcep]) in order to monitor the path
computation chain and gather various performance metrics.
As defined in [RFC4655], there are circumstances where more than one
PCE is involved in the computation of a TE LSP. A typical example is
when the PCC requires the computation of a TE LSP where the head-end
and the tail-end of the TE LSP do not reside in adjacent domains and
there is no single PCE with the visibility of both the head-end and
tail-end domain. We call the set of PCEs involved in the computation
of a TE LSP a "path computation chain". As further discussed in
Section 3.1, the PCE chain may either be static (pre-configured) or
dynamically determined during the path computation process.
As discussed in [RFC4655], a TE LSP may be computed by one PCE
(referred to as single PCE path computation) or several PCEs
(referred to as multiple PCE path computation). In the former case,
the PCC may be able to use IGP extensions to check the liveness of
the PCE (see [RFC5088] and [RFC5089]) or PCEP using Keepalive
messages. In contrast, when multiple PCEs are involved in the path
computation chain an example of which is the BRPC procedure defined
in [I-D.ietf-pce-brpc], the PCC's visibility may be limited to the
first PCE involved in the path computation chain. Thus, it is
critical to define mechanisms in order to monitor the state of the
path computation chain.
This document specifies PCEP extensions in order to gather various
state metrics along the path computation chain. In this document we
call a "state metric" a metric that characterizes a PCE state. For
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example, such metric can have a form of a bolean (PCE is alive or
not, PCE is congested or not) or a performance metric (path
computation time at each PCE).
PCE state metrics can be gathered in two different contexts: in band
or out of band. By "In band" we refer to the situation whereby a PCC
requests to gather metrics in the context of a path computation
request. For example, a PCC may send a path computation request to a
PCE and may want to know the processing time of that request in
addition to the computed path. Conversely, if the request is "out of
band", PCE state metric collection is performed as a standalone
request (e.g. check the liveness of a specific PCE chain, collect the
average processing time computed over the last 5mn period on one or
more PCEs").
In this document we define two monitoring request types: general and
specific. A general monitoring request relates to the collection of
a PCE state metrics that is not coupled to a particular path
computation request (e.g. average CPU load on a PCE). Conversely, a
specific monitoring request relates to a particular path computation
request (processing time to complete the path computation for a TE
LSP).
The message formats in this document are specified using Backus Naur
Format (BNF) encoding as specified in [I-D.farrel-rtg-common-bnf].
2. Terminology
PCC (Path Computation Client): any client application requesting a
path computation to be performed by a Path Computation Element.
PCE (Path Computation Element): an entity (component, application or
network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints.
TE LSP: Traffic Engineering Label Switched Path.
3. Path Computation Monitoring messages
As defined in [I-D.ietf-pce-pcep], a PCEP message consists of a
common header followed by a variable length body made of a set of
objects that can either be mandatory or optional. As a reminder, an
object is said to be mandatory in a PCEP message when the object must
be included for the message to be considered as valid. The P flag
(defined in [I-D.ietf-pce-pcep]) is located in the common header of
each PCEP object and can be set by a PCEP peer to require a PCE to
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take into account the related information during the path
computation. Because the P flag exclusively relates to a path
computation request, it MUST be cleared in the two PCEP messages
(PCEMonReq and PCMonRep message) defined in this document.
For each PCEP message type a set of rules is defined that specify the
set of objects that the message can carry. An implementation MUST
form the PCEP messages using the object ordering specified in this
document.
In this document we define two PCEP messages referred to as the Path
Computation Monitoring Request (PCMonReq) and Path Computation
Monitoring Reply (PCMonRep) messages so as to handle "out of band"
monitoring request. The aim of the PCMonReq message sent by a PCC to
a PCE is to gather one or more PCE state metrics on a set of PCEs
involved in a path computation chain. The PCMonRep message sent by a
PCE to a PCC is used to provide such data.
3.1. Path Computation Monitoring Request message (PCMonReq)
The Message-Type field of the PCEP common header for the PCMonReq
message is set to 8 (To be confirmed by IANA).
There is one mandatory object that MUST be included within a PCMonReq
message: the MONITORING object (see section Section 4.1). If the
MONITORING object is missing, the receiving PCE MUST send a PCErr
message with Error-type=6 (Mandatory Object missing) and Error-
value=4 (MONITORING Object missing). Other objects are optional.
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Format of a PCMonReq message (out of band request):
<PCMonReq Message>::= <Common Header>
<MONITORING>
[<pce-list>]
[<svec-list>]
[<request-list>]
where:
<svec-list>::=<SVEC>
[<OF>]
[<svec-list>]
<request-list>::=<request>[<request-list>]
<request>::= <RP>
<END-POINTS>
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<RRO>]
[<IRO>]
[<LOAD-BALANCING>]
[<XRO>]
<metric-list>::=<METRIC>[<metric-list>]
<pce-list>::=<PCE-ID>[<pce-list>]
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Format of a PCReq message with monitoring data requested (in band
request):
<PCReq Message>::= <Common Header>
<MONITORING>
[<pce-list>]
[<svec-list>]
<request-list>
where:
<svec-list>::=<SVEC>[<svec-list>]
<request-list>::=<request>[<request-list>]
<request>::= <RP>
<END-POINTS>
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<RRO>[<BANDWIDTH>]]
[<IRO>]
[<LOAD-BALANCING>]
where:
<metric-list>::=<METRIC>[<metric-list>]
<pce-list>::=<PCE-ID>[<pce-list>]
The SVEC, RP, END-POINTS, LSPA, BANDWIDTH, METRIC, RRO, IRO and LOAD-
BALANCING objects are defined in [I-D.ietf-pce-pcep]. The XRO object
is defined in [I-D.ietf-pce-pcep-xro] and the OF object is defined in
[I-D.ietf-pce-of].
The PCMonReq message is used to gather various PCE state metrics
along a path computation chain. The path computation chain may be
determined by the PCC (in the form of a series of a series of PCE-ID
objects defined in Section 4.2.) or may alternatively be determined
by the path computation procedure. For example, if the BRPC
procedure ([I-D.ietf-pce-brpc]) is used to compute an inter-domain TE
LSP, the PCE chain may be determined dynamically. In that case, the
PCC sends a PCMonReq message that contains the PCEP objects that
charaterize the TE LSP attributes along with the MONITORING object
(see Section 4.1) that lists the set of metrics of interest.
Several PCE state metrics may be requested that are specified by a
set of objects defined in Section 4. Note that this set of objects
may be extended in the future.
As pointed out in [I-D.ietf-pce-pcep] several situations can arise:
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o Bundle of a set of independent and non-synchronized path
computation requests,
o Bundle of a set of independent and synchronized path computation
requests (SVEC object defined below required),
o Bundle of a set of dependent and synchronized path computation
requests (SVEC object defined below required).
In the case of a bundle of a set of request, the MONITORING object
SHOULD only be present in the first PCReq or PCMonReq message and the
monitoring request applies to all the requests of the bundle, even in
the case of dependent and/or synchronized requests sent using more
than one PCReq or PCMonReq message.
Examples of requests. For the sake of illustration, consider the
three following examples:
Example 1 (out of band request): PCC1 requests to check the path
computation chain that would be used should it request a path
computation for a specific TE LSP named T1. A PCMonReq message is
sent that contains a MONITORING object specifying a path computation
check, along with the appropriate set of objects (e.g. RP, END-
POINTS, ...) that would be included in a PCReq message for T1.
Example 2 (in band request): PCC1 requests a path computation for a
TE LSP and also request to gather the processing time along the path
computation chain selected for the computation of T1. A PCReq
message is sent that also contains a MONITORING object that specifies
the performance metrics of interest.
Example 3 (out of band request): PCC2 requests to gather performance
metrics along the specific path computation chain <pce1, pce2, pce3,
pce7>. A PCMonreq message is sent to PCE1 that contains a MONITORING
object and a sequence of PCE-ID objects that identify PCE1, PCE2,
PCE3 and PCE7 respectively.
In all of the examples above, a PCRep message (in-band request) or
PCMonReq message (out of band request) is sent in response to the
request that reports the computed metrics.
3.2. Path Monitoring Reply message (PCMonRep)
The PCMonRep message is used to provide PCE state metrics back to the
requester for "out of band" monitoring requests. The Message-Type
field of the PCEP common header for the PCMonRep message is set to 9
(To be confirmed by IANA).
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There is one mandatory object that MUST be included within a PCMonRep
message: the MONITORING object (see Section 4.1). If the MONITORING
object is missing, the receiving PCE MUST send a PCErr message with
Error-type=6 (Mandatory Object missing) and Error-value=4 (MONITORING
Object missing).
