Hi Tony, I fully support the recommendation that we spend another year devising our final recommendation.
Here is some suggested text to add after "3.1.3 Map & Encap". The two MHF techniques are: ETR Address Forwarding (EAF) - for IPv4 (A4g) 30 bits for the ETR address http://tools.ietf.org/html/draft-whittle-ivip4-etr-addr-forw Prefix Label Forwarding (PLF) - for IPv6 (A4f) 19 or 20 bits to identify the BGP advertised prefix of the ETR http://www.firstpr.com.au/ip/ivip/ivip6/ Regards - Robin 3.1.4 Map & Forward with Modified Header Forwarding (MHF) An alternative mechanism to Map & Encap retains the mapping system and overall structure of tunneling the traffic packet across the DFZ to a tunnel endpoint device at the RLOC address - which forwards the packet directly to the destination network. Instead of encapsulation, Modified Header Forwarding (MHF) alters the IP header of the original packet to include sufficient bits to specify part or all of the RLOC address of the tunnel endpoint device. That device restores the original state of the IP header and forwards the traffic packet directly to the destination network. Strategy A4f (below) provides enough bits in a modified IPv6 header for routers to forward the packet to the ISP network which contains the RLOC device. Strategy A4g encodes a 30 bit RLOC address into a modified IPv4 header so the packet can be forwarded all the way to the tunnel endpoint. The primary advantages of these techniques are elimination of encapsulation overhead and of the Path MTU Discovery problems which are inherent in any encapsulation-based tunneling solution. The primary disadvantage is the need for all DFZ, and some internal, routers to be upgraded to recognise the altered IP header format. For IPv4 an additional constraint is lack of support for fragmented packets or fragmentable packets longer than some constant, likely to be somewhat less than 1500 bytes. However, similar constraints may apply to any system which adequately manages the PMTUD problems caused by encapsulation. These techniques could be used by adapting any Map & Encap architecture which does not need to carry further bits of information with the traffic packet and which does not require the tunnel endpoint to be able to determine which device tunneled the packet. For such an architecture, MHF could be used as a more efficient long-term alternative to encapsulation. Alternatively, if the routers could be upgraded in time for the introduction of the scalable routing solution, these techniques could be used from the outset, eliminating the need for development of encapsulation techniques and of solutions to the resultant PMTUD problems. _______________________________________________ rrg mailing list [email protected] http://www.irtf.org/mailman/listinfo/rrg
