nanog mailing list archives
Re: MTU path discovery and IPSec
From: Owen DeLong <owen () delong com>
Date: Wed, 03 Dec 2003 08:37:40 -0800
A subtle correction... A router where all MTUs are the same will never have to fragement anything. A router where all MTUs are >=1500 will probably not need to fragment anything. However, it is possible to attach a host via GIG-E or other media which supports jumbo frames (Frame relay, for example) and need to fragment to support a 1500 octet MTU. Currently, this would be a rare occurrence, but, it is possible in some circumstances. Eventually, if this assumption were to circulate widely, it could have similar consequences to many other errant assumptions on the internet. Owen--On Wednesday, December 3, 2003 11:19 AM -0500 "Steven M. Bellovin" <smb () research att com> wrote:
In message <120320031605.8838.1dea () comcast net>, jgraun () comcast net writes:Two questions: 1) I assume MTU path discovery has to been in enabled on each router in the pa th in order for it work correctly?!No -- it only has to be enabled on routers with smaller outbound MTUs than inbound. A router for which all links have a 1500-byte MTU doesn't need path MTU discovery; it will never need to fragment anything. --Steve Bellovin, http://www.research.att.com/~smb
-- If it wasn't crypto-signed, it probably didn't come from me.
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Current thread:
- MTU path discovery and IPSec jgraun (Dec 03)
- Re: MTU path discovery and IPSec Steven M. Bellovin (Dec 03)
- Re: MTU path discovery and IPSec Owen DeLong (Dec 03)
- Re: MTU path discovery and IPSec Valdis . Kletnieks (Dec 03)
- Re: MTU path discovery and IPSec Owen DeLong (Dec 03)
- <Possible follow-ups>
- RE: MTU path discovery and IPSec cproctor (Dec 03)
- Re: MTU path discovery and IPSec David Sinn (Dec 03)
- Firewall stateful handling of ICMP packets Sean Donelan (Dec 03)
- Re: Firewall stateful handling of ICMP packets Owen DeLong (Dec 03)
- Re: Firewall stateful handling of ICMP packets Valdis . Kletnieks (Dec 03)
- Re: Firewall stateful handling of ICMP packets Owen DeLong (Dec 03)
- Re: MTU path discovery and IPSec David Sinn (Dec 03)
- Re: Firewall stateful handling of ICMP packets Henry Linneweh (Dec 03)
- Re: MTU path discovery and IPSec Steven M. Bellovin (Dec 03)
- Re: MTU path discovery and IPSec Tony Rall (Dec 04)