llnwd.net is a domain used by customers of the Limelight Networks content distribution network (CDN), they host content such as downloads and streaming media for companies like EA Games, BBC and Microsoft.
You will probably notice a lot of internet traffic going to this domain, that is because it hosts streaming content etc. So, for example you visit bbc.co.uk and listen to the radio online for 1 hour you will only get say 5MB of traffic to bbc.co.uk but 50MB of traffic to the llnwd.net domain.
WhoIs information for this domain can be found here.
Example BBC URL you might see in any proxy or firewall logs :-
The official direct website for Limelight Networks is https://www.limelight.com/
This website is safe and contains no malicious content – for an updated check on this site click here