Network Working Group Y. Kikuchi Internet-Draft Kochi University of Technology Intended status: Informational S. Matsushima Expires: January 8, 2008 Softbank Telecom Corp. K. Nagami Intec Netcore Inc. S. Uda Japan Advanced Institute of Science and Technology July 07, 2007 Quality Measurement Requirements for Tunneling Protocols draft-kikuchi-tunnel-measure-req-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 Internet-Draft will expire on January 8, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Kikuchi, et al. Expires January 8, 2008 [Page 1] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 Abstract This draft describes the necessary requirements to passively measure the quality of end-to-end tunnels and to monitor them via applicable ways. This feature is crucial for Service Providers (SPs), especially, who provide transports to users using tunnels. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 2. Service Model . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. General Requirements . . . . . . . . . . . . . . . . . . . . . 6 4.1. Active vs. Passive . . . . . . . . . . . . . . . . . . . . 6 4.2. Quality Evaluation . . . . . . . . . . . . . . . . . . . . 6 4.3. Getting Quality Information . . . . . . . . . . . . . . . 6 4.4. Overhead Consideration . . . . . . . . . . . . . . . . . . 7 5. Requirements with Sequence Numbering . . . . . . . . . . . . . 8 5.1. Indication of Sequence Number . . . . . . . . . . . . . . 8 5.2. Field Length . . . . . . . . . . . . . . . . . . . . . . . 8 6. An Example . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Kikuchi, et al. Expires January 8, 2008 [Page 2] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 1. Introduction This draft describes the necessary requirements to passively measure the quality of end-to-end tunnels passively and to monitor them via some applicable ways. In this document, tunnel refers to the various technologies used to provide networks or datalinks virtually. Examples of tunneling are GRE [2], IP Encapsulation within IP (IPIP) [3], and Pseudo Wire Emulation Edge-to-Edge (PWE3) [4]. Measuring end-to-end quality of tunnels is necessary for Transport Service Providers (TSPs) who provide transport to users using tunnels. However, the standards do not define the measurement and monitoring of a network, which is helpful when TSPs want to know the quality of their traffic through tunnels. Therefore, measurement and monitoring standards need to be defined. 1.1. Requirements notation 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 [1]. Kikuchi, et al. Expires January 8, 2008 [Page 3] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 2. Service Model Figure 1 shows that TSP X provides a transport between user A and user B using a tunnel. The users construct an application over the transport. The TSP may apply two or more tunnels to provide one transport. USER A USER B | | + ................... Application .................. + | | LAN A ---* ........ Transport by TSP X ........ *--- LAN B | | --- ISP 1 --- ISP 2 --- ... --- ISP n --- Figure 1: A Service Model of TSP TSPs provide a reachability of IP datagrams or layer 2 frames to users. Typically users are not able to identify the path details, that is the sequence of transit ISPs, under the transport because the tunnel eliminates the path so that the users must recognize that both ends of the transport as a neighbor. In addition, TSPs may be able to provide better transports when the TSPs have several tunnels via different paths. Furthermore, TSPs may be able to provide protocols needed by the users even if there are no such protocols served by the ISPs. TSPs provide simplified and virtual transports by hiding the underlying layers from the users. The users are able to reduce the cost of operation and management because they need not maintain the underlying layers. The reachability maintenance and the quality management are served as TSPs' communication services. There must be a Service Level Agreement (SLA) in the contract between a TSP and its user. The SLA specifies the level that the TSP must maintain, which is a set of measurable characteristics such as the total unavailable time in a month, maximum out-of-sequence rates and some qualities for real time applications. Kikuchi, et al. Expires January 8, 2008 [Page 4] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 3. Motivations TSPs need to know the quality of their tunnels in order to know whether the tunnels are in a normal state or not. The measured quality could be an important information to trace down the cause of the trouble when an applications is not working properly. Without the necessary information, it is difficult for TSPs to determine whether problems come from the user, the TSP itself, or the ISPs. TSPs also need to know the tunnels' quality when they have multiple tunnels to serve transports. TSPs may be able to serve appropriate transports to users by selecting better quality tunnels. In addition, the TSPs may be able to distribute the load of a transport to different path tunnels. The tunnel quality measurement is specially needed by TSPs because they have SLAs to their customers. They must be aware of the status of underlying tunnels well and must report it as an evidence of quality for the users. This is the reason why the quality should be measured not for regular traffic in general but for tunnel traffic. Kikuchi, et al. Expires January 8, 2008 [Page 5] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 4. General Requirements This section describes each requirement necessary to measure end-to- end tunnel quality for TSPs. 4.1. Active vs. Passive There are two ways to measure the quality of a tunnel, one is active and the other is passive. Active measurement uses additional probing packets to determine the quality of the channel. Passive measurement uses the traffic packets to measure quality. From the TSPs point of view, passive measurement SHOULD be supported. SLAs should refer to the users' packets themselves, therefore, the measurement should be determined passively rather than actively. On the other hand, it is not necessary to let the protocol have a quality measurement function with active measurement. TSPs can construct the active measurement method independently from the target protocol. A typical example is PING, which uses Internet Control Message Protocol (ICMP) [5]. 4.2. Quality Evaluation The standard that define a passive measurement of a tunnelling protocol MUST contain two items, one is `WHAT' type of quality the protocol measure, and the other is `HOW' the protocol evaluate the quality. It is REQUIRED to detect whether the packets in a tunnel are in- sequence or out-of-sequence. It SHOULD measure loss, duplication and reordering. It MAY support to measure delay and/or jitter of packets' arrivals of a tunnel. It is RECOMMENDED to disable the measurement function for avoiding the measurement overhead in case when TSPs need not to measure the tunnel quality. See also the discussion in the section Section 4.4. 