(Fwd'd from 'int-area'): Please see attached for a proposal that addresses the MTU issues for *-in-IPv4 tunnels. It also addresses the multi-mtu subnet issue, since it does not rely on ICMP "packet too big" messages from the last-hop router. Elements of the proposal include: - trailing "footer" and data as part of encapsulation - tiny echo requests wrapped in encapsulation headers and trailing padding - used as probes to elicit tiny echo replies - tunnel endpoint discovers tunnel far end EMTU_R and reassemby timeout values in initial probes - periodic probing to discover the tunnel path MTU, plus EMTU_R; reassembly timeout fluctuations - inner fragmentation to create inner packets no larger than EMTU_R - outer fragmentation to create outer packets no larger than the tunnel path MTU - coservative use of fragmentation to avoid packet loss within the tunnel - TE drops unfragmentable packets larger than EMTU_R and sends ICMP PTB w/o wasting tunnel resources - protection against fragment misassociations - protection against off-path attacks - protection against wrapped ip_id - backwards compatibility - incremental deployment - NAT traversal Please review and send comments. Thanks - Fred fred.l.templin@boeing.com
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- Subject: I-D ACTION:draft-templin-inetmtu-00.txt
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- Date: Tue, 18 Sep 2007 12:15:01 -0700
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- Thread-topic: I-D ACTION:draft-templin-inetmtu-00.txt
A New Internet-Draft is available from the on-line Internet-Drafts directories. Title : Packetization Layer Path MTU Discovery for IP/*/IPv4 Tunnels Author(s) : F. Templin Filename : draft-templin-inetmtu-00.txt Pages : 20 Date : 2007-9-18 The nominal Maximum Transmission Unit (MTU) MTU of the Internet has become 1500 bytes, but existing IP/*/IPv4 tunneling mechanisms impose an encapsulation overhead that can reduce the effective path MTU to smaller values. Additionally, existing IP/*/IPv4 tunneling mechanisms are limited in their ability to discover and utilize larger MTUs. This document specifies new mechanisms for conveying packets over IP/*/IPv4 tunnels that address these issues. A URL for this Internet-Draft is: http://www.ietf.org/internet-drafts/draft-templin-inetmtu-00.txt To remove yourself from the I-D Announcement list, send a message to i-d-announce-request@ietf.org with the word unsubscribe in the body of the message. You can also visit https://www1.ietf.org/mailman/listinfo/I-D-announce to change your subscription settings. Internet-Drafts are also available by anonymous FTP. Login with the username "anonymous" and a password of your e-mail address. After logging in, type "cd internet-drafts" and then "get draft-templin-inetmtu-00.txt". A list of Internet-Drafts directories can be found in http://www.ietf.org/shadow.html or ftp://ftp.ietf.org/ietf/1shadow-sites.txt Internet-Drafts can also be obtained by e-mail. Send a message to: mailserv@ietf.org. In the body type: "FILE /internet-drafts/draft-templin-inetmtu-00.txt". NOTE: The mail server at ietf.org can return the document in MIME-encoded form by using the "mpack" utility. To use this feature, insert the command "ENCODING mime" before the "FILE" command. To decode the response(s), you will need "munpack" or a MIME-compliant mail reader. Different MIME-compliant mail readers exhibit different behavior, especially when dealing with "multipart" MIME messages (i.e. documents which have been split up into multiple messages), so check your local documentation on how to manipulate these messages. Below is the data which will enable a MIME compliant mail reader implementation to automatically retrieve the ASCII version of the Internet-Draft.Attachment: ATT8176442.TXT
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