nanog mailing list archives
Re: VoIP over IPsec
From: Iljitsch van Beijnum <iljitsch () muada com>
Date: Tue, 18 Feb 2003 10:13:01 +0100 (CET)
On Tue, 18 Feb 2003, Petri Helenius wrote:
Maybe a stupid question... why would you need GRE tunneling while IPsec has a tunnel mode of its own?
Probably because a major router vendor, despite of repeated customer requests, declined to implement routing across such tunnel mode.
So if the router uses tunnel mode (as per the RFC) despite the GRE tunnel the packet has three IP headers... So that's 160 bits ethernet layer 1 + 18 bytes ethernet layer 2 overhead, 24 bytes for the GRE tunnel, 20 bytes for the IPsec tunnel mode IP header, 10 - 12 bytes for the ESP header, 16 bytes for the initialization vector, 20 bytes for the original IP header and finally 20 bytes for the RTP header. With a 40 byte payload that adds up to 188 bytes on the wire of which 78% is overhead...
Current thread:
- VoIP over IPsec Charles Youse (Feb 16)
- Re: VoIP over IPsec Petri Helenius (Feb 16)
- Re: VoIP over IPsec Jared Mauch (Feb 17)
- Re: VoIP over IPsec Stephen Sprunk (Feb 16)
- Re: VoIP over IPsec Steven M. Bellovin (Feb 17)
- Re: VoIP over IPsec Charlie Clemmer (Feb 17)
- Re: VoIP over IPsec Stephen Sprunk (Feb 17)
- Re: VoIP over IPsec Steve Feldman (Feb 17)
- Re: VoIP over IPsec Iljitsch van Beijnum (Feb 17)
- Re: VoIP over IPsec Petri Helenius (Feb 17)
- Re: VoIP over IPsec Iljitsch van Beijnum (Feb 18)
- RE: VoIP over IPsec David Luyer (Feb 18)
- RE: VoIP over IPsec Vadim Antonov (Feb 18)
- Re: VoIP over IPsec Stephen Sprunk (Feb 18)
- Re: VoIP over IPsec Iljitsch van Beijnum (Feb 18)
- Re: VoIP over IPsec Vadim Antonov (Feb 18)
- Re: VoIP over IPsec Iljitsch van Beijnum (Feb 17)
- Re: VoIP over IPsec Petri Helenius (Feb 16)
- Re: VoIP over IPsec Kurt Erik Lindqvist (Feb 18)
- <Possible follow-ups>
- RE: VoIP over IPsec Charles Youse (Feb 17)
- RE: VoIP over IPsec Charles Youse (Feb 17)
- RE: VoIP over IPsec Ejay Hire (Feb 17)
- RE: VoIP over IPsec Charles Youse (Feb 17)