Garlic routing is a variant of onion routing that encrypts multiple messages together to make it more difficult for attackers to perform traffic analysis.
Garlic routing is one of the key factors that distinguishes I2P from Tor and other privacy/encryption networks. The name comes from actual garlic, whose structure this protocol resembles.
List of P2P applications that use garlic routing 
- I2P - an anonymizing overlay network which allows applications to run on top of it (open source, written in Java)
- Perfect Dark - a P2P client which relies on a mixnet and distributed datastore to provide anonymity (freeware, written for Windows)