Site to Site VPN Slow

I have a site to site VPN with 2 NSA 220 (New) with latest Sonic OS and Optimum Cablevision ISP 100/35 at both sites

all works fine, but the VPN link seems to be a bit slow.

I have a Domain Controller in Site A ( Subnet) and Site B ( Subnet) only computers.

I have the DNS under DHCP scope pointing to the Domain Controller’s DNS then i have the ISPs as 2nd and 3rd.

we have optimum cable internet (101/35) which is rated at 101(download) Megabits (Mbps) over 35 upload

I am getting speeds of 3 MBps over the WAN/VPN link when i transfer files.

I would like to see that number go up. Any ideas?

thanks in advance.
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Aaron TomoskyConnect With a Mentor Technology ConsultantCommented:
Lets start off with megabits and megabytes. Internet connection speeds are bits, file transfers are usually thought of in bytes.

You are transferring that file at 3.15 megaBYTES per second (x8 = 25.2 megabits per second). Given that the connection is rated at 35 Mbps (bits) you are pretty close. The difference can mostly be attributed to the SMB protocol not really being great at higher latency file transfers.

So basically, you are getting what you paid for and there isn't much we can do.
I recommend that you ONLY assign your own DNS servers via DHCP. Using ISP DNS servers for Active Directory joined machines leads to unpredictable access to domain resources.
giltjrConnect With a Mentor Commented:
Aaron Tomosky is spot on.

Just a little more info, since both sides are 100/35, the maximum you will get transferring data between the two sites is 35Mb/s (little b is bits and big B is Bytes).  Even though you can send at 100 Mb/s, the other side can only receive at 35 Mb/s.

In networking (actually all things) the fast throughput you can get is equal to the slowest point.

Rough est. of Bytes per second is the link speed in bits divided by 10.  So 35Mb/s divided by 10 = 3.5MB/s.

Since you are using a VPN there is some overhead that takes up some of the link and then each protocol (HTTP, SMB, CIFS, FTP, ect. )  has its own overhead the eats into the link speed.

If you are getting 3MB/s through-put doing a SMB copy over a VPN when the link speed is 35Mb/s you are doing real good.
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