Memcached supports two main protocols; the classic ASCII, and the newer binary. It's simpler to write clients and debug problems via the ASCII protocol, but binary affords us many new abilities.

• Text Protocol
• Binary Protocol
• Slides on binary protocol by Toru Maesaka (2008)

Further, there are sub protocols and proposals

• SASL Authentication
• Range operations - Not to be supported in core, but defined for storage engines and compatible clients.