Solved

TCP/IP Checksum Offload Issues

Posted on 2012-03-14
1
3,005 Views
Last Modified: 2016-11-23
Hello Guru’s

I have been troubleshooting some random performance issues regarding network throughput etc. and found something interesting.  While using the wireshark I’m noticing high amount of errors - outgoing packets marked black with red Text and the note [incorrect, should be xxxx (maybe caused by "TCP checksum offload"?)].

I have noticed that I can make some changes  - Control Panel->Network and Internet Connections->Network Connections, right click the connection to change and choose 'Properties'. Press the 'Configure...' button, choose the 'Advanced' tab to see or modify the "Offload Transmit TCP Checksum" and "Offload Receive TCP Checksum" values.

However, my Dell 2950 using a Broadcom BCM5708C NetXtreme II GigE driver with
IPv4 Checksum Offload (Tc/Rx enabled) . I would like to know what this really does? Why is this causing these check sum errors? Is there a repercussion of disabling this feature or not? I should also note that we are running on GIG backbone if that matters or not.

Thanks in advance.
0
Comment
Question by:Littlemorris
1 Comment
 
LVL 10

Accepted Solution

by:
mat1458 earned 500 total points
ID: 37724162
If you use TCP Offload you let a processor in the NIC perform the checksum calculation. So a software like Wireshark that runs in the OS does not see the correct checksum. A high number of checksum errors today is rather rare, in my opinion it can be sourced by the way you capture.

Do you capture the entire packet? Otherwise the checksum checking does not make much sense. There are some hints about the errors you are seeing in the Wireshark Wiki:
http://wiki.wireshark.org/TCP_Checksum_Verification
http://www.wireshark.org/docs/wsug_html_chunked/ChAdvChecksums.html
0

Featured Post

What Security Threats Are You Missing?

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

Join & Write a Comment

Usually shares are where we want them for our users and we tend to take them for granted. There are times, however, when those shares may disappear causing difficulty for your users. One of the first things to try is searching for files that shou…
Creating an OSPF network that automatically (dynamically) reroutes network traffic over other connections to prevent network downtime.
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

747 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

11 Experts available now in Live!

Get 1:1 Help Now