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diff --git a/doc/rfc1702.txt b/doc/rfc1702.txt new file mode 100644 index 0000000..50b57ae --- /dev/null +++ b/doc/rfc1702.txt @@ -0,0 +1,227 @@ + + + + + + +Network Working Group S. Hanks +Request for Comments: 1702 NetSmiths, Ltd. +Category: Informational T. Li + D. Farinacci + P. Traina + cisco Systems + October 1994 + + + Generic Routing Encapsulation over IPv4 networks + +Status of this Memo + + This memo provides information for the Internet community. This memo + does not specify an Internet standard of any kind. Distribution of + this memo is unlimited. + +Introduction + + In an earlier memo [RFC 1701], we described GRE, a mechanism for + encapsulating arbitrary packets within an arbitrary transport + protocol. This is a companion memo which describes the use of GRE + with IP. This memo addresses the case of using IP as the delivery + protocol or the payload protocol and the special case of IP as both + the delivery and payload. This memo also describes using IP + addresses and autonomous system numbers as part of a GRE source + route. + +IP as a delivery protocol + + GRE packets which are encapsulated within IP will use IP protocol + type 47. + +IP as a payload protocol + + IP packets will be encapsulated with a Protocol Type field of 0x800. + + For the Address Family value of 0x800, the Routing Information field + will consist of a list of IP addresses and indicates an IP source + route. The first octet of the Routing Information field constitute a + 8 bit integer offset from the start of the Source Route Entry (SRE), + called the SRE Offset. The SRE Offset indicates the first octet of + the next IP address. The SRE Length field consists of the total + length of the IP Address List in octets. + + + + + + + +Hanks, Li, Farinacci & Traina [Page 1] + +RFC 1702 GRE over IPv4 networks October 1994 + + + This has the form: + + 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Address Family | SRE Offset | SRE Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | IP Address List ... + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + For the Address Family value of 0xfffe, the Routing Information field + will consist of a list of Autonomous System numbers and indicates an + AS source route. The third octet of the Routing Information field + contains an 8 bit unsigned integer offset from the start of the + Source Route Entry (SRE), called the SRE Offset. The SRE Offset + indicates the first octet of the next AS number. THe SRE Length + field consists of the total length of the AS Number list in octets. + + 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Address Family | SRE Offset | SRE Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | AS Number List ... + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +IP as both delivery and payload protocol + + When IP is encapsulated in IP, the TTL, TOS, and IP security options + MAY be copied from the payload packet into the same fields in the + delivery packet. The payload packet's TTL MUST be decremented when + the packet is decapsulated to insure that no packet lives forever. + +IP source routes + + When a system is processing a SRE with an Address Family indicating + an IP source route, it MUST use the SRE Offset to determine the next + destination IP address. If the next IP destination is this system, + the SRE Offset field should be increased by four (the size of an IP + address). If the SRE Offset is equal to the SRE Length in this SRE, + then the Offset field in the GRE header should be adjusted to point + to the next SRE (if any). This should be repeated until the next IP + destination is not this system or until the entire SRE has been + processed. + + If the source route is incomplete, then the Strict Source Route bit + is checked. If the source route is a strict source route and the + next IP destination is NOT an adjacent system, the packet MUST be + + + +Hanks, Li, Farinacci & Traina [Page 2] + +RFC 1702 GRE over IPv4 networks October 1994 + + + dropped. Otherwise, the system should use the IP address indicated + by the Offset field to replace the destination address in the + delivery header and forward the packet. + +Autonomous system source routes + + When a system is processing a SRE with an Address Family indicating + an AS source route, it MUST use the SRE Offset field to determine the + next autonomous system. If the next autonomous system is the local + autonomous system, the SRE Offset field should be increased by two + (the size of an autonomous system number). If the SRE Offset is + equal to the SRE Length in this SRE, then the Offset field in the GRE + header should be adjusted to point to the next SRE (if any). This + should be repeated until the next autonomous system number is not + equal to the local autonomous system number or until the entire SRE + has been processed. + + If the source route is incomplete, then the Strict Source Route bit + is checked. If the source route is a strict source route and the + next autonomous system is NOT an adjacent autonomous system, the + packet should be dropped. Otherwise, the system should use the + autonomous system number indicated by the SRE Offset field to replace + the destination address in the delivery header and forward the + packet. The exact mechanism for determining the next delivery + destination address given the AS number is outside of the scope of + this document. + +Security Considerations + + Security issues are not discussed in this memo. + + + + + + + + + + + + + + + + + + + + + +Hanks, Li, Farinacci & Traina [Page 3] + +RFC 1702 GRE over IPv4 networks October 1994 + + +Authors' Addresses + + Stan Hanks + NetSmiths, Ltd. + 2025 Lincoln Highway + Edison, NJ 08817 + + EMail: stan@netsmiths.com + + + Tony Li + cisco Systems, Inc. + 1525 O'Brien Drive + Menlo Park, CA 94025 + + EMail: tli@cisco.com + + + Dino Farinacci + cisco Systems, Inc. + 1525 O'Brien Drive + Menlo Park, CA 94025 + + EMail: dino@cisco.com + + + Paul Traina + cisco Systems, Inc. + 1525 O'Brien Drive + Menlo Park, CA 94025 + + EMail: pst@cisco.com + +References + + RFC 1701 + Hanks, S., Li, T, Farinacci, D., and P. Traina, "Generic Routing + Encapsulation", RFC 1701, NetSmiths, Ltd., and cisco Systems, + October 1994. + + + + + + + + + + + + +Hanks, Li, Farinacci & Traina [Page 4] + |