PSAMP WG Meeting Minutes IETF #54 July 16, 2002 110 people attending Minutes by Andy Bierman and Nick Duffield Minutes ------- The meeting started with a note from the Area Director that the PSAMP WG has been chartered and new WG Chairs were appointed just before and after the meeting (Andy Bierman and Juergen Quittek). The meeting was chaired by Nick Duffield, who will step down as WG Chair in order to remain an author of WG documents. Nick reviewed the goals of the WG. The major technical issues facing the WG are specifying packet selection operations, the choice of report format and protocol, and the choice of transport protocol. These issues were addressed in more detail, later in the meeting. Refer to the slides for more details on the goals of the PSAMP WG. Matt Grossglauser presented slides on transport issues and multiple measurement banks for sample collection. Multiple Measurement Banks: these enable multiple concurrent measurement tasks at different time and space scales. It is not envisaged that the WG would mandate a specific number of banks. Transport Reliability: The transport does not have to be reliable because loss of sample reports is not deemed to be important. Furthermore, requirements on exporters to support reliable transport would prevent ubiquitous adoption of PSAMP. The collector applications must know if samples have been lost, but should not rely on every sample being reported. Congestion Awareness: RFC 2914 specifies requirements for Internet protocols in order to prevent congestion collapse. The alternatives for PSAMP are to run over a congestion-aware transport or to control the sample report generator explicitly from a collector application, which would detect congestion (e.g. missing sample report packets) and send control messages to the appropriate sample report generator to reduce the sample rate and/or the export rate to that collector. Issues were raised in the meeting regarding the actual mechanism for this approach, the frequency and latency of the control messages, the protocol used, etc. These issues will have to be resolved by the WG over time. Loss of Connectivity: This can be handled by a heartbeat protocol operation, in which the sample export packets to a particular collector will be terminated if heartbeat packets from that report collector stop reaching the sample generator for a specific time period. The details are still TBD. Derek Chiou presented slides on hardware implementation of packet sampling technology. The purpose was to demonstrate that current hardware technology can support operations, including packet selection, currently under discussion in the WG, at a very high packet rate. An issue was raised that the PSAMP WG should specify functional requirements and not specify a particular implementation strategy. It was emphasized that these slides were intended to identify the general capabilities of current hardware technologies, not imply that a PSAMP implementation needed to be done using this approach. Refer to the slides for details on this issue. Matt Grossglauser presented slides on some potential applications of packet sampling technology. These include performance monitoring and troubleshooting. The sampling mechanisms need to be simple enough to be widely implemented. The load on network devices (not just additional traffic on the network) needs to be considered. Packet filtering techniques are important, to allow an application to focus in on a particular problem (e.g. set of protocols or group of host addresses). Hash-based sampling enables measurement of packet paths through the network, which is useful for both engineering and diagnostic purposes. Refer to the slides for more details on this topics. The potential relationship between PSAMP and RMON was brought up. The RMONMIB WG may choose to define a mechanism in the future to use PSAMP exported data as a data source for some RMON collection functions. No impact on the PSAMP WG is needed for this feature. The interaction between the PSAMP and IPFIX WGs was discussed. There is potential overlap in several areas, and it is hoped to avoid duplication of effort. In his presentation, Nick Duffield differentiated three areas of potential interaction: Packet Selection: a PSAMP device providing sampled packet input to IPFIX metering process; this motivates use of PSAMP sampling configuration and methods in the IPFIX information model. This has also been discussed in the IPFIX WG. Report Formation: There is potential for PSAMP to reuse the IPFIX information model for reporting. The PSAMP WG needs to determine its requirements for reporting, and the extent to which they could be supported within IPFIX. Members of both WGs would need to work together if a compatible reporting framework were to be adopted. Report Export: PSAMP's specific requirements for export, and the need for congestion awareness, can be supported by in the framework described by Matt Grossglauser. There may be different transport requirements for the two technologies, which need to be examined and resolved. The IPFIX WG has yet to select a congestion aware unreliable transport; when this choice is made it can be evaluated for PSAMP. There appears to be a sufficient number of people interested in both the IPFIX and PSAMP WGs to insure that these issues will be addressed during the development of PSAMP documents. Additional concerns about security, support for IPv6, and additional applications such as packet traceback were raised during the Q&A session. These issues (and others) will be addressed on the WG mailing list, during development of the WG documents.