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57

I'm going to put this as gently as I can: Wireless networks (802.11) suck. The 2.4GHz band (802.11b, g, and some n devices) is a festering pit of radio noise. Everything from baby monitors to microwave ovens pollute this section of the spectrum, and the wanton proliferation of wireless networks has it so congested that you're frankly lucky to get 1Mbit ...


48

For all intents and purposes, no, this is not possible. Even if it were, the technical and contractual logistics required would cripple your business. Think through this a bit more: Joe user at University signs up for your service. You then approach one of the University's many providers (which one? How might you know what provider Joe user's traffic ...


47

Since this has been elevated to be the canonical question on hairpin NAT, I thought it should probably have an answer that was more generally-valid than the currently-accepted one, which (though excellent) relates specifically to FreeBSD. This question applies to services provided by servers on RFC1918-addressed IPv4 networks, which are made available to ...


41

Require SSL, keep SELinux turned on, monitor the logs, and use a current PostgreSQL version. Server side Require SSL In postgresql.conf set ssl=on and make sure you have your keyfile and certfile installed appropriately (see the docs and the comments in postgresql.conf). You might need to buy a certificate from a CA if you want to have it trusted by ...


29

Depending on the frequency at which you exchange data with the customer, it could be cheaper, faster, and more efficient to mail them a storage drive, then pay to have it overnighted back to you when populated with data. This would cost a tiny fraction of what your agreement plan would cost long-term. Turnaround time may be nearly the same if lots of data is ...


27

The website runs on a server process. When you shut down the server process, the server does not magically turn off. Also not when you misconfigure your firewall (and block port 80) neither does the server go off nor does the ICMP rule in the firewall get deleted.


24

First, Bandwidth is not the same as latency. A faster connection won't necessarily reduce your latency. 450ms does seem a little slow but not that far off if you are going 1/2 way across the world. As a frame of reference a high speed, low latency link will take ~70-80ms to cross the US. You might be able to eek a bit less latency by changing your provider ...


23

This is a bit of a complicated Question, so I'll start with the basics. Forgive me if you know all this already. MTU is the Maximum Transmission Unit, the largest packet of data that a computer interface will send. For Ethernet the default is 1500 Bytes. Ethernet frames typically are allowed to be up to 1522-1542 (depends on what you count) and the extra ...


20

The netmask is wrong on the enp4s1 (WAN) interface. This system has configured an IP address of 49.x.x.x and a netmask of 255.0.0.0 (prefix /8). But this is not the netmask that your ISP gave you. As a result, you will be unable to access almost all websites whose IP addresses also start with 49. To resolve the problem, fix the netmask or prefix ...


20

ISPs often prioritize traffic to speedtest.net so that they can brag how fast their connections are, while in reality, they don't provide that much bandwidth. They're perfectly aware that most users will only check that site for confirmation. You also have to keep in mind that transfer speed relies both on the client and the server. In today's world most ...


18

Out of the box, you are guaranteed that iptables will start before the interface is brought up by the order of the startup scripts. Look at the "chkconfig" line in each startup script and you will see the runlevels it is "on" when active, the start order, and the stop order. You are not guaranteed that the interface will not be brought up if the iptables ...


17

Well, 1.1.1.1 is an IP address. As far as who it is - it's public address space that bad internet citizens tend to use as a placeholder: inetnum: 1.1.1.0 - 1.1.1.255 netname: Debogon-prefix descr: APNIC Debogon Project descr: APNIC Pty Ltd country: AU admin-c: AR302-AP tech-c: AR302-AP mnt-by: ...


17

It sounds like in effect you want to pay a users ISP to zero-rate traffic to your site, similar how to some cell carriers allow you to stream video from certain websites without impacting your allocation. If you are a major company like Google or Netflix then this has a ghost of a chance of being feasible, otherwise most companies will not talk to you -- ...


14

Many sites will tell you in the HTTP headers: $ curl -s -I hotmail.com | grep Server Server: Microsoft-IIS/7.5 $ curl -s -I pinterest.com | grep Server Server: nginx/0.8.54 Some include the OS and sometimes version: $ curl -s -I linuxquestions.com | grep Server Server: Apache/2.2.9 (Unix) $ curl -s -I red.com | grep Server Server: Apache/2.2.3 (Red Hat) ...


14

Typically, autonomous systems (ASNs) use an IGP (which can be OSPF, IS-IS or iBGP) so routers in their network know how to reach eachother. Networks connected to these routers and reachable through them can be distributed via this IGP as well, but iBGP may be used for that too. ASNs exchange routing information via BGP. Typically, only aggregated prefixes ...


14

In addition to the other reasons posted, TCP connections don't work well with large files when the bandwidth-delay product becomes large. Like on an otherwise fast connection to an island. See Wikipedia's entry on TCP tuning. So Speedtest can dump a small file through the connection at 95 mb/sec, but wget can only get 10 mb/sec on a 20 MB file.


13

It certainly varies by vendor of the wireless product but in my experience it usually works something like this: Your laptop makes a wireless connection to an intelligent access point, which may be connected to a centralized management station. Your first web request is intercepted and replied to with a Location: header that redirects you to a login/policy ...


13

It's not your DNS servers that you would have to worry about. It's the client machines that got infected by this malware. Basically what happened was that when the FBI arrested the authors of the virus they took control of the DNS servers that they where running. Now, they can't run them forever using tax payer's money and they are on a limited amount of ...


13

Please don't be offended, but if you don't know the answer to this question, you're not ready to do this. System and network administration at the service provider level requires some pretty in depth industry knowledge. The OSS/BSS involved (operational support systems, business support systems) alone could take years to learn. There's a reason why ...


13

Back the bus up here for a minute: Your client has a machine of unknown provenance that wasn't wiped and reinstalled from known good media, and they've been using it for who-only-knows-what (hopefully not banking or business), and you want to waste time troubleshooting it?! I'm sorry, but You're Doing It Wrong my friend. Forget troubleshooting: wipe that ...


13

That is indeed one of the problems with CGN. Sharing a resource means that all suffer the consequences when one abuses the resource. A bank that I consulted for implemented IPv6 on the server side exactly for that reason: more and more users end up behind CGN, hopefully also with IPv6. When their security department has to block an IPv4 address of a CGN, ...


12

I would setup a copy of smokeping on some system on your network. It doesn't ping every second, and you probably don't need it do. Instead it will periodically send out a burst of ~20 pings at the same time, and then count how many respond, and how fast each returns. The results are graphed. Here is results for my a system at home, over my Comcast ...


12

If you do not need screen sharing, why not just ssh to the machine to do whatever it is you need to . If you do need screen sharing (why) you could just use vnc.


12

You can look for OS fingerprinting functionality built into NMap. However, if you're looking for something like "What is Google running?" you won't get far since you won't know what's behind their load balancers, or firewalls will block it, and fingerprinting can only be so accurate so you can get false reports back and you may not get anywhere when the ...


11

A "faster" connection (as you're referring to it) doesn't lower latency. A "faster" connection allows more data to be placed on the wire in a given period of time. Bandwidth is a measure of capacity. Latency is a measure of delay. EDIT Here's an example of the difference between bandwidth and latency: Imagine 2 internet connections, one 10Mbps and the ...


11

No one has mentioned sshfs yet. If you're on a modern linux distro and have ssh access to the remote host, it's as simple as: sshfs user@hostname:/remote/directory /local/directory Performance is quite acceptable (but not nearly as fast as a streamed sync like rsync if you require the whole directory).


11

I'm basically parroting Michael here, but this is too much to paste into a comment: ;sai.ngo. IN A ngo. 172800 IN NS b0.nic.ngo. ngo. 172800 IN NS d0.nic.ngo. ngo. 172800 IN NS a2.nic.ngo. ngo. 172800 IN NS a0....


10

Back in college, we would use Vocalnet to broadcast such alerts. The investigator would stick his/her head out of the office door and shout "HEY EVERYBODY, THE INTERNET IS DOWN!" into the hallway.


10

Try dhclient eth0 if it's a direct connection to your ISP or there's a DHCP server in your network. Can you ping hosts in your network, if any? Please post the output of ifconfig eth0 and route -n.


10

1.) Bandwidth != latency, and jitter matters. A dedicated leased line's latency is constant and is generally substantially lower than a DSL or FIOS connection. This can be a critical point for certain types of applications. The upstream bandwidth from a given POP is certainly a point of variability, but generally far less so than consumer-oriented ...


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