Review your favorite Linux distribution.
Go Back > Forums > Linux Forums > Linux - Networking
User Name
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.


  Search this Thread
Old 04-23-2016, 05:02 AM   #1
Registered: Sep 2012
Posts: 125

Rep: Reputation: Disabled
what is the maximum concurrent connection (session) that a firewall can support ?

One of the benchmarking item of the firewall device is the maximum concurrent connection that it can support.
I have some question about:
1- what does exactly mean maximum concurrent connection (session) and why is important (performance considerations or memory considerations) ?
2- When a new entry and where is created in linux and what tools create this entry ?

3- again, When a new entry is created (for example for TCP by SYN-packets or syn, syn-ack and ack packets)?
4- if we just send a syn packet, one entry is created in connection table, is it correct ?
Old 04-24-2016, 01:26 AM   #2
Registered: Apr 2010
Location: Kinshasa, Democratic Republic of Congo
Distribution: RHEL, Fedora, CentOS
Posts: 525

Rep: Reputation: 95

I will try to answer your questions from what I know of firewall.

1- A firewall works at the border of internal network (your LAN) and an external one (Internet). When for example an internal machine tries to go to Internet, the FW will mask the internal IP address while forwarding the request out on Internet. The FW will keep track of the mapping between the internal IP (and random original port) and its external IP (and its also random and original port), in order to be able to redirect correctly the responses back. So the maximum concurrent connection is the mximum size of that mapping table. It is important because that the core of FW function. Obviously the mapping table is held in memory, and somehow handled by the processor. So it has impacts on both.
2- In Linux the FW function is handled by the kernel. While iptables of firewall-cmd (or firewalld) are command tool to ease the addressing to the kernel. The entry are created when the connection is established, and destroyed when it ends.
3- I think it is at the SYN from the client.
4- Yes. And if there is no response, it should time out and get cleaned.


concurrent connections, connection, sessions

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
SSH concurrent session limit and idle session time out lasygsd Linux - Newbie 3 10-30-2014 07:56 AM
Resolve maximum number of concurrent connections sibar Linux - Networking 4 12-10-2009 02:03 AM
Apache to support large number of concurrent users? your_shadow03 Linux - Newbie 1 11-09-2009 08:56 AM
SFTP max concurrent connection breaktime123 Linux - General 1 02-01-2009 01:46 PM
How to prevent concurrent user connection accessing squid proxy? suhas! Linux - Server 1 07-12-2007 06:46 AM > Forums > Linux Forums > Linux - Networking

All times are GMT -5. The time now is 06:09 PM.

Main Menu
Write for LQ is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration