One document matched: draft-wang-ccamp-latency-te-metric-02.txt
Differences from draft-wang-ccamp-latency-te-metric-01.txt
Network Working Group X. Fu
Internet-Draft M. Betts
Intended status: Standards Track Q. Wang
Expires: August 21, 2011 ZTE Corporation
February 17, 2011
GMPLS extensions to communicate latency as a traffic engineering
performance metric
draft-wang-ccamp-latency-te-metric-02
Abstract
Latency is such requirement that must be achieved according to the
Service Level Agreement (SLA) between customers and service
providers. A SLA is a part of a service contract where the level of
service is formally defined between service providers and customers.
For example, the service level includes platinum, golden, silver and
bronze. Different service level may associate with different
protection/restoration requirement. Latency can also be associated
with different service level. The user may select a private line
provider based on the ability to meet a latency SLA.
The key driver for latency is stock/commodity trading applications
that use data base mirroring. A few milli seconds can impact a
transaction. Financial or trading companies are very focused on end-
to-end private pipe line latency optimizations that improve things
2-3 ms. Latency and latency SLA is one of the key parameters that
these "high value" customers use to select a private pipe line
provider. Other key applications like video gaming, conferencing and
storage area networks require stringent latency and bandwidth.
This document describes the requirements and mechanisms to
communicate latency as a traffic engineering performance metric in
today's network which is consisting of potentially multiple layers of
packet transport network and optical transport network in order to
meet the latency SLA between service provider and his customers.
This document also extends RSVP-TE and IGP to support these
requirement. These extensions are intended to advertise and convey
the latency information of nodes and links as traffic engineering
performance metric.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 21, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions Used in This Document . . . . . . . . . . . . 5
2. Identification of Requirements . . . . . . . . . . . . . . . . 5
3. Control Plane Solution . . . . . . . . . . . . . . . . . . . . 9
3.1. Latency Advertisement . . . . . . . . . . . . . . . . . . 9
3.1.1. Routing Extensions . . . . . . . . . . . . . . . . . . 10
3.1.1.1. OSPF-TE Extension . . . . . . . . . . . . . . . . 10
3.1.1.2. IS-IS-TE Extension . . . . . . . . . . . . . . . . 10
3.2. Latency SLA Parameters Conveying . . . . . . . . . . . . . 10
3.2.1. Signaling Extensions . . . . . . . . . . . . . . . . . 10
3.2.1.1. Latency SLA Parameters ERO subobject . . . . . . . 11
3.2.1.2. Signaling Procedure . . . . . . . . . . . . . . . 12
3.3. Latency Accumulation and Verification . . . . . . . . . . 12
3.3.1. Signaling Extensions . . . . . . . . . . . . . . . . . 12
3.3.1.1. Latency Accumulation Object . . . . . . . . . . . 12
3.3.1.2. Latency Accumulation sub-TLV . . . . . . . . . . . 13
3.3.1.3. Signaling Procedures . . . . . . . . . . . . . . . 14
4. Security Considerations . . . . . . . . . . . . . . . . . . . 15
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Normative References . . . . . . . . . . . . . . . . . . . 15
6.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
In a network, latency, a synonym for delay, is an expression of how
much time it takes for a packet/frame of data to get from one
designated point to another. In some usages, latency is measured by
sending a packet/frame that is returned to the sender and the round-
trip time is considered the latency of bidirectional co-routed or
associated LSP. One way time is considered as the latency of
unidirectional LSP. The one way latency may not be half of the
round-trip latency in the case that the transmit and receive
directions of the path are of unequal lengths.
Latency on a connection has two sources: Node latency which is caused
by the node as a result of process time in each node and: Link
latency as a result of packet/frame transit time between two
neighbouring nodes or a FA-LSP/Composit Link [CL-REQ]. Latency
variation is a parameter that is used to indicate the variation range
of the latency value. These values should be made available to the
control plane and management plane prior to path computation. This
allows path computation to select a path that will meet the latency
SLA.
