What is the bandwidth overhead for IPSEC tunnel with 3DES encryption ?

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Jan 5th, 2009

If I create an IPSEC / 3DES tunnel between to sites where the both have a 1.5MB connection what is the effective size of the tunnel? 1.5MB - 8% = 1.38MB?

I have this problem too.
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dominic.caron Tue, 01/06/2009 - 07:49


An Ip packet should have 1500 bytes. The ESP encapsulation is variable but is no bigger then 58 bytes. This give you a 3.8% drop in effective size for big packet. If you trafic is all made of small packet, the drop will be bigger. (9.6 % for 600 bytes packets)

dominic.caron Tue, 01/06/2009 - 07:54

By the way, the encryption used has no effect on the link size. The ESP encapsulation overhead will stay the same. It will have an impact on the encrypting hardware at both site. Since 1.5 Mbps is low, most router should handle is just fine.


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