I think the packet too big problem can also occur with P2P traffic, if I understand correctly that one proposed solution is to forward all P2P traffic through an edge router...
- Ralph On Jun 1, 2010, at 5:02 AM, Erik Nordmark <erik.nordm...@oracle.com> wrote: > On 05/31/10 09:06 AM, culler wrote: >> Since we route WITHIN a RPL network, rather than THROUGH a RPL network, >> it would seem that the case mentioned does not arise. Right? > > It can still happen. > If the sender is outside of the RPL network and sends a packet, and then at > the edge of the RPL network the routing header is added and the packet is > forwarded. If then a downstream RPL router sees that the packet is to big, it > will generate an ICMP "packet too big" and send it to the source of the > packet. > > Erik > >> >> >> On May 30, 2010, at 7:56 AM, Erik Nordmark wrote: >> >>> >>> The draft says: >>> A RPL Router MAY insert a Type 4 Routing header if one does not >>> already exist. The conditions for inserting a Type 4 Routing header >>> are out of scope of this document. >>> >>> Having routers insert headers in packets they forward is know to be >>> problematic in general, since it breaks path MTU discovery. >>> Taking an example of a host which sends a packet which is 1500 bytes, >>> and then receives an ICMP packet too big error saying "please limit >>> packets to 1500 bytes", will not change the host's behavior. But that >>> can happen if some router grows the packet to be more than 1500 bytes. >>> >>> Thus in general, the only safe way to insert headers in a packet is to >>> have the "inserter" put an extra IP header, with itself as a source, >>> then the inserted header, and then the original packet. >>> That extra IP header ensures that any ICMP error go back to the >>> "inserter", which can then compensate for its insertion before sending >>> the ICMP error towards the sender of the original packet. >>> >>> Thus I think there is a question for 6man whether we think the >>> constrained environment of ROLL is such that we can relax this. But it >>> does require that all the routers at the edge of the ROLL network >>> adjust the ICMP errors they forward to compensate for any inserted RH4 >>> headers. >>> >>> Erik >>> >> >> -------------------------------------------------------------------- >> IETF IPv6 working group mailing list >> ipv6@ietf.org >> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 >> -------------------------------------------------------------------- > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
