Network Working Group S. Shalunov Internet Draft Internet2 Expiration Date: January 2002 B. Teitelbaum Advanced Network & Services and Internet2 July 2001 A One-way Active Measurement Protocol Requirements 1. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft shadow directories can be accessed at http://www.ietf.org/shadow.html This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. 2. Abstract With growing availability of good time sources to network nodes, it becomes increasingly possible to measure one-way IP performance metrics with high precision. To do so in an interoperable manner, a common protocol for such measurements is required. This document specifies requirements for a one-way active measurement protocol (OWAMP) standard. The protocol can measure one-way delay, as well as unidirectional characteristics such as one-way loss and others. Shalunov and Teitelbaum [Page 1] INTERNET-DRAFT One-way Delay Protocol Requirements July 2001 3. Motivations and Goals The IETF IP Performance Metrics (IPPM) working group has proposed draft standard metrics for one-way packet delay [RFC2679] and loss [RFC 2680] across Internet paths. Although there are now several measurement platforms that implement the collection of these metrics ([CQOS], [BRIX], [RIPE], [SURVEYOR]), there is not currently a standard for interoperability. With the increasingly wide availability of affordable global positioning system (GPS) and CDMA based time sources, hosts increasingly have available to them very accurate time sources--either directly or through their proximity to NTP primary (stratum 1) time servers. By standardizing a technique for collecting IPPM one-way active measurements, we hope to create an environment where these metrics may be collected across a far broader mesh of Internet paths than is currently possible. One particularly compelling vision is of widespread deployment of open one-way active measurement beacons that would make measurements of one-way delay as commonplace as measurements of round-trip time are today using ICMP- based tools like ping. To support interoperability between alternative OWDP implementations and make possible a world where "one-way ping" could become commonplace, a standard is required that specifies how test streams are initiated, how test packets are exchanged, and how test results are retrieved. Detailed functional requirements are given in the subsequent section. 4. Functional Requirements The protocol(s) should provide ability to measure, record, and distribute the results of measurements of one-way singleton network characteristics such as characteristics defined in [RFC2679] and [RFC2680]. It should be possible to measure arbitrary one-way singleton characteristics (e.g., loss, average delay, mean delay, jitter, 90th percentile of delay, etc.). Since RFC2679 and RFC2680 standardize on Poisson streams of test packets, Poisson streams at least should be supported. Non-singleton characteristics (such as those related to trains of packets, back-to-back tuples, and so forth) and application traffic simulation aren't areas that the protocol(s) need to address. Shalunov and Teitelbaum [Page 2] INTERNET-DRAFT One-way Delay Protocol Requirements July 2001 4.1. Keeping All Data for Post-processing To facilitate the broadest possible use of obtained measurement results, the protocol(s) should not necessitate any required post- processing. All data obtained during a measurement session should be available after it is finished if desired by endpoint so that various characteristics can be computed from the raw data using arbitrary algorithms. 4.2. Result Distribution A means to distribute measurement results (between hosts participating in a measurement session and beyond) should be provided. Since there can exist a wide variety of scenarios as to where the final data destination should be, these should be invoked separately from measurement requests (e.g., receiver should not have to automatically send measurement results to the sender, since it may be the receiver or a third host that are the ultimate data destination). At the same time, ability to transfer results directly to their destination (without need for potentially large intermediate transfers) should be provided. 4.3. Protocol Separation Since measurement session setup and the actual measurement session (i) are different tasks; (ii) require different levels of functionality, flexibility, and implementation effort; (iii) may need to run over different transport protocols, there should exist different protocols for conducting the actual measurement session on one side and for session setup/teardown/confirmation/retrieval on the other. These protocols are further referred to as OWDP-Test and OWDP-Control, respectively. It should be possible to use devices that only support OWDP-Test but not OWDP-Control to conduct measurement sessions (such devices will necessarily need to support one form of session setup protocol or the other, but it doesn't have to be known to external parties). OWDP-Control would thus become a common protocol for different domains, which may or may not use it for session setup internally. Shalunov and Teitelbaum [Page 3] INTERNET-DRAFT One-way Delay Protocol Requirements July 2001 4.4. Test Protocol The test protocol needs to be implemented on all measurement nodes and should therefore have the following characteristics: + Be lightweight and easy to implement. + Be suitable for implementation on a wide range of measurement nodes. + Since the protocol needs to be able to measure individual packet delivery time and has to run on various machines, it needs to