MPLS Working Group S. Bryant
Internet-Draft M. Chen
Intended status: Standards Track Z. Li
Expires: October 28, 2017 Huawei
G. Swallow
S. Sivabalan
Cisco Systems
G. Mirsky
ZTE Corp.
G. Fioccola
Telecom Italia
April 26, 2017
RFC6374 Synonymous Flow Labels
draft-bryant-mpls-rfc6374-sfl-04
Abstract
This document describes a method of making RFC6374 performance
measurements on flows carried over an MPLS Label Switched path. This
allows loss and delay measurements to be made on multi-point to point
LSPs and allows the measurement of flows within an MPLS construct
using RFC6374.
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
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 October 28, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. RFC6374 Packet Loss Measurement with SFL . . . . . . . . . . 4
4. RFC6374 Single Packet Delay Measurement . . . . . . . . . . . 4
5. Data Service Packet Delay Measurement . . . . . . . . . . . . 4
6. Some Simplifying Rules . . . . . . . . . . . . . . . . . . . 6
7. Multiple Packet Delay Characteristics . . . . . . . . . . . . 6
7.1. Method 1: Time Buckets . . . . . . . . . . . . . . . . . 7
7.2. Method 2 Classic Standard Deviation . . . . . . . . . . . 9
7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format 10
7.3. Per Packet Delay Measurement . . . . . . . . . . . . . . 11
7.4. Average Delay . . . . . . . . . . . . . . . . . . . . . . 11
8. Sampled Measurement . . . . . . . . . . . . . . . . . . . . . 13
9. Carrying RFC6374 Packets over an LSP using an SFL . . . . . . 13
9.1. RFC6374 SFL TLV . . . . . . . . . . . . . . . . . . . . . 15
10. Applicability to Pro-active and On-demand Measurement . . . . 16
11. RFC6374 Combined Loss-Delay Measurement . . . . . . . . . . . 16
12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
13. Security Considerations . . . . . . . . . . . . . . . . . . . 17
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
14.1. Allocation of PW Associated Channel Type . . . . . . . . 17
14.2. MPLS Loss/Delay TLV Object . . . . . . . . . . . . . . . 17
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
15.1. Normative References . . . . . . . . . . . . . . . . . . 17
15.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
[RFC6374] was originally designed for use as an OAM protocol for use
with MPLS Transport Profile (MPLS-TP) [RFC5921] LSPs. MPLS-TP only
supports point-to-point and point-to-multi-point LSPs. This document
describes how to use RFC6374 in the general MPLS case, and also
introduces a number of more sophisticated measurements of
applicability to both cases.
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[I-D.ietf-mpls-flow-ident] describes the requirement for introducing
flow identities when using RFC6374 [RFC6374] packet Loss Measurements
(LM). In summary RFC6374 uses the loss-measurement (LM) packet as
the packet accounting demarcation point. Unfortunately this gives
rise to a number of problems that may lead to significant packet
accounting errors in certain situations. For example:
1. Where a flow is subjected to Equal Cost Multi-Path (ECMP)
treatment packets can arrive out of order with respect to the LM
packet.
2. Where a flow is subjected to ECMP treatment, packets can arrive
at different hardware interfaces, thus requiring reception of an
LM packet on one interface to trigger a packet accounting action
on a different interface which may not be co-located with it.
This is a difficult technical problem to address with the
required degree of accuracy.
3. Even where there is no ECMP (for example on RSVP-TE, MPLS-TP LSPs
and PWs) local processing may be distributed over a number of
processor cores, leading to synchronization problems.
4. Link aggregation techniques may also lead to synchronization
issues.
5. Some forwarder implementations have a long pipeline between
processing a packet and incrementing the associated counter again
leading to synchronization difficulties.
An approach to mitigating these synchronization issue is described in
[I-D.tempia-ippm-p3m] and
[I-D.chen-ippm-coloring-based-ipfpm-framework] in which packets are
batched by the sender and each batch is marked in some way such that
adjacent batches can be easily recognized by the receiver.
An additional problem arises where the LSP is a multi-point to point
LSP, since MPLS does not include a source address in the packet.
