Questions tagged [latency]

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

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120 votes
9 answers
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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 ...
Jeff Atwood's user avatar
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74 votes
8 answers
269k views

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. ...
Peter Perháč's user avatar
44 votes
7 answers
17k views

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 ...
exo_cw's user avatar
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42 votes
4 answers
52k views

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 ...
sleske's user avatar
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38 votes
3 answers
49k views

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 ...
Phil's user avatar
  • 523
32 votes
6 answers
27k views

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 ...
pufferfish's user avatar
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29 votes
7 answers
44k views

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 ...
nick_eu's user avatar
  • 391
26 votes
4 answers
81k views

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 ...
jacg's user avatar
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20 votes
6 answers
30k views

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 ...
neezer's user avatar
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18 votes
3 answers
29k views

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 ...
Daniel Griscom's user avatar
18 votes
2 answers
45k views

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 ...
yzfr1's user avatar
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16 votes
4 answers
30k views

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's user avatar
16 votes
1 answer
69k views

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. ...
Jimm's user avatar
  • 303
15 votes
3 answers
7k views

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 ...
Don's user avatar
  • 151
14 votes
2 answers
40k views

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 ...
Alex V's user avatar
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13 votes
6 answers
45k views

sssd and ldap authentication cache

On our box running OpenSUSE 12.2 we have installed OpenLDAP and sssd daemon. We are using these two services for user authentication. Recently we created a script which creates new web-users for our ...
Seth Rayer's user avatar
11 votes
1 answer
11k views

difference between taskset and cpuset

I'm trying to reduce the latency of my linux network application. I've learned that there are two tools for "binding" a program to particular CPU core: taskset and cpuset. Which one should I prefer? ...
John Linberg's user avatar
10 votes
2 answers
8k views

Ping with long delay but short reported time

What does it mean when a ping reports a reasonable time (~10ms) but actually takes quite a long wall clock time (~15 seconds)? (Additionally, passing the -U option for "full user-to-user latency" has ...
Cascabel's user avatar
  • 288
9 votes
3 answers
12k views

Why do tracert latencies not add up to ping latency?

One might expect the sum of the tracert latencies to equal 267ms:
pulsar's user avatar
  • 193
9 votes
2 answers
550 views

Higher TCP latencies in the latest versions of Linux

In my research group, we recently upgraded the OS on our machines from Red Hat 6.2 to Debian 8.3 and observed that the TCP round trip time through the integrated Intel 1G NICs between our machines had ...
Stephen's user avatar
  • 91
8 votes
4 answers
12k views

High latency, yet ping shows low latency

We're seeing latencies of ~100-300ms for services accessing a remote resource within the same subnet, yet when we use ping (ping size was of a similar size as of packets sent normally), we see ...
Mindaugas Mozūras's user avatar
8 votes
2 answers
24k views

What is best tool to measure network latency?

How do you measure network latency in Windows ? I know ping as one of the tool. Can Windows Performance monitor do it ? Any ideas which counters should I add to measure it. This is for SharePoint ...
Madhur Ahuja's user avatar
8 votes
3 answers
22k views

Internet latency map

I would like to see a latency map, showing the lowest latencies achieved between various destinations around the world. What is for example the lowest latencies achieved between Denmark and India. ...
David's user avatar
  • 447
8 votes
2 answers
6k views

Is there anything I can do to decrease waiting time for my static http requests (in chrome's network panel)?

I am running amazon aws ec2 micro instance on Ubuntu 14.04 with apache 2.4.9. The reason for having this instance is just to test and to solve some bugs before rolling up the project. Currently there ...
Salvador Dali's user avatar
7 votes
7 answers
17k views

Latency in TCP/IP-over-Ethernet networks

What resources (books, Web pages etc) would you recommend that: explain the causes of latency in TCP/IP-over-Ethernet networks; mention tools for looking out for things that cause latency (e.g. ...
NPE's user avatar
  • 679
7 votes
2 answers
3k views

Does routing distance affect performance significantly?

When I say routing distance, I mean on a global scale. For instance, if my target audience is in China, do I look for a host within China?
gAMBOOKa's user avatar
  • 999
7 votes
6 answers
17k views

MySQL performance over a (local) network much slower than I would expect

MySQL queries in my production environment are taking much longer than I would expect them too. The site in question is a fairly large Drupal site, with many modules installed. The webserver (Nginx) ...
user15241's user avatar
  • 103
7 votes
3 answers
2k views

TCP Window Scaling for Satellite Connections

A satellite connection generally has a RTT around 500ms. Connections generally suffer sub-optimal transfer speeds, in spite of large amounts of bandwidth because TCP acknowledgements take too long to ...
directedition's user avatar
7 votes
1 answer
17k views

High latency/drops between Cisco switches in two locations. How to troubleshoot?

