One document matched: draft-frost-mpls-tp-loss-delay-02.txt
Differences from draft-frost-mpls-tp-loss-delay-01.txt
MPLS D. Frost, Ed.
Internet-Draft S. Bryant, Ed.
Intended status: Standards Track Cisco Systems
Expires: December 31, 2010 June 29, 2010
Packet Loss and Delay Measurement for the MPLS Transport Profile
draft-frost-mpls-tp-loss-delay-02
Abstract
An essential Operations, Administration and Maintenance requirement
of the MPLS Transport Profile (MPLS-TP) is the ability to monitor
performance metrics for packet loss and one-way and two-way delay for
MPLS-TP pseudowires, Label Switched Paths, and Sections. This
document specifies protocol mechanisms to facilitate the efficient
and accurate measurement of these performance metrics.
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].
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 December 31, 2010.
Copyright Notice
Copyright (c) 2010 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
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(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Review of Requirements . . . . . . . . . . . . . . . . . . 4
1.1.1. Requirements for Packet Loss Measurement . . . . . . . 4
1.1.2. Requirements for Delay Measurement . . . . . . . . . . 4
1.2. Protocol Summary . . . . . . . . . . . . . . . . . . . . . 5
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1. Implementation Considerations . . . . . . . . . . . . . . 8
2.2. Packet Loss Measurement . . . . . . . . . . . . . . . . . 9
2.3. Delay Measurement . . . . . . . . . . . . . . . . . . . . 11
2.3.1. Timestamp Format . . . . . . . . . . . . . . . . . . . 12
2.4. Delay Variation Measurement . . . . . . . . . . . . . . . 13
2.5. Unidirectional Connections . . . . . . . . . . . . . . . . 13
2.6. Distributed Systems . . . . . . . . . . . . . . . . . . . 14
3. Packet Format . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1. Loss Measurement Message Format . . . . . . . . . . . . . 15
3.2. Delay Measurement Message Format . . . . . . . . . . . . . 17
3.3. Timestamp Field Formats . . . . . . . . . . . . . . . . . 19
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.1. Loss Measurement Procedures . . . . . . . . . . . . . . . 20
4.1.1. Initiating a Loss Measurement Operation . . . . . . . 20
4.1.2. Transmitting a Loss Measurement Query . . . . . . . . 20
4.1.3. Receiving a Loss Measurement Query . . . . . . . . . . 21
4.1.4. Transmitting a Loss Measurement Response . . . . . . . 21
4.1.5. Receiving a Loss Measurement Response . . . . . . . . 22
4.1.6. Loss Calculation . . . . . . . . . . . . . . . . . . . 22
4.1.7. Message Loss and Packet Misorder Conditions . . . . . 22
4.2. Delay Measurement Procedures . . . . . . . . . . . . . . . 23
4.2.1. Transmitting a Delay Measurement Query . . . . . . . . 23
4.2.2. Receiving a Delay Measurement Query . . . . . . . . . 24
4.2.3. Transmitting a Delay Measurement Response . . . . . . 24
4.2.4. Receiving a Delay Measurement Response . . . . . . . . 25
4.2.5. Timestamp Format Negotiation . . . . . . . . . . . . . 25
5. Packet Profiles and Quality of Service . . . . . . . . . . . . 26
5.1. Quality of Service . . . . . . . . . . . . . . . . . . . . 27
5.2. Loss Measurement of OAM Messages . . . . . . . . . . . . . 27
6. Congestion Considerations . . . . . . . . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.1. Normative References . . . . . . . . . . . . . . . . . . . 29
9.2. Informative References . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
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1. Introduction
The MPLS Transport Profile (MPLS-TP) [I-D.ietf-mpls-tp-framework]
comprises the set of protocol functions that meet the requirements
[RFC5654] for the application of MPLS to the construction and
operation of packet-switched transport networks.
RFC 5860 [RFC5860] specifies Operations, Administration and
Maintenance (OAM) definitions and requirements for the measurement of
packet loss and one-way and two-way delay for MPLS-TP pseudowires
(PWs), Label Switched Paths (LSPs), and Sections. For convenience
these definitions and requirements are summarized in the following
subsections.
1.1. Review of Requirements
1.1.1. Requirements for Packet Loss Measurement
The MPLS-TP OAM toolset must provide a function to enable the
quantification of packet loss ratio over a PW, LSP or Section.
The loss of a packet is defined in [RFC2680] (Section 2.4). This
definition is used here.
Packet loss ratio is defined here to be the ratio of the number of
user packets lost to the total number of user packets sent during a
defined time interval.
This function may either be performed pro-actively or on-demand.
This function should be performed between End Points of PWs, LSPs and
Sections.
It should be possible to rely on user traffic to perform this
function.
The protocol solution(s) developed to perform this function must
apply to point-to-point co-routed bidirectional LSPs, point-to-point
associated bidirectional LSPs, point-to-point unidirectional LSPs and
point-to-multipoint (unidirectional) LSPs.
1.1.2. Requirements for Delay Measurement
The MPLS-TP OAM toolset must provide a function to enable the
quantification of the one-way, and if appropriate, the two-way, delay
of a PW, LSP or Section.
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o The one-way delay is defined in [RFC2679] to be the time elapsed
from the start of transmission of the first bit of a packet by an
End Point until the reception of the last bit of that packet by
the other End Point.
o The two-way delay is defined in [RFC2681] to be the time elapsed
from the start of transmission of the first bit of a packet by an
End Point until the reception of the last bit of that packet by
the same End Point.
Two-way delay may be quantified using data traffic loopback at the
remote End Point of the PW, LSP or Section.
Accurate quantification of one-way delay may require clock
synchronization, the means for which are outside the scope of this
document.
This function should be performed on-demand and may be performed pro-
actively.
This function should be performed between End Points of PWs, LSPs and
Sections.
In addition to point-to-point co-routed bidirectional LSPs, the
protocol solution(s) developed to perform this function must also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs and point-to-multipoint (unidirectional) LSPs,
but only to enable the quantification of the one-way delay.
1.2. Protocol Summary
This document specifies two closely-related protocols, one for packet
loss measurement (LM) and one for packet delay measurement (DM).
These protocols have the following characteristics and capabilities:
o The LM and DM protocols are designed to be simple and to support
efficient hardware processing.
o The LM and DM protocols support measurement of loss and delay over
MPLS-TP pseudowires and sections, over associated and co-routed
bidirectional point-to-point MPLS-TP LSPs, and over unidirectional
point-to-point and point-to-multipoint MPLS-TP LSPs.
o The LM and DM protocols support pro-active and on-demand modes of
operation.
o The LM and DM protocols use a simple query/response model over
bidirectional connections that allows a single node - the querier
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- to measure the loss or delay of both directions of the
connection.
o The LM and DM protocols use query messages to measure the loss or
delay of a unidirectional connection. The measurement can either
be carried out at the downstream node(s) or at the querier if an
out-of-band return path is available.
o The LM and DM protocols do not require that the transmit and
receive interfaces be the same at an endpoint of a bidirectional
connection.
o The DM protocol is stateless.
o The LM protocol is "almost" stateless: loss is computed as a delta
between successive messages, and thus the data associated with the
last message received must be retained.
o The LM protocol provides perfect loss measurement if the necessary
implementation support is available.
o The LM protocol supports both 32-bit and 64-bit packet counters.
o The DM protocol supports multiple timestamp formats, and provides
a simple means for the two endpoints of a bidirectional connection
to agree on a preferred format. This procedure reduces to a
triviality for implementations supporting only a single timestamp
format.
o The DM protocol supports varying the measurement message size in
order to measure delays associated with different packet sizes.
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1.3. Terminology
Term Definition
------- ------------------------------------------
ACH Associated Channel Header
DM Delay Measurement
G-ACh Generic Associated Channel
LM Loss Measurement
LSE Label Stack Entry
LSP Label Switched Path
LSR Label Switching Router
MPLS-TP MPLS Transport Profile
NTP Network Time Protocol
OAM Operations, Administration and Maintenance
PTP Precision Time Protocol
PW Pseudowire
TC Traffic Class
2. Overview
The basic procedures for measuring loss and delay over a
bidirectional connection are conceptually simple. The following
figure shows the reference scenario.
T1 T2
+-------+/ Query \+-------+
| | - - - - - - - - ->| |
| A |===================| B |
| |<- - - - - - - - - | |
+-------+\ Response /+-------+
T4 T3
Figure 1
The figure shows a bidirectional connection between two nodes, A and
B, and illustrates the temporal reference points T1-T4 associated
with a measurement operation that takes place at A. The operation
consists of A sending a query message to B, and B sending back a
response. Each reference point indicates the point in time at which
either the query or the response message is transmitted or received
over the connection.
In this situation, A can arrange to measure the packet loss over the
connection in the forward and reverse directions by sending Loss
Measurement (LM) query messages to B each of which contains the count
of packets transmitted prior to time T1 over the connection to B
(A_TxP). When the message reaches B, it appends two values and
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reflects the message back to A: the count of packets received prior
to time T2 over the connection from A (B_RxP), and the count of
packets transmitted prior to time T3 over the connection to A
(B_TxP). When the response reaches A, it appends a fourth value, the
count of packets received prior to time T4 over the connection from B
(A_RxP).
These four counter values enable A to compute the desired loss
statistics. Because the transmit count at A and the receive count at
B (and vice versa) may not be synchronized at the time of the first
message, and to limit the effects of counter wrap, the loss is
computed in the form of a delta between messages.
To measure at A the delay over the connection to B, a Delay
Measurement (DM) query message is sent from A to B containing a
timestamp recording the instant at which it is transmitted, i.e. T1.
When the message reaches B, a timestamp is added recording the
instant at which it is received (T2). The message can now be
reflected from B to A, with B adding its transmit timestamp (T3) and
A adding its receive timestamp (T4). These four timestamps enable A
to compute the one-way delay in each direction, as well as the two-
way delay for the connection. The one-way delay computations require
that the clocks of A and B be synchronized; mechanisms for clock
synchronization are outside the scope of this document.
In the case of a unidirectional connection rooted at A, the first
half of each of the above procedures can be carried out to measure
the forward one-way loss and delay associated with the connection.
At this point the measurement can either take place at the terminal
node(s) of the connection rather than at A, or an out-of-band channel
can be used, if available, to communicate the data back to A.
In the context of MPLS-TP, LM and DM messages flow over the Generic
Associated Channel (G-ACh) [RFC5586] of an MPLS-TP pseudowire, LSP,
or Section. The term "connection" is used in this document to mean
"pseudowire, LSP, or Section". Although this document often speaks
of "measuring the loss or delay associated with a connection" for
simplicity, LM and DM actually occur with respect to a particular
class of packets flowing over a connection. This is discussed in
more detail in Section 5.
2.1. Implementation Considerations
The challenge in carrying out the above procedures lies with the
implementation. For accurate loss measurement to occur, packets must
not be sent between the time the transmit count for an outbound LM
message is determined and the time the message is actually
transmitted. Similarly, packets must not be received and processed
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between the time an LM message is received and the time the receive
count for the message is determined. For accurate delay measurement,
timestamps must be recorded in DM messages at a point in time as
close as possible to when the message is actually transmitted or
received over the connection.
These accuracy requirements imply that a hardware-based forwarding
implementation may require hardware support for the processing of LM
and DM messages. An important consideration of the LM/DM protocol
and message format is therefore support for efficient hardware
processing.
