Internet DRAFT - draft-fioccola-ippm-alt-mark-active
draft-fioccola-ippm-alt-mark-active
Network Working Group G. Fioccola
Internet-Draft Telecom Italia
Intended status: Informational A. Clemm
Expires: September 14, 2017 S. Bryant
Huawei
M. Cociglio
Telecom Italia
M. Chandramouli
Cisco Systems
A. Capello
Telecom Italia
March 13, 2017
Alternate Marking Extension to Active Measurement Protocol
draft-fioccola-ippm-alt-mark-active-01
Abstract
This document describes how to extend the existing Active Measurement
Protocol, in order to implement alternate marking methodology
detailed in [I-D.ietf-ippm-alt-mark]. The extension for Two-Way
Active Measurement Protocol (TWAMP) RFC 5357 [RFC5357] and One-way
Active Measurement Protocol (OWAMP) RFC 4656 [RFC4656] will be
considered. RFC6374 [RFC6374] Use Case is also reported. This
proposal defines a simplified mechanism with benefits to the metric
precision and computational load. Hybrid measurements are also
enabled.
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
Fioccola, et al. Expires September 14, 2017 [Page 1]
Internet-Draft Active Alternate Marking March 2017
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 September 14, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Description of the method . . . . . . . . . . . . . . . . . . 3
2.1. Packet loss measurement . . . . . . . . . . . . . . . . . 4
2.2. Delay measurement . . . . . . . . . . . . . . . . . . . . 5
2.3. Delay variation measurement . . . . . . . . . . . . . . . 6
3. Hybrid measurement . . . . . . . . . . . . . . . . . . . . . 6
4. Protocol Extension overview . . . . . . . . . . . . . . . . . 7
4.1. Control Phase . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Test Phase . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Calculation Phase . . . . . . . . . . . . . . . . . . . . 9
5. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Extension of TWAMP/OWAMP Control Protocol . . . . . . . . 10
5.2. Extension of TWAMP/OWAMP Test Protocol . . . . . . . . . 10
6. RFC6374 Use Case . . . . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
Fioccola, et al. Expires September 14, 2017 [Page 2]
Internet-Draft Active Alternate Marking March 2017
1. Introduction
The Two-Way Active Measurement Protocol (TWAMP), specified in RFC
5357 [RFC5357] adds two-way or round-trip measurement capabilities to
the One-way Active Measurement Protocol (OWAMP) specified in RFC 4656
[RFC4656]. OWAMP can be used bi-directionally to measure one-way
metrics in both directions between two network elements. The TWAMP
measurement architecture is usually comprised of two hosts with
specific roles, and this allows for some protocol simplifications,
making it an attractive alternative in some circumstances. Another
example is Cisco's Service-Level Assurance Protocol (Cisco's SLA
Protocol) RFC 6812 [RFC6812], a Performance Measurement protocol that
has been widely deployed. Details are explained in
[I-D.fioccola-ippm-rfc6812-alt-mark-ext].
One technique for passive performance measurements is described in
[I-D.ietf-ippm-alt-mark]. This technique involves marking production
flows as they traverse the network, then analyzing flow data
associated with those marked flows. Passive measurements are very
accurate in that they measure actual production traffic. However,
there are scenarios in which passive measurements are not an option.
For example, there may be no suitable flows currently occurring
between pairs of nodes to be measured, or traffic may be tunneled and
not be accessible to marking. Furthermore active measurements permit
a precise control of the monitored traffic than passive measurements.
So in such cases, active measurements using synthetic test traffic
need to be considered.
This document specifies how to implement active measurement with the
same techniqe described in [I-D.ietf-ippm-alt-mark]. Instead of time
stamping test traffic, test traffic is marked and measurements occur
by analyzing resulting flow data. There are some key aspects of the
mechanism described in this document to be considered:
o Improve metric precision: the packet timestamp can be take in an
more efficient way because it is not inserted within the Test
packet.
o Reduce computational load: no sequence numbers and no timestamps
within the Test packets.
o Enable hybrid measurements thanks to the Alternate Marking.
2. Description of the method
In order to perform packet loss, delay and jitter measurements on a
traffic flow, different approaches exist. The method proposed
consists in counting and timestamping the packets sent from one end,
Fioccola, et al. Expires September 14, 2017 [Page 3]
Internet-Draft Active Alternate Marking March 2017
the packets received on the other end, and compare the two values.
Therefore the devices performing the measurement have to refer
exactly to the same set of packets. So the flow is virtually spit in
consecutive blocks by coloring the packets so that the packets
belonging to the same block will have the same color, whilst
consecutive blocks will have different colors. Each change of color
represents a sort of auto-synchronization signal that guarantees the
consistency of measurements taken by different devices along the
path.
