Browse Prior Art Database

Protection of BGP Sessions via the TCP MD5 Signature Option (RFC2385) Disclosure Number: IPCOM000002957D
Original Publication Date: 1998-Aug-01
Included in the Prior Art Database: 2019-Feb-15
Document File: 6 page(s) / 9K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

A. Heffernan: AUTHOR

Related Documents

10.17487/RFC2385: DOI


This memo describes a TCP extension to enhance security for BGP. [STANDARDS-TRACK]

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 28% of the total text.

Network Working Group A. Heffernan Request for Comments: 2385 cisco Systems Category: Standards Track August 1998

Protection of BGP Sessions via the TCP MD5 Signature Option

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.

Copyright Notice

Copyright (C) The Internet Society (1998). All Rights Reserved.


This document describes currrent existing practice for securing BGP against certain simple attacks. It is understood to have security weaknesses against concerted attacks.


This memo describes a TCP extension to enhance security for BGP. It defines a new TCP option for carrying an MD5 [RFC1321] digest in a TCP segment. This digest acts like a signature for that segment, incorporating information known only to the connection end points. Since BGP uses TCP as its transport, using this option in the way described in this paper significantly reduces the danger from certain security attacks on BGP.

1.0 Introduction

The primary motivation for this option is to allow BGP to protect itself against the introduction of spoofed TCP segments into the connection stream. Of particular concern are TCP resets.

To spoof a connection using the scheme described in this paper, an attacker would not only have to guess TCP sequence numbers, but would also have had to obtain the password included in the MD5 digest. This password never appears in the connection stream, and the actual form of the password is up to the application. It could even change

Heffernan Standards Track [Page 1]

RFC 2385 TCP MD5 Signature Option August 1998

during the lifetime of a particular connection so long as this change was synchronized on both ends (although retransmission can become problematical in some TCP implementations with changing passwords).

Finally, there is no negotiation for the use of this option in a connection, rather it is purely a matter of site policy whether or not its connections use the option.

2.0 Proposal

Every segment sent on a TCP connection to be protected against spoofing will contain the 16-byte MD5 digest produced by applying the MD5 algorithm to these items in the following order:

1. the TCP pseudo-header (in the order: source IP address, destination IP address, zero-padded protocol number, and segment length) 2. the TCP header, excluding options, and assuming a checksum of zero 3. the TCP segment data (if any) 4. an independently-specified key or password, known to both TCPs and presumably connection-specific

The header and pseudo-header are in network byte order. The nature of the key is deliberately left unspecified, but it must be known by both ends of the connection. A particular TCP implementation will determine what the application m...