I'm receiving user complaints about poor network application performance between two parts of a large warehouse facility. The software is a curses-based terminal application running on a Linux server. ...
ewwhite's user avatar
  • 198k
6 votes
5 answers
5k views

Reducing Latency Between US and India/South Asia or Desktop Access on CentOS 7+ GNOME

We have a server in US DC that is getting accessed from US and India, S Asia and SE Asia. With 128GB RAM, CPU and Cent OS 7 + GNOME desktop and it runs VNC server - the server gets access through VNC ...
SS891's user avatar
  • 71
6 votes
8 answers
21k views

Latency in Internet connections from Europe to USA

I'm looking for a (cheap) Web hoster. Basically all the hosting providers that I can find, and match my requirements are located in the USA. But my target audience is in (Western-)Europe, I know for ...
GvS's user avatar
  • 255
6 votes
1 answer
4k views

iproute: disable "tc" command

I'm after running this command to simulate a network latency of 500ms with 100ms std deviation: tc qdisc add dev eth2 root netem delay 500ms 100ms Trouble is, I forget how to cancel this command! My ...
Eamorr's user avatar
  • 636
6 votes
3 answers
4k views

Akamai vs smaller CDN for small/medium-size ecommerce traffic? (caching, latency, NetStorage)

The small/medium sized online retail company I work for uses Akamai as our CDN for static images, but I'm wondering whether it might be hurting rather than helping and, if it's suboptimal, what we ...
Aaron's user avatar
  • 223
6 votes
5 answers
6k views

OpenVPN over TCP, terrible latency but only on Win7 x64

I know TCP encapsulated over TCP is a terrible idea in general, but I can deal with the occasional decreased performance and MTU issues, and the snowball effect TCP within TCP provides where error ...
mr_daemon's user avatar
  • 490
5 votes
5 answers
13k views

finding the best network latency between two countries

I know there are many tools to test for bandwidth and latency, but they all rely on having at least one host from which you can run those tests. I wonder whether there's an online source or some ...
Yoav Aner's user avatar
  • 581
5 votes
1 answer
2k views

Using tc to decrease bandwidth to a specific destination address

I am trying to find the shortest path between two hosts H1 and H2 using Dijkstra code. Setting a condition in one of the switches on that path. the condition is: if the packet sending to H2 then ...
a66a's user avatar
  • 53
5 votes
1 answer
2k views

Esxi with iSCSI SAN slows down with many multiple VMs running

I have a server with ESXi 5 and iSCSI attached network storage(4x1Tb Raid-Z on freenas). Those two machines are connected to each other with Gigabit ethernet, and a procurve switch in between. After ...
Esa Varemo's user avatar
5 votes
6 answers
14k views

Intermittent high ping/latency problem

I have been working with my ISP (which is a WISP, actually Fixed Broadband Wireless) trying to figure out why I intermittently get high latency. The latency is detectable in online games and other ...
Hugh Jeffner's user avatar
5 votes
2 answers
589 views

Latency on a small Linux NFS4 client/server system

We are a computer science department at a small university, running a RHEL 7 server using NFS4 and Fedora 24 clients (~40 client machines, ~150 users--rarely concurrent). We are having latency ...
Sprenkliest's user avatar
5 votes
2 answers
193 views

Trans-atlantic VOIP

We're a Canadian business on the east coast and will soon be opening up a new call centre in Australia. This new call centre will be handling our graveyard shift and will be overlapping with the ...
jonathanserafini's user avatar
5 votes
1 answer
591 views

Hardware/topology recommendations for low latency UDP network

I'm setting up a LAN comprised of 60 end nodes that are receiving a high volume of UPD datagrams from one master server. The server sends 60 unique datagrams every 100ms, each datagram is 64 bytes. ...
Mattias's user avatar
  • 285
5 votes
2 answers
2k views

Linux TCP/IP tuning for low throughput network?

I have two linux machines connected by a radio modem. The bandwidth is about 2kbps, with ping times of around 400ms (5% packet loss). Currently, ssh sessions have a delay in the order of 5 seconds, ...
John K's user avatar
  • 51
5 votes
0 answers
297 views

Linux machine unable to send IPv6 packets for five minutes about once per day [closed]

I am operating a router based on a Linux server running Debian stable (Buster). It uses Quagga to speak BGP4 to four peers (one of which sends the entire Internet routing table for IPv4 and IPv6, the ...
ftc's user avatar
  • 91
5 votes
0 answers
2k views

Latency (wait ttfb) on EC2

My application is crawling a website. I use this crawler : https://github.com/rfussien/leboncoin-crawler On my dev environment, the latency is acceptable (3-4 sec) but on my prod server (ec2 T2....
Julien Malige's user avatar
4 votes
1 answer
4k views

Why the time taken to fetch results of a query for 10,000 times from a RDS is so uneven? (experiment)

tl;dr : Why the time taken to fetch results of a SELECT statement for 10,000 times from a RDS when requested from an EC2 is so uneven? Updated the question with results of small and medium RDS ...
Sumit Sinha's user avatar
4 votes
1 answer
62k views

what is acceptable datastore latency on VMware ESXi host?

Looking at our performance figures on our existing VMware ESXi 4.1 host at the Datastore/Real-time performance data Write Latency Avg 14 ms Max 41 ms Read Latency Avg 4.5 ms Max 12 ms People don'...
BeowulfNode42's user avatar
4 votes
2 answers
365 views

Networking Hardware Suggestions For Low-Latency Networking

We've come to the stage of our project where we want to take the software to the next level, generally response times of 20µs or less. Software wise its as good as it gets (though there's room for a ...
Seminar's user avatar
  • 41
4 votes
2 answers
12k views

Network latency -- how long does it take for a packet to travel halfway around the world? [duplicate]

Possible Duplicates: How does geography affect network latency? How much network latency is “typical” for east - west coast USA? If I'm hosting an app in NY, what kind of delay can ...
kaneuniversal's user avatar
4 votes
3 answers
4k views

Route traffic to node with lowest latency in HAproxy

Is it possible to route requests via HAproxy to a server that has the lowest latency from the source IP? This seems like a much needed requirement but I can't seem to find anything. My problem is ...
rehanift's user avatar
4 votes
8 answers
9k views

How can I control the network latency?

My company is developing a network software and its network stability is very important. So my supervisor want me to set up the testing environment for our QA team. I can take care of almost ...
Sam's user avatar
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