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New Member

Slow Speeds with 3660??

We are looking to set up a VPn between two 3660's. Both have the encryption modules and have been tested using a variety of packet sizes.

Now the tests were performed by our network people and they say that the 3660's are struggling to reach 12Mbps using 3DES, because most of the packets generated by the host application are 64 bit.

Now excuse my ignorance, but I thought that the host PC would, in most situations, use the default MTU for data transmission.

Any suggestions would be welcome

New Member

Re: Slow Speeds with 3660??

This depends somewhat on the service and protocol. The requirement to fill a packet is calculated and governed by a number of forwarding criterion.

Even the cisco router itself has a nagle algorithm for despatch. Where the first characters of a stream are forwarded at the expense of packet size, and assuming the session has some block characteristic, goes onwards then to improve packet size. I'd expect them to be 64Bytes not bits.

Where you encrypt you implicitly compress, so that doesn't help when there is payload redundancy of information. If only TRANSIT routers could coalesce small packets to make bigger ones...

Can't comment on the 12Mbit/sec performance personally. I'd be happy with that in my applications.