Stratum

Stratum is a proposal for an open source client-server "overlay" protocol that enables thin clients. It is currently used by Electrum. While originally announced right before 2012, the protocol has not yet been completed and proposed as a BIP for standardisation.

Mining extensions

The stratum protocol was extended to support pooled mining as a replacement for obsolete getwork protocol in late 2012. The mining service specification was initially announced via Slush's pool's website. Shortly thereafter, alternative "cheat sheet" style documentation was provided by BTCGuild. As the extension lacks a formal BIP describing an official standard, it has further developed only by discussion and implementation.

Software support

Tables showing miner/server support for Stratum mining protocol:

• Mining software
• Poolservers

Pool support

Server	get transactions	dynamic difficulty	job frequency	resume
Bitminter	No	Yes	30s	No
Slush's pool	No	Yes	30s	No
BTCGuild	No	Yes	30s	No
Eloipool	Yes	Yes	55s	No
HHTT	No	No (User selected difficulty)	30s	No
50BTC	No	No (User selected difficulty)	5s	No
Ozcoin	No	Yes or user selected	30s	No

Criticism

Closed development

The mining extensions have been criticised as having been developed behind closed doors without input from the wider development and mining community, resulting in various obvious problems that could have been addressed had it followed the standard BIP drafting process.

Displacing GBT

The mining extensions were announced after the community had spent months developing a mostly superior open standard protocol for mining (getblocktemplate). Because stratum's mining extensions launched backed by a major mining pool, GBT adoption suffered, and decentralised mining is often neglected while stratum is deployed.