Network management operations require the measurement of packet loss
between a source and destination. It is thus necessary to introduce
some source specific information into the packet to identify packet
batches from a specific source.
[I-D.bryant-mpls-sfl-framework] describes a method of encoding per
flow instructions in an MPLS label stack using a technique called
Synonymous Flow Labels (SFL) in which labels which mimic the
behaviour of other labels provide the packet batch identifiers and
enable the per batch packet accounting. This memo specifies how SFLs
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are used to perform RFC6374 packet loss and RFC6374 delay
measurements.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
3. RFC6374 Packet Loss Measurement with SFL
The data service packets of the flow being instrumented are grouped
into batches, and all the packets within a batch are marked with the
SFL [I-D.ietf-mpls-flow-ident] corresponding to that batch. The
sender counts the number of packets in the batch. When the batch has
completed and the sender is confident that all of the packets in that
batch will have been received, the sender issues an RFC6374 Query
message to determine the number actually received and hence the
number of packets lost. The RFC6374 Query message is sent using the
same SFL as the co-responding batch of data service packets. The
format of the Query and Response packet is described in Section 9.
4. RFC6374 Single Packet Delay Measurement
RFC6374 describes how to measure the packet delay by measuring the
transit time of an RFC6374 packet over an LSP. Such a packet may not
need to be carried over an SFL since the delay over a particular LSP
should be a function of the TC bits.
However where SFLs are being used to monitor packet loss or where
label inferred scheduling is used [RFC3270] then the SFL would be
REQUIRED to ensure that the RFC6374 packet which was being used as a
proxy for a data service packet experienced a representative delay.
The format of an RFC6374 packet carried over the LSP using an SFL is
shown in Section 9.
5. Data Service Packet Delay Measurement
Where it is desired to more thoroughly instrument a packet flow and
to determine the delay of a number of packets it is undesirable to
send a large number of RFC6374 packets acting as proxy data service
packets Section 4. A method of directly measuring the delay
characteristics of a batch of packets is therefore needed.
Given the long intervals over which it is necessary to measure packet
loss, it is not necessarily the case that the batch times for the two
measurement types would be identical. This it is proposed that the
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two measurements are relatively independent. The notion that they
are relatively independent arises for the potential for the two
batches to overlap in time, in which case either the delay batch time
will need to be cut short or the loss time will need to be extended
to allow correct reconciliation of the various counters.
The problem is illustrated in Figure 1 below:
(1) AAAAAAAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB
SFL Marking of a packet batch for loss measurement
(2) AADDDDAAAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB
SFL Marking of a subset if the packets for delay
(3) AAAAAAAADDDDBBBBBBBBAAAAAAAAAABBBBBBBBBB
SFL Marking of a subset of the packets across a
packet loss measurement boundary
(4) AACDCDCDAABBBBBBBBBBAAAAAAAAAABBBBBBBBBB
The case of multiple delay measurements within
a packet loss measurement
Figure 1: RFC6734 Query Packet with SFL
In case 1 of Figure 1 we show the case were loss measurement alone is
being carried out on the flow under analysis. For illustrative
purposes consider that in the time interval being analyzed, 10
packets always flow.
Now consider case 2 of Figure 1 where a small batch of packets need
to analyzed for delay. These are marked with a different SFL type
indicating that they are to be monitored for both loss and delay.
The SFL=A indicates loss batch A, SFL=D indicates a batch of packets
that are to be instrumented for delay, but SFL D is synonymous with
SFL A, which in turn is synonymous with the underlying FEC. Thus a
packet marked D will be accumulated into the A loss batch, into the
delay statistics and will be forwarded as normal. Whether the packet
is actually counted twice (for loss and delay) or whether the two
counters are reconciled during reporting is a local matter.
Now consider case 3 of Figure 1 where a small batch of packets are
marked for delay across a loss batch boundary. These packets need to
considered as part of batch A or a part of batch B, and any RFC6374
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Query needs to take place after all the packets A or D (which ever
option is chosen) have arrived at the receiving LSR.
