IPsec implementation over 64K connection.

[Darshan Argekar]

One of the customer is running over MPLS network over 64K connection. The current line utilisation over MPLS connection shows it to be around 40Kbps. The Plan is to deploy GRE over IPsec over transport mode. GRE over IPSec with transport mode introduces ~55 bytes overhead but is there any calculation which can depict how this will affect over line utilisation? by how much percent the line utilisation might shoot up?

[Herbert Baerten]

Darshan,

well since the overhead is per packet, it will depend a lot on the average packet size.

If they're small (e.g. voice) then worst case you're looking at 87,5% overhead (a 64 byte packet  will be 120 bytes after encryption).

If they're big (e.g. file transfer) then overhead can be as low as 4% (e.g. a 1442 byte packet will be 1496 bytes after encryption).  Be careful not to introduce fragmentation though,or you loose some of that precious bandwidth.

If the packet size is varying, the result can be anywhere in between...

hth

Herbert