Slow network performance with Large Send Offload is enabled

[guest]

I have a Windows 2008 server with two NIC's (Intel PRO/1000 PL and Intel PRO/1000 PM), and one virtual external switch connected to each NIC.

With the 01/14/08 network driver, I get very low throughput on both NIC's (~10KB/sec when downloading from my server when it should be around 11MB/sec).

I've found that disabling "TCP Large Send Offload (IPv4)" on the virtual switch and "Large Send Offload v2 (IPv4)" on the physical adapters solves the problem.

Is this a bug in the driver?

[guest]

TCP offloading appears to be problematic in most cases (except for the rare cases where the infrastructure actually makes use of it).

It causes chunking of network traffic (you could also say it bursts).

In cases without Hyper-V disabling offloading will generally improve network performance for most cases.