In situations where such accuracy is not required, or the necessary
level of support is not available, an implementation MAY still
generate and respond to LM and DM messages but SHOULD make its
accuracy limitations clear to the user. In general the DM procedures
described in this document remain viable under these conditions, but
the procedures for LM may be inadequate.
The LM procedures described in this document have the advantage of
providing perfect packet loss accounting if the necessary
implementation support is available. This is a desirable capability
in an LM protocol for MPLS-TP given that loss levels for typical
MPLS-TP connections are expected to be quite low, and that even small
amounts of loss on such connections may be unacceptable. This
capability, however, may well come at the expense of more costly
hardware, and in some environments this cost may be prohibitive.
Thus it is desirable to define an additional set of LM procedures for
MPLS-TP that support deployments in which perfect loss accounting is
not required. Such alternative procedures rely on the generation of
either existing or new MPLS-TP OAM message types, which are subjected
to loss accounting as a proxy for user traffic in order to infer
approximate loss levels of the latter. This alternative approach to
LM is for further study and will be described in a companion
document.
2.2. Packet Loss Measurement
Suppose a bidirectional connection such as an MPLS-TP pseudowire,
bidirectional LSP, or Section exists between the LSRs A and B. The
objective is to measure at A the following two quantities associated
with the connection:
A_TxLoss (transmit loss): the number of packets transmitted by A
over the connection but not received at B;
A_RxLoss (receive loss): the number of packets transmitted by B
over the connection but not received at A.
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This is accomplished by initiating a Loss Measurement (LM) operation
at A, which consists of transmission of a sequence of LM query
messages (LM[1], LM[2], ...) over the connection at a specified rate,
such as one every 100 milliseconds. Each message LM[n] contains the
following value:
A_TxP[n]: the total count of packets transmitted by A over the
connection prior to the time this message is transmitted.
When such a message is received at B, the following value is recorded
in the message:
B_RxP[n]: the total count of packets received by B over the
connection at the time this message is received (excluding the
message itself).
At this point, B inserts an appropriate response code into the
message and transmits it back to A, recording within it the following
value:
B_TxP[n]: the total count of packets transmitted by B over the
connection prior to the time this response is transmitted.
When the message response is received back at A, the following value
is recorded in the message:
A_RxP[n]: the total count of packets received by A over the
connection at the time this response is received (excluding the
message itself).
The transmit loss A_TxLoss[n-1,n] and receive loss A_RxLoss[n-1,n]
within the measurement interval marked by the messages LM[n-1] and
LM[n] are computed by A as follows:
A_TxLoss[n-1,n] = (A_TxP[n] - A_TxP[n-1]) - (B_RxP[n] - B_RxP[n-1])
A_RxLoss[n-1,n] = (B_TxP[n] - B_TxP[n-1]) - (A_RxP[n] - A_RxP[n-1])
where the arithmetic is modulo the counter size.
The derived values
A_TxLoss = A_TxLoss[1,2] + A_TxLoss[2,3] + ...
A_RxLoss = A_RxLoss[1,2] + A_RxLoss[2,3] + ...
are updated each time a response to an LM message is received and
processed, and represent the total transmit and receive loss over the
connection since the LM operation was initiated.
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When computing the values A_TxLoss[n-1,n] and A_RxLoss[n-1,n] the
possibility of counter wrap must be taken into account. Consider for
example the values of the A_TxP counter at times n-1 and n. Clearly
if A_TxP[n] is allowed to wrap to 0 and then beyond to a value equal
to or greater than A_TxP[n-1], the computation of an unambiguous
A_TxLoss[n-1,n] value will be impossible. Therefore the LM message
rate MUST be sufficiently high, given the counter size and the speed
and minimum packet size of the underlying connection, that this
condition cannot arise. For example, a 32-bit counter for a 100 Gbps
link with a minimum packet size of 64 bytes can wrap in 2^32 /
(10^11/(64*8)) = ~22 seconds, which is therefore an upper bound on
the LM message interval under such conditions.
2.3. Delay Measurement
Suppose a bidirectional connection such as an MPLS-TP pseudowire,
bidirectional LSP, or Section exists between the LSRs A and B. The
objective is to measure at A one or more of the following quantities
associated with the connection:
o The one-way delay associated with the forward (A to B) direction
of the connection;
o The one-way delay associated with the reverse (B to A) direction
of the connection;
o The two-way delay (A to B to A) associated with the connection.
In the case of two-way delay, there are actually two possible metrics
of interest. The "strict" two-way delay is the sum of the one-way
delays in each direction and reflects the two-way delay of the
connection itself, irrespective of processing delays within the
remote endpoint B. The "loose" two-way delay is the definition of
two-way delay stated in Section 1.1.2 and includes in addition any
delay associated with remote endpoint processing.
Measurement of the one-way delay quantities requires that the clocks
of A and B be synchronized, whereas the two-way delay can be measured
directly even when this is not the case (provided A and B have stable
clocks).
The measurement is accomplished by sending a Delay Measurement (DM)
query message over the connection to B which contains the following
timestamp:
T1: the time the DM query message is transmitted from A.
When the message arrives at B, the following timestamp is recorded in
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the message:
T2: the time the DM query message is received at B.
At this point B inserts an appropriate response code into the message
and transmits it back to A, recording within it the following
timestamp:
T3: the time the DM response message is transmitted from B.
When the message arrives back at A, the following timestamp is
recorded in the message:
T4: the time the DM response message is received back at A.
At this point, A can compute the strict two-way delay associated with
the connection as
strict two-way delay = (T4 - T1) - (T3 - T2)
and the loose two-way delay as
loose two-way delay = T4 - T1.
If the clocks of A and B are known at A to be synchronized, then both
one-way delay values, as well as the strict two-way delay, can be
computed at A as
forward one-way delay = T2 - T1
reverse one-way delay = T4 - T3
strict two-way delay = forward delay + reverse delay.
