Yes, the L2 header is replaced at the end of each L2 segment/hop. The L2 error detection will do the job - discard and report erroneous packet - on each L2 segment/hop. One or more L2 segments/hops may correspond to one IP hop, so a packet error detection and discard on any of the L2 segments/hops will be equivalent to the IP hop error detection and discard. Alex -----Original Message----- From: Manfredi, Albert E [mailto:[EMAIL PROTECTED] Sent: Friday, February 01, 2008 3:36 PM To: Alex Conta Cc: ipv6@ietf.org Subject: RE: Checksum in IPv6 header
But there's no reason to believe that the L2 is the same as you enter the tunnel. You're going through a router, often to a different link layer. The L2 overhead is stripped off and replaced. Bert _____ From: Alex Conta [mailto:[EMAIL PROTECTED] Sent: Friday, February 01, 2008 8:09 AM To: Manfredi, Albert E Cc: ipv6@ietf.org Subject: RE: Checksum in IPv6 header I am not seeing the problem. The "non-secure IPv6 link" you're mentioning is a "virtual link", over a "real" physical link. The "real" physical link, the "real" L2, provides the error detection, which uncovers packet errors in the IPv6 tunnel packets, like on any other IPv6 packet. -----Original Message----- From: Manfredi, Albert E [mailto:[EMAIL PROTECTED] Sent: Thursday, January 31, 2008 3:09 PM To: Alex Conta Cc: ipv6@ietf.org Subject: RE: Checksum in IPv6 header [....] _____ From: Alex Conta [mailto:[EMAIL PROTECTED] Sent: Thursday, January 31, 2008 12:50 PM To: 'Rahim Choudhary'; Templin, Fred L; 'Fred Baker' Cc: ipv6@ietf.org Subject: RE: Checksum in IPv6 header The reason is IPsec tunnels, where encrypted packets are tunneled through a non-secure IPv6 link. In such cases, you can't count on L2 checksums when going across the tunnel boundaries. Or did I miss part of that recent thread? Bert
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