Other objects are optional.
Format of a PCMonRep (out of band request):
<PCMonRep Message>::= <Common Header>
<MONITORING>
[<RP>]
[<metric-pce-list>]
where:
<metric-pce-list>::=<metric-pce>[<metric-pce-list>]
<metric-pce>::=<PCE-ID>
[<PROC-TIME>]
[<CONGESTION>]
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Format of a PCRep message with monitoring data (in band):
<PCRep Message> ::= <Common Header>
<response-list>
where:
<response-list>::=<response>[<response-list>]
<response>::=<RP>
<MONITORING>
[<NO-PATH>]
[<attribute-list>]
[<path-list>]
[<metric-pce-list>]
<path-list>::=<path>[<path-list>]
<path>::= <ERO><attribute-list>
where:
<attribute-list>::=[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]
<metric-list>::=<METRIC>[<metric-list>]
<metric-pce-list>::=<metric-pce>[<metric-pce-list>]
<metric-pce>::=<PCE-ID>
[<PROC-TIME>]
[<CONGESTION>]
The RP object is defined in [I-D.ietf-pce-pcep].
4. Path Computation Monitoring Objects
The PCEP objects defined in the document are compliant with the PCEP
object format defined in [I-D.ietf-pce-pcep]. The P flag and the I
flag of the PCEP objects defined in this document SHOULD always be
set to 0 on transmission and MUST be ignored on receipt since these
flags are exclusively related to path computation requests.
Several objects are defined in this section that can be carried
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within the PCEP PCReq or PCRep messages defined in
[I-D.ietf-pce-pcep] in case of "in band" monitoring requests (the PCC
requests the computation of the TE LSP in addition to gathering PCE
state metrics). In case of "out of band" monitoring requests, the
objects defined in this section are carried within PCMonReq and
PCMonRep messages.
4.1. MONITORING Object
The MONITORING object MUST be present within PCMonReq and PCMonRep
messages ("out of band" monitoring requests) and MAY be carried
within PCRep and PCReq messages ("in band" monitoring requests).
There SHOULD NOT be more than one instance of the MONITORING object:
if more than one instance of the MONITORING object is present, the
recipient MUST process the first instance and MUST ignore other
instances.
The MONITORING object is used to specify the set of requested PCE
state metrics.
The MONITORING Object-Class is to be assigned by IANA (recommended
value=19)
The MONITORING Object-Type is to be assigned by IANA (recommended
value=1)
The format of the MONITORING 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 | Flags |I|C|P|G|L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Monitoring-id-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV(s) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags: 24 bits
The following flags are currently defined:
L (Liveness) - 1 bit: when set, this indicates that the state metric
of interest is the PCE's liveness and thus the PCE MUST include a
PCE-ID object in the corresponding reply. The L bit MUST always be
ignored in a PCMonRep or PCRep message.
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G (General) - 1 bit: when set, this indicates that the monitoring
request is a general monitoring request. When the requested
performance metric is specific, the G bit MUST be cleared. The G bit
MUST always be ignored in a PCMonRep or PCRep message.
P (Processing Time) - 1 bit: the P bit of the MONITORING object
carried in a PCMonReq or a PCReq message is set to indicate that the
processing times is a metric of interest. If allowed by policy, a
PROC-TIME object MUST be inserted in the corresponding PCMonRep or
PCRep message. The P bit MUST always be ignored in a PCMonRep or
PCRep message.
C (Congestion) - 1 bit: The C bit of the MONITORING object carried in
a PCMonReq or a PCReq message is set to indicate that the congestion
status is a metric of interest, in which case a CONGESTION object
MUST be inserted in the corresponding PCMonRep or PCRep message. The
C bit MUST always be ignored in a PCMonRep or PCRep message.
I (Incomplete) - 1 bit: If a PCE supports a received PCMonReq message
and that message does not trigger any policy violation, but the PCE
cannot provide any of the set of requested performance metrics for
unspecified reasons, the PCE MUST set the I bit. The I bit has no
meaning in a request and SHOULD be ignored on receipt.