In many cases, latency is a sensitive topic. For example, two stock
exchanges (e.g.,one in Chicago and another in New York) need to
communicate with each other. A few ms can result in large impact on
service. Some customers would pay for the latency performance. SLA
contract which includes the requirement of latency is signed between
service providers and customers. Service provider should assure that
the network path latency MUST be limited to a value lower than the
upper limit. In the future, latency optimization will be needed by
more and more customers. For example, some customers pay for a
private pipe line with latency constraint (e.g., less than 10 ms)
which connects to Data Center. If this "provisioned" latency of this
private pipe line couldn't meet the SLA, service provider may
transfer customer's service to other Data Centers. Service provider
may have many layers of pre-defined restoration for this transfer,
but they have to duplicate restoration resources at significant cost.
So service provider needs some mechanisms to avoid the duplicate
restoration and reduce the network cost.
Measurement mechanism for link latency has been defined in many
technologies. For example, the measurement mechanism for link
latency has been provided in ITU-T [G.8021] and [Y.1731] for
Ethernet. The link transit latency between two Ethernet equipments
can be measured by using this mechanism. Similarly, overhead byte
and measurement mechanism of latency has been provided in OTN (i.e.,
ITU-T [G.709]). In order to measure the link latency between two OTN
nodes, PM&TCM which include Path Latency Measurement field and flag
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used to indicate the beginning of measurement of latency is added to
the overhead of ODUk. Node latency can also be recorded at each node
by recording the process time between the beginning and the end. The
measurement mechanism of links and nodes is out scope of this
document.
Current operation and maintenance mode of latency measurement is high
in cost and low in efficiency. The latency can only be measured
after the connection has been established, if the measurement
indicates that the latency SLA is not met then another path is
computed, set up and measured. This "trial and error" process is
very inefficient. To avoid this problem a means of making an
accurate prediction of latency before a path is establish is
required.
This document describes the requirements and mechanisms to
communicate latency as a traffic engineering performance metric in
today's network which is consisting of potentially multiple layers of
packet transport network and optical transport network in order to
meet the latency SLA between service provider and his customers.
This document extends IGP to advertise and convey the latency
attributes and latency variation as traffic engineering performance
metric. Thus path computation entity can have a good knowledge of
the latency traffic engineering database.
This document extends RSVP-TE protocol to accumulate (e.g., sum)
latency information of links and nodes along one LSP across multi-
domain (e.g., Inter-AS, Inter-Area or Multi-Layer) so that an latency
verification can be made at source node. One-way and round-trip
latency collection along the LSP by signaling protocol can be
supported. So the end points of this LSP can verify whether the
total amount of latency could meet the latency agreement between
operator and his user.
1.1. 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 [RFC2119].
2. Identification of Requirements
End-to-end service optimization based on latency (e.g., minimum
latency) is a key requirement for service provider. This type of
function will be adopted by their "premium" service customers. They
would like to pay for this "premium" service. After these premium
services are deployed, they will also expand to their own customers.
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Following key requirements associated with latency is identified.
o Communication latency of links and nodes including minimum latency
and latency variation as a traffic engineering performance metric
is a very important requirement. The latency performance metric
MUST be advertised into path computation entity by IGP(etc.,
OSPF-TE or IS-IS-TE) to perform route computation and network
planning based on latecny SLA target. Latency characteristics of
these links may change dynamically. In order to control IGP
messaging and avoid being unstable when the latency and latency
variation value changes, a threshold and a limit on rate of change
MUST be configured to control plane.
* Data plane is responsible for measuring the latency (e.g.,
minimum latency and latency variation). Latency measurement
can be provided by different technologies. This information
will be provided to the Control Plane. In order to monitor the
performance, pro-active latency measurement is required.
Generally, every 15 minutes or 24 hours, the value of latency
and latency variation should be collected. Similarly, on
demand latency measurement is required due to the goal of
maintenance. This can be done every fixed time interval (e.g.,
5 minutes or 1 hour). The method used to measure the latency
of links and nodes is out scope of this document.
* Control plane is responsible for advertising and collecting the
latency value of links and nodes by IGP (i.e., OSPF-TE/
IS-IS-TE).
o End-to-end service optimization based on latency (e.g., minimum
latency) is a key requirement for service provider. Latency on a
route level will help carriers' customers to make his provider
selection decision. Path computation entity MUST have the
capability to compute one end-to-end path with latency constraint.