This approach, called Alternate Marking method, is efficient both for
passive performance monitoring and for active performance monitoring.
In this document we describe the implementation for Active
Measurement.
+----------------+ +-------------------+
| | | |
| Session-Sender | | Session-Reflector |
| |========================>| |
| |<========================| |
+----------------+ Traffic flow +-------------------+
. .
. .
<----------------------->
End-to-End Packet loss, Delay and Jitter
Figure 1: Available measurements
Previous Figure represents two end points (Session-Sender and
Session-Reflector) that exchange two equal data flows in both
direction. The data flows start and end together. Packets are
colored and the color changes every marking interval. The method can
be used to measure packet loss, delay and jitter.
2.1. Packet loss measurement
The basic idea is to virtually split traffic flows into consecutive
blocks: each block represents a measurable entity unambiguously
recognizable by all network devices along the path. By counting the
number of packets in each block and comparing the values measured by
Sender and Reflector, it is possible to measure packet loss occurred
in any single block between the two end points.
A simple way to create the blocks is to "color" the traffic (two
colors are sufficient) so that packets belonging to different
consecutive blocks will have different colors. Whenever the color
changes, the previous block terminates and the new one begins. The
number of packets in each block depends on the criterion used to
Fioccola, et al. Expires September 14, 2017 [Page 4]
Internet-Draft Active Alternate Marking March 2017
create the blocks: if the color is switched after a fixed number of
packets, then each block will contain the same number of packets
(except for any losses); but if the color is switched according to a
fixed timer, then the number of packets may be different in each
block depending on the packet rate.
2.2. Delay measurement
The same principle used to measure packet loss can be applied also to
one-way delay measurement. There are two alternatives, shown below:
o Delay for each packet: For active measurement two alternate
marking data flows are generated in both direction, so the
alternation of colors can be used as a time reference to calculate
the delay. Whenever the color changes (that means that a new
block has started) an end point can store the timestamps of all
packets of the new block. The timestamps can be compared with the
timestamps of the same packets on the other end point to compute
packet delay. This method for measuring the delay is sensitive to
out of order reception of packets. In order to overcome this
problem between packets there should be a security time gap to
avoid out of order issues. If the packet rate exchanged between
the two end points is adequate each end points can store all the
timestamp of the block and the packet delay can be computed for
all the packets of the block, included minimum, maximum, mean and
median delay values.
o Mean delay: A different approach, based on the concept of mean
delay, can be take in account for active measurement. The mean
delay is calculated by considering the average arrival time of the
packets within a single block. The network device locally stores
a timestamp for each packet received within a single block:
summing all the timestamps and dividing by the total number of
packets received, the average arrival time for that block of
packets can be calculated. By subtracting the average arrival
times of the two end points it is possible to calculate the mean
delay. This method is robust to out of order packets and also to
packet loss (only a small error is introduced). Moreover, it
greatly reduces the number of timestamps (only one per block for
each end point) that have to be collected and transmitted for the
calculation. On the other hand, it only gives one measure for the
duration of the block, and it doesn't give the minimum, maximum
and median delay values. RFC 6703 [RFC6703] recommends to report
both median and mean delay in order to obtain additional
information about the distribution. But the same procedure of the
mean delay is not applicable to median delay because the median is
not a linear operator. So the mean delay could be considered as a
light measurement because the calculation is achieved by
Fioccola, et al. Expires September 14, 2017 [Page 5]
Internet-Draft Active Alternate Marking March 2017
exchanging only the average timestamp for each colored block
(without exchanging all the timestamps). For this reason the mean
delay is not the main technique, but a secondary option in case we
have to save computational resources.
By summing the one-way delay measurements of the two directions of a
path, it is also possible to measure the two-way delay (round-trip
delay).
In brief, there are three choices to compute delay for active
measurement:
o The two end points could store all packets timestamps in both
directions. At the end of the period all timestamps are
exchanged. In this way, delay is calculated for each packet.
o The two end points calculate only the average timestamp that is
exchanged at the end of the period. In this way only the mean
delay is calculated.
o The two end points sent packets with a specified and shared
traffic profile and each end point could make its own calculation
(data are not exchanged so it is not so accurate, but it depends
on hardware and software capabilities).
Note: How data and timestamps are exchanged is outside the scope of
this document.
2.3. Delay variation measurement
Similarly to one-way delay measurement, the method can also be used
to measure the inter-arrival jitter. The alternation of colors can
be used as a time reference to measure delay variations. The inter-
arrival jitter can be easily derived from one-way delay measurement,
by evaluating the delay variation of consecutive samples.
The concept of mean delay can also be applied to delay variation, by
evaluating the variation of average interval between consecutive
packets of the flow.
