3 ms·

> The current IPv4 is unnecessarily slow I've never heard of IPv6 being faster than IPv4. Does anybody know what they're talking about?

by dpedu 4y ago

LinuxBender 4y ago
Not sure. The only thing that comes to mind are clients that prefer ipv6 over ipv4. In Linux this is defined or defaulted via /etc/gai.conf. If the file is absent ipv6 will be preferred by some DNS libraries and applications. Those clients will try ipv6 DNS lookups and if that does not exist will retry with ipv4. That adds the delay of RTT of the DNS server combined with cache or lack thereof.
- chomp 4y ago
  I guess SLAAC is faster than DHCP also?
fweimer 4y ago
IPv6 was optimized for simple software forwarding implementations. For example, the header checksum was eliminated, so that the TTL (or hop limit) update does not need to recompute the checksum. But the IPv4 header checksum is so weak that it is entirely possible to update the checksum directly without full recomputation across the entire header, so this was only a significant win compared to an unoptimized IPv4 implementation. More importantly, IPv6 requires a linked list traversal to find the TCP/UDP port numbers, rather than a simple computation of a variable offset. Maybe it was difficult to predict in the 1990s that hardware implementations that need to look at port numbers would be common by the end of the decade. But the claim that the IPv6 header was optimized for efficient forwarding stuck around even after it became clear that the increased flexibility really interfered with hardware implementations of packet filters.
duskwuff 4y ago
Routing for IPv6 traffic is sometimes marginally faster than v4 (cf. https://www.google.com/intl/en/ipv6/statistics.html https://www.google.com/intl/en/ipv6/statistics.html), but this is probably more a matter of v6 traffic not using some older, slower v4-only networks.
p1mrx 4y ago
IPv4 addresses used to be free; now they're like $50 per address from an IPv4 broker. Many ISPs use Carrier Grade NAT, which conserves addresses but may reduce performance. IPv6 may route packets more directly without a NAT in the way. Facebook once reported seeing a lot of devices where IPv6 is faster: https://www.internetsociety.org/blog/2015/04/facebook-news-feeds-load-20-40-faster-over-ipv6/ https://www.internetsociety.org/blog/2015/04/facebook-news-f...

> The current IPv4 is unnecessarily slow I've never heard of IPv6 being faster than IPv4. Does anybody know what they're talking about?

by dpedu 4y ago

> The current IPv4 is unnecessarily slow I've never heard of IPv6 being faster than IPv4. Does anybody know what they're talking about?

LinuxBender 4y ago

Not sure. The only thing that comes to mind are clients that prefer ipv6 over ipv4. In Linux this is defined or defaulted via /etc/gai.conf. If the file is absent ipv6 will be preferred by some DNS libraries and applications. Those clients will try ipv6 DNS lookups and if that does not exist will retry with ipv4. That adds the delay of RTT of the DNS server combined with cache or lack thereof.

chomp 4y ago
I guess SLAAC is faster than DHCP also?

fweimer 4y ago

IPv6 was optimized for simple software forwarding implementations. For example, the header checksum was eliminated, so that the TTL (or hop limit) update does not need to recompute the checksum. But the IPv4 header checksum is so weak that it is entirely possible to update the checksum directly without full recomputation across the entire header, so this was only a significant win compared to an unoptimized IPv4 implementation. More importantly, IPv6 requires a linked list traversal to find the TCP/UDP port numbers, rather than a simple computation of a variable offset. Maybe it was difficult to predict in the 1990s that hardware implementations that need to look at port numbers would be common by the end of the decade. But the claim that the IPv6 header was optimized for efficient forwarding stuck around even after it became clear that the increased flexibility really interfered with hardware implementations of packet filters.

duskwuff 4y ago

Routing for IPv6 traffic is sometimes marginally faster than v4 (cf. https://www.google.com/intl/en/ipv6/statistics.html https://www.google.com/intl/en/ipv6/statistics.html), but this is probably more a matter of v6 traffic not using some older, slower v4-only networks.

p1mrx 4y ago

IPv4 addresses used to be free; now they're like $50 per address from an IPv4 broker. Many ISPs use Carrier Grade NAT, which conserves addresses but may reduce performance. IPv6 may route packets more directly without a NAT in the way. Facebook once reported seeing a lot of devices where IPv6 is faster: https://www.internetsociety.org/blog/2015/04/facebook-news-feeds-load-20-40-faster-over-ipv6/ https://www.internetsociety.org/blog/2015/04/facebook-news-f...