2.3.1. Timestamp Format
There are two significant timestamp formats in common use: the
timestamp format of the Internet standard Network Time Protocol
(NTP), described in [RFC1305] and [RFC2030], and the timestamp format
used in the IEEE 1588 Precision Time Protocol (PTP) [IEEE1588].
[Editor's note: There are actually two PTP timestamp formats: the
1588v1 format consists of a 32-bit seconds field and a 32-bit
nanoseconds field; in 1588v2 the seconds field was extended to 48
bits.]
The NTP format has the advantages of wide use and long deployment in
the Internet, and was specifically designed to make the computation
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of timestamp differences as simple and efficient as possible. On the
other hand, there is also now a significant deployment of equipment
designed to support the PTP format.
The approach taken in this document is therefore to include in DM
messages fields which identify the timestamp formats used by the two
devices involved in a DM operation. This implies that an LSR
attempting to carry out a DM operation may be faced with the problem
of computing with and possibly reconciling different timestamp
formats. Support for multiple timestamp formats is OPTIONAL. An
implementation SHOULD, however, make clear which timestamp formats it
supports and the extent of its support for computation with and
reconciliation of different formats for purposes of delay
measurement.
In recognition of the wide deployment, particularly in hardware-based
timing implementations, of IEEE 1588 PTP, the PTP timestamp format is
the default format used in DM messages. This format MUST be
supported.
2.4. Delay Variation Measurement
Packet Delay Variation [RFC3393] is another performance metric
important in some applications. The PDV of a pair of packets within
a stream of packets is defined for a selected pair of packets in the
stream going from measurement point MP1 to measurement point MP2.
The PDV is the difference between the one-way delay of the selected
packets.
A PDV measurement can therefore be derived from successive delay
measurements obtained through the procedures in Section 2.3. An
important point regarding PDV measurement, however, is that it can be
carried out based on one-way delay measurements even when the clocks
of the two systems involved in those measurements are not
synchronized.
2.5. Unidirectional Connections
In the case that the connection from A to (B1, ..., Bk) is
unidirectional, i.e. is a unidirectional LSP, LM and DM measurements
can be carried out at B1, ..., Bk instead of at A.
For LM this is accomplished by initiating an LM operation at A and
carrying out the same procedures as for bidirectional connections,
except that no responses from B1, ..., Bk to A are generated.
Instead, each terminal node B uses the A_TxP and B_RxP values in the
LM messages it receives to compute the receive loss associated with
the connection in essentially the same way as described previously,
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i.e.
B_RxLoss[n-1,n] = (A_TxP[n] - A_TxP[n-1]) - (B_RxP[n] - B_RxP[n-1])
For DM, of course, only the forward one-way delay can be measured and
the clock synchronization requirement applies.
Alternatively, if an out-of-band connection from a terminal node B
back to A is available, the LM and DM message responses can be
communicated to A via this connection so that the measurements can be
carried out at A.
2.6. Distributed Systems
The overview of the bidirectional measurement process presented in
Section 2 is also applicable when the transmit and receive interfaces
at A or B differ from one another, as may occur when the connection
is an MPLS-TP LSP that is not co-routed. Some additional
considerations, however, do apply in this case:
o If the transmit and receive interfaces reside on different line
cards, the clocks of those line cards must be synchronized in
order to compute the two-way delay.
o The DM protocol specified in this document requires that the
timestamp formats used by the interfaces that receive a DM query
and transmit a DM response agree.
o The LM protocol specified in this document supports both 32-bit
and 64-bit counter sizes, but the use of 32-bit counters at any of
the up to four interfaces involved in an LM operation will result
in 32-bit LM calculations for both directions of the connection.
[Editor's note: The last two restrictions could be relaxed if
desired, at the expense of some additional protocol complexity.]
3. Packet Format
Loss Measurement and Delay Measurement messages flow over the Generic
Associated Channel (G-ACh) [RFC5586] of an MPLS-TP connection
(pseudowire, LSP or Section).
[Editor's note: The question of ACH TLV usage and the manner of
supporting metadata such as authentication keys and node identifiers
is deliberately omitted. These issues will be addressed in a future
version of the document.]
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3.1. Loss Measurement Message Format
The format of a Loss Measurement message, beginning with the
Associated Channel Header (ACH), 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | 0xHH (MPLS-TP Loss) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Flags | Control Code | Session Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Counter 1 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Counter 4 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Loss Measurement Message Format
The meanings of the fields following the ACH are summarized in the
following table.
Field Meaning
--------------------- -----------------------------------------------
Version Protocol version
Flags Message control flags
Control Code Code identifying the query or response type
Session Identifier Set arbitrarily by the querier
Sequence Number 64-bit sequence number, incremented for each
message
Counter 1-4 Packet counter values in network byte order
The possible values for these fields are as follows.
Version: Currently set to 0.
Flags: Each bit represents a message control flag. The flags, listed
in left-to-right (most- to least-significant-bit) order, are:
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Q/R: Set to 0 for a Query and 1 for a Response.
X: Extended data format. Indicates support for extended (64-bit)
counter values. Initialized to 1 upon creation (and prior to
transmission) of an LM Query and copied from an LM Query to an LM
response. Set to 0 when the LM message is transmitted or received
over an interface that writes 32-bit counter values.
Remaining bits: Reserved for future specification and set to 0.
Control Code: Set as follows according to whether the message is a
Query or a Response as identified by the Q/R flag.
For a Query:
0x0: Query (in-band response requested). Indicates that this
query has been sent over a bidirectional connection and the
response is expected over the same connection.
0x1: Query (out-of-band response requested). Indicates that
the response should be sent via an out-of-band channel.
0x2: Query (no response requested). Indicates that no response
to the query should be sent.
For a Response:
0x1: Success. Indicates that the operation was successful.
