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Questions tagged [latency]

Latency is the time period between a signal being sent and a signal being received

Latency is the time period between a signal being sent and a signal being received. In computer networking this can be the time between a sending of a packet and receiving of a packet.

To illustrate we can use the ping command:

PING google.be (173.194.66.94) 56(84) bytes of data.
64 bytes from google.be (173.194.66.94): icmp_req=1 ttl=47 time=76.6 ms
64 bytes from google.be (173.194.66.94): icmp_req=2 ttl=47 time=74.8 ms
64 bytes from google.be (173.194.66.94): icmp_req=3 ttl=47 time=79.6 ms

The latency here is 76.6 ms.

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How much network latency is "typical" for east - west coast USA?

At the moment we're trying to decide whether to move our datacenter from the west coast to the east coast. However, I am seeing some disturbing latency numbers from my west coast location to the east coast. Here's a sample result, retrieving a small…
Jeff Atwood
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Why is the response on localhost so slow?

I am working on a tiny little PHP project for a friend of mine, and I have a WAMP environment setup for local development. I remember the days when the response from my local Apache 2.2 was immediate. Alas, now that I got back from a long, long…
Peter Perháč
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Troubleshooting latency spikes on ESXi NFS datastores

I'm experiencing fsync latencies of around five seconds on NFS datastores in ESXi, triggered by certain VMs. I suspect this might be caused by VMs using NCQ/TCQ, as this does not happen with virtual IDE drives. This can be reproduced using…
exo_cw
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Why do mobile networks have high latencies? How can they be reduced?

I'm increasingly seeing mobile networking technologies being used to get internet access in areas where it is otherwise not available. While mobile networking is usually not yet viable as the primary internet connection, mobile technology looks like…
sleske
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Data obtained from ping: is it round trip or one way?

I have 2 servers, each in two separate locations. I need to host an application on one, and the database server on the other. From the app server, if I ping the database server, on average I get about 30ms. My question is: When I query the database…
Phil
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Speed up SFTP uploads on high latency network?

I'm trying to transfer a set of large files internationally using SFTP, but I am finding my international partner can't get upload speeds above ~50k despite very good connections on either side. We can get multiple connections uploading at this…
nick_eu
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Measure total latency of SSH session

Is there a way to measure/report the overall latency in a tunneled SSH session? My particular setup is: Client (OS X + wifi router + ADSL modem) Gateway SSH server exposed to Internet Internal SSH target to which I'm tunneling I'm interested in…
pufferfish
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Intermittently high ping times to router via Wi-Fi

On my local network there are (among others) 5 machines (running Debian Jessie or Arch) wirelessly connected to a Netgear WNDR4000 router. Below is a graph of the ping times to the router from each of the machines, collected over a period of around…
jacg
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How does geography affect network latency?

I have the option of hosting our database/web server at a managed hosting company on the East Coast (US) or one on the West Coast (US). Our company is based out of New York City, and both hosting providers give our box a dedicated T1 line. How much…
neezer
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Do changes in SPF records take time to propagate?

I'm setting up SPF records for my domain, and am not getting the results that I expect. It's quite possible I'm making some sort of mistake, but first I'd like to ask: does it take time for the changes I make to SPF records to propagate?
Daniel Griscom
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Limit incoming and outgoing bandwidth and latency in linux

I realise many similar questions have already been asked, but so far I've yet to find a solution to my problem. I have a virtual linux server (running Debian Squeeze) that I use for testing of website speeds in order to measure increase and decrease…
yzfr1
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How to troubleshoot latency between 2 linux hosts

The latency between 2 linux hosts is about .23ms. They are connected by one switch. Ping & Wireshark confirm the latency number. But, i dont have any visibility into what is causing this latency. How can i know if the latency is due to NIC on host A…
Jimm
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Determining a realistic measure of requests per second for a web server

I'm setting up a nginx stack and optimizing the configuration before going live. Running ab to stress test the machine, I was disappointed to see things topping out at 150 requests per second with a significant number of requests taking > 1 second…
Don
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Tuning NFS for minimum latency

How can I achieve low latency for NFS exports in order to e.g. have developers work nicely in Eclipse/Visual Studio with their workspaces mounted over NFS?
Robert Munteanu
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Low latency TCP settings on Ubuntu

There is a server for measurements running on Ubuntu in my lab. And there is C program, which receives data through TCP connection and should as soon as possible send a reply. Configuration CPUs: 2 processors x 4 cores - Intel(R) Xeon(R) CPU E5345…
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