Now consider case 4 of Figure 1. Here we have a case where it is
required to take a number of delay measurements within a batch of
packets that we are measuring for loss. To do this we need two SFLs
for delay (C and D) and alternate between them (on a delay batch by
delay batch basis) for the purposes of measuring the delay
characteristics of the different batches of packets.
6. Some Simplifying Rules
It is possible to construct a large set of overlapping measurement
type, in terms of loss, delay, loss and delay and batch overlap. If
we allow all combination of cases, this leads to configuration,
testing and implementation complexity and hence increased operation
and capital cost. The following simplifying rules represent the
default case:
1. Any system that needs to measure delay MUST be able to measure
loss.
2. Any system that is to measure delay MUST be configured to measure
loss. Whether the loss statistics are collected or not is a
local matter.
3. A delay measurement MAY start at any point during a loss
measurement batch, subject to rule 4.
4. A delay measurement interval MUST be short enough that it will
complete before the enclosing loss batch completes.
5. The duration of a second delay (D in Figure 1 batch must be such
that all packets from the packets belonging to a first delay
batch (C in Figure 1)will have been received before the second
delay batch completes.
Given that the sender controls both the start and duration of a loss
and a delay packet batch, these rules are readily implemented in the
control plane.
7. Multiple Packet Delay Characteristics
A number of methods are described. The expectation is that the MPLS
WG possibly with the assistance of the IPPM WG will select one or
maybe more than one of these methods for standardization.
Three Methods are discussed:
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1. Time Buckets
2. Classic Standard Deviation
3. Average Delay
7.1. Method 1: Time Buckets
In this method the receiving LSR measures the inter-packet gap,
classifies the delay into a number of delay buckets and records the
number of packets in each bucket. As an example, if the operator
were concerned about packets with a delay of up to 1us, 2us, 4us,
8us, and over 8us then there would be five buckets and packets that
arrived up to 1us would cause the 1us bucket counter to increase,
between 1us and 2us the 2us bucket counter would increase etc. In
practice it might be better in terms of processing and potential
parallelism if, when a packet had a delay relative to its predecessor
of 2us both the up to 1us and the 2us counter were incremented and
any more detailed information was calculated in the analytics system.
This method allows the operator to see more structure in the jitter
characteristics than simply measuring the average jitter, and avoids
the complication of needing to perform a per packet multiply, but
will probably need to time intervals between buckets to be
programmable by the operator.
The packet format of an RFC6374 Bucket Jitter Measurement Message is
shown below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Flags | Control Code | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QTF | RTF | RPTF | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session Identifier | DS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of | Reserved |
| Buckets | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interval in 10ns units |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number pkts in Bucket |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
~ TLV Block ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Bucket Jitter Measurement Message Format
The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF,
Session Identifier, and DS Fields are as defined in section 3.7 of
RFC6374. The remaining fields are as follows:
o Number of Buckets in the measurement
o Reserved must be sent as zero and ignored on receipt
o Interval in 10ns units is the inter-packet interval for
this bucket
o Number Pkts in Bucket is the number of packets found in
this bucket.
There will be a number of Interval/Number pairs depending on the
number of buckets being specified by the Querier. If an RFC6374
message is being used to configure the buckets, (i.e. the responder
is creating or modifying the buckets according to the intervals in
the Query message), then the Responder MUST respond with 0 packets in
each bucket until it has been configured for a full measurement
period. This indicates that it was configured at the time of the
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last response message, and thus the response is valid for the whole
interval. As per the [RFC6374] convention the Number of pkts in
Bucket fields are included in the Query message and set to zero.
Out of band configuration is permitted by this mode of operation.
Note this is a departure from the normal fixed format used in
RFC6374. We need to establish if this is problematic or not.
This RFC6374 message is carried over an LSP in the way described in
[RFC6374] and over an LSP with an SFL as described in Section 9.
7.2. Method 2 Classic Standard Deviation
In this method, provision is made for reporting the following delay
characteristics:
1. Number of packets in the batch (n).
2. Sum of delays in a batch (S)
3. Maximum Delay.
4. Minimum Delay.
5. Sum of squares of Inter-packet delay (SS).
Characteristic's 1 and 2 give the mean delay. Measuring the delay of
each pair in the batch is discussed in Section 7.3.