For example, it MUST have the capability to compute a route with x
amount bandwidth and less than y ms of latency limit based on the
latency traffic engineering database. It should also support
combined routing constraints with pre-defined priorities, e.g.,
SRLG diversity, latency and cost.
o One end-to-end LSP may be across some Composite Links [CL-REQ].
Even if the transport technology (e.g., OTN) implementing the
component links is identical, the latency characteristics of the
component links may differ. When the composite link is advertised
into IGP, the latency of composite link should be the maximum
latency value of all component links.
In order to assigne the LSP to one of component links with
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different latency characteristics, RSVP-TE message MUST convey
latency SLA parameter (e.g., minimum latency) to the end points of
Composite Links where it can select one of component links or
trigger the creation of lower layer connection which MUST meet
latency SLA parameter. Following related requirements are from
[CL-REQ].
* The solution SHALL provide a means to indicate that a traffic
flow shall select a component link with the minimum latency
value.
* The solution SHALL provide a means to indicate that a traffic
flow shall select a component link with a maximum acceptable
latency value as specified by protocol.
* The solution SHALL provide a means to indicate that a traffic
flow shall select a component link with a maximum acceptable
latency variation value as specified by protocol.
The RSVP-TE message needs to carry minimum latency, maximum
acceptable latency and maximum acceptable delay variation for the
component link selection or creation. The composite link will
take these parameters into account when assigning traffic of LSP
to a component link.
o One end-to-end LSP (e.g., in IP/MPLS or MPLS-TP network) may
traverse a FA-LSP of server layer (e.g., OTN rings). The boundary
nodes of the FA-LSP SHOULD be aware of the latency information of
this FA-LSP (e.g., minimum latency and latency variation). If the
FA-LSP is able to form a routing adjacency and/or as a TE link in
the client network, the latency value of the FA-LSP can be as an
input to a transformation that results in a FA traffic engineering
metric and advertised into the client layer routing instances.
Note that this metric will include the latency of the links and
nodes that the trail traverses.
If the latency information of the FA-LSP changes (e.g., due to a
maintenance action or failure in OTN rings), the boundary node of
the FA-LSP will receive the TE link information advertisement
including the latency value which is already changed and if it is
over than the threshold and a limit on rate of change, then it
will compute the total latency value of the FA-LSP again. If the
total latency value of FA-LSP changes, the client layer MUST also
be notified about the latest value of FA. The client layer can
then decide if it will accept the increased latency or request a
new path that meets the latency requirement.
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When one end-to-end LSP traverse a server layer, there will be
some latency constraint requirement for the segment route in
server layer. So RSVP-TE message needs to carry minimum latency,
maximum acceptable latency and maximum acceptable delay variation
for the FA selection or FA-LSP creation. The boundary nodes of
FA-LSP will take these parameters into account for FA selection or
FA-LSP creation.
o Standardized measurement should be a goal for SLA validation. It
is out scope of this document. RSPV-TE should support the
accumulation (e.g., sum) of latency information of links and nodes
along one LSP across multi-domain (e.g., Inter-AS, Inter-Area or
Multi-Layer) so that an latency validation decision can be made at
the source node. One-way and round-trip latency collection along
the LSP by signaling protocol and latency verification at the end
of LSP should be supported.
o Restoration, protection and equipment variations can impact
"provisioned" latency (e.g., latency increase). The change of one
end-to-end LSP latency performance MUST be known by source and/or
sink node. So it can inform the higher layer network of a latency
change. The latency change of links and nodes will affect one
end-to-end LSP's total amount of latency. Applications can fail
beyond an application-specific threshold. Some remedy mechanism
could be used.
* Congestion in packet network can affect the latency. If the
latency of a provisioned end-to-end LSP could not meet the
latency agreement between operator and his user again, a
mechanism may cause the LSPs for some traffic flows to move to
some points in the network that is not congested. It is out
scope of this document.
