IP Flow Information Export Working S. Leinen Group SWITCH Internet-Draft July 12, 2004 Expires: January 10, 2005 IP Flow Information Export (IPFIX) Over TCP draft-leinen-ipfix-tcp-00 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 10, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This documents describes how the IP Flow Information Export (IPFIX) protocol should be mapped to the Transmission Control Protocol (TCP). 1. Introduction IP Flow Information Export (IPFIX) [1] is a protocol to convey accounting information from an exporter to a collector. It has been proposed that the protocol operate over the Stream Control Transmission Protocol [7] with the Partial Reliability extension Leinen Expires January 10, 2005 [Page 1] Internet-Draft IPFIX over TCP July 2004 (SCTP-PR) [8]. In this document, we specify an alternate mapping of IPFIX to TCP [2], which can be used when SCTP-PR isn't available, and reliable transmission and/or congestion handling are required. 2. OPEN ISSUES 2.1 Handshake Should we introduce a handshake sequence at the start of the connection? A simple ASCII-based handshake could be used to request TLS. 2.2 TLS It would make sense to add TLS support even in the absence of a handshake. It would be the responsibility of the collector (connection initiator) to know whether TLS setup is required. 2.3 Directionality The fact that the connection is initiated by the collector is a departure from the way it is done in the SCTP mapping. Personally I find it more natural this way. There are not very many practical differences anyway. Collector-initiated connections are easier to handle when the collector is behind a NAT or typical firewall, while exporter-initiated connections are easier when the exporter is behind a NAT or firewall. Collector-initiated connections are faster to restart when a collector terminates, exporter-initated connections are faster to restart when an exporter restarts. One difference is that in the case of multiple observation domains, one may want to establish parallel IPFIX export connections. The current definition makes this difficult. Perhaps the most natural way to do this would be to have the exporter initiate the connection, require the collector to handle multiple connections, and allow the exporter to establish one connection per observation domain. 3. Operation The following sections describe how an IPFIX-over-TCP connection is created, how IPFIX data is transferred over it, and how a connection is to be terminated. In the following, the term "exporter" refers to an IPFIX exporting process, while a "collector" refers to an IPFIX collecting process. Leinen Expires January 10, 2005 [Page 2] Internet-Draft IPFIX over TCP July 2004 3.1 Connection Establishment The IPFIX collector initiates a TCP connection to the exporter. By default, the exporter listens for connections on TCP port XXXX (to be assigned by IANA). It MUST be possible to configure the exporter to listen on a different TCP port. An exporter MAY support more than one active connection to different collectors (including the case of different collecting processes on the same host). It MUST be possible to configure, on an exporter, which collector(s) are allowed to establish a connection. It SHOULD be possible to configure this in terms of strong identities such as IKE [6] public-key certificates or pre-shared keys. An exporter SHOULD detect and log unauthorized connection attempts. 3.2 Data Transmission Once a TCP connection is established, the exporter starts sending IPFIX messages to the collector. 3.2.1 IPFIX Message Encoding IPFIX Messages are sent over the TCP connection without any special encoding. The LENGTH field in the message header defines the end of each message and thus the start of the next message. This means that IPFIX messages cannot be interleaved. The 16-bit LENGTH field limits the length of a message to 65536 octets including the header. A collector MUST be able to handle message lengths of up to 65536 octets. If an exporter exports data from multiple observation domain, it should be careful to choose message lengths appropriately to avoid head-of-line blocking between different observation domains. 3.2.2 Templates For each template, the exporter SHOULD send the Template Record before exporting Data Records that refer to this template. A collector MUST record all Template and Option Template Records for the duration of the connection, as an exporter is not required to re-export templates. Leinen Expires January 10, 2005 [Page 3] Internet-Draft IPFIX over TCP July 2004 3.2.3 Congestion Handling TCP will detect congestion anywhere in the end-to-end path between the exporter and the collector, and limit the transfer rate accordingly. Every time an IPFIX exporter has flow data to export, but notices that transmission to TCP is temporarily impossible ("would block"), it basically has two possibilities: Either it can wait until sending is possible again, or it can decide to drop the flow export data. In the latter case, the dropped export data MUST be accounted for, so that the amount of dropped export data can later be exported in an option data record. When an exporter finds that the rate at which flow records should be exported is consistently higher than the rate at which TCP permits to send, it SHOULD adapt the metering process so that it generates a lower amount of data, for example by increasing the sampling interval, or by increasing the amount of aggregation. If it does this, the exporter SHOULD periodically attempt to switch back to the original metering configuration when congestion subsides. 3.3 Connection Release When an exporter has no more data to send, it SHOULD close the TCP connection normally. When a collector no longer wants to receive IPFIX messages, it SHOULD close its end of the connection. The collector SHOULD continue to read IPFIX messages until the exporter has closed its end. When an exporter detects that the TCP connection to the collector is broken, it MUST continue to listen for a new connection. When a collector detects that the TCP connection to the exporter is broken, it SHOULD try to re-establish the connection. Connection timeouts and retry schedules SHOULD be configurable. In the default configuration, a collector MUST NOT attempt to establish a connection more frequently than once per minute. 4. Security Considerations In the current proposal, there is no handshake protocol once a TCP connection is established, so negotiation-based transport-layer security protocols such as TLS [9] cannot be used in a straightforward manner to ensure authenticity and confidentiality. Exporters and collectors MUST implement IPSEC [3] with the Authentication Header (AH) [4] to ensure authenticity of the exporter and the collector. Exporters SHOULD implement IPSEC Encapsulating Leinen Expires January 10, 2005 [Page 4] Internet-Draft IPFIX over TCP July 2004 Security Payload (ESP) [5] to ensure confidentiality of the exported data. The use of AH and ESP MUST be configurable for each exporter/ collector pair. Exporters and collectors MUST implement the Internet Key Exchange (IKE) [6] protocol with pre-shared keys and public-key certificates. The use of these identities is described in Section 3.1. 5. IANA Considerations No new registry is required for this specific protocol mapping. IANA should assign a well-known TCP port number for IPFIX over TCP. It is recommended that the same well-known port number is used as a default for the IPFIX over SCTP [1] and IPFIX over UDP mappings. 6. References 6.1 Normative References [1] Claise, B., "IPFIX Protocol Specifications", draft-ietf-ipfix-protocol-03 (work in progress), February 2004. [2] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [3] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. [4] Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402, November 1998. [5] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload (ESP)", RFC 2406, November 1998. [6] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, November 1998. 6.2 Informative References [7] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson, "Stream Control Transmission Protocol", RFC 2960, October 2000. [8] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M. and P. Conrad, "Stream Control Transmission Protocol (SCTP) Partial Reliability Extension", RFC 3758, May 2004. Leinen Expires January 10, 2005 [Page 5] Internet-Draft IPFIX over TCP July 2004 [9] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999. Author's Address Simon Leinen SWITCH Limmatquai 138 P.O. Box CH-8021 Zurich Switzerland Phone: +41 1 268 1536 EMail: simon@switch.ch Leinen Expires January 10, 2005 [Page 6] Internet-Draft IPFIX over TCP July 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2004). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Leinen Expires January 10, 2005 [Page 7]