On October 6, 2019 at 16:35 jhellenthal@dataix.net (J. Hellenthal) wrote:
And in which part of the header is this to be added ?
I assume you mean the additional address. The IHL provides for up to 60 bytes of IP header length. 20 bytes is needed for the usual IPv4 header so an additional 40 bytes are available or 20 bytes for each of source and destination, adding the 4 bytes already present that's 24 bytes for each of source and destination or a theoretical total of 192 bits of (each) source and dest address. All a strictly IPv4 only host/router would need to understand in that case is the IHL, which it does already, and how to interpret whatever flag/option is used to indicate the presence of additional address bits mostly to ignore it or perhaps just enough to know to drop it if it's not implemented.
-- J. Hellenthal
The fact that there's a highway to Hell but only a stairway to Heaven says a lot about anticipated traffic volume.
On Oct 6, 2019, at 15:58, bzs@theworld.com wrote:
On October 6, 2019 at 15:18 mpalmer@hezmatt.org (Matt Palmer) wrote:
On Sat, Oct 05, 2019 at 04:36:50PM -0400, bzs@theworld.com wrote:
On October 4, 2019 at 15:26 owen@delong.com (Owen DeLong) wrote:
OK… Let’s talk about how?
How would you have made it possible for a host that only understands 32-bit addresses to exchange traffic with a host that only has a 128-bit address?
A bit in the header or similar (version field) indicating extending addressing (what we call IPv6, or similar) is in use for this packet.
How does that allow the host that only understands 32-bit addresses to exchange traffic with a host which sets this header bit?
As I said, it doesn't, but it lets each host decide that rather than the router tho if the host just knows enough to copy out the entire src/dst address (imagine the bits beyond the first 32 were in something like an extended ICMP options field w/in the IP header) then the rest could operate identically to ipv4.
So all you'd need added to a host IPv4 stack would be if you see this extended addressing flag/bit/whatever then there's more that needs to be copied out to each outgoing IP packet.
It would be the routers' job to interpret those extra bits for routing.
-- -Barry Shein
Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*
-- -Barry Shein Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*