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Slow site to site VPN Performance



Recently my company decided to save money by transitioning away from MPLS and metro ethernet based connectivity to Internet based site to site VPN's.    For our stores we are installing Time Warner and Comcast business class Internet.  Generally either 100/10 or 100/20 with one location being on a Comcast fiber based Internet circuit that is 30/30.


So far our experience has not been all that great.  Our data center currently has a 100/100 fiber based Internet connection (1g to be installed next week).  Our 100mb is not oversubscribed at this point.  Whenever I try to do a windows based drag and drop from the data center to the store on average I get from 1.5-2.5MB on the copy.  so basically 12-20 megabit despite the fact that my store has a 100mb download pipe.  If I try to use FTP over the VPN I get the same speed.  However if I take the same server at the DC and do a 1 to 1 NAT and then FTP to it from the same store over the Internet and not through the VPN I see close to the 100mb speed that we are subscribed to.  Interstingly whenever I copy from the store to the DC I almost always get the full 20mb upload speed.   Finally at our 30/30 store I get all 30mb both directions.  


My data center has a 500D and all of my stores have a 140D.  So I would think there is enough horsepower to be able to handle the occasionally large file copy.  We don't generally move a lot of data over our VPN's.  Mainly web based applications with some videos.  However when we need it, it would be nice to have a nice file copy speed.  I understand there is some overhead on VPN's but not to this degree.   I have already tried various MTU sizes on WAN interfaces at both the DC and my lab store.


At this point I am stumped.  Why is my VPN running so slowly?  Is it possible that TW and/or comcast throttles UDP 500/4500 or the ESP protocol?   At this point I along with our CIO is ready to abort this project and go with Fiber in all 90 locations.  But I am not quite ready to give up.  


Any help would be appreciated.




emnoc wrote:

I am afraid I don't know exactly how to see if ESP is being wrapped in UDP packets. Is there a diag command or something that will show that?


ESP is it's own protocol , like tcp,udp,gre,icmp  ....and is not encapsulated into another protocol. IKSAKMP uses UDP.


wiki or google ESP and protocol #50  or protocol #51 ( AH )


That is my understanding.   TCP being 6 and UDP being 17.   Trying to leave no stone unturned here.  If someone was able to get max speed between a fiber peer and a coax peer I would love to know how.   Maybe these Comcast modems can not handle anything in volume other than IP 6 and 17.   I don't know


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