3. Hybrid measurement
In order to have both end to end measurements and intermediate
measurements (hybrid measurements) Sender and Reflector exchanges
traffic flows and apply alternate marking over these flows. In the
intermediate points artificial traffic is managed in the same way as
real traffic and measured as specified before.
Fioccola, et al. Expires September 14, 2017 [Page 6]
Internet-Draft Active Alternate Marking March 2017
4. Protocol Extension overview
The Alternate Marking extension to Active Measurement Protocol like
OWAMP or TWAMP, consists of three distinct phases, Control Phase,
Test Phase and Calculation Phase.
The Control Phase is the first phase of message exchanges and forms
the base protocol. This phase establishes the identity of the Sender
and provides information for the Test Phase.
The Test Phase forms the second phase and is comprised of an exchange
of two equal alternate marking data flows between Sender and
Reflector. Sender and Reflector generate test traffic and apply
marking, no traffic is reflected and no timestamping is added to
packets.
The Calculation Phase is introduced "ad hoc" for Alternate Marking
implementation because it does not exist in other Active Measurement
Protocol. After test execution there are some alternatives to
compute packet loss, delay and delay variation:
o Local assessment: Sender initiates a Calculation Request message
and Reflector sends back a Calculation Response message. Sender
and Reflector, upon receipt test traffic, create data structure
with timestamped records then computes service level metrics from
that data structure. Let's call this data structure the test
receipt.
o Central assessment: A "central" entity (e.g. a controller)
compares the test receipt collected by the Reflector with data
structure obtained from the Sender, then computes the service
levels by means of comparing.
o Local assessment with reference recording: Both sender and
receiver play out the same test traffic. Assessment is done
locally not by computing metrics over the test receipt, but by
"overlaying" the original with the one that was received and
computing the delta.
The number and frequency with which messages are sent SHOULD be
controlled by configuration on the Sender element, along with the
waiting time for a Control Response.
The following sequence diagram depicts the message exchanges:
Fioccola, et al. Expires September 14, 2017 [Page 7]
Internet-Draft Active Alternate Marking March 2017
+-+-+-+-+-+-+-+ Control Request +-+-+-+-+-+-+-+
| | | |
| Sender | | Reflector |
| | | |
| | | |
+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+
| |
| Control Phase |
|<-------------------------------------------->|
| |
| |
| Test Phase |
|<============================================>|
| |
| |
| Calculation Phase |
|<-------------------------------------------->|
| |
To utilize existing Active Measurement Protocol, some extensions are
needed. The Sender indicates that alternate marking techniques are
to be used and that traffic is going to be marked. Likewise, it can
indicate to the Reflector to not simply reflect the marked traffic,
but to generate a separate stream of marked test traffic back to the
sender. The marking pattern will be conveyed (including the markings
to be used and duration of the marking intervals). The
implementation of measurements involves analyzing the marked traffic
as needed. Conveying of results of the analysis of observed traffic
occurs through separate means, not specified here.
4.1. Control Phase
The Control Phase consists of agreement between Sender and Reflector.
Only an extension to the exixting procols is needed. Please refer to
the guidelines defined in Section 3 of OWAMP RFC 4656 [RFC4656] TWAMP
RFC 5357 [RFC5357] or RFC 6812 [RFC6812].
4.2. Test Phase
Upon successing the Control Phase, the second phase of the protocol,
the Test Phase, is initiated. In the Test Phase the Sender sends a
stream of measurement messages. The measurement message stream
consists of packets/frames that are spaced a configured number of
milliseconds.
The Measurement messages is simplified in comparison to OWAMP RFC
4656 [RFC4656] TWAMP RFC 5357 [RFC5357] or RFC 6812 [RFC6812]. In
Fioccola, et al. Expires September 14, 2017 [Page 8]
Internet-Draft Active Alternate Marking March 2017
particular the fields that can be removed are: Sender Timestamp,
Receive Timestamp, Sequence Number.
The format of the Measurement messages is the same for the exchange
in both directions, that is when sent from the Sender to the
Reflector and from the Reflector to the Sender.
Note: Marking field can be chosen in two ways for OWAMP RFC 4656
[RFC4656] and TWAMP RFC 5357 [RFC5357]: marking Packet Padding or MBZ
fields.
Note: Marking field can be chosen for RFC 6812 [RFC6812] in two ways:
marking UDP payload or marking IPv4 header.
Note: No timestamp, No sequence number. The two data flows are
indipendent.
4.3. Calculation Phase
As mentioned above, the Calculation Phase is introduced "ad hoc" for
Alternate Marking implementation because it does not exist in OWAMP
RFC 4656 [RFC4656] TWAMP RFC 5357 [RFC5357] or RFC 6812 [RFC6812].