Characteristics 3 and 4 give the outliers.
Characteristics 1, 2 and 5 can be used to calculate the variance of
the inter-packet gap and hence the standard deviation giving a view
of the distribution of packet delays and hence the jitter. The
equation for the variance (var) is given by:
var = (SS - S*S/n)/(n-1)
There is some concern over the use of this algorithm for measuring
variance, because SS and S*S/n can be similar numbers, particularly
where variance is low. However the method commends it self by not
requiring a division in the hardware. A future version of this
document will look at using improved statistical methods such as the
assumed mean.
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7.2.1. RFC6374 Multi-Packet Delay Measurement Message Format
The packet format of an RFC6374 Multi-Packet Delay Measurement
Message is shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Flags | Control Code | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QTF | RTF | RPTF | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session Identifier | DS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Packets |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sum of Delays for Batch |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Delay |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Delay |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sum of squares of Inter-packet delay |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
~ TLV Block ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Multi-packet Delay Measurement Message Format
The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF,
Session Identifier, and DS Fields are as defined in section 3.7 of
RFC6374. The remaining fields are as follows:
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o Number of Packets is the number of packets in this batch
o Sum of Delays for Batch is the duration of the batch in the
time measurement format specified in the RTF field.
o Minimum Delay is the minimum inter-packet gap observed during
the batch in the time format specified in the RTF field.
o Maximum Delay is the maximum inter-packet gap observed during
the batch in the time format specified in the RTF field.
This RFC6374 message is carried over an LSP in the way described in
[RFC6374] and over an LSP with an SFL as described in Section 9.
7.3. Per Packet Delay Measurement
If detailed packet delay measurement is required then it might be
possible to record the inter-packet gap for each packet pair. In
other that exception cases of slow flows or small batch sizes, this
would create a large demand on storage in the instrumentation system,
bandwidth to such a storage system and bandwidth to the analytics
system. Such a measurement technique is outside the scope of this
document.
7.4. Average Delay
Introduced in [I-D.ietf-ippm-alt-mark] is the concept of a one way
delay measurement in which the average time of arrival of a set of
packets is measured. In this approach the packet is time-stamped at
arrival and the Responder returns the sum of the time-stamps and the
number of times-tamps. From this the analytics engine can determine
the mean delay. An alternative model is that the Responder returns
the time stamp of the first and last packet and the number of
packets. This method has the advantage of allowing the average delay
to be determined at a number of points along the packet path and
allowing the components of the delay to be characterized.
The packet format of an RFC6374 Average Delay Measurement Message is
shown below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Flags | Control Code | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QTF | RTF | RPTF | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session Identifier | DS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Packets |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time of First Packet |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time of Last Packet |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sum of Timestamps of Batch |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
~ TLV Block ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Average Delay Measurement Message Format
The Version, Flags, Control Code, Message Length, QTF, RTF, RPTF,
Session Identifier, and DS Fields are as defined in section 3.7 of
RFC6374. The remaining fields are as follows:
o Number of Packets is the number of packets in this batch.
o Time of First Packet is the time of arrival of the first
packet in the batch.
o Time of Last Packet is the time of arrival of the last
packet in the batch.
o Sum of Timestamps of Batch.
This RFC6374 message is carried over an LSP in the way described in
[RFC6374] and over an LSP with an SFL as described in Section 9. As
is the convention with RFC6374, the Query message contains
placeholders for the Response message. The placeholders are sent as
zero.
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8. Sampled Measurement
In the discussion so far it has been assumed that we would measure
the delay characteristics of every packet in a delay measurement
interval defined by an SL of constant colour. In
[I-D.ietf-ippm-alt-mark] the concept of a sampled measurement is
considered. That is the Responder only measures a packet at the
start of a group of packets being marked for delay measurement by a
particular colour, rather than every packet in the marked batch. A
measurement interval is not defined by the duration of a marked batch
of packets but the interval between a pair of RFC6374 packets taking
a readout of the delay characteristic. This approach has the
advantage that the measurement is not impacted by ECMP effects.
9. Carrying RFC6374 Packets over an LSP using an SFL
The packet format of an RFC6374 Query message using SFLs is shown in
Figure 5.