Monitoring-id-number (32 bits): The monitoring-id-number value
combined with the PCEP-ID of the PCC identifies the monitoring
request context. The monitoring-id-number MUST start at a non-zero
value and MUST be incremented each time a new monitoring request is
sent to a PCE. Each increment SHOULD have a value of 1 and may cause
a wrap back to one. If no reply to a monitoring request is received
from the PCE, and the PCC wishes to resend its path computation
monitoring request, the same monitoring-id-number MUST be used.
Conversely, a different monitoring-id-number MUST be used for
different requests sent to a PCE. The path computation monitoring
reply is unambiguously identified by the monitoring-id-number and the
PCEP-ID of the replying PCE. A PCEP implementation SHOULD checkpoint
the Monitoring-id-number of pending monitoring requests in case of
restart thus avoiding the re-use of a Monitoring-id-number of an in-
process monitoring request.
Unassigned bits are considered as reserved and MUST be set to zero on
transmission and ignored on reception.
No optional TLVs are currently defined.
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4.2. PCE-ID Object
The PCE-ID Object is used to specify a PCE's IP address.
A set of PCE-ID objects may be inserted within a PCReq or a PCMonReq
message to specify the PCE for which PCE state metrics are requested
and in a PCMonRep or a PCRep message to record the IP address of the
PCE reporting PCE state metrics or that was involved in the path
computation chain.
Two PCE-ID objects (for IPv4 and IPv6) are defined. PCE-ID Object-
Class is to be assigned by IANA (recommended value=20) PCE-ID Object-
Type is to be assigned by IANA (recommended value=1 for IPv4 and 2
for IPv6)
The format of the PCE-ID Object is as follows:
The format of the PCE-ID object body for IPv4 and IPv6 are 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The PCE-ID object body has a fixed length of 4 octets for IPv4 and 16
octets for IPv6.
When a dynamic discovery mechanism is used for PCE discovery, a PCE
advertises its PCE address in the PCE-ADDRESS sub-TLV defined in
[RFC5088] and [RFC5089]. A PCC MUST use this address in PCReq and
PCMonReq messages and a PCE MUST also use this address in PCRep and
PCMonRep messages.
4.3. PROC-TIME Object
If allowed by policy, the PCE includes a PROC-TIME object within a
PCMonRep or a PCRep message if the P bit of the MONITORING object
carried within the corresponding PCMonReq or PCReq message is set.
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The PROC-TIME object is used to report various processing time
related metrics.
1) Case of general monitoring requests
A PCC may request processing time metrics for general monitoring
requests (e.g. the PCC may want to know the minimum, maximum and
average processing times on a particular PCE). In this case, general
requests can only be made by using PCMonReq/PCMonRep messages. The
Current-processing-time field (as explained below) is exclusively
used for specific monitoring requests and MUST be cleared for general
monitoring requests. The algorithms used by a PCE to compute the
Min, Average, Max and Variance of the processing times are out of the
scope of this document (A PCE may decide to compute the minimum
processing time over a period of times, for the last N path
computation requests, ...).
2) Case of specific monitoring requests
In the case of a specific request, the algorithms used by a PCE to
compute the Procesing-time metrics are out of the scope of this
document but a flag is specified that is used to indicate to the
requester whether the processing time value was estimated or
computed. The PCE may either (1) estimate the processing time
without performing an actual path computation or (2) effectively
perform the computation to report the processing time. In the former
case, the E bit of the PROC-TIME object MUST be set. The G bit MUST
be cleared and the Min-processing-time, Max-processing-time, Average-
processing-time and Variance-processing-time MUST be set to
0x00000000.
When the processing time is requested in addition to a path
computation (case where the MONITORING object is carried within a
PCReq message), the PROC-TIME object always reports the actual
processing time for that request and thus the E bit MUST be cleared.
The PROC-TIME Object-Class is to be assigned by IANA (recommended
value=21)
The PROC-TIME Object-Type is to be assigned by IANA (recommended
value=1)
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The format of the PROC-TIME 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 | Flags |E|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Current-processing-time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Min-processing-time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max-processing-time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Average-processing time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variance-processing-time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags: 16 bits - one flag is currently defined:
E (Estimated) - 1 bit: when set, this indicates that the reported
metric value is based on estimated processing time as opposed to
actual computations.
Unassigned bits are considered as reserved and MUST be set to zero on
transmission.
Current-processing-time: This field indicates in milliseconds the
processing time for the path computation of interest characterized in
the corresponding PCMonReq message.
