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[1], 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. Developed behind closed doors, the mining service specification was initially announced via Slush's pool's website[2]. Shortly thereafter, alternative "cheat sheet" style documentation was provided by BTCGuild[3]. As the extension lacks a formal BIP describing an official standard, it has further developed only by discussion and implementation[4].
Software support
Tables showing miner/server support for Stratum mining protocol:
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 |