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+-------------------------------+
| |
| LSP |
| Label |
+-------------------------------+
| |
| Synonymous Flow |
| Label |
+-------------------------------+
| |
| GAL |
| |
+-------------------------------+
| |
| ACH Type = 0xA |
| |
+-------------------------------+
| |
| RFC6374 Measurement Message |
| |
| +-------------------------+ |
| | | |
| | RFC6374 Fixed | |
| | Header | |
| | | |
| +-------------------------+ |
| | | |
| | Optional SFL TLV | |
| | | |
| +-------------------------+ |
| | | |
| | Optional Return | |
| | Information | |
| | | |
| +-------------------------+ |
| |
+-------------------------------+
Figure 5: RFC6734 Query Packet with SFL
The MPLS label stack is exactly the same as that used for the user
data service packets being instrumented except for the inclusion of
the GAL [RFC5586] to allow the receiver to distinguish between normal
data packets and OAM packets. Since the packet loss measurements are
being made on the data service packets, an RFC6374 direct loss
measurement is being made, and which is indicated by the type field
in the ACH (Type = 0x000A).
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The RFC6374 measurement message consists of the three components, the
RFC6374 fixed header as specified in [RFC6374] carried over the ACH
channel type specified the type of measurement being made (currently:
loss, delay or loss and delay) as specified in RFC6374.
Two optional TLVs MAY also be carried if needed. The first is the
SFL TLV specified in Section 9.1. This is used to provide the
implementation with a reminder of the SFL that was used to carry the
RFC6374 message. This is needed because a number of MPLS
implementations do not provide the MPLS label stack to the MPLS OAM
handler. This TLV is required if RFC6374 messages are sent over UDP
[RFC7876]. This TLV MUST be included unless, by some method outside
the scope of this document, it is known that this information is not
needed by the RFC6374 Responder.
The second set of information that may be needed is the return
information that allows the responder send the RFC6374 response to
the Querier. This is not needed if the response is requested in-band
and the MPLS construct being measured is a point to point LSP, but
otherwise MUST be carried. The return address TLV is defined in
RFC6378 and the optional UDP Return Object is defined in [RFC7876].
9.1. RFC6374 SFL TLV
Editor's Note we need to review the following in the light of further
thoughts on the associated signaling protocol(s). I am fairly
confident that we need all the fields other than SFL Batch and SFL
Index. The Index is useful in order to map between the label and
information associated with the FEC. The batch is part of the
lifetime management process.
The required RFC6374 SFL TLV is shown in Figure 6. This contains the
SFL that was carried in the label stack, the FEC that was used to
allocate the SFL and the index into the batch of SLs that were
allocated for the FEC that corresponds to this SFL.
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 |MBZ| SFL Batch | SFL Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SFL | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: SFL TLV
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Where:
Type Type is set to Synonymous Flow Label (SFL-TLV).
Length The length of the TLV as specified in RFC6374.
MBZ MUST be sent as zero and ignored on receive.
SFL Batch The SFL batch that this SFL was allocated as part
of see [I-D.bryant-mpls-sfl-control]
SPL Index The index into the list of SFLs that were assigned
against the FEC that corresponds to the SFL.
SFL The SFL used to deliver this packet. This is an MPLS
label which is a component of a label stack entry as
defined in Section 2.1 of [RFC3032].
Reserved MUST be sent as zero and ignored on receive.
FEC The Forwarding Equivalence Class that was used to
request this SFL. This is encoded as per
Section 3.4.1 of TBD
This information is needed to allow for operation with hardware that
discards the MPLS label stack before passing the remainder of the
stack to the OAM handler. By providing both the SFL and the FEC plus
index into the array of allocated SFLs a number of implementation
types are supported.
10. Applicability to Pro-active and On-demand Measurement
A future version of the this document will discuss the applicability
of the various methods to pro-active and on-demand Measurement.
11. RFC6374 Combined Loss-Delay Measurement
This mode of operation is not currently supported by this
specification.