0x8: Notification - Data Format Invalid. Indicates that the
query was processed but the format of the data fields in this
response may be inconsistent. Consequently these data fields
MUST NOT be used for measurement.
0x10: Error - Unspecified Error. Indicates that the operation
failed for an unspecified reason.
0x11: Error - Unsupported Version. Indicates that the
operation failed because the protocol version supplied in the
query message is not supported.
0x12: Error - Unsupported Control Code. Indicates that the
operation failed because the Control Code requested an
operation that is not available for this connection.
0x13: Error - Authentication Failure. Indicates that the
operation failed because the authentication data supplied in
the query was missing or incorrect.
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0x14: Error - Invalid Source Node Identifier. Indicates that
the operation failed because the Source Node Identifier
supplied in the query is not expected.
0x15: Error - Invalid Destination Node Identifier. Indicates
that the operation failed because the Destination Node
Identifier supplied in the query is not the identifier of this
node.
0x16: Error - Connection Mismatch. Indicates that the
operation failed because the connection identifier supplied in
the query did not match the connection over which the query was
received.
0x17: Error - Query Rate Exceeded. Indicates that the
operation failed because the rate of query messages exceeded
the configured threshold.
0x18: Error - Administrative Block. Indicates that the
operation failed because it has been administratively
disallowed.
0x19: Error - Temporary Resource Exhaustion. Indicates that
the operation failed because node resources were not available.
Session Identifier: Set arbitrarily in a query and copied in the
response, if any.
Counter 1-4: Referring to Section 2.2, when a query is sent from A,
Counter 1 is set to A_TxP and the other counter fields are set to 0.
When the query is received at B, Counter 2 is set to B_RxP. At this
point, B copies Counter 1 to Counter 3 and Counter 2 to Counter 4,
and re-initializes Counter 1 and Counter 2 to 0. When B transmits
the response, Counter 1 is set to B_TxP. When the response is
received at A, Counter 2 is set to A_RxP. All counter values MUST be
in network byte order.
When a 32-bit counter value is written to one of the counter fields,
that value SHALL be written to the low-order 32 bits of the field;
the high-order 32 bits of the field MUST, in this case, be set to 0.
3.2. Delay Measurement Message Format
The format of a Delay Measurement message, beginning with the
Associated Channel Header (ACH), is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | 0xHH (MPLS-TP Delay) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Flags | Control Code | Session Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Length | QTF | RTF | RPTF | Resv |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp 1 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp 4 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Padding ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Delay Measurement Message Format
The meanings of the fields following the ACH are summarized in the
following table.
Field Meaning
--------------------- -------------------------------------------
Version Protocol version
Flags Message control flags
Control Code Code identifying the query or response type
Session Identifier Set arbitrarily by the querier
Message Length Total length of this message in bytes
QTF Querier timestamp format
RTF Responder timestamp format
RPTF Responder's preferred timestamp format
Resv (Reserved) Reserved for future specification
Timestamp 1-4 64-bit timestamp values
Padding Optional padding
The possible values for these fields are as follows.
Version: Currently set to 0.
Flags: As specified in Section 3.1.
Control Code: As specified in Section 3.1.
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Session Identifier: Set arbitrarily in a query and copied in the
response, if any.
Message Length: Set to the total length of this message, excluding
the ACH, in bytes.
Querier Timestamp Format: The format of the timestamp values written
by the querier, as specified in Section 3.3.
Responder Timestamp Format: The format of the timestamp values
written by the responder, as specified in Section 3.3.
Responder's Preferred Timestamp Format: The timestamp format
preferred by the responder, as specified in Section 3.3.
Resv (Reserved): Currently set to 0.
Timestamp 1-4: Referring to Section 2.3, when a query is sent from A,
Timestamp 1 is set to T1 and the other timestamp fields are set to 0.
When the query is received at B, Timestamp 2 is set to T2. At this
point, B copies Timestamp 1 to Timestamp 3 and Timestamp 2 to
Timestamp 4, and re-initializes Timestamp 1 and Timestamp 2 to 0.
When B transmits the response, Timestamp 1 is set to T3. When the
response is received at A, Timestamp 2 is set to T4. The actual
formats of the timestamp fields written by A and B are indicated by
the Querier Timestamp Format and Responder Timestamp Format fields
respectively.
Padding: One or more octets of padding may optionally follow the
Timestamp 4 field in a query, in order to allow for delay measurement
based on packets of a particular size. The value of the first octet
of padding provides information about the padding. If in a Query the
first bit of the first pad octet is 1, the padding SHALL be copied to
the response, assuming one was requested. If this bit is 0, the
response MUST NOT include padding. The remaining bits in the first
pad octet are reserved and SHALL be set to 0. The values of the
remaining pad octets, if present, are arbitrary.
3.3. Timestamp Field Formats
The following timestamp format field values are specified in this
document:
0x0: Network Time Protocol version 4 timestamp format [RFC2030].
This format consists of a 32-bit seconds field followed by a 32-
bit fractional seconds field, so that it can be regarded as a
fixed-point 64-bit quantity.
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0x2: IEEE 1588-2002 (1588v1) Precision Time Protocol timestamp
format [IEEE1588]. This format consists of a 32-bit seconds field
followed by a 32-bit nanoseconds field.
In recognition of the wide deployment, particularly in hardware-based
timing implementations, of IEEE 1588 PTP, the PTP timestamp format is
the default format used in Delay Measurement messages. This format
MUST be supported. Support for other timestamp formats is OPTIONAL.
Timestamp formats of n < 64 bits in size SHALL be encoded in the 64-
bit timestamp fields specified in this document using the n high-
order bits of the field. The remaining 64 - n low-order bits in the
field SHOULD be set to 0 and MUST be ignored when reading the field.