4.3. Getting Quality Information Tunneling protocols MUST support monitoring when the protocols have quality measurement functions. The protocol MUST define how to monitor the result of the quality measurement of tunnels, such as SNMP [6]. In addition, it MAY modify parameters used in the measurement mechanisms by TSPs' operators. Moreover, it MAY notify exceptional situations and illegal operations to the operators. Kikuchi, et al. Expires January 8, 2008 [Page 6] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 4.4. Overhead Consideration Protocol designers SHOULD take into account the computing and space costs of the implementations where the standard defines the measurement and monitoring. This includes overhead of traffic transmission, which may reflect the cost of equipment introductions and operational expenses. The designers SHOULD not adopt non- scalable mechanisms and SHOULD pay particular attention to resource consumption sensitive protocols such as mobile protocols. The types of overheads are as follows. o the space of additional information in protocol header, o the time of sending and receiving the information above, and o the computing resources for quality measurement implemented in routers. We should adopt a simplified determination in some cases when both a precise complex determination and a simpler one exist. For example, when we do not need a precise state but rather an approximation of the degree of the difference from the normal operation. Kikuchi, et al. Expires January 8, 2008 [Page 7] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 5. Requirements with Sequence Numbering Some tunnelling protocols have sequence number fields in the header. It is easy for the protocols with sequence numbers to introduce some of those functions above by watching the continuity. A simple method is proposed in [7]. In this section, we describes the requirements for such the protocols. 5.1. Indication of Sequence Number The protocol MUST indicate whether sequence numbering is enabled or not. There are two ways to indicate whether the sequence numbers are enabled or not. One is to prepare an indication field in the header independent from the sequence number field. The other is to indicate a special sequence number, typically 0, meaning disabled. In this case, the measurement process needs additional steps on wrapping sequence number overflow because the sequence number will skip 0 that does not seem continuous even if the tunnel packets are still in-sequence. 5.2. Field Length The length of sequence number field SHOULD be long enough according to the transmission speed. Otherwise, the period of a lap of the sequence number becomes too short and the reliability of the measurement decreases. For example, the algorithm may determine packets loss as reordering, when there is a set of burst packets loss in case of the path change. It is necessary to determine whether a burst packet loss occurred or if it was simply the arrival of a very past packet when the difference of the sequence numbers between two continuous packets is very large. The typical technique is to use half of the representable maximum value. This is simple and adequate if the field is long enough. However, the existence of the sequence number field generates more amount of transmission packets. Thus, if an insufficiently long field creates overhead for protocols that are sensitive to resource consumption. The sequence number field length should be considered as a tradeoff between bandwidth efficiency and quality assurance. Kikuchi, et al. Expires January 8, 2008 [Page 8] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 6. An Example In this section, we discuss about an existing protocol to apply the requirement above. In an extreme case, IPIP does not have any extra field on encapsulation, therefore it is difficult to measure traffics passively. However many tunnelling protocols have some information in their headers such as GRE [8]. If a protocol has a sequence number field, it is easy to determine the tunnel is in-sequence or not. Moreover, it can recognize the reason such as loss, duplication and reordering. Because GRE has sequence numbers in their headers, they are possible to measure the qualities. If there is a timestamp in the header of a tunnelling protocol, even the timestamps might be synchronized to a reference clock, it can measure delay and jitter. For example, because GRE does not have such a feature, neither delay nor jitter can be measured. The GRE standard defines the sequence number field only for egress internal processing, which allows to discard out-of-sequence packets and/or to align the sequence with buffering. It should define how to get the quality information because there is no mechanism to inform the upper layer. About the overheads of the quality measurement of GRE tunnels, firstly it needs 32bits sequence number field in the GRE header. Secondly at least 4 32bits registers per tunnel are required in the GRE egress. The computing cost are in O(n) if the algorithm illustrated in [7] is adapted where n is the number of tunnels. Kikuchi, et al. Expires January 8, 2008 [Page 9] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 7. Security Considerations Fraud sequence numbers and time stamps cause the measurement process to become disorganized. This discussion boils down to the issues of the header protection. Kikuchi, et al. Expires January 8, 2008 [Page 10] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 Appendix A. Acknowledgements The authors would like to thank for helpful discussions in TEReCo research project sponsored in part by the ministry of internal affairs and communications Japan (SCOPE 072309007). Kikuchi, et al. Expires January 8, 2008 [Page 11] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 8. References 8.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 8.2. Informative References [2] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000. [3] Perkins, C., "IP Encapsulation within IP", RFC 2003, October 1996. [4] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005. [5] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981. [6] Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture for Describing Simple Network Management Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, December 2002. [7] Kikuchi, Y., "One-way Passive Measurement of End-to-End Quality", draft-kikuchi-passive-measure-00 (work in progress), July 2007. [8] Dommety, G., "Key and Sequence Number Extensions to GRE", RFC 2890, September 2000. Kikuchi, et al. Expires January 8, 2008 [Page 12] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 Authors' Addresses KIKUCHI Yutaka Kochi University of Technology 306B Research Collaboration Center 185 Miyanokuchi, Tosayamada-cho Kami-shi, Kochi 782-0003 JP Email: yu@kikuken.org MATSUSHIMA Satoru Softbank Telecom Corp. 1-9-1 Higashi-Shinbashi Minato-ku, Tokyo JP Email: satoru@ft.solteria.net NAGAMI Ken'ichi Intec Netcore Inc. 1-3-3 Shin-suna Koto-ku, Tokyo JP Phone: +81-3-5565-5069 Email: nagami@inetcore.com UDA Satoshi Japan Advanced Institute of Science and Technology Email: zin@jaist.ac.jp Kikuchi, et al. Expires January 8, 2008 [Page 13] Internet-Draft draft-kikuchi-tunnel-measure-req-01.txt July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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