[1] Hanks, S. Li, T., Farinacci, D. Traina, P., "Generic Routing Encapsulation (GRE)", RFC 1701, October 1994.
[2] Hanks, S. Li, T., Farinacci, D. Traina, P., "Generic Routing Encapsulation (GRE) over IPv4 Networks", RFC 1702, October 1994.
[3] Lloyd, B. Simpson, W., "PPP Authentication Protocols", RFC 1334, October 1992.
[4] Postel, J. B., "Transmission Control Protocol", RFC 791, September 1981
[5] Postel, J. B., "User Data Protocol", RFC 768, August 1980.
[6] Reynolds, J., Postel, J., "Assigned Numbers", RFC 1700, October, 1994.
[7] Simpson, W., editor, "The Point-to-Point Protocol (PPP)", RFC 1661, July 1994.
[8] Ethertype for PPP, Reserved with Xerox Corporation.