3 ms·
It sounds like IPv6 acknowledges that most protocols try hard to avoid fragmentation anyway, so fragmented packets are the exception. And it's not like fragmen
by tveita 9y ago
It sounds like IPv6 acknowledges that most protocols try hard to avoid fragmentation anyway, so fragmented packets are the exception.
And it's not like fragmentation hasn't caused problems with firewalls in IPv4 either.
E.g. http://all.net/Analyst/netsec/1995-09.html http://all.net/Analyst/netsec/1995-09.html
The fix is for equipment to handle the fragmented packets properly, just like for IPv4. How is forward fragmentation, which involves creating multiple new packets + headers with recomputed checksums, easier than simply parsing a header, which is apparently "anathema to a switch"?
- skywhopper 9y agoThe problem is that the fragmentation header in IPv6 is not deterministic, so it can't be parsed in constant time, which is what makes it "anathema to a switch" which needs to be able to guarantee certain levels of packet throughput. IPv4-style fragmentation can be done in constant time.
- pas 9y agoIt is still bounded time, which is still O(1). Yes, the standard doesn't limit the number of extension headers, but looking at the fixed header, and at most 5-6 extenion headers is the maximum time required to process a packet. And that'd be enough for 100% of traffic. The exact limit is the number of header types known to the processing node. Because encountering an unknown header should result in Parameter Error, and only one header can be used multiple times (the Destination Options), but that should be after the Frag one anyway.