After test execution there are some alternatives to compute packet
loss, delay and delay variation:
o Local assessment: Sender initiates a Calculation Request message
and Reflector sends back a Calculation Response message. Sender
and Reflector, upon receipt test traffic, create data structure
with timestamped records then computes service level metrics from
that data structure. Let's call this data structure the test
receipt).
o Central assessment: A "central" entity (e.g. a controller)
compares the test receipt collected by the Reflector with data
structure obtained from the Sender, then computes the service
levels by means of comparing.
o Local assessment with reference recording: Both sender and
receiver play out the same test traffic. Assessment is done
locally not by computing metrics over the test receipt, but by
"overlaying" the original with the one that was received and
computing the delta.
5. Open Issues
Fioccola, et al. Expires September 14, 2017 [Page 9]
Internet-Draft Active Alternate Marking March 2017
5.1. Extension of TWAMP/OWAMP Control Protocol
to be added
5.2. Extension of TWAMP/OWAMP Test Protocol
to be added
6. RFC6374 Use Case
RFC6374 [RFC6374] uses the 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. [I-D.ietf-mpls-flow-ident] discusses the desired
capabilities for MPLS flow identification in order to perform a
better in-band performance monitoring of user data packets. A method
of accomplishing identification is Synonymous Flow Labels (SFL)
introduced in [I-D.bryant-mpls-sfl-framework].
[I-D.bryant-mpls-rfc6374-sfl] describes RFC6374 packet loss
measurement with SFL and is based on alternate marking methodology
for passive performance monitoring as described in the companion
document [I-D.ietf-ippm-alt-mark].
[I-D.bryant-mpls-rfc6374-sfl] describes also a valuable use case
about the application of alternate marking on existing Active
Measurement Protocol. RFC6374 [RFC6374] describes how to measure the
packet delay by measuring the transit time of an RFC6374 packet over
an LSP. The main motivation to use Marking method is that if 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.
7. IANA Considerations
IANA Considerations to be added.
8. Security Considerations
Security Considerations to be added.
9. Acknowledgements
Mauro Cociglio and Giuseppe Fioccola worked in part on the Leone
research project, which received funding from the European Union
Seventh Framework Programme [FP7/2007-2013] under grant agreement
number 317647.
Fioccola, et al. Expires September 14, 2017 [Page 10]
Internet-Draft Active Alternate Marking March 2017
10. References
10.1. Normative References
[I-D.bryant-mpls-rfc6374-sfl]
Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S.,
Mirsky, G., and G. Fioccola, "RFC6374 Synonymous Flow
Labels", draft-bryant-mpls-rfc6374-sfl-03 (work in
progress), October 2016.
[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-03 (work in progress), March
2017.
[I-D.fioccola-ippm-rfc6812-alt-mark-ext]
Fioccola, G., Clemm, A., Cociglio, M., Chandramouli, M.,
and A. Capello, "Alternate Marking Extension to Cisco SLA
Protocol RFC6812", draft-fioccola-ippm-rfc6812-alt-mark-
ext-01 (work in progress), March 2016.
[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.
[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>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<http://www.rfc-editor.org/info/rfc4656>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<http://www.rfc-editor.org/info/rfc5357>.
Fioccola, et al. Expires September 14, 2017 [Page 11]
Internet-Draft Active Alternate Marking March 2017
[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>.
[RFC6812] Chiba, M., Clemm, A., Medley, S., Salowey, J., Thombare,
S., and E. Yedavalli, "Cisco Service-Level Assurance
Protocol", RFC 6812, DOI 10.17487/RFC6812, January 2013,
<http://www.rfc-editor.org/info/rfc6812>.
10.2. Informative References
[RFC6703] Morton, A., Ramachandran, G., and G. Maguluri, "Reporting
IP Network Performance Metrics: Different Points of View",
RFC 6703, DOI 10.17487/RFC6703, August 2012,
<http://www.rfc-editor.org/info/rfc6703>.
Authors' Addresses
Giuseppe Fioccola
Telecom Italia
Via Reiss Romoli, 274
Torino 10148
Italy
Email: giuseppe.fioccola@telecomitalia.it
Alexander Clemm
Huawei
USA
Email: alexander.clemm@huawei.com
Stewart Bryant
Huawei
Email: stewart.bryant@gmail.com
Mauro Cociglio
Telecom Italia
Via Reiss Romoli, 274
Torino 10148
Italy
Email: mauro.cociglio@telecomitalia.it
Fioccola, et al. Expires September 14, 2017 [Page 12]
Internet-Draft Active Alternate Marking March 2017
Mouli Chandramouli
Cisco Systems
Email: moulchan@cisco.com
Alessandro Capello
Telecom Italia
Via Reiss Romoli, 274
Torino 10148
Italy
Email: alessandro.capello@telecomitalia.it
Fioccola, et al. Expires September 14, 2017 [Page 13]
