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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

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