4. Operation
4.1. Loss Measurement Procedures
4.1.1. Initiating a Loss Measurement Operation
An LM operation for a particular MPLS-TP connection consists of
sending a sequence (LM[1], LM[2], ...) of LM query messages over the
connection at a specific rate and processing the responses received,
if any. As described in Section 2.2, the packet loss associated with
the connection during the operation is computed as a delta between
successive messages; these deltas can be accumulated to obtain a
running total of the packet loss for the connection.
The query message transmission rate MUST be sufficiently high, given
the LM message counter size (which can be either 32 or 64 bits) and
the speed and minimum packet size of the underlying connection, that
the ambiguity condition noted in Section 2.2 cannot arise. The
implementation SHOULD assume, in evaluating this rate, that the
counter size is 32 bits unless explicitly configured otherwise, or
unless (in the case of a bidirectional connection) all local and
remote interfaces involved in the LM operation are known to be 64-
bit-capable, which can be inferred from the value of the X flag in an
LM response.
4.1.2. Transmitting a Loss Measurement Query
When transmitting an LM Query over an MPLS-TP connection, the Version
and Reserved fields MUST be set to 0. The Q/R flag MUST be set to 0.
The X flag MUST be set to 1 if the transmitting interface writes 64-
bit LM counters, and otherwise MUST be set to 0 to indicate that 32-
bit counters are written. The remaining flag bits MUST be set to 0.
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The Control Code field MUST be set to one of the values for Query
messages listed in Section 3.1; if the connection is unidirectional,
this field MUST NOT be set to 0x0 (Query: in-band response
requested).
The Session Identifier field can be set arbitrarily.
The Sequence Number field MUST be set to 0 for the first message sent
after device initialization or explicit reset, and incremented by 1
for each subsequent message sent.
The Counter 1 field SHOULD be set to the total count of packets
transmitted over the connection prior to this LM Query. The
remaining Counter fields MUST be set to 0.
4.1.3. Receiving a Loss Measurement Query
Upon receipt of an LM Query message, the Counter 2 field SHOULD be
set to the total count of packets received over the connection prior
to this LM Query. If the receiving interface writes 32-bit LM
counters, the X flag MUST be set to 0.
At this point the LM Query message must be inspected. If the Control
Code field is set to 0x2 (no response requested), an LM Response
message MUST NOT be transmitted. If the Control Code field is set to
0x0 (in-band response requested) or 0x1 (out-of-band response
requested), then an in-band or out-of-band response, respectively,
SHOULD be transmitted unless this has been prevented by an
administrative, security or congestion control mechanism.
4.1.4. Transmitting a Loss Measurement Response
When constructing a Response to an LM Query, the Version and Reserved
fields MUST be set to 0. The Q/R flag MUST be set to 1. The the X
flag MUST be set to 0 if the transmitting interface writes 32-bit LM
counters; otherwise its value MUST be copied from the LM Query. The
remaining flag bits MUST be set to 0.
The Session Identifier and Sequence Number fields MUST be copied from
the LM Query. The Counter 1 and Counter 2 fields from the LM Query
MUST be copied to the Counter 3 and Counter 4 fields, respectively,
of the LM Response.
The Control Code field MUST be set to one of the values for Response
messages listed in Section 3.1. The value 0x10 (Unspecified Error)
SHOULD NOT be used if one of the other more specific error codes is
applicable.
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If the response is transmitted in-band, the Counter 1 field SHOULD be
set to the total count of packets transmitted over the connection
prior to this LM Response. If the response is transmitted out-of-
band, the Counter 1 field MUST be set to 0. In either case, the
Counter 2 field MUST be set to 0.
4.1.5. Receiving a Loss Measurement Response
Upon in-band receipt of an LM Response message, the Counter 2 field
SHOULD be set to the total count of packets received over the
connection prior to this LM Response. If the receiving interface
writes 32-bit LM counters, the X flag MUST be set to 0.
Upon out-of-band receipt of an LM Response message, the Counter 1 and
Counter 2 fields MUST NOT be used for purposes of loss measurement.
If the Control Code in an LM Response is anything other than 0x1
(Success), the counter values in the response MUST NOT be used for
purposes of loss measurement. When the Control Code indicates an
error condition, the LM operation SHOULD be suspended and an
appropriate notification to the user generated. If a temporary error
condition is indicated, the LM operation MAY be restarted
automatically.
4.1.6. Loss Calculation
Calculation of packet loss is carried out according to the procedures
in Section 2.2. The X flag in an LM message informs the device
performing the calculation whether to perform 32-bit or 64-bit
arithmetic. If the flag value is equal to 1, all interfaces involved
in the LM operation have written 64-bit counter values, and 64-bit
arithmetic can be used. If the flag value is equal to 0, at least
one interface involved in the operation has written a 32-bit counter
value, and 32-bit arithmetic is carried out using the low-order 32
bits of each counter value.
4.1.7. Message Loss and Packet Misorder Conditions
Because an LM operation consists of a message sequence with state
maintained from one message to the next, LM is subject to the effects
of lost messages and misordered packets in a way that DM is not.
Because this state exists only on the querier, the handling of these
conditions is, strictly speaking, a local matter. This section,
however, presents RECOMMENDED procedures for handling such
conditions.
The first kind of anomaly that may occur is that one or more LM
messages may be lost in transit. The effect of such loss is that
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when an LM Response is next received at the querier, an unambiguous
interpretation of the counter values it contains may be impossible,
for the reasons described at the end of Section 2.2. Whether this is
so depends on the number of messages lost and the other variables
mentioned in that section, such as the LM message rate and the
connection parameters.
Another possibility is that LM messages are misordered in transit, so
that for instance the response to LM[n] is received prior to the
response to LM[n-1]. A typical implementation will discard the late
response to LM[n-1], so that the effect is the same as the case of a
lost message.
