SOCKS Protocol Version 5 (RFC1928)

Network Working Group M. Leech Request for Comments: 1928 Bell-Northern Research Ltd Category: Standards Track M. Ganis International Business Machines Y. Lee NEC Systems Laboratory R. Kuris Unify Corporation D. Koblas Independent Consultant L. Jones Hewlett-Packard Company March 1996

SOCKS Protocol Version 5

Status of this Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Acknowledgments

This memo describes a protocol that is an evolution of the previous version of the protocol, version 4 [1]. This new protocol stems from active discussions and prototype implementations. The key contributors are: Marcus Leech: Bell-Northern Research, David Koblas: Independent Consultant, Ying-Da Lee: NEC Systems Laboratory, LaMont Jones: Hewlett-Packard Company, Ron Kuris: Unify Corporation, Matt Ganis: International Business Machines.

1. Introduction

The use of network firewalls, systems that effectively isolate an organizations internal network structure from an exterior network, such as the INTERNET is becoming increasingly popular. These firewall systems typically act as application-layer gateways between networks, usually offering controlled TELNET, FTP, and SMTP access. With the emergence of more sophisticated application layer protocols designed to facilitate global information discovery, there exists a need to provide a general framework for these protocols to transparently and securely traverse a firewall.

Leech, et al Standards Track [Page 1]

RFC 1928 SOCKS Protocol Version 5 March 1996

There exists, also, a need for strong authentication of such traversal in as fine-grained a manner as is practical. This requirement stems from the realization that client-server relationships emerge between the networks of various organizations, and that such relationships need to be controlled and often strongly authenticated.

The protocol described here is designed to provide a framework for client-server applications in both the TCP and UDP domains to conveniently and securely use the services of a network firewall. The protocol is conceptually a "shim-layer" between the application layer and the transport layer, and as such does not provide network- layer gateway services, such as forwarding of ICMP messages.

2. Existing practice

There currently exists a protocol, SOCKS Version 4, that provides for unsecured firewall traversal for TCP-based client-server applications, including TELNET, FTP and the popular information- discovery protocols such as HTTP, WAIS and GOPHER.

This new protocol extends the SOCKS Version 4 model to include UDP, and extends the framework to include provisions for generalized strong authentication schemes, and extends the addressing scheme to encompass d...