Accurate way to check latency between Server

iplatency

First of all, I hope my post are is posted in the right section . Below are something i got confused hope you one can help.

My business partner 's IP server are in: Sanjose, CA , and I am looking for a datacenter which give the least latency to that IP. I found 2 . 1st datcenter is in San Francisco, CA . 2nd data center is in Newyork.

Then I do the ping from each datacenter to the my partner's IP.

1st datcenter's result: 75ms

2nd datacenter's result: 2ms

I 've done multiple time, 2nd datacenter always give better result. Now my question is:

Isn't the 1st datacenter suppose to give better result, since their location are closer ? How come the result produce different, what is the accurate way to check latency ?

Best Answer

To check latency over time, I recommend Matt's Traceroute: http://www.bitwizard.nl/mtr/

That being said, geography is not always the determining factor for latency. Latency is often caused by the number of network hops it takes to reach your target machine, but there is a large array of factors that can come into play.

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Difference Between IP Address 0.0.0.0 and 127.0.0.1

The only thing is that you're not saying "all addresses should have access" -- that's done in your firewall(s) and/or the server software and/or other security layers like tcpwrappers.

0.0.0.0, in this context, means "all IP addresses on the local machine" (in fact probably, "all IPv4 addresses on the local machine"). So, if your webserver machine has two IP addresses, 192.168.1.1 and 10.1.2.1, and you allow a webserver daemon like apache to listen on 0.0.0.0, it will be reachable at both of those IP addresses. But only to what can contact those IP addresses and the web port(s).

Note that, in a different context (routing) 0.0.0.0 usually means the default route (the route to "the rest of" the internet, aside from routes in your local network etc.).

Networking – Typical Network Latency for East to West Coast USA

Speed of Light:
You are not going beat the speed of light as an interesting academic point. This link works out Stanford to Boston at ~40ms best possible time. When this person did the calculation he decided the internet operates at about "within a factor of two of the speed of light", so there is about ~85ms transfer time.

TCP Window Size:
If you are having transfer speed issues you may need to increase the receiving window tcp size. You might also need to enable window scaling if this is a high bandwidth connection with high latency (Called a "Long Fat Pipe"). So if you are transferring a large file, you need to have a big enough receiving window to fill the pipe without having to wait for window updates. I went into some detail on how to calculate that in my answer Tuning an Elephant.

Geography and Latency:
A failing point of some CDNs (Content Distribtuion Networks) is that they equate latency and geography. Google did a lot of research with their network and found flaws in this, they published the results in the white paper Moving Beyond End-to-End Path Information to Optimize CDN Performance:

First, even though most clients are served by a geographically nearby CDN node, a sizeable fraction of clients experience latencies several tens of milliseconds higher than other clients in the same region. Second, we find that queueing delays often override the benefits of a client interacting with a nearby server.

BGP Peerings:
Also if you start to study BGP (core internet routing protocol) and how ISPs choose peerings, you will find it is often more about finances and politics, so you might not always get the 'best' route to certain geographic locations depending on your ISP. You can look at how your IP is connected to other ISPs (Autonomous Systems) using a looking glass router. You can also use a special whois service:

whois -h v4-peer.whois.cymru.com "69.59.196.212"
PEER_AS | IP               | AS Name
25899   | 69.59.196.212    | LSNET - LS Networks
32869   | 69.59.196.212    | SILVERSTAR-NET - Silver Star Telecom, LLC

It also fun to explore these as peerings with a gui tool like linkrank, it gives you a picture of the internet around you.

Best Answer

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Difference Between IP Address 0.0.0.0 and 127.0.0.1

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