Hi, Up to now, the SEAL spec has focused on "tunnel mode", and had the singular statement:
"(A transport-mode of operation is also possible, but out of scope for this document.)" in the introduction. (Indeed, the first edition of SEAL (RFC5320) did specify a transport mode of operation, but that document will be obsolete by the second edition.) So, in light of these discussions I decided that now might be a good time to bring transport mode back into scope and as such have added the following new section to the document. Please send comments and suggestions. I will post a new draft version by the end of the day that will include both tunnel and transport modes. Thanks - Fred fred.l.temp...@boeing.com 6. SEAL Transport Mode Specification SEAL is also used for transport-mode operation. Transport mode refers to a SEAL encapsulation in which a layer-4 header appears immediately following the SEAL header. The type of layer-4 header is indicated in the "NEXTHDR" field the same as for tunnel mode. The SEAL header is identical to the version used for tunnel mode, except that the "LINK_ID" and "LEVEL" fields are omitted, and the transport layer port numbers are included in each non-initial segment (see: Figure 6). 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NEXTHDR |VER|C|P|I|V|R|M| Offset | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port (when Offset!=0) | Dest Port (when Offset!=0) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Integrity Check Vector (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Figure 6: SEAL Header Format The "Source Port" and "Dest Port" are taken from the corresponding fields in the transport layer next header that appears immediately following the SEAL header in the initial segment. For example, for UDP [RFC0768] the transport layer source/dest ports are 16 bits in length and are copied from the transport layer header. All segmentation is exactly as specified in SEAL tunnel mode, and the SEAL Control Message Protocol (SCMP) operates the same as for tunnel mode. For example, the source node can probe the path MTU to the destination by setting the P bit in a probe packet and waiting for an acknowledgement from the destination. SEAL transport mode is useful for transport layer protocols that have no way to segment the large packets they send. It is a universal format that can be applied to any such transport. -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------