3
votes
1answer
640 views

How to find out the reason(s) why the network interface is dropping packets?

Is there a way on Linux to get statistics about the various reasons packets were dropped? On all network interfaces (openSUSE 12.3) on several servers, ifconfig and netstat -i are reporting dropped ...
1
vote
1answer
121 views

Debug: Cisco VPN Router runs 100% CPU

I've turned logging on and all I am currently getting are Debug/Kernel logs. Nothing above debug. This was also during offsite hours when hardly any traffic was going on. I have also upgraded to the ...
7
votes
1answer
2k views

Unexpectedly shrunk window

I run a major media upload/download site and I noticed these: Is this serious or background noise due to the big file sizes and is there any tweaks I can add to /etc/sysctl.conf to improve and ...
1
vote
2answers
1k views

Disable ICMP Unreachable replies

I am using a Debian 6 - 64bit OS and my server is ddosed/flooded through udp protocol from time to time. I basically host game-servers and my firewall is set to rate-limit the packets on allowed ports ...
1
vote
1answer
3k views

Testifying rasing net.core.somaxconn can make a difference

I got into an argument on the net.core.somaxconn parameter: I was told that it will not make any difference if we change the default 128. I believed this might be enough proof: "If the backlog ...
2
votes
3answers
4k views

CentOS 6: strange page allocation failure messages [duplicate]

I set up a new Server with CentOS 6.4 final as successor for an old mysql server and I'm facing some problems with it. From time to time mysql connections are being disconnected. Furthermore the ...
0
votes
1answer
322 views

Realtek R8168 network driver 8.034.00 not compiling under CentOS 5.8 64-bit [closed]

I'm trying to compile Realtek R8168 driver 8.034.00 on CentOS 5.8 64-bit and I got this: make -C /lib/modules/2.6.18-308.16.1.el5/build SUBDIRS=/r8168-8.034.00/src clean make[1]: Wejście do ...
1
vote
1answer
131 views

ip_conntrack ideal or not for server stability

By default the module ip_conntrack is installed into the kernel. My question is simple, is having ip_conntrack a performance booster for better tracking of connections? On VPS nodes they do not have ...
1
vote
1answer
415 views

Networking / Multipath dropping

I'm having problem with few linux boxes running xen. They are acting as hypervisors and they are connected to SAN using multipath setup to provide storage to guest vms. Every now and then one of two ...
1
vote
4answers
1k views

rtl8139 driver in modern linux kernels - is it included?

I need to support the realtek rtl8139 network card - is this included in modern (> 3.0) linux kernels? do I have to load any modules or install anything?
3
votes
2answers
327 views

How any routing protocol packet reaches(flows of operations) from NIC card (physical layer) to any Routing (OSPF/RIP/BGP) daemon?

The problem is rearding the routing protocol packet flow in any linux/unix device where multiple routing protocol daemons are running. How any routing protocol packet reaches(flows of operations) ...
18
votes
3answers
32k views

Improving TCP performance over a gigabit network with lots of connections and high traffic of small packets

I’m trying to improve my TCP throughput over a “gigabit network with lots of connections and high traffic of small packets”. My server OS is Ubuntu 11.10 Server 64bit. There are about 50.000 (and ...
6
votes
2answers
1k views

TCP SYN Flooding Detection Method in the Linux Kernel

When the Linux kernel detects SYN Flooding it logs a message like: possible SYN flooding on port 80. Sending cookies Does anyone know the exact method that the kernel uses to detect this?
1
vote
2answers
1k views

server will not reply (syn -ack)

I like to use the following commands to manage 'TIME_WAIT', in the hope to free up resources. echo 20 > /proc/sys/net/ipv4/tcp_fin_timeout sysctl -w net.ipv4.tcp_tw_reuse=1 sysctl -w ...
1
vote
2answers
262 views

How to control NIC traffic against process on RHEL6 or Fedora15?

Now i have some processes, e.g 2. named P1, P2. P1 and P2 will need to transmit data from NIC. Maybe we can take P1,P2 as two browser. I have two questions: 1) I want to limit P1 max to 100KB/s, and ...
5
votes
3answers
4k views

Kernel Log “TCP: Treason uncloaked!”

On one linux server (Gentoo hardened), we are experiencing bursts of the following messages in dmesg from time to time: TCP: Treason uncloaked! Peer xx.xx.xxx.xxx:65039/80 shrinks window ...