### 3.7 Poor Man's Multiplexing

By default, Polipo does not use Poor Man's Multiplexing (see Poor Mans Multiplexing). If the variable `pmmSize` is set to a positive value, Polipo will use PMM when speaking to servers that are known to support pipelining. It will request resources by segments of `pmmSize` bytes. The first segment requested has a size of `pmmFirstSize`, which defaults to twice `pmmSize`.

PMM is an intrinsically unreliable technique. Polipo makes heroic efforts to make it at least usable, requesting that the server disable PMM when not useful (by using the ‘`If-Range`’ header) and disabling it on its own if a resource turns out to be dynamic. Notwithstanding these precautions, unless the server cooperates1, you will see failures when using PMM, which will usually result in blank pages and broken image icons; hitting Reload on your browser will usually cause Polipo to notice that something went wrong and correct the problem.

#### Footnotes

[1] More precisely, unless CGI scripts cooperate.