app layer protocol
request, response
what fields in msgs & how fields are delineated
meaning of info in fields
rules for when and how processes send & respond to messages
defined in RFCs
allows for interoperability
http / smtp
e.g. skype
request, response
what fields in msgs & how fields are delineated
meaning of info in fields
rules for when and how processes send & respond to messages
defined in RFCs
allows for interoperability
http / smtp
e.g. skype