Dale Worley <> writes: > I remember filing this erratum, and at the time, someone pointed out how > the 255 hop-limit is used, etc. as Kerry describes. I'm surprised that > the erratum hasn't been closed previously. > > The flagged statement in the RFC isn't clear if one isn't steeped in > 6lowpan networking, though it isn't necessary to understand and apply > the RFC. > Hop Limit referred to here is an IPv6 header field that, according to Sect 3 of RFC 8200, is "decremented by 1 by each node that forwards the packet."
IPv6 Neighbor Discovery [RFC 4861] sets Hop Limit to 255 according Sect 11.2: "Because routers decrement the Hop Limit on all packets they forward, received packets containing a Hop Limit of 255 must have originated from a neighbor." So the sentence referred to in the errata is correct, but could be marginally clarified by adding " (e.g. by IPv6 Neighbor Discovery [RFC4861]." Kerry > Dale On Fri, Sep 3, 2021 at 6:05 PM Kerry Lynn <[email protected]> wrote: > On Fri, Sep 3, 2021 at 5:29 PM Erik Kline <[email protected]> wrote: > >> All, >> >> I've been trying to catch up on and close all outside INT area errata. >> In so doing, I've come across: >> >> https://www.rfc-editor.org/errata/eid4814 >> >> filed against RFC 6282. >> >> My inclination is to reject this erratum, since 255 is in fact "used to >> verify that a communication occurs over a single-hop", and this sentence >> provides some background for the document treating 255 later on (section >> 3.1.1). >> >> I agree that the errata as submitted appears to be incorrect. However, > that doesn't necessarily > mean the statement in the RFC is clear. Let's start with the proposed > wording "... a Hop Limit > value of 1 is often used to verify that a communication occurs over a > single hop." I believe a > sender would set a value of 1 to _ensure_ a packet only travels over a > single hop. A receiver > might use the comparison value of 255 to _verify_ a received packet has > not been routed. > However, the preceding sentence in RFC 6282 suggests that 64 is also a > common value for > outbound traffic. In the event, a value of 64 _might_ indicate the packet > has not been routed, > but it might also indicate the packet traveled 255 - 64 = 191 hops before > reaching the receiver, > so 255 seems the only reliable comparison value. (Why would a receiver > need to know this?) > > Kerry > > > If anyone feels I've misread or misunderstood something do let me know. >> >> Thanks, >> -Erik >> _______________________________________________ >> 6lo mailing list >> [email protected] >> https://www.ietf.org/mailman/listinfo/6lo >> >
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