Introduction

The number of fragments in a fragment series is dependant on both the size of the original packet and the MTU of the link following the point at which the original packet was fragmented. These graphs display the number of fragments per series. A high number of two and three fragment series is expected for packets whose MTU is a bit too large for the following link. The graphs on this page show only fragments from complete series -- fragment series in which we saw all of the fragments that made up the original packet. There are several reasons a series would have missing fragments, including some fragments taking different paths to the destination and consequently not traveling along the UCSD-CERF link, and fragments being dropped somewhere along the path between the source and our monitor box.

Analysis

The link we monitor at the Ames Internet Exchange is load-balanced -- our monitor captures only a fraction of the traffic through AIX. Since individual packets can be routed through any of the links at AIX, and not necessarily the link our monitor can "see", we see far fewer complete fragment series. 93.0 percent of the fragments monitored on the UCSD-CERF link are members of a complete series, compared to between 9.6 and 10.8 percent of the fragments at AIX. The effect of load balancing masks any other phenomena, suppressing the normal distribution of series lengths.

frag_cerf_2000-05-17_12-11

This trace was taken on the UCSD-CERF link from Wed May 17 14:40:39 PDT 2000 to Fri Jun 2 20:42:48 PDT 2000. 50,375,114 packets containing 50,945,519,628 bytes of data composing 19,054,937 fragment series were captured in this interval. Of those, 17,718,285 (93.0%) were complete series.

Of note in this graph is the prevalence of series with a large number of fragments, and the prevalence of 21-fragment series preceding a sharp dropoff in the number of fragments in higher-fragment-value series.

aix_frag_958848611

This trace was taken from the Ames Internet Exchange from Sat May 20 11:50:42 PDT 2000 to Tue May 23 23:04:01 PDT 2000. 9,781,240 packets containing 11,406,413,861 bytes of data composing 7,183,794 series fragment series were captured in this interval. Of those, 692,184 (9.6%) were complete series.

aix_frag_959148226

This trace was taken from the Ames Internet Exchange from Tue May 23 23:04:17 PDT 2000 to Fri May 26 11:00:28 PDT 2000. 8,599,458 packets containing 9,327,540,025 bytes of data composing 6,922,673 fragment series were captured in this interval. Of those, 747,401 (10.7%) were complete series.

aix_frag_959364017

This trace was taken from the Ames Internet Exchange from Fri May 26 11:00:48 PDT 2000 to Wed May 31 00:27:38 PDT 2000. 12,273,208 packets containing 13,645,419,937 bytes of data composing 9,832,899 fragment series were captured in this interval. Of those, 1,069,074 (10.8%) were complete series.