Serialization Delay (or Transmission Delay)
Serialization delay is the time it takes for a unit of data, such as a packet, to be serialized for transmission on a narrow (e.g. serial) channel such as a cable. Serialization delay is dependent on size, which means that longer packets experience longer delays over a given network path. Serialization delay is also dependent on channel capacity ("bandwidth"), which means that for equal-size packets, the faster the link, the lower the serialization delay.
Serialization delays are incurred at processing nodes, when packets are stored-and-copied between links and (router/switch) buffers. This includes the copying over internal links in processing nodes, such as router backplanes/switching fabrics.
In the core of the Internet, serialization delay has largely become a non-issue, because link speeds have increased much faster over the past years than packets sizes. Therefore, the "hopcount" as shown by e.g. traceroute is a bad predictor for delay today.
Example Serialization Delays
To illustrate the effects of link rates and packet sizes on serialization delay, here is a table of some representative values. Note that the maximum packet size for most computers is 1500 bytes today, but 9000-byte "jumbo frames" are already supported by many research networks.
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Link Rate |
64 kb/s |
1 Mb/s |
10 Mb/s |
100 Mb/s |
1 Gb/s |
10 Gb/s |
---|---|---|---|---|---|---|
Packet Size |
|
|
|
|
|
|
64 bytes |
8 ms |
0.512 ms |
51.2 µs |
5.12 µs |
0.512 µs |
51.2 ns |
512 bytes |
64 ms |
4.096 ms |
409.6 µs |
40.96 µs |
4.096 µs |
409.6 ns |
1500 bytes |
187.5 ms |
12 ms |
1.2 ms |
120 µs |
12 µs |
1.2 µs |
9000 bytes |
1125 ms |
72 ms |
7.2 ms |
720 µs |
72 µs |
7.2 µs |
– Main.SimonLeinen - 28 Oct 2004 - 17 Jun 2010