Here ATP stands for Asymmetric Transport Protocol (somewhat for historical reason), not Appletalk Transaction Protocol. Welcome to http://atp.ebloggy.com/ to add comment. Known problems: Lack of references section; Lack of elliptic curve parameter definition; and much more:) Briefly: ATP aims to provide mobility and multi-home support in transport layer. But why not patching TCP, extending SCTP, or exploiting HIP? The answer is that when taking account of syndicate effect, it is more efficient to use ATP. Patching TCP software to support mobility and multi-home is not difficult. But widely deploying the new TCP implementation may be an enduring work. SCTP supports multi-home, and it is quite easy to extend it to support mobility. But as SCTP is already quite heavy weighted, and its congestion control mechanism arguably suffers same trouble as TCP, it is difficulty to persuade mass users to accept SCTP. HIP decouples identity and locator role of IP address by adding a new layer. It is quite exquisite. But unfortunately to add a new layer is to add a new, non-trivial trouble of reliability. The name of Asymmetric Transport Protocol is somewhat historical. ATP takes advantages of asymmetric cryptography (and asymmetry of communication). It is designed to be an alternate of transport layer protocols, alongside of TCP and UDP [RFC768]. ATP aims to ² Decouple locator and identity role of network layer address by keep it from taking part in transport layer identity and/or address. ² Support mobility ² Support multi-home ² Facilitate high performance parallel communication ² Facilitate high efficiency transactional communication ² Provide transport encryption service ² Provide some QoS service ² Keep simple ATP supports mobility and multi-home by decoupling locator and identity role of network layer address with connection key. There are three connection modes in ATP: fast-mode, normal mode and encrypted transport mode. In the host environment, each ATP connection is uniquely associated with a 64-bit connection key. In the context of each normal mode ATP connection, there is a shared secret. The shared secret is established in Elliptic Curve Diffie-Hellman [ECC] key agreement process when the connection is set up. ATP endpoint seals every ATP packet with Integrity/Identity Check Code (ICC). In normal mode ICC is calculated by applying HMAC-SHA1 [RFC2104] [RFC3174] on the ATP packet header with the shared secret as the key. As far as only the connected peers know both the connection key and the shared secret, integrity of the ATP packet header and identity of the ATP packet source are secured by ICC. In fast mode, ATP endpoints do not establish a shared secret, and agree on the connection key only. The 64-bit connection key solely acts the identity check role. ICC is a CCITT-CRC-16 code [CRC] that weakly protects packet integrity. In encrypted transport mode ATP endpoints use AES-IV-SHA1-80 algorithm to protect privacy of the payload, integrity of the full packet, and identity of the packet source. AES-IV-SHA1-80 algorithm is integration of AES [FIPS-197] and SHA1-80 [RFC3174]. AES encryption key is installed by the upper layer application (ULA), or derived from the shared secret on request of ULA; 64-bit initial vector is the low-order 64-bit part of the result of applying SHA1-80 on the ATP packet header. High-order 16 bits are exploited for preliminary integrity check. Encrypted transport mode is not only a feature of mobility and multi-home but a simple and useful feature of security as well. Mobility support is further reinforced by the feature of re-locating via courier. ATP supports high performance, high efficiency parallel and/or transactional communication with connection clone and auto-reconnect features. ATP also features First-In-First-Deplete traffic class, in addition to traditional best-effort traffic class. ATP DOES NOT provide reliable multicast support, nor does it do full-fledged congestion control. However, ATP does have cooperative congestion control feature. We assume that ² Mobility context is L4-comfortable. That is, frequency of IP address change is limited so that the IP addresses of two endpoints remain stable as long as they are negotiating a connection. ² Ownership of upper layer application over connection key is secure. ² Upper Layer Application is willing and able to defense against man-in-the-middle attack. ² Acceptable information asymmetry. One participant in communication, the responder, is willing to and able to make the other participant, the initiator, know the rendezvous key, but not necessarily vice versa. _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf