Network Working Group O. Gsenger Internet-Draft March 2007 Expires: September 2, 2007 Anycast TCP stream relaying draft-gsenger-anycast-tcp-stream-relay-00 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 September 2, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Gsenger Expires September 2, 2007 [Page 1] Internet-Draft Anycast TCP stream relaying March 2007 Abstract The anycast tunneling (anytun) protocol defines a protocol used for communication between unicast clients and anycast servers. It can be used for tunneling information between 2 clients over the servers or in relay mode to transmit data form the client over the servers to a third party not using the protocol and vice versa. Gsenger Expires September 2, 2007 [Page 2] Internet-Draft Anycast TCP stream relaying March 2007 1. full anycast tcp 1.1. Introduction TCP is statefull, this is a big problem, because every anycast server has to know the tcp state. The TCP state has to be synced between the servers, that meens a lot of overhead. To keep this amount small and therefor make anycast TCP connections efficient some tricks MUST be used. This is considered to be a real hack, so it is not recommendid to use this mode unless it is really necessary. It might for instance be necessary to build connection trough special kind of NAT routers or firewalls. 1.2. Reducing syncronisaton overhead 1.2.1. Fragmentation The only way of fully supporting fragmentation would be to syncronise fragments between all anycast servers. This is considered to be to much overhead, so there are two non perfect solutions for this problems. Either fragmentation HAS TO be disabled or if not all fragments arrive at the same server the ip datagramm HAS TO be discarded. As routing changes are not expected to occure very frequently, the ip datagram will get retransmitted by TCP and all fragments will arrive at the new server. 1.2.2. sequence number It is nessarary to send tcp segments with a correct sequence number, that appear to come from the same host, in order to get a valid connecton to the client. Syncronisation of sequence numbers would mean to much overhead, so it hast to be provided by the relayed data. The relayed data from the anycast serveres point of view, consits of multible datastream, each directed from one client to anotherIn tunneling mode all anytun packets from the client 1.3. keep alive message request Most NAT routers need a tcp connection to transmit some packets once in while to stay open. In full anycast tcp mode anytun hast to predict the tcp state including the sequence number. Synconisation of the sequence number would be to much overhead, so a keep alive intervall is agreed. This interval is used to calculate the sequemce number. Gsenger Expires September 2, 2007 [Page 3] Internet-Draft Anycast TCP stream relaying March 2007 Appendix A. The appan Gsenger Expires September 2, 2007 [Page 4] Internet-Draft Anycast TCP stream relaying March 2007 2. References [1] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers", RFC 3068, June 2001. Gsenger Expires September 2, 2007 [Page 5] Internet-Draft Anycast TCP stream relaying March 2007 Author's Address Othmar Gsenger Sporgasse 6 Graz 8010 AT Phone: Email: otti@wirdorange.org URI: http://anytun.org/ Gsenger Expires September 2, 2007 [Page 6] Internet-Draft Anycast TCP stream relaying March 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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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Gsenger Expires September 2, 2007 [Page 7]