Finally, LM is subject to the possibility that data packets are
misordered relative to LM messages. This condition can result, for
example, in a transmit count of 100 and a corresponding receive count
of 101. The effect here is that the A_TxLoss[n-1,n] value (for
example) for a given measurement interval will appear to be extremely
(if not impossibly) large. The other case, where an LM message
arrives earlier than some of the packets, simply results in those
packets being counted as lost, which is usually what is desired.
[Editor's note: Text to be added here about handling the above
conditions with sequence numbers and thresholds.]
4.2. Delay Measurement Procedures
4.2.1. Transmitting a Delay Measurement Query
When transmitting a DM Query over an MPLS-TP connection, the Version
and Reserved fields MUST be set to 0. The Q/R flag MUST be set to 0
and the remaining flag bits MUST be set to 0.
The Control Code field MUST be set to one of the values for Query
messages listed in Section 3.1; if the connection is unidirectional,
this field MUST NOT be set to 0x0 (Query: in-band response
requested).
The Session Identifier field can be set arbitrarily.
The Querier Timestamp Format field MUST be set to the timestamp
format used by the querier when writing timestamp fields in this
message; the possible values for this field are listed in
Section 3.3. The Responder Timestamp Format and Responder's
Preferred Timestamp Format fields MUST be set to 0.
The Timestamp 1 field SHOULD be set to the time at which this DM
Query is transmitted, in the format indicated by the Querier
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Timestamp Format field. The other timestamp fields MUST be set to 0.
One or more pad octets MAY follow the Timestamp 4 field, as described
in Section 3.2.
4.2.2. Receiving a Delay Measurement Query
Upon receipt of a DM Query message, the Timestamp 2 field SHOULD be
set to the time at which this DM Query is received.
At this point the DM Query message must be inspected. If the Control
Code field is set to 0x2 (no response requested), a DM Response
message MUST NOT be transmitted. If the Control Code field is set to
0x0 (in-band response requested) or 0x1 (out-of-band response
requested), then an in-band or out-of-band response, respectively,
SHOULD be transmitted unless this has been prevented by an
administrative, security or congestion control mechanism.
4.2.3. Transmitting a Delay Measurement Response
When constructing a Response to a DM Query, the Version and Reserved
fields MUST be set to 0. The Q/R flag MUST be set to 1 and the
remaining flag bits MUST be set to 0.
The Session Identifier and Querier Timestamp Format (QTF) fields MUST
be copied from the DM Query. The Timestamp 1 and Timestamp 2 fields
from the DM Query MUST be copied to the Timestamp 3 and Timestamp 4
fields, respectively, of the DM Response.
The Responder Timestamp Format (RTF) field MUST be set to the
timestamp format used by the responder when writing timestamp fields
in this message, i.e. Timestamp 4 and (if applicable) Timestamp 1;
the possible values for this field are listed in Section 3.3.
Furthermore, the RTF field MUST be set equal either to the QTF or the
RPTF field. See Section 4.2.5 for guidelines on selection of the
value for this field.
The Responder's Preferred Timestamp Format (RPTF) field MUST be set
to one of the values listed in Section 3.3 and SHOULD be set to
indicate the timestamp format with which the responder can provide
the best accuracy for purposes of delay measurement.
The Control Code field MUST be set to one of the values for Response
messages listed in Section 3.1. The value 0x10 (Unspecified Error)
SHOULD NOT be used if one of the other more specific error codes is
applicable.
If the response is transmitted in-band, the Timestamp 1 field SHOULD
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be set to the time at which this DM Response is transmitted. If the
response is transmitted out-of-band, the Timestamp 1 field MUST be
set to 0. In either case, the Timestamp 2 field MUST be set to 0.
If the response is transmitted in-band and the Control Code in the
message is 0x1 (Success), then the Timestamp 1 and Timestamp 4 fields
MUST have the same format, which will be the format indicated in the
Responder Timestamp Format field.
Padding SHALL be included in the response if, and only if, padding
was present in the DM Query and the first bit of the first octet of
that padding was set to 1, in which case the response padding MUST be
identical to the query padding.
4.2.4. Receiving a Delay Measurement Response
Upon in-band receipt of a DM Response message, the Timestamp 2 field
SHOULD be set to the time at which this DM Response is received.
Upon out-of-band receipt of a DM Response message, the Timestamp 1
and Timestamp 2 fields MUST NOT be used for purposes of delay
measurement.
If the Control Code in a DM Response is anything other than 0x1
(Success), the timestamp values in the response MUST NOT be used for
purposes of delay measurement. When the Control Code indicates an
error condition, an appropriate notification to the user SHOULD be
generated.
4.2.5. Timestamp Format Negotiation
In case either the querier or the responder in a DM transaction is
capable of supporting multiple timestamp formats, it is desirable to
determine the optimal format for purposes of delay measurement on a
particular connection. The procedures for making this determination
SHALL be as follows.
Upon sending an initial DM Query over a connection, the querier sets
the Querier Timestamp Format (QTF) field to its preferred timestamp
format.
Upon receiving any DM Query message, the responder determines whether
it is capable of writing timestamps in the format specified by the
QTF field. If so, the Responder Timestamp Format (RTF) field is set
equal to the QTF field. If not, the RTF field is set equal to the
Responder's Preferred Timestamp Format (RPTF) field.
The process of changing from one timestamp format to another at the
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responder may result in the Timestamp 1 and Timestamp 4 fields in an
in-band DM Response having different formats. If this is the case,
the Control Code in the response MUST NOT be set to 0x1 (Success).
Unless an error condition has occurred, the Control Code MUST be set
to 0x2 (Notification - Data Format Invalid).
Upon receiving a DM Response, the querier knows from the RTF field in
the message whether the responder is capable of supporting its
preferred timestamp format: if it is, the RTF will be equal to the
QTF. The querier also knows the responder's preferred timestamp
format from the RPTF field. The querier can then decide whether to
retain its current QTF or to change it and repeat the negotiation
procedures.