* Some customers may insist on having the ability to re-route if
the latency SLA is not being met. If a "provisioned" end-to-
end LSP latency could not meet the latency agreement (e.g.,
minimum latency or latency variation) between operator and his
user, then re-routing could be triggered based on the local
policy. Pre-defined or dynamic re-routing could be triggered
to handle this case. The latency performance of pre-defined or
dynamic re-routing LSP MUST meet the latency SLA parameter. In
the case of predefined re-routing, the large amounts of
redundant capacity may have a significant negative impact on
the overall network cost. Dynamic re-routing also has to face
the risk of resource limitation. So the choice of mechanism
MUST be based on SLA or policy.
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* As a result of the change of links and nodes latency in the
LSP, current LSP may be frequently switched to a new LSP with a
appropriate latency value. In order to avoid this, the
solution SHOULD indicate the switchover of the LSP according to
maximum acceptable change latency value.
3. Control Plane Solution
In order to meet the requirements which have been identified in
section 3, this document defines following four phases.
o The first phase is the advertisement of the latency information by
routing protocol (i.e., OSPF-TE/IS-IS-TE), including latency of
nodes and links, a FA-LSP or Composite Link [CL-REQ] between two
neighbour and latency variation, so path computation entity can be
aware of the latency of nodes and links.
o In the second phase, path computation entity is responsible for
end-to-end path computation with latency constraint (e.g., less
than 10 ms) combining other routing constraint parameters (e.g.,
SRLG, cost and bandwidth).
o The third phase is to convey the latency SLA parameters for the
selection or creation of component link or FA/FA-LSP. One end-to-
end LSP may be across some Composite Links or server layers, so it
can convey latency SLA parameters by RSVP-TE message.
o The last phase is the latency collection and verification. This
stage could be optional. It could accumulate (e.g., sum) latency
information along the LSP across multi-domain (e.g., Inter-AS,
Inter-Area or Multi-Layer) by RSVP-TE signaling message to verify
the total latency at the end of path.
3.1. Latency Advertisement
A node in the packet transport network or optical transport network
can detect the latency value of link which connects to it. Also the
node latency can be recorded at every node. Then latency values of
TE links, Composit Links [CL-REQ] or FAs, latency values of nodes and
latency variation are notified to the IGP and/or PCE. If any latency
values change and over than the threshold and a limit on rate of
change, then the change MUST be notified to the IGP and/or PCE again.
As a result, path computation entity can have every node and link
latency values and latency variation in its view of the network, and
it can compute one end-to-end path with latency constraint. It needs
to extend IGP protocol (i.e., OSPF-TE/IS-IS-TE).
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3.1.1. Routing Extensions
Following is the extensions to OSPF-TE/IS-IS-TE to support the
advertisement of the node latency value, link latency and latency
variation.
3.1.1.1. OSPF-TE Extension
OSPF-TE routing protocol can be used to carry latency performance
metric by adding a sub-TLV to the TE link defined in [RFC4203]. As
defined in [RFC3630] and [RFC4203], the top-level TLV can take one of
two values (1) Router address or (2) Link. Latency sub-TLV of node
and link is added behind the top-level TLV. The link latency sub-TLV
has the same format as node latency sub-TLV. They both include
minimum latency and latency variation value. Following is the
Latency sub-TLV 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(IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Latency Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latency Variation Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Format of the Latency sub-TLV
o Minimum Latency Value: a value indicates the minumum latency of
link or node.
o Latency Variation Value: a value indicates the variation range of
the minimum latency value.
3.1.1.2. IS-IS-TE Extension
TBD
3.2. Latency SLA Parameters Conveying
3.2.1. Signaling Extensions
This document defines extensions to and describes the use of RSVP-TE
[RFC3209], [RFC3471], [RFC3473] to explicitly convey the latency SLA
parameter for the selection or creation of component link or FA/
FA-LSP. Specifically, in this document, Latency SLA Parameters TLV
are defined and added into ERO as a subobject.
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3.2.1.1. Latency SLA Parameters ERO subobject
A new OPTIONAL subobject of the EXPLICIT_ROUTE Object (ERO) is used
to specify the latency SLA parameters including minimum latency,
maximum acceptable latency and maximum acceptable latency variation.
