Slow speeds across an office link

We have recently been trying to implement a Server 2012 instance of DFS across 2 of our main sites.  The servers are Dell R720xd with Intel NICs installed with all the latest firmware drivers and updates installed.  When the machines were on the same site, transfer speeds where 100-105MB/s transferring between them, however as soon as one was transferred to another site, these speeds have become 1-2MB/s.  The link between the offices is a dedicated 100MB link with a single hop between our 2 main sites; ping response between the 2 sites is between 26ms (empty office) to 35ms (both offices at peak times).  Our other site in London has a ping response of 20-21ms to our Liverpool site and doesn't experience these issues at all; achieving around 9.5MB/s transfer during peak times (it will hit almost 11MB/s when offices are quiet).

We have had our ISP investigate the link between our Manchester and Liverpool sites and can't find anything wrong at all; when we try and transfer a file from our old Netapp appliance (FAS2020) to the other site we achieve a much quicker 6-8MB/s (although it starts at around 2-3MB and climbs slowly).

We tried the various tweaks and policy changes on 2012 (disabling autotuning, rss, tcp chimney offload, bandwidth throttling, SMB signing etc) but to no avail.  So we downgraded one of the servers to 2008 R2 and performed the same steps - unfortunately we still experience the same problems!

I am rapidly running out of ideas here - I thought the bandwidth throttling reg fix would sort our issues, but it appears not; although I had my suspicions that a 30ms ping time would not be classified as high latency enough to throttle back bandwidth.

Can anyone help??
Amaze_ITAsked:
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Jim Dettman (Microsoft MVP/ EE MVE)President / OwnerCommented:
One thing that comes to mind is MTU size; you say this is point to point, but are your running a VPN to get that or is it truly a dedicated point to point (which is getting to be rare)?   If so, you might be fragmenting a lot of packets.

Jim.
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Dirk MareSystems Engineer (Acting IT Manager)Commented:
Are you getting those speeds on all portocols?
FTP?
HTTP?

Can you run speedtest using TCP and UDP?
http://www.smallnetbuilder.com/lanwan/lanwan-howto/30408-measuring-network-performance-jperf

+ 1 for MTU settings
http://www.networkworld.com/article/2224654/cisco-subnet/mtu-size-issues.html

DirkMare
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Amaze_ITAuthor Commented:
We are not running a VPN between the sites, we are running straight links with acls through our ISP to avoid as much latency as possible (NOT public links!)  i've been through the configuration with our ISP and we have attempted to modify the MTU size on both our servers and through their routers, but the problem persists regardless.

The strange thing is, when we reboot a router (power off) the speed jumps up and then will gradually die off again over a period of 12 hours of so?  Seems to be regardless of protocols
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frankhelkCommented:
Just a suspicion: maybe you have some kind of name resolution problem ? If the machines run into a timeout every time they try to resolve a name that would slow many things down ... that might be i.e. if you have set upü name resolution by DNS and the machines try to resolve with WINS first ... check the preceedence of the name services or put the critical ones into the HOSTS file, which is evaluated first.

There are possibly more trapdoors like that ...
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Amaze_ITAuthor Commented:
I did check with regards to name resolution as a saw a few people mention this as a possible issue; i even went so far as to reinstall and configure WINS across the sites to ensure there was no problem there; then i did the registry key to force the system to use DNS only - all to no avail.  The have AD integrated DNS, each DC is also a DNS server, primary server is the local site, then secondary is always the central site main DNS server.  All looks to be good!  Althought to be honest I did not test the use of HOSTS file entries for the DNS/AD servers as well.  worth a shot i guess..
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frankhelkCommented:
Maybe a look at the HOSTS file would help .. if there are wrong entries, name resoution would be a hassle.

The HOSTS file is evaluated first ... sometimes anti-malware-tools put many entries in to prevent malware from calling home. If i contains hundreds of entries, checking it could have an impact on name resolution performance.
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frankhelkCommented:
Maybe a look at the HOSTS file would help .. if there are wrong entries, name resoution would be a hassle.

The HOSTS file is evaluated first ... sometimes anti-malware-tools put many entries in to prevent malware from calling home. If i contains hundreds of entries, checking it could have an impact on name resolution performance.
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Windows Server 2012

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