Min-processing-time: This field indicates in milliseconds the minimum
processing time.
Max-processing-time: This field indicates in milliseconds the maximum
processing time.
Average-processing-time: This field indicates in milliseconds the
average processing time.
Variance-processing-time: This field indicates in milliseconds the
variance of the processing times.
4.4. CONGESTION Object
The CONGESTION object is used to report a PCE processing congestion
state. The CONGESTION object MUST be present within a PCMonRep or a
PCRep message if the C bit of the MONITORING object carried within
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the corresponding PCMonReq or PCReq message is set and the PCE is
experiencing a congested state. The CONGESTION Object-Class is to be
assigned by IANA (recommended value=22) The CONGESTION Object-Type is
to be assigned by IANA (recommended value=1)
The format of the CONGESTION 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved | Congestion Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags: 8 bits - No flag is currently defined:
Congestion duration - 16 bits: This field indicates in the amount of
time in seconds that the responding PCE expects that it may continue
to be congested from the time that the response message was
generated. The receiver MAY use this value to decide whether or not
so send further requests to the same PCE.
It is worth noting that a PCE along a PCE chain involved in the
monitoring request may decide to learn from the congestion
information received by one of downstream PCE in the chain.
5. Policy
The receipt of a PCMonReq message may trigger a policy violation on
some PCE in which case the PCE MUST send a PCErr message with Error-
Type=5 and Error-value=3 (To be Confirmed by IANA).
6. Elements of Procedure
I bit processing: as indicated in section Section 4.1, if a PCE
supports a received PCMonReq message and that message does not
trigger any policy violation, but the PCE cannot provide any of the
set of requested performance metrics for unspecified reasons, the PCE
MUST set the I bit. Once set, the I bit MUST NOT be changed by a
receiving PCE.
Upon receiving a PCMonReq message:
1) As specified in [I-D.ietf-pce-pcep], if the PCE does not support
the PCMonReq message, the PCE peer MUST send a PCErr message with
Error-value=2 (capability not supported). According to the procedure
defined in section 6.9 of [I-D.ietf-pce-pcep], if a PCC/PCE receives
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unrecognized messages at a rate equal of greater than specified rate,
the PCC/PCE must send a PCEP CLOSE message with close
value="Reception of an unacceptable number of unknown PCEP message.
In this case, the PCC/PCE must also close the TCP session and must
not send any further PCEP messages on the PCEP session.
2) If the PCE supports the PCMonReq message but the monitoring
request is prohibited by policy, the PCE must follow the procedure
specified in section 5. As pointed out in section 4.3, a PCE may
still partially satisfy a request, leaving out some of the required
data if not allowed by policy.
3) If the PCE supports the PCMonReq and the monitoring request is not
prohibited by policy, the receiving PCE MUST first determine whether
it is the last PCE of the path computation chain. If the PCE is not
the last element of the path computation chain, the PCMonReq message
is relayed to the next hop PCE: such next-hop may either be specified
by means of a PCE-ID object present in the PCMonReq message or
dynamically determined by means of a procedure outside of the scope
of this document. Conversely, if the PCE is the last PCE of the path
computation chain, the PCE originates a PCMonRep message that
contains the requested objects according to the set of requested PCE
states metrics listed in the MONITORING object carried in the
corresponding PCMonReq message.
Upon receiving a PCReq message that carries a MONITORING and
potentially other monitoring objects (e.g. PCE-ID object):
1) As specified in [I-D.ietf-pce-pcep], if the PCE does not support
(in band) monitoring, the PCE peer MUST send a PCErr message with
Error-value=2 (capability not supported). According to the procedure
defined in section 6.9 of [I-D.ietf-pce-pcep], if a PCC/PCE receives
unrecognized messages at a rate equal of greater than specified rate,
the PCC/PCE must send a PCEP CLOSE message with close
value="Reception of an unacceptable number of unknown PCEP message.
In this case, the PCC/PCE must also close the TCP session and must
not send any further PCEP messages on the PCEP session.
2) If the PCE supports the monitoring request but the monitoring
request is prohibited by policy, the PCE must follow the procedure
specified in section 5. As pointed out in section 4.3, a PCE may
still partially satisfy a request, leaving out some of the required
data if not allowed by policy.