It can be used for the following scenarios.
o One end-to-end LSP may traverse a server layer FA-LSP. This
subobject of ERO can indicate that FA selection or FA-LSP creation
shall be based on this latency constraint. The boundary nodes of
multi-layer will take these parameters into account for FA
selection or FA-LSP creation.
o One end-to-end LSP may be across some Composite Links [CL-REQ].
This subobject of ERO can indicate that a traffic flow shall
select a component link with some latency constraint values as
specified in this subobject.
This Latency SLA Parameters ERO subobject has the following format.
It follows a subobject containing the IP address, or the link
identifier [RFC3477], associated with the TE link on which it is to
be used.
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(IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Latency Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Acceptable Latency Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Acceptable Latency Variation Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Format of Latency SLA Parameters TLV
o Minimum Latency Value: a value indicates that a traffic flow shall
select a component link with the minimum latency value [CL-REQ].
It can also indicate one end-to-end LSP shall select a FA or
trigger a FA-LSP creation with the minimum latency value when it
traverse a server layer.
o Maximum Acceptable Latency Value: a value indicates that a traffic
flow shall select a component link with a maximum acceptable
latency value [CL-REQ]. It can also indicate one end-to-end LSP
shall select a FA or trigger a FA-LSP creation with a maximum
acceptable latency value when it traverse a server layer.
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o Maximum Acceptable Latency Variation Value: a value indicates that
a traffic flow shall select a component link with a maximum
acceptable latency variation value [CL-REQ]. It can also indicate
one end-to-end LSP shall select a FA or trigger a FA-LSP creation
with a maximum acceptable latency variation value when it traverse
a server layer.
3.2.1.2. Signaling Procedure
When a intermediate node receives a PATH message containing ERO and
finds that there is a Latency SLA Parameters ERO subobject
immediately behind the IP address or link address sub-object related
to itself, if the node determines that it's a region edge node of FA-
LSP or an end point of a composite link [CL-REQ], then, this node
extracts latency SLA parameters (i.e., minimum, maximum acceptable
and maximum acceptable latency variation value) from Latency SLA
Parameters ERO subobject. This node used these latency parameters
for FA selection, FA-LSP creation or component link selection. If
the intermediate node couldn't support the latency SLA, it MUST
generate a PathErr message with a "Latency SLA unsupported"
indication (TBD by INNA). If the intermediate node couldn't select a
FA or component link, or create a FA-LSP which meet the latency
constraint defined in Latency SLA Parameters ERO subobject, it must
generate a PathErr message with a "Latency SLA parameters couldn't be
met" indication (TBD by INNA).
3.3. Latency Accumulation and Verification
Latency accumulation and verification applies where the full path of
an multi-domain (e.g., Inter-AS, Inter-Area or Multi-Layer) TE LSP
can't be or is not determined at the ingress node of the TE LSP.
This is most likely to arise owing to TE visibility limitations. If
all domains support to communicate latency as a traffic engineering
metric parameter, one end-to-end optimized path with delay constraint
(e.g., less than 10 ms) which satisfies latency SLAs parameter could
be computed by BRPC [RFC5441] in PCE. Otherwise, it could use the
mechanism defined in this section to accumulat the latency of each
links and nodes along the path which is across multi-domain. Latency
accumulation and verification also applies where not all domains
could support the communication latency as a traffic engineering
metric parameter.
3.3.1. Signaling Extensions
3.3.1.1. Latency Accumulation Object
An Latency Accumulation Object is defined in this document to support
the accumulation and verification of the latency. This object which
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can be carried in a Path/Resv message may includes two sub-TLVs.
Latency Accumulation Object 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(IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latency Accumulation sub-TLV (from source to sink) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latency Accumulation sub-TLV (from sink to source) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Format of Accumulated Latency Object
o Latency Accumulation sub-TLV (from source to sink):It is used to
accumulate the latency from source to sink along the
unidirectional or bidirectional LSP. A Path message for
unidirectional and bidirectional LSP must includes this sub-TLV.
