On 9 Mar 2009, at 07:50, Nathan Ward wrote:
What is the HLIM of the IPv6 packets? (not the IPv4 encapsulation, I mean the IPv6 packet carried inside the IPv4 packet)
That is usually a good indicator.
tcpdump: listening on en0, link-type EN10MB (Ethernet), capture size 96 bytes 08:14:43.978005 IP (tos 0x0, ttl 40, id 34166, offset 0, flags [none], proto IPv6 (41), length 76) 199.212.90.13 > 192.88.99.1: IP6 (hlim 64, next-header: ICMPv6 (58), length: 16) 2002:c7d4:5a0d:1::1 > 2001:4860:0:2001::68: [icmp6 sum ok] ICMP6, echo request, length 16, seq 33 08:14:44.106483 IP (tos 0x0, ttl 245, id 20518, offset 0, flags [none], proto IPv6 (41), length 76) 192.88.99.1 > 199.212.90.13: IP6 (hlim 57, next-header: ICMPv6 (58), length: 16) 2001:4860:0:2001::68 > 2002:c7d4:5a0d:1::1: [icmp6 sum ok] ICMP6, echo reply, length 16, seq 33 08:14:44.978054 IP (tos 0x0, ttl 40, id 61522, offset 0, flags [none], proto IPv6 (41), length 76) 199.212.90.13 > 192.88.99.1: IP6 (hlim 64, next-header: ICMPv6 (58), length: 16) 2002:c7d4:5a0d:1::1 > 2001:4860:0:2001::68: [icmp6 sum ok] ICMP6, echo request, length 16, seq 34 08:14:45.108964 IP (tos 0x0, ttl 245, id 53045, offset 0, flags [none], proto IPv6 (41), length 76) 192.88.99.1 > 199.212.90.13: IP6 (hlim 57, next-header: ICMPv6 (58), length: 16) 2001:4860:0:2001::68 > 2002:c7d4:5a0d:1::1: [icmp6 sum ok] ICMP6, echo reply, length 16, seq 34 08:14:45.978108 IP (tos 0x0, ttl 40, id 22305, offset 0, flags [none], proto IPv6 (41), length 76) 199.212.90.13 > 192.88.99.1: IP6 (hlim 64, next-header: ICMPv6 (58), length: 16) 2002:c7d4:5a0d:1::1 > 2001:4860:0:2001::68: [icmp6 sum ok] ICMP6, echo request, length 16, seq 35 08:14:46.106890 IP (tos 0x0, ttl 245, id 20747, offset 0, flags [none], proto IPv6 (41), length 76) 192.88.99.1 > 199.212.90.13: IP6 (hlim 57, next-header: ICMPv6 (58), length: 16) 2001:4860:0:2001::68 > 2002:c7d4:5a0d:1::1: [icmp6 sum ok] ICMP6, echo reply, length 16, seq 35 The observed latency seems quite different between v4 and v6 using a 6to4 source address: --- ipv6.l.google.com ping6 statistics --- 100 packets transmitted, 100 packets received, 0% packet loss round-trip min/avg/max = 127.896/129.753/131.936 ms --- www.l.google.com ping statistics --- 100 packets transmitted, 100 packets received, 0% packet loss round-trip min/avg/max/stddev = 13.179/14.467/16.221/0.640 ms The 6to4 relay I'm using for outbound packets is local: --- 192.88.99.1 ping statistics --- 100 packets transmitted, 100 packets received, 0% packet loss round-trip min/avg/max/stddev = 0.850/1.127/9.522/1.178 ms Using a non-6to4 source address, with native v6 and goog peering which matches v4: --- ipv6.l.google.com ping6 statistics --- 100 packets transmitted, 100 packets received, 0% packet loss round-trip min/avg/max = 27.400/30.183/50.567 ms I guess this suggests they are not using a local 6to4 relay, or at least not as local as they could. Joe