Network Working Group O. Gsenger Internet-Draft March 2007 Expires: September 2, 2007 secure anycast tunneling protocol (satp) draft-gsenger-secure-anycast-tunneling-protocol-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 secure anycast tunneling protocol (satp) March 2007 Abstract The secure anycast tunneling protocol (satp) defines a protocol used for communication between any combination of unicast and anycast tunnel endpoints. It allows tunneling of every ETHER TYPE protocol (e.g. ethernet, ip, arp ...). SATP directly includes cryptography and message authentication based on the methodes used by SRTP. It is intended to deliver a generic, scaleable and secure solution for tunneling and relaying of packets of any protocol. Gsenger Expires September 2, 2007 [Page 2] Internet-Draft secure anycast tunneling protocol (satp) March 2007 1. Introduction SATP is somehow a mixture of a generic encapsulation protocol like GRE [1] and a secure tunneling protocol as IPsec [2] in tunnel mode. To save some header overhead it uses the encryption technices of SRTP [3]. It supports peer to peer tunnels, where tunnel endpoints can be any combination of unicast, multicast or anycast hosts, so it defines a Host Anycast Service [4] Gsenger Expires September 2, 2007 [Page 3] Internet-Draft secure anycast tunneling protocol (satp) March 2007 2. Motivation and usage scenarios This section gives an overview of possible usage scenarios. Please note, that the protocols used in the figures are only examples and that SATP itself does not care about either transport protocols or encapsulated protocols. Routing is not done by SATP and each implemetation MAY choose it's own way of doing this task (e.g. using functions provided by the operating system). SATP is used only to encapsulate and encrypt data. 2.1. Usage scenarions 2.1.1. tunneling from unicast hosts over anycast routers to other unicast hosts An example of SATP used to tunnel in a unicast client - anycast server model --------- router ----------- / \ unicast ------+---------- router ------------+------ unicast host \ / host --------- router ----------- unicast | encrypted | anycast | encrypted | unicast tunnel | communication | tunnel | communication | tunnel endpoint | using SATP | endpoint | using SATP | endpoint Figure 1 In this scenario the payload gets encapsuleted into a SATP packet by a unicast host and gets transmitted to one of the anycast routers. It than gets decapsulated by the router. This router makes a routing descision based on the underlying protocol and transmits a new SATP package to one or more unicast hosts depending on the routing descition. Gsenger Expires September 2, 2007 [Page 4] Internet-Draft secure anycast tunneling protocol (satp) March 2007 2.1.2. tunneling from unicast hosts to anycast networks An example of SATP used to encrypt data between a unicast host and anycast networks -------Router -+---- DNS Server / \ / --- 6to4 Router / unicast -------+----------Router --+--- DNS Server host \ \ \ --- 6to4 Router \ -------Router -+---- DNS Server \ --- 6to4 Router unicast | encrypted | anycast | plaintext tunnel | communication | tunnel | anycast endpoint | using SATP | endpoint | services Figure 2 2.1.3. redundant tunnel connection of 2 networks An example of SATP used to connect 2 networks Router ----------- ---------------Router / \ / \ Network - Router ------------x Network A \ / \ / B Router ----------- ---------------Router | packets | packets | packets | plaintext | get | take a | get | plaintext packets | de/encrypted | random | de/encrypted | packets |de/encapsulated| path |de/encapsulated| Figure 3 Network A has multiple routers, that act as gateway/tunnel endpoints to another network B. This is done to build a redundant encrypted tunnel connection between the two networks. All tunnel endpoints of network A share the same anycast address and all tunnel endpoints of network B share another anycast address. When a packet from network A gets transmitted to network B, it first arrives on one of network Gsenger Expires September 2, 2007 [Page 5] Internet-Draft secure anycast tunneling protocol (satp) March 2007 A's border routers. Which router is used is determined by network A's internal routing. This router encapsulates the package and sends it to the anycast address of the network B routers. The SATP packet arrives at one of network B's routers and gets decapsulated and routed to it's destination within network B. 2.2. Encapsulation SATP does not depend on which lower layer protocols is used, but it's most likely used on top of IP or UDP. This section should only discuss some issues on IP and UDP in combination with anycasting and tunnels. Examples of SATP used with different lower layer and payload protocols +------+-----+-------------------------------+ | | | + ---------------+------ | | IPv6 | UDP | SATP | Ethernet 802.3 | ... | | | | | +----------------+-----+ | +------+-----+-------------------------------+ Tunneling of Ethernet over UDP/IPv6 +------+-----+---------------------------+ | | | +------+-----+-----+ | | IPv4 | UDP | SATP | IPv6 | UDP | RTP | | | | | +------+-----+-----+ | +------+-----+---------------------------+ Tunneling of IPv6 over UDP/IPv4 with RTP payload +------+-------------------------------+ | | + ---------------+------ | | IPv6 | SATP | Ethernet 802.3 | ... | | | | +----------------+-----+ | +------+-------------------------------+ Tunneling of Ethernet over IPv6 +------+---------------------------+ | | +------+-----+-----+ | | IPv4 | SATP | IPv6 | UDP | RTP | | | | +------+-----+-----+ | +------+---------------------------+ Tunneling of IPv6 over IPv4 with RTP payload Gsenger Expires September 2, 2007 [Page 6] Internet-Draft secure anycast tunneling protocol (satp) March 2007 Figure 4 When using UDP no flow control or retransmission is done, neither by UDP nor anytun. The encapsulated protocol HAS TO take care of this tasks if needed. UDP however has a checksum of the complete UDP datagram, so a packet gets discarded if there is a biterror in the payload 2.3. Fragmentation The only way of fully supporting fragmentation would be to synchronise fragments between all anycast servers. This is considered to be too much overhead, so there are two non perfect solutions for these 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 encapsulated protocol can do a retransmission and all fragments will arrive at the new server. Gsenger Expires September 2, 2007 [Page 7] Internet-Draft secure anycast tunneling protocol (satp) March 2007 3. Protocol specification 3.1. Header format Protocol Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | sequence number | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+ | | sender ID # | | +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+ + | | | .... payload ... | | | |-------------------------------+-------------------------------+ | | | padding (OPT) | pad count(OPT)| payload type | | +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+-+ | ~ MKI (OPTIONAL) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : authentication tag (RECOMMENDED) : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | +- Encrypted Portion* Authenticated Portion ---+ Figure 5 3.2. sender ID The sender ID is a 16bit unsigned integer. It HAS TO be unique for every sender sharing the same anycast address 3.3. sequence number The sequence number is a 32 bit unsigned integer in network byte order. It starts with a random value and is increased by 1 for every sent packet. After the maximum value, it starts over from 0. This overrun causes the ROC to be increased. 3.4. payload A packet of the type payload type (e.g. an IP packet). 3.5. padding (OPTIONAL) Padding of max 255 octets. None of the pre-defined encryption transforms uses any padding; for these, the plaintext and encrypted payload sizes match exactly. Transforms are based on transforms of the SRTP protocol and these transforms might use the RTP padding Gsenger Expires September 2, 2007 [Page 8] Internet-Draft secure anycast tunneling protocol (satp) March 2007 format, so a RTP like padding is supported. If padding field is present, than the padding count field MUST be set to the padding lenght. 3.6. padding count The number of octets of the padding field. This field is optional. It's presence is signaled by the key management and not by this protocol. If this field isn't present, the padding field MUST NOT be present as well. 3.7. payload type field The payload type field defines the payload protocol. ETHER TYPE protocol numbers are used. See IANA assigned ethernet numbers [5] . The values 0000-05DC are reserverd and MUST NOT be used. Some examples for protocol types HEX 0000 Reserved .... Reserved 05DC Reserved 0800 Internet IP (IPv4) 6558 transparent ethernet bridging 86DD IPv6 Figure 6 3.8. Encryption Encryption is done in the same way as for SRTP [3]. This section will only discuss some small changes that HAVE TO be made. Gsenger Expires September 2, 2007 [Page 9] Internet-Draft secure anycast tunneling protocol (satp) March 2007 4. References [1] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000. [2] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. [3] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC 3711, March 2004. [4] Partridge, C., Mendez, T., and W. Milliken, "Host Anycasting Service", RFC 1546, November 1993. [5] Gsenger Expires September 2, 2007 [Page 10] Internet-Draft secure anycast tunneling protocol (satp) March 2007 Author's Address Othmar Gsenger Puerstingerstr 32/7 Saalfelden 5760 AT Phone: Email: satp@gsenger.com URI: http://www.gsenger.com/satp/ Gsenger Expires September 2, 2007 [Page 11] Internet-Draft secure anycast tunneling protocol (satp) 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 12]