Subject: Re: protocol numbers
To: Jared D. McNeill <>
From: Andrew Brown <>
List: current-users
Date: 12/27/2000 13:19:54
>> No, still 8bit in v6:
>I don't mean to be confrontational about this, as I don't know
>much about IPv6. However, Microsoft's documentation on this seems to
>Taken from :
>IPv4 headers and IPv6 headers are not interoperable. A host or router must
>use an implementation of both IPv4 and IPv6 in order to recognize and
>process both header formats. The new IPv6 header is only twice as large as
>the IPv4 header, even though IPv6 addresses are four times as large as IPv4

the addresses are four times bigger (4 octets in ipv4 vs. 16 octets in
ipv6) and the headers are larger (usually 20 octets in ipv4, but
possibly up to 60 vs. a fixed 40 in ipv6), but the header's protocol
field (or next header field in ipv6) is eight bits (one octet) in both

look at section 3 in rfc791 and rfc2460.

|-----< "CODE WARRIOR" >-----|             * "ah!  i see you have the internet (Andrew Brown)                that goes *ping*!"       * "information is power -- share the wealth."