3) If the PCE supports the monitoring request and that request is not
prohibited by policy, the receiving PCE MUST first determine whether
it is the last PCE of the path computation chain. If the PCE is not
the last element of the path computation chain, the PCReq message
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(with the MONITORING object and potentially other monitoring objects
such as the PCE-ID) is relayed to the next hop PCE: such next-hop may
either be specified by means of a PCE-ID object present in the PCReq
message or dynamically determined by means of a procedure outside of
the scope of this document. Conversely, if the PCE is the last PCE
of the path computation chain, the PCE originates a PCRep message
that contains the requested objects according to the set of requested
PCE states metrics listed in the MONITORING and potentially other
monitoring objects carried in the corresponding PCReq message.
Upon receiving a PCMonRep message: upon receiving a PCMonRep message,
the PCE processes the request, adds the relevant objects to the
PCMonRep message and forwards the PCMonRep message to the upstream
requesting PCE or PCC.
Upon receiving a PCRep message that carrries monitoring data, the
message is processed, additional monitoring data is added according
to this specification and the message is forwarded upstream to the
requesting PCE or PCC.
Special case of Multi-destination monitoring: monitoring request
related to more than one destinations may involve a set of path
computation chains. In that case, a PCE sends each copy of the
PCMonReq message to each downstream PCE of each path computation
chain.
7. Manageability Considerations
7.1. Control of Function and Policy
It MUST be possible to configure the activation/deactivation of PCEP
monitoring on a PCEP speaker. In addition to the parameters already
listed in section 8.1 of [I-D.ietf-pce-pcep], a PCEP implementation
SHOULD allow configuring on a PCE whether specific, generic, in band
and out of band monitoring requests are allowed or not. Also a PCEP
implementation SHOULD allow configuring on a PCE a list of authorized
state metrics (aliveness, congestion, processing time, etc). This
may apply to any session the PCEP speaker participates in, to a
specific session with a given PCEP peer or to a specific group of
sessions with a specific group of PCEP peers, for instance the PCEP
peers of a neighbor AS.
7.2. Information and Data Models
A new MIB Module may be defined that provides local PCE state
metrics, as well as state metrics of other PCEs gathered using
mechanisms defined in this document.
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7.3. Liveness Detection and Monitoring
This document provides mechanisms to monitor the liveliness and
performances of a given PCE chain.
7.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[I-D.ietf-pce-pcep].
7.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any requirements on
other protocols in addition to those already listed in
[I-D.ietf-pce-pcep].
7.6. Impact On Network Operations
The frequency of PCMonReq messages may impact the operations of PCEs.
An implementation SHOULD allow a limit to be placed on the rate of
PCMonReq messages sent by a PCEP speaker and processed from a peer.
It SHOULD also allow sending a notification when a rate threshold is
reached. An implementation SHOULD allow handling PCReq messages with
a higher priority than PCMonReq messages. An implementation SHOULD
allow the configuration of a second limit for the PCReq message
requesting monitoring data.
8. IANA Considerations
8.1. New PCEP Message
Each PCEP message has a message type value.
Two new PCEP (specified in [I-D.ietf-pce-pcep]) messages are defined
in this document:
Value Description Reference
8 Path Computation Monitoring Request (PCMonReq) This document
9 Path Computation Monitoring Reply (PCMonRep) This document
8.2. New PCEP Objects
Each PCEP object has an Object-Class and an Object-Type. The
following new PCEP objects are defined in this document.
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Object-Class Value Name Object-Type Reference
19 MONITORING 1 This document
20 PCE-ID 1: IPv4 addresses This document
2: IPv6 addresses This document
21 PROC-TIME 1 This document
22 CONGESTION 1 This document
8.3. New Error-Type and Error-Values
A registry has been created for the Error-type and Error-value of the
PCEP Error Object.
A new Error-value for the PCErr message Error-types=5 (Policy
Violation) (see [I-D.ietf-pce-pcep]) is defined in this document
(Error-value to be assigned by IANA).
Error-Type Meaning Error-value Reference
5 Policy violation 3 This document
Monitoring message supported
but rejected due to
policy violation
A new Error-value for the PCErr message Error-types=6 (Mandatory
Object missing) (see [I-D.ietf-pce-pcep]) is defined in this document
(Error-Type and Error-value to be assigned by IANA).
Error-type Meaning Error-value Reference
6 Mandatory Object missing 4 This document
MONITORING Object missing
8.4. MONITORING Object Flag Field
IANA is requested to create a registry to manage the Flag field of
the MONITORING object.
