wdiff draft-ietf-bier-pmmm-oam-05.txt draft-ietf-bier-pmmm-oam-06.txt

BIER Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Standards Track L. Zheng
Expires: June 13, 2019 January 2, 2020 M. Chen
Huawei Technologies
G. Fioccola
Telecom Italia
December 10, 2018
Huawei Technologies
July 1, 2019

Performance Measurement (PM) with Marking Method in Bit Index Explicit
Replication (BIER) Layer
draft-ietf-bier-pmmm-oam-05
draft-ietf-bier-pmmm-oam-06

Abstract

This document describes a hybrid performance measurement method for
multicast service over through a Bit Index Explicit Replication (BIER) domain.

Status of This Memo

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provisions of BCP 78 and BCP 79.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. OAM Field in BIER Header . . . . . . . . . . . . . . . . . . 3
4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 3 4
4.1. Single Mark Single-Marking Enabled Measurement . . . . . . . . . . . . . 4
4.2. Double Mark Double-Marking Enabled Measurement . . . . . . . . . . . 5
4.3. Operational Considerations . . 5 . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 6 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 8

1. Introduction

[RFC8279] introduces and explains the Bit Index Explicit Replication
(BIER) architecture and how it supports the forwarding of multicast
data packets. [RFC8296] specified that in the case of BIER
encapsulation in an MPLS network network, a BIER-MPLS label, the label that
is at the bottom of the label stack, uniquely identifies the
multicast flow. [RFC8321] describes a hybrid performance measurement
method, per [RFC7799] RFC7799's classification of measurement methods. methods
[RFC7799]. The method, called Packet Network Performance Monitoring
(PNPM), which can be used to measure packet loss, latency, and jitter on
live traffic. traffic complies with requirements #5 and #12 listed in
[I-D.ietf-bier-oam-requirements]. Because this method is based on
marking consecutive batches of packets packets, the method is often referred
to as
Marking Method (MM). a marking method.

This document defines how the marking method can be used on the BIER
layer to measure packet loss and delay metrics of a multicast flow in
an MPLS network.

2. Conventions used in this document
2.1. Terminology

BFR: Bit-Forwarding Router

BFER: Bit-Forwarding Egress Router

BFIR: Bit-Forwarding Ingress Router

BIER: Bit Index Explicit Replication

MM: Marking Method

OAM: Operations, Administration and Maintenance

2.2. 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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

3. OAM Field in BIER Header

[RFC8296] defined the two-bit two-bits long field, referred to as OAM,
designated for the marking performance measurement method. OAM. The
OAM field MUST NOT be used in defining forwarding and/or quality of
service treatment of a BIER packet. The OAM field MUST can be used only for the marking performance measurement of data traffic in BIER layer. method.
Because the setting of the field to any value does not affect
forwarding and/or quality of service treatment of a packet, using the
marking method
OAM field for PNPM in BIER layer can be viewed as the example of the
hybrid performance measurement method.

The

Figure 1 displays format the interpretation of the OAM field defined in this
specification for the use by PNPM method.

0
0 1
+-+-+-+-+
| L S | D |
+-+-+-+-+

Figure 1: OAM field of BIER Header format

where:

o L S - Loss Single-Marking flag;

o D - Delay Double-Marking flag.

4. Theory of Operation

The marking method can be successfully used in the multicast environment supported
by BIER layer. Without limiting any generality consider multicast
network presented in Figure 2. Any combination of
markings, Loss and/or Delay, markings can be
applied to a multicast flow by
any the Bit Forwarding Ingress Router (BFR)
(BFIR) at either ingress or egress point to perform node, link,
segment or end-to-end measurement to detect performance degradation
defect and localize it efficiently.

-----
--| D |
----- / -----
--| B |--
/ ----- \ -----
/ --| E |
----- / -----
| A |--- -----
----- \ --| F |
\ ----- / -----
--| C |--
----- \ -----
--| G |
-----

Figure 2: Multicast network

Using the marking method, a BFR BFIR creates distinct sub-flows in the
particular multicast traffic over BIER layer. Each sub-flow consists
of consecutive blocks, consisting blocks of identically marked packets. For example, a
block of N packets, that with each packet being marked as X, is followed
by the block of M packets with each packet being marked as Y. These
blocks are unambiguously recognizable by a monitoring point at any BFR
Bit Forwarding Router (BFR) and can be measured to calculate packet
loss and/or packet delay metrics. It is expected that the marking
values be set and cleared at the edge of BIER domain. Thus for the
scenario presented in Figure 2 if the operator initially monitors the
A-C-G and A-B-D segments he may enable measurements on segments C-F
and B-E at any time.

4.1. Single Mark Single-Marking Enabled Measurement

As explained in the [RFC8321], marking can be applied to delineate blocks
of packets based either on the equal number of packets in a block or
based on the equal time interval. The latter method offers better
control as it allows a better account for capabilities of downstream
nodes to report statistics related to batches of packets and, at the
same time, time resolution that affects defect detection interval.

If the Single Mark Single-Marking measurement is used to measure packet loss,
then the D flag MUST be set to zero on transmit and ignored by the
monitoring point.

The L S flag is used to create alternate flows sub-flows to measure the packet loss by
switching the value of the L S flag every N-th packet or at certain
time intervals. Delay metrics MAY be calculated with the
alternate flow sub-flow
using any of the following methods:

o First/Last Packet Delay calculation: whenever the marking, i.e. i.e.,
the value of L S flag changes, a BFR can store the timestamp of the
first/last packet of the block. The timestamp can be compared
with the timestamp of the packet that arrived in the same order
through a monitoring point at a downstream BFR to compute packet
delay. Because timestamps collected based on the order of arrival
this method is sensitive to packet loss and re-ordering of packets
(see Section 4.3 for more details).

o Average Packet Delay calculation: an average delay is calculated
by considering the average arrival time of the packets within a
single block. A BFR may collect timestamps for each packet
received within a single block. Average of the timestamp is the
sum of all the timestamps divided by the total number of packets
received. Then the difference between averages the average packet arrival
time calculated for the downstream monitoring point and the same
metric but calculated at two the upstream monitoring points point is the
average packet delay on that segment. the segment between these two points.
This method is robust to out of order packets and also to packet
loss (only on the segment between the measurement points (packet loss
may cause a small error minor loss of accuracy in the calculated metric
because the number of packets used is introduced). different at each
measurement point). This method only provides a single metric for
the duration of the block block, and it doesn't give the minimum and
maximum delay values. This limitation of producing only the
single metric could be overcome by reducing the duration of the block
by means of
block. As a highly optimized implementation result, the calculated value of the method. average delay
will better reflect the minimum and maximum delay values of the
block's duration time.

4.2. Double Mark Double-Marking Enabled Measurement

Double Mark

Double-Marking method allows measurement of minimum and maximum
delays for the monitored flow flow, but it requires more nodal and network
resources. If the Double Mark Double-Marking method used, then the L S flag MUST be is
used to create the alternate flow, i.e. sub-flow, i.e., mark larger batches blocks of packets. The D
flag MUST be is used to mark single packets within a block to measure delay
and jitter.

The first marking (L (S flag alternation) is needed for packet loss and
also for average delay measurement. The second marking (D flag is
put to one) creates a new set of marked packets that are fully
identified over the BIER network, so that a BFR can store the
timestamps of these packets; these timestamps can be compared with
the timestamps of the same packets on a second BFR to compute packet
delay values for each packet. The number of measurements can be
easily increased by changing the frequency of the second marking.
But On
the other hand, the higher frequency of the second marking must be not too high in order
to avoid out will cause
a higher volume of order issues. the measurement data being transported through the
BIER domain. An operator should consider and balance both effects.
This method is useful to measure not only the average delay but also
the minimum and maximum delay values and, in wider terms, to know
more about the statistic distribution of delay values.

4.3. Operational Considerations

For the ease of operational procedures, the initial marking of a
multicast flow is performed at BFIR. and cleared, by way of removing
BIER encapsulation form a payload packet, at the edge of the BIER
domain by BFERs.

Since at the time of writing this specification, there are no
proposals to using auto-discovery or signaling mechanism to inform
downstream nodes what methodology is used each monitoring point MUST
be configured beforehand.

Section 4.3 [RFC8321] provides a detailed analysis of how packet re-
ordering and the duration of the block in the Single-Marking mode of
the marking method impact the accuracy of the packet loss
measurement. Re-ordering of packets in the Single-Marking mode will
be noticeable only at the edge of a block of packets (re-ordering
within the block cannot be detected in the Single-Marking mode). If
the extra delay for some packets is much smaller than half of the
duration of a block, then it should be easier to attribute re-ordered
packets to the proper block and thus maintain the accuracy of the
packet loss measurement.

5. IANA Considerations

This document requests IANA to register format of the OAM field of
BIER Header as the following:

+--------------+---------+--------------------------+---------------+

+--------------+---------+-----------------+---------------+
| Bit Position | Marking | Description | Reference |
+--------------+---------+--------------------------+---------------+
+--------------+---------+-----------------+---------------+
| 0 | S | Single Mark Measurement Single-Marking | This document |
| 1 | D | Double Mark Measurement Double-Marking | This document |
+--------------+---------+--------------------------+---------------+
+--------------+---------+-----------------+---------------+

Table 1: OAM field of BIER Header

6. Security Considerations

This document list

Regarding using the marking method, [RFC8321] stressed two types of
security concerns. First, the potential harm caused by the
measurements, is a lesser threat as [RFC8296] defines OAM requirement for BIER-enabled domain field used
by the marking method so that the value of "two bits have no effect
on the path taken by a BIER packet and
does not raise any have no effect on the quality
of service applied to a BIER packet." Second security concerns or issues in addition concern,
potential harm to ones
common the measurements can be mitigated by using policy,
suggested in [RFC8296], to networking. accept BIER packets only from trusted
routers, not from customer-facing interfaces.

All the security considerations for BIER discussed in [RFC8296] are
inherited by this document.

7. Acknowledgement

TBD

8. References

8.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.

[RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate-Marking Method for Passive and Hybrid
Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
January 2018, <https://www.rfc-editor.org/info/rfc8321>.

8.2. Informative References

[I-D.ietf-bier-oam-requirements]
Mirsky, G., Nordmark, E., Pignataro, C., Kumar, N.,
Aldrin, S., Zheng, L., Chen, M., Akiya, N., and S.
Pallagatti, "Operations, Administration and Maintenance
(OAM) Requirements for Bit Index Explicit Replication
(BIER) Layer", draft-ietf-bier-oam-requirements-07 (work
in progress), February 2019.

[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.

[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.

Authors' Addresses

Greg Mirsky
ZTE Corp.

Email: gregimirsky@gmail.com

Lianshu Zheng
Huawei Technologies

Email: vero.zheng@huawei.com

Mach Chen
Huawei Technologies

Email: mach.chen@huawei.com
Giuseppe Fioccola
Telecom Italia
Huawei Technologies

Email: giuseppe.fioccola@telecomitalia.it giuseppe.fioccola@huawei.com