4.2.5.1. Single-Format Procedures
When an implementation supports only one timestamp format, the
procedures above reduce to the following simple behavior:
o All DM Queries are transmitted with the same QTF;
o All DM Responses are transmitted with the same RTF, and the RPTF
is always set equal to the RTF;
o All DM Responses received with RTF not equal to QTF are discarded;
o On a unidirectional connection, all DM Queries received with QTF
not equal to the supported format are discarded.
5. Packet Profiles and Quality of Service
Although this document has referred, for simplicity, to measuring the
packet loss or delay associated with a connection, it is more precise
to say that these measurement operations occur with respect to a
specific class of packets transiting the connection. Such a class is
referred to as a "packet profile".
Care must be taken to ensure that the endpoints of an LM or DM
operation agree on the packet profile. For DM this reduces to
ensuring that query and response messages are assigned to the same
traffic class, while for LM it requires that the LM counters at each
endpoint count the same kinds of packets.
This document considers two aspects of packet profile support
pertinent to loss and delay measurement:
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o Quality of Service
o Loss Measurement of OAM Messages
5.1. Quality of Service
For connections that support multiple traffic classes, such as those
that employ the Traffic Class (TC) field [RFC5462] in the MPLS Label
Stack Entry (LSE) for Differentiated Services [RFC3270], the
implementation MUST provide the capability to perform delay
measurement on a per-traffic-class basis, by assigning the DM
messages themselves to the corresponding class.
For connections that support multiple traffic classes, the
implementation SHOULD provide the capability to perform loss
measurement on a per-traffic-class basis, and MAY provide the more
general capability to perform loss measurement on a subset of the
traffic classes supported by the connection, by restricting the LM
packet profile (i.e. the class of packets counted by the LM counters)
accordingly. LM messages themselves SHOULD be assigned to a traffic
class equal to or better than the best traffic class within the LM
packet profile.
5.2. Loss Measurement of OAM Messages
By default the LM packet profile MUST include packets transmitted and
received over the Generic Associated Channel (G-ACh) associated with
a connection. An implementation MAY provide the means to alter the
LM packet profile to exclude some or all G-ACh messages.
6. Congestion Considerations
An MPLS-TP network may be traffic-engineered in such a way that the
bandwidth required both for client traffic and for control,
management and OAM traffic is always available. The following
congestion considerations therefore apply only when this is not the
case.
The proactive generation of Loss Measurement and Delay Measurement
messages for purposes of monitoring the performance of an MPLS-TP
connection naturally results in a degree of additional load placed on
both the network and the terminal nodes of the connection. When
configuring such monitoring, operators should be mindful of the
overhead involved and should choose transmit rates that do not stress
network resources unduly; such choices must be informed by the
deployment context. In case of slower links or lower-speed devices,
for example, lower Loss Measurement message rates can be chosen, up
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to the limits noted at the end of Section 2.2.
In general, lower measurement message rates place less load on the
network at the expense of reduced granularity. For delay measurement
this reduced granularity translates to a greater possibility that the
delay associated with a connection temporarily exceeds the expected
threshold without detection. For loss measurement, it translates to
a larger gap in loss information in case of exceptional circumstances
such as lost LM messages or misordered packets.
When carrying out a sustained measurement operation such as an LM
operation or continuous pro-active DM operation, the querier SHOULD
take note of the number of lost measurement messages (queries for
which a response is never received) and set a corresponding
Measurement Message Loss Threshold. If this threshold is exceeded,
the measurement operation SHOULD be suspended so as not to exacerbate
the possible congestion condition. This suspension SHOULD be
accompanied by an appropriate notification to the user so that the
condition can be investigated and corrected.
From the receiver perspective, the main consideration is the
possibility of receiving an excessive quantity of measurement
messages. An implementation SHOULD employ a mechanism such as rate-
limiting to guard against the effects of this case. Authentication
procedures can also be used to ensure that only queries from
authorized devices are processed.
7. Security Considerations
There are two main types of security considerations associated with
the exchange of performance monitoring messages such as those
described in this document: the possibility of a malicious or
misconfigured device generating an excessive quantity of messages,
causing service impairment; and the possibility of an unauthorized
device learning the data contained in or implied by such messages.
The first consideration is discussed in Section 6. If reception of
performance-related data by unauthorized devices is an operational
concern, message authentication procedures such as those described in
[xref] should be used to ensure that only queries from authorized
devices are processed.
8. IANA Considerations
A future version of this document will detail IANA considerations
for:
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o ACH Channel Types for LM and DM messages
o Timestamp format registry
o LM and DM Control Codes
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
and S. Ueno, "Requirements of an MPLS Transport Profile",
RFC 5654, September 2009.
[RFC5860] Vigoureux, M., Ward, D., and M. Betts, "Requirements for
Operations, Administration, and Maintenance (OAM) in MPLS
Transport Networks", RFC 5860, May 2010.
9.2. Informative References
[I-D.ietf-mpls-tp-framework]
Bocci, M., Bryant, S., Frost, D., Levrau, L., and L.
Berger, "A Framework for MPLS in Transport Networks",
draft-ietf-mpls-tp-framework-12 (work in progress),
May 2010.
[IEEE1588]
IEEE, "1588-2008 IEEE Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems", March 2008.
[RFC1305] Mills, D., "Network Time Protocol (Version 3)
Specification, Implementation", RFC 1305, March 1992.
[RFC2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
for IPv4, IPv6 and OSI", RFC 2030, October 1996.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
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Packet Loss Metric for IPPM", RFC 2680, September 1999.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999.
[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, May 2002.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, February 2009.
Authors' Addresses
Dan Frost (editor)
Cisco Systems
Email: danfrost@cisco.com
Stewart Bryant (editor)
Cisco Systems
Email: stbryant@cisco.com
Frost & Bryant Expires December 31, 2010 [Page 30]
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