nanog mailing list archives
Re: job screening question
From: Jason Baugher <jason () thebaughers com>
Date: Thu, 05 Jul 2012 18:51:34 -0500
Geez, I'd be happy to find someone with a good attitude, a solid work ethic, and the desire and aptitude to learn. :)
Jason On 7/5/2012 5:18 PM, William Herrin wrote:
On Thu, Jul 5, 2012 at 5:05 PM, Derek Andrew <Derek.Andrew () usask ca> wrote:You implement a firewall on which you block all ICMP packets. What part of the TCP protocol (not IP in general, TCP specifically) malfunctions as a result?Isn't MTU discovery on IP and not TCP?If you want to overthink the question, the failure in the TCP protocol is that it doesn't adjust the MSS to match the path MTU. It continues to rely on the incorrect path MTU estimate, sending too-large packets which will never arrive. This happens because TCP doesn't receive a notification that the path MTU estimate has changed from the default because the lower layer PMTUD algorithm never receives the expected ICMP packet. This is, incidentally, is a detail I'd love for one of the candidates to offer in response to that question. Bonus points if you discuss MSS clamping and RFC 4821. The less precise answer, path MTU discovery breaks, is just fine. Regards, Bill Herrin -- William D. Herrin ................ herrin () dirtside com bill () herrin us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004
Current thread:
- Re: job screening question, (continued)
- Re: job screening question David Coulson (Jul 05)
- Re: job screening question William Herrin (Jul 05)
- Re: job screening question David Coulson (Jul 05)
- Re: job screening question Scott Howard (Jul 05)
- Re: job screening question William Herrin (Jul 05)
- Re: job screening question Ray Soucy (Jul 05)
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- Re: job screening question Derek Andrew (Jul 05)
- Re: job screening question William Herrin (Jul 05)
- Re: job screening question Randy (Jul 05)
- Re: job screening question William Herrin (Jul 05)
- Re: job screening question Owen DeLong (Jul 05)
- Re: job screening question Derek Andrew (Jul 05)
- Re: job screening question Jason Baugher (Jul 05)
- Re: job screening question Mike Hale (Jul 05)
- Re: job screening question Jon Lewis (Jul 05)
- Re: job screening question Owen DeLong (Jul 05)
- Re: job screening question William Herrin (Jul 05)
- Re: job screening question George Herbert (Jul 05)
- Re: job screening question Jon Lewis (Jul 05)
- Re: job screening question William Herrin (Jul 05)
- Re: job screening question Randy (Jul 05)
- Re: job screening question David Edelman (Jul 05)
- Re: job screening question William Herrin (Jul 05)
- Re: job screening question David Coulson (Jul 05)