how to queue incoming downloads and schedule them by priority?

Question

In a office network, how to queue incoming downloads and later, it will be scheduled by priority?

Is there any such open source project /tool available?

I have heard about squid proxy, but does it allow re scheduling ?

Answer 1

There isn't anything magical that will "queue" downloads coming from different machines over arbitrary protocols. What you can do is use the QoS features of your firewalls/routers to prioritize bandwidth allocation either by source or destination (or both). This can let you make rules like "downloads for patches from Microsoft, Apple, and Ubuntu have the highest priority, while everything else gets 1/16th that throughput". Or you can make a rule like "steve's downloads get 8x the bandwidth of Fred's downloads if they are running at the same time." Some HTTP proxies (like Squid) may have QoS features as well.

So, if Joe starst a download from microsoft.com, it will fill your office's connection. If Sally then starts browsing YouTube, Sally will steal at most 1/16th of your office connection's bandwidth. Note that QoS rules can an get really complicated really quickly, with thresholds, minimum and maximum throughput, etc. It can be unmanageable after a while, even on a small network. In fact, the only QoS rules we still use on our corporate network are "VoIP, NTP, and ICMP get highest priority. SMTP, FaceBook, and YouTube get the lowest priority. Everything else is normal priority."

Note that you may have to coordinate QoS with your ISP, as you cannot control the QoS of traffic that gets sent to your network (unless you intentionally drop packets that could be delivered in order to trick the sender into slowing down, but that is really complicated and only works for TCP traffic).