support UDP as transport protocol. + It should be possible to use varying packet sizes and network services, as negotiated using OWDP-Control. + To be a lowest common denominator, OWDP-Test packet format should only include universally meaningful fields, and minimum number of them. + It should be possible to make packets generated by OWDP-Test as small as possible, to be able to accurately measure paths where packet-splitting technologies such as ATM are used. 4.5. Control Protocol Control protocol needs to provide abilities to: + authenticate peers to each other using a common authentication method that doesn't require building any new authentication infrastructure, such as user ID and a shared secret; + schedule zero or more OWDP-Test sessions (which do not have to be between the peers of OWDP-Control conversation); + start sessions simultaneously or at a pre-scheduled per-session times; + retrieve OWDP-Test session results (of OWDP-Test sessions scheduled in the current and other OWDP-Control sessions); + confirm graceful completion of session or abort them prematurely (for both sides). Shalunov and Teitelbaum [Page 4] INTERNET-DRAFT One-way Delay Protocol Requirements July 2001 The OWDP-Control design should not preclude the ability to record extended periods of losses. It should provide peers with the ability to always distinguish between network and peer failures. 5. Scalability While some measurement architecture designs have inherent scalability problems (e.g., a full mesh of always-on measurements among N measurement nodes requires O(N^2) total resources, such as storage space and link capacity), OWDP itself should not exaggerate the problem or make it impossible (where it is in principle possible) to design other architectures that are free of scalability deficiencies. 6. Security Considerations 6.1. Being Hard to Detect The design of the protocol should make it possible to run sessions that would make it very difficult for any intermediate party to make results appear better than they would be if no interference was attempted. 6.2. Secrecy/Confidentiality It should be possible to make it infeasible for any outside party without knowledge of shared secret being used to learn what information is exchanged using OWDP-Control by inspecting OWDP- Control stream or by actively modifying it. (It is recognized that some information will inevitably leak from the mere fact of communication and from presence and timing of concurrent and subsequent OWDP-Test traffic.) 6.3. Authentication It should be possible to authenticate peers to each other using a user ID and a shared secret. It should be infeasible for any external party without knowledge of the shared secret to obtain any information about it by observing, initiating, or modifying protocol transactions. It should also be infeasible for such party to use any information obtained by observing, modifying or initiating protocol transactions Shalunov and Teitelbaum [Page 5] INTERNET-DRAFT One-way Delay Protocol Requirements July 2001 to impersonate (other) valid users. 6.4. Integrity Facility to authenticate each message of the control protocol and their exact sequence and attribution to a given session has to be provided, so that any interference during a conversation (other than detention of some messages) can be detected. Facility to authenticate each message of the test protocol and its attribution to a specific session has to be provided, so that modifications of OWDP-Test messages can be detected. Facility to do the latter in such a way that timestamps themselves aren't encrypted and security properties are only valid for an attacker that cannot observe valid traffic between OWDP-Test sender and receiver has to be provided. 6.5. Modes of Operation Since the protocol(s) will be used in widely varying circumstances using widely varying equipment, it is necessary to have more than one mode of operation security-wise. A mode that is completely "open" (an unauthenticated mode) should be provided, where no security mechanisms are used. A mode where all security mechanisms are enabled and security objectives are realized to fullest extent possible (an encrypted mode) should be provided. Since timestamp encryption takes certain time, which may be hard to predict on some devices (with a time-sharing OS), a mode similar to encrypted mode, but where timestamps aren't encrypted, should be provided. In said mode, all security properties of encrypted mode that can be retained without timestamp encryption should be present. 7. IANA Considerations Relevant IANA considerations will be placed into the protocol specification document itself, and not into the requirements document. Shalunov and Teitelbaum [Page 6] INTERNET-DRAFT One-way Delay Protocol Requirements July 2001 8. References [BRIX] Brix 1000 Verifier, http://www.brixnet.com/products/brix1000.html [CQOS] CQOS Home Page, http://www.cqos.com/ [RFC2679] G. Almes, S. Kalidindi, and M. Zekauskas, "A One-way Delay Metric for IPPM", RFC 2679, September 1999. [RFC2680] G. Almes, S. Kalidindi, and M. Zekauskas, "A One-way Packet Loss Metric for IPPM", RFC 2680, September 1999. [RIPE] RIPE NCC Test-Traffic Measurements home, http://www.ripe.net/test-traffic/ [SURVEYOR] Surveyor Home Page, http://www.advanced.org/surveyor/ 9. Authors' Addresses Stanislav Shalunov Internet2 200 Business Park Drive Armonk, NY 10504 USA Phone: +1 914 765 1182 EMail: shalunov@internet2.edu Benjamin Teitelbaum Advanced Network & Services 200 Business Park Drive Armonk, NY 10504 USA Phone: +1 914 765 1118 EMail: ben@advanced.org Expiration date: January 2002 Shalunov and Teitelbaum [Page 7]