12. Privacy Considerations
The inclusion of originating and/or flow information in a packet
provides more identity information and hence potentially degrades the
privacy of the communication. Whilst the inclusion of the additional
granularity does allow greater insight into the flow characteristics
it does not specifically identify which node originated the packet
other than by inspection of the network at the point of ingress, or
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inspection of the control protocol packets. This privacy threat may
be mitigated by encrypting the control protocol packets, regularly
changing the synonymous labels and by concurrently using a number of
such labels.
13. Security Considerations
The issue noted in Section 5 is a security consideration. There are
no other new security issues associated with the MPLS dataplane. Any
control protocol used to request SFLs will need to ensure the
legitimacy of the request.
14. IANA Considerations
14.1. Allocation of PW Associated Channel Type
As per the IANA considerations in [RFC5586], IANA is requested to
allocate the following Channel Type in the "PW Associated Channel
Type" registry:
Value Description TLV Follows Reference
----- --------------------------------- ----------- ---------
TBD RFC6374 Bucket Jitter Measurement No This
TBD RFC6374 Multi-Packet Delay No This
Measurement
TBD RFC6374 Average Delay Measurement No This
14.2. MPLS Loss/Delay TLV Object
IANA is request to allocate a new TLV from the 0-127 range on the
MPLS Loss/Delay Measurement TLV Object Registry:
Type Description Reference
---- --------------------------------- ---------
TBD Synonymous Flow Label This
A value of 4 is recommended.
15. References
15.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<http://www.rfc-editor.org/info/rfc3032>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<http://www.rfc-editor.org/info/rfc5586>.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374,
DOI 10.17487/RFC6374, September 2011,
<http://www.rfc-editor.org/info/rfc6374>.
[RFC7876] Bryant, S., Sivabalan, S., and S. Soni, "UDP Return Path
for Packet Loss and Delay Measurement for MPLS Networks",
RFC 7876, DOI 10.17487/RFC7876, July 2016,
<http://www.rfc-editor.org/info/rfc7876>.
15.2. Informative References
[I-D.bryant-mpls-sfl-control]
Bryant, S., Swallow, G., and S. Sivabalan, "MPLS Flow
Identification Considerations", draft-bryant-mpls-sfl-
control-01 (work in progress), March 2017.
[I-D.bryant-mpls-sfl-framework]
Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S.,
and G. Mirsky, "Synonymous Flow Label Framework", draft-
bryant-mpls-sfl-framework-04 (work in progress), April
2017.
[I-D.chen-ippm-coloring-based-ipfpm-framework]
Chen, M., Zheng, L., Mirsky, G., Fioccola, G., and T.
Mizrahi, "IP Flow Performance Measurement Framework",
draft-chen-ippm-coloring-based-ipfpm-framework-06 (work in
progress), March 2016.
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[I-D.ietf-ippm-alt-mark]
Fioccola, G., Capello, A., Cociglio, M., Castaldelli, L.,
Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate Marking method for passive performance
monitoring", draft-ietf-ippm-alt-mark-04 (work in
progress), March 2017.
[I-D.ietf-mpls-flow-ident]
Bryant, S., Pignataro, C., Chen, M., Li, Z., and G.
Mirsky, "MPLS Flow Identification Considerations", draft-
ietf-mpls-flow-ident-04 (work in progress), February 2017.
[I-D.tempia-ippm-p3m]
Capello, A., Cociglio, M., Fioccola, G., Castaldelli, L.,
and A. Bonda, "A packet based method for passive
performance monitoring", draft-tempia-ippm-p3m-03 (work in
progress), March 2016.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, DOI 10.17487/RFC3270, May 2002,
<http://www.rfc-editor.org/info/rfc3270>.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
<http://www.rfc-editor.org/info/rfc5921>.
Authors' Addresses
Stewart Bryant
Huawei
Email: stewart.bryant@gmail.com
Mach Chen
Huawei
Email: mach.chen@huawei.com
Zhenbin Li
Huawei
Email: lizhenbin@huawei.com
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George Swallow
Cisco Systems
Email: swallow.ietf@gmail.com
Siva Sivabalan
Cisco Systems
Email: msiva@cisco.com
Gregory Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
Giuseppe Fioccola
Telecom Italia
Email: giuseppe.fioccola@telecomitalia.it
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