New bit numbers may be allocated only by an IETF Consensus action.
Each bit should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit)
o Capability Description
o Defining RFC
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Several bits are defined for the MONITORING Object flag field in this
document:
Codespace of the Flag field (MONITORING Object)
Bit Description Reference
0-18 Unassigned
19 Incomplete This document
20 Congestion This document
21 Processing Time This document
22 General This document
23 Liveness This document
8.5. PROC-TIME Object Flag Field
IANA is requested to create a registry to manage the Flag field of
the PROC-TIME object.
New bit numbers may be allocated only by an IETF Consensus action.
Each bit should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit)
o Capability Description
o Defining RFC
One bit is defined for the PROC-TIME Object flag field in this
document:
Codespace of the Flag field (PROC-TIME Object)
Bit Description Reference
0-14 Unassigned
15 Estimated This document
8.6. CONGESTION Object Flag field
IANA is requested to create a registry to manage the Flag field of
the CONGESTION object.
New bit numbers may be allocated only by an IETF Consensus action.
Each bit should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit)
o Capability Description
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o Defining RFC
One bit is defined for the CONGESTION Object flag field in this
document:
Codespace of the Flag field (CONGESTION Object)
Bit Description Reference
0-6 Unassigned
7 Congestion This document
9. Security Considerations
The use of monitoring data can be used for various attacks such as
denail of service attacks (for example by setting the C bit and
congestion during field of the CONGESTION object to stop PCCs from
using a PCE). Thus it is recommended to make use of the security
mechanisms discussed in [I-D.ietf-pce-pcep] to secure a PCEP session
(authenticity, integrity, privacy, DoS protection, etc) to secure the
PCMonReq, PCMonRep messages and PCE state metric objects defined in
this document. An implementation SHOULD allow limiting the rate at
which PCMonReq or PCReq messages carrying monitoring requests
received from a specific peer are processed (input shapping), or from
another domain (see also section 7.6).
10. Acknowledgements
The authors would like to thank Eiji Oki, Mach Chen, Fabien Verhaeghe
and Dimitri Papadimitriou for their useful comments. Special thank
to Adrian Farrel for his detailed review.
11. References
11.1. Normative References
[I-D.farrel-rtg-common-bnf]
Farrel, A., "Reduced Backus-Naur Form (RBNF) A Syntax Used
in Various Protocol Specifications",
draft-farrel-rtg-common-bnf-07 (work in progress),
November 2008.
[I-D.ietf-pce-of]
Roux, J., Vasseur, J., and Y. Lee, "Encoding of Objective
Functions in the Path Computation Element Communication
Protocol (PCEP)", draft-ietf-pce-of-06 (work in progress),
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December 2008.
[I-D.ietf-pce-pcep]
Ayyangar, A., Farrel, A., Oki, E., Atlas, A., Dolganow,
A., Ikejiri, Y., Kumaki, K., Vasseur, J., and J. Roux,
"Path Computation Element (PCE) Communication Protocol
(PCEP)", draft-ietf-pce-pcep-19 (work in progress),
November 2008.
[I-D.ietf-pce-pcep-xro]
Takeda, T., Oki, E., and A. Farrel, "Extensions to the
Path Computation Element Communication Protocol (PCEP) for
Route Exclusions", draft-ietf-pce-pcep-xro-06 (work in
progress), July 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informative References
[I-D.ietf-pce-brpc]
Vasseur, J., Zhang, R., Bitar, N., and J. Roux, "A
Backward Recursive PCE-based Computation (BRPC) Procedure
To Compute Shortest Constrained Inter-domain Traffic
Engineering Label Switched Paths", draft-ietf-pce-brpc-09
(work in progress), April 2008.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"IS-IS Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5089, January 2008.
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Authors' Addresses
JP Vasseur (editor)
Cisco Systems, Inc
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: jpv@cisco.com
JL Le Roux
France Telecom
2, Avenue Pierre-Marzin
Lannion, 22307
FRANCE
Email: jeanlouis.leroux@orange-ftgroup.com
Yuichi Ikejiri
NTT Communications Corporation
1-1-6, Uchisaiwai-cho, Chiyoda-ku
Tokyo, 100-8019
Japan
Email: : y.ikejiri@ntt.com
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