Value,Description,Reference
1,Routing Information,"[Xerox System Integration Standard: Internet Transport 
Protocols. XSIS 028112, December 1981.]"
2,Echo,"[Xerox System Integration Standard: Internet Transport 
Protocols. XSIS 028112, December 1981.]"
3,Error,"[Xerox System Integration Standard: Internet Transport 
Protocols. XSIS 028112, December 1981.]"
4,Packet Exchange,"[Xerox System Integration Standard: Internet Transport 
Protocols. XSIS 028112, December 1981.]"
5,Sequenced Packet,"[Xerox System Integration Standard: Internet Transport 
Protocols. XSIS 028112, December 1981.]"
12,PUP,"[Boggs, D., J. Shoch, E. Taft, and R. Metcalfe, ""PUP: 
An Internetwork Architecture"",
XEROX Palo Alto Research Center, CSL-79-10, July 1979; also in
IEEE Transactions on Communication, Volume COM-28, Number 4, April 1980.]"
13,DoD IP,
20-37,Experimental,