When sink node receives the Path message including this sub-TLV,
it must copy this sub-TLV into Resv message. So the source node
can receive the latency accumulated value (i.e., sum) from itself
to sink node which can be used for latency verification.
o Latency Accumulation sub-TLV (from sink to source):It is used to
accumulate the latency from sink to source along the bidirectional
LSP. A Resv message for the bidirectional LSP must includes this
sub-TLV. So the source node can get the latency accumulated value
(i.e., sum) of round-trip which can be used for latency
verification.
3.3.1.2. Latency Accumulation sub-TLV
The Sub-TLV format is defined in the next picture.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Accumulated Minimum Latency Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Accumulated Latency Variation Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Format of Latency Accumulation sub-TLV
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o Type: sub-TLV type
* 0: It indicates the sub-TLV is for the latency accumulation
from source to sink node along the LSP.
* 1: It indicates the sub-TLV is for the latency accumulation
from sink to source node along the LSP.
o Length: length of the sub-TLV value in bytes.
o Accumulated Minimum Latency Value: a value indicates the sum of
each links and nodes' minumum latency along one direction of LSP.
o Accumulated Latency Variation Value: a value indicates the sume of
each links and nodes' minumum latency variation along one
direction of LSP.
3.3.1.3. Signaling Procedures
When the source node desires to accumulate (i.e., sum) the total
latency of one end-to-end LSP, the "Latency Accumulating desired"
flag (value TBD) should be set in the LSP_ATTRIBUTES object of Path/
Resv message, object that is defined in [RFC5420].
A source node initiates latency accumulation for a given LSP by
adding Latency Accumulation object to the Path message. The Latency
Accumulation object only includes one sub-TLV (sub-TLV type=0) where
it is going to accumulate the latency value of each links and nodes
along path from source to sink.
When the downstream node receives Path message and if the "Latency
Accumulating desired" is set in the LSP_ATTRIBUTES, it accumulates
the latency of link and node based on the accumulated latency value
of the sub-TLV (sub-TLV type=0) in Latency Accumulation object before
it sends Path message to downsteam.
If the intermediate node couldn't support the latency accumulation
function, it MUST generate a PathErr message with a "Latency
Accumulation unsupported" indication (TBD by INNA).
When the sink node of LSP receives the Path message and the "Latency
Accumulating desired" is set in the LSP_ATTRIBUTES, it copy the
latency value in the Latency Accumulation sub-TLV (sub-TLV type=0) of
Path message into the Resv message which will be forwarded hop by hop
in the upstream direction until it arrives the source node. Then
source node can get the latency sum value from source to sink for
unidirectional and bidirectional LSP.
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If the LSP is a bidirectional one and the "Latency Accumulating
desired" is set in the LSP_ATTRIBUTES, it adds another Latency
Accumulation sub-TLV (sub-TLV type=1) into the Latency Accumulation
object of Resv message where latency of each links and nodes along
path will be accumulated from sink to source into this sub-TLV.
When the upstream node receives Resv message and if the "Latency
Accumulating desired" is set in the LSP_ATTRIBUTES, it accumulates
the latency of link and node based on the latency value in sub-TLV
(sub-TLV type=1) before it continues to sends Resv message.
After source node receive Resv message, it can get the total latency
value of one way or round-trip from Latency Accumulation object. So
it can confirm whether the latency value meet the latency SLA or not.
4. Security Considerations
TBD
5. IANA Considerations
TBD
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.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, January 2003.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
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[RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4203, October 2005.
6.2. Informative References
[CL-REQ] C. Villamizar, "Requirements for MPLS Over a Composite
Link", draft-ietf-rtgwg-cl-requirement-02 .
[G.709] ITU-T Recommendation G.709, "Interfaces for the Optical
Transport Network (OTN)", December 2009.
Authors' Addresses
Xihua Fu
ZTE Corporation
Email: fu.xihua@zte.com.cn
Malcolm Betts
ZTE Corporation
Email: malcolm.betts@zte.com.cn
Qilei Wang
ZTE Corporation
Email: wang.qilei@zte.com.cn
Fu, et al. Expires August 21, 2011 [Page 16]
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