What proxy server / Internet gateway to choose for an office of 100-200 people?

Question

Squid

The server which would let out users in the Internet is necessary. The requirements are as follows:
- It is highly desirable that it works under *nix
- Open Source is desirable
- Proxying with http and https logging. Web proxy should work transparently. Those. The ip address of the client must be preserved after passing through the proxy. Approximately as it happens in squid with the setting:
http_port 3129 tproxy
- It is necessary to be able to disable NAT on the output. Those. The ip address of the client must be preserved after passing through the proxy. At the exit to the Internet there is already a piece of iron that deals with NAT, shaping, balancing, channel reservation. Additional NAT on the proxy will only interfere with the balancer.
- Filtering http and https by URLs and domains
- Filtering traffic by ip addresses and port numbers
- Possibility of authorization through AD. The presence of the following user authorization option: the user launches the browser, enters the address, the system gives him an authorization form, after authorization the user is redirected to the requested URL. The system remembers the ip address of the client and releases it to the Internet.
- No need to install any clients in the user's system
- IPv4 and IPv6 support
- Web interface
We've been using traffic inspector for a long time, but it's paid and works under windows.
Abills seems like a dark horse to me, and the author has such a feeling that he deliberately keeps his wiki in a deplorable state so that people pay him for consultations. Has anyone used Abills in production? What are your impressions of Abills?
Kerio is a good system, but it's expensive.
Microsoft Forefront Threat Management Gateway is Microsoft, and that says it all.
Are there any other solutions?
Z.Y. I have my own prototype, written in python, which meets almost all the stated requirements. Adding functionality is not a problem. The problem is to bring it to production, and all this is beautifully designed. This takes time, and time is not enough. As a matter of fact, this prototype is now working for us.

Answer 1

so than did not suit squid? or here is the topic Distributions of software routers