I have few Windows and Linux Machines and am in verse to monitor what upload and download is being performed as the network system are running in slow pace.Any one who can recommend a tool or utility which can track uploads and download in a network.If it can track who is downloading or uploading with what size of data could really benefit.

You could try netop also if you can get access to a mirrored port on a switch that uploads to your router, or can place a hub between your computers and the Router, or lastly you could place a computer bewtween your router and network, then you could monitor it easier with a multitude of other software, even in realtime using something like iftop.

It seems to be Paid one.
Any Free software?

You could contrive some netfilter rules with iptables, which would selectively log the traffic of interest. The results can be inspected using the '-L -v' commands of iptables. This can be done with a script that parses the resulting output of iptables to maintain history logs, etc.
Example:
This script creates a chain 'HOSTX', which does nothing, but is invoked every time a packet passes the INPUT or OUTPUT chain of the filter table. These rules would cause all traffic to or from the host named 'hostx.your.domain' to be seen by the chain 'HOSTX'. A side effect of this is that the packet and byte count of the chain 'HOSTX' is accumulated by the filter. Later, perhaps on a scheduled interval, we can inspect the packet and byte count:
The accumulated counts can be zeroed with the -Z switch.
For your application, you would want to create rules in the INPUT, OUTPUT, or FORWARD chains that are selective about hosts, domains and ports of interest to you.

This would run on an individual server, monitoring only traffic seen on the server. If you actually want to monitor your network at large, you will need to use some kind of sniffer, like tcpdump (or it's GUI cousin, wireshark), but this also requires assistance from a smart switch on a switched ethernet network.

--- rod.

nettop is not a paid solution it is free, you could also try nagios, the free version, and several others

i think cacti or mrtg would be best for this.
http://www.cacti.net/screenshots.php

But cacti only works on SNMP managed devices, if he has an unmanaged switch he is likely to not be able to get any data. I have that problem in my network, only my router is managed so I can monitor those ports but I have no real idea of the other traffic except what I glean from netop and iftop which sits on a hub at the point where all the daisy chained switches connect to the router LAN port. I wish I had managed switches, though I am looking at getting one and daisy chaining each swith to it so at least I can isolate network traffic to individual switches.

nettop?? i assume you mean ntop..

yea sorry