Rate Measurement Problem Statement
draft-morton-ippm-rate-problem-01

Abstract

There is a rate measurement scenario which has wide-spread attention of users and seemingly all industry participants, including regulators. This memo presents an access rate-measurement problem statement for IP Performance Metrics. Key aspects require the ability to control packet size on the tested path and enable asymmetrical packet size testing in a controller-responder architecture.

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/.

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This Internet-Draft will expire on July 15, 2012.

Copyright Notice

Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

• 1. Introduction
• 2. Purpose and Scope
• 3. Active Rate Measurement
• 4. Test Protocol Control & Generation Requirements
• 5. Security Considerations
• 6. IANA Considerations
• 7. Acknowledgements
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Author's Address

1. Introduction

There are many possible rate measurement scenarios. This memo describes one rate measurement problem and presents a rate-measurement problem statement for IP Performance Metrics (IPPM).

The access-rate scenario or use case has wide-spread attention of users and seemingly all industry participants, including regulators. It is being approached with many different measurement methods.

2. Purpose and Scope

The scope and purpose of this memo is to define the measurement problem statement for access rate measurement. We characterize this scenario as follows:

• Rates at the edge of the network are several orders of magnitude less than aggregation and core portions.
• Asymmetrical ingress and egress rates are prevalent.
• Extremely large scale of access services requires low complexity devices participating at the user end of the path.

Today, the majority of widely deployed access services achieve rates less than 100 Mbit/s, and this is the rate-regime for which a solution is sought now.

This problem statement assumes that the most-likely bottleneck device or link is adjacent to the remote (user-end) measurement device, or is within one or two router/switch hops of the remote measurement device.

Other use cases for rate measurement involve situations where the packet switching and transport facilities are leased by one operator from another and the actual capacity available cannot be directly determined (e.g., from device interface utilization). These scenarios could include mobile backhaul, Ethernet Service access networks, and/or extensions of a layer 2 or layer 3 networks. The results of rate measurements in such cases could be employed to select alternate routing, investigate whether capacity meets some previous agreement, and/or adapting the rate of certain traffic sources if a capacity bottleneck is found via the rate measurement. In these cases, the tester is assumed to have a sender and receiver location under their control. We refer to this scenario below as the aggregated leased network case.

Only active measurement methods will be addressed here, consistent with the IPPM working group's current charter. Active measurements require synthetic traffic dedicated to testing, and do not use user traffic.

It is a non-goal to solve the measurement protocol specification problem in this memo.

3. Active Rate Measurement

This section lists features of active measurement methods needed to measure access rates in production networks.

Test coordination between Src and Dst devices through control messages, and other basic capabilities described in the methods of IPPM RFCs [RFC2679][RFC2680] are taken as given (these could be listed later, if desired).

One key tenant of IPPM methods is to minimize test traffic effects on user traffic in the production network. Section 5 of [RFC2680] lists the problems with high measurement traffic rates, and the most relevant for rate measurement is the tendency for measurement traffic to skew the results, followed by the possibility to introduce congestion on the access link. Obviously, methods that use less active test traffic than others with similar accuracy SHALL be preferred.

The measurement architecture MAY be either of one-way (e.g., [RFC4656]) or two-way (e.g., [RFC5357]), but the scale and complexity aspects of end-user or aggregated access measurement clearly favor two-way. However, the asymmetric rates of many access services means that the measurement system MUST be able to assess each direction of transmission separately. In the case of aggregated leased networks, available capacity may also be asymmetric. In the two-way architecture, it is expected that both directions of transmission MAY affect the ability to launch streams or collect the results of measurements (this has always been true, it is not a unique problem for rate measurements).

The following paragraphs describe features for the roles of test packet SENDER, RECEIVER, and results REPORTER.

SENDER:

Ability to generate streams of test packets with various characteristics as desired. The SENDER may be located at the user end of the access path, or may be located elsewhere in the production network, such as at one end of an aggregated leased network segment.

1. Variable payload lengths among packet streams
2. Variable stream length among packet streams
3. Variable header markings among packet streams
4. others?

RECEIVER:

Ability to collect streams of test packets with various characteristics (as described above), and make the measurements necessary to support rate measurement at the other end of an end-user access or aggregated leased network segment.

REPORTER:

Ability to use information from test packets and local processes to measure delivered packet rates.

4. Test Protocol Control & Generation Requirements

Essentially, the test protocol MUST support the measurement features described in Section 3. This REQUIRES:

1. Communicating all test variables to the Sender and Receiver
2. Results collection in a one-way architecture
3. Remote device control for a two-way architecture
4. Asymmetric and/or pseudo-one-way test capability in a two-way measurement architecture

5. Security Considerations

The security considerations that apply to any active measurement of live networks are relevant here as well. See [RFC4656] and [RFC5357].

[QUESTION: Is there an additional consideration if there is a legal SLA involved with the access network segment provider to make sure this information is not leaked?]

6. IANA Considerations

This memo makes no requests of IANA.

7. Acknowledgements

Dave McDysan provided comments and text for the aggregated leased use case.

8. References

8.1. Normative References

8.2. Informative References

Author's Address