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

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3answers
937 views

Geographic testing for latency

Really struggling to find tools that report latency loading a website from multiple geo-graphic locations. Are there such tools? I have begun replicating infrastructure in other EC2 regions, but find ...
3
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2answers
646 views

Cisco ASA Latency

What is the typical latency added when using a Cisco firewall such as ASA 5505? Are we talking less than 50 microseconds?
10
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4answers
5k 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 ...
0
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2answers
190 views

DSL :: Connection top speed is ok, but acceleration is low

My 2048 Kb/S ADSL connection downloads at the expected download speed 220 KB/s , but it takes too long to get to that speed, in other words the top speed is fine but the acceleration is terrible. This ...
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1answer
85 views

Why would reducing capacity under load improve latency on a server?

In this talk at Berkeley, Jeff Dean's slides contain the following note, about a third of the way through the presentation: Non-intuitive: remove capacity under load to improve latency (?!) The ...
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2answers
2k views

Need help troubleshooting highly variable ping times

I'm at work using Citrix (think Remote Desktop) to connect to client sites. With my job I have to write a fair bit of code while I'm connected remotely via Citrix, so the latency of my internet ...
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2answers
798 views

Is it bad that latency for our internal LAN varies greatly within the 15 - 40 ms range?

I've always thought the "typical" latency for a small office wired Ethernet network would be <5 ms. However, pinging the default gateway yields an average of 14 ms, and any host is around 30 ms. ...
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1answer
1k 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 ...
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3answers
1k 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 ...
4
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1answer
337 views

Combining Heroku with custom external services (e. g. Varnish or Postgres on EC2)

I'm planning to set up a Django site on Heroku. It will run on Heroku's Cedar stack, which allows Python apps, but doesn't include or support HTTP upstream caching with Varnish like the other stacks ...
4
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2answers
473 views

How to find the lowest latency midpoint between two geographic locations?

I'm looking for a geographic location (not service) to host internet services that will give me the lowest latency on connections from two other locations. How would I best determine the most ideal ...
4
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1answer
782 views

Hyper-V guests: intermittent latency

I am seeing latency on a Hyper-V host and its guests lately. When I run ping -f from a Linux prompt, I see the dots "pulsate" like a heartbeat indicating 2 successive latency spikes within 1 second ...
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5answers
3k 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 ...
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1answer
1k views

tcpdump udp data capture latency

I am using tcpdump to capture UDP packets and analyze network latency between a UDP broadcaster and my server. To calculate latency I compare the source host timestamps reported in UDP application ...
0
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2answers
1k views

What is the internal latency of a Cisco 3560?

Our trading network is very latency sensitive. We use Arista switches for the latency sensitive parts, and we know that the latency there is 600 ns. However, we have a Cisco 3560 in part of the ...
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3answers
260 views

Cached content causing a huge number of 404 errors, too many connections

My site has been largely unresponsive for three days due to a large amount of traffic. A JavaScript element on the page regularly requested images from the server, and the number of connections ...
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4answers
4k 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 ...
0
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1answer
84 views

use a offside proxy server to optimize site delivery?

Actually we have following setup for our website that gets traffic around the world: All JS, Images, Photos are stored on a CDN: Cloud Files ("Akamai light" powered). The WebApp server who send the ...
2
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1answer
814 views

Distributed File System Replication (DFSR) between Server 2008 & Server 2008 R2 over Gateway to Gateway VPN causing extreme network latency

The company I work for is in the process of setting up a branch office for one of our clients. We have 1.5 Mbps up/down T1s at each location, a Cisco RV042 router at each location hosting a Gateway ...
0
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2answers
44 views

Ways to estimate which network destination result is shorter/faster network path?

I am writing a program that allows users to supply a list of hostsname or IPs which I will then find out which host connectivity is faster and connect to it. And right as I am typing the question in ...
0
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3answers
109 views

How to log latency from remote sites to web server?

I have a web server that works great for North American users, but users from Asia will have problems every once in a while. I need to collect some data and the first set is to get some trending for ...
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2answers
224 views

Latency, Ping and Other Questions [closed]

In a high traffic application, like an online auction system, few ms could determine 'to win or 'to lose' the 'battle'. I'm from Brazil. Here, I 'ping' local sites - like UOL - and receive replies ...
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1answer
72 views

Fastest secure machine-machine network configuration [closed]

We currently host a large number of our application servers in a 3rd party data centre. Connectivity is then provided to our users across Europe through the vendor’s network. These machines run ...
1
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1answer
404 views

Network communication between dedicated web and database server

We're at the juncture (I can even say, right time) that we need to separate our database server apart from our application web server. This we arrived at after careful & thorough monitoring of ...
1
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1answer
739 views

What is the maximum normal latency for internal gateway switch?

I've been observing the ping latency to my server's internal gateway switch from my server machine. I noticed the ping spikes to as high as 500ms at times. Is this a possible indication that the ...
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2answers
154 views

OS parameters tuning for latency improvement

We are trying to improve the average latency of Java proxy application. The Java application receives a message from a client and proxies it to a necessary server. The protocol is binary, ...
3
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1answer
878 views

Diagnose cause of long running requests in IIS 7.0

We are running an ASP.NET web application on IIS 7.0, Windows Server 2008 R2, with SQL Server 2008 R2 for DB. On weekends, when the traffic is high, the request queue length in the IIS servers ...
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3answers
2k views

What can make windows fileshares slow without affecting ping latency, remote desktop, cpu usage or disk access?

I've got a server named Babylon. It's running Windows Server 2003 SP2 and lives in the midwest. I can ping Babylon from remote machines in the same building by hostname and IP. The latency is ...
0
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1answer
126 views

What settings should I modify to tune a Linux server for very small yet very high packet rate UDP receive loads?

I am tuning a server that needs to handle small (average of about 50 bytes) UDP packets. The average packet rate is approximately 100,000 packets/second. The data is very burst and can sometimes burst ...
1
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1answer
312 views

ping6 overhead compared to ping overhead

I am testing IPv6 latency from a Linux box, and I noticed this weird difference between IPv4 ping and IPv6 ping: # ping -n -A -q -c 500 speedtest.steffann.nl PING speedtest.steffann.nl (10.3.10.20) ...
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3answers
232 views

Monitoring Internet latency

I've been using smokeping to monitor internet latency (for early problem detection) at 8.8.8.8 for several months. On Friday the average latency went from 12ms to 55ms and has been at the 55ms plateau ...
2
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2answers
158 views

Set up server far away from target audience? [closed]

I live in Canada, and I want to move out of online web hosting and host stuff on my own server. The problem is, my website caters to a huge amount of US traffic, about 90 percent of traffic is US. ...
2
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2answers
95 views

QoS switch messing with local http traffic?

WE just moved our rack to a datacenter in the building. In our rack is a blade running centos and apache for intranet stuff. When we moved to the DC, we essentially extended our LAN there via adding a ...
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2answers
2k views

Remote Desktop Software with low latency

I am searching for a remote desktop software (Linux/Windows/Mac) which has a very low latency between input+output (lower then 1 sec). Some VNC (UltraVNC, RealVNC) solutions have a latency of 1-2 ...
2
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2answers
898 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 ...
1
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1answer
107 views

Strange server connection issue between two networks

I have two sites connected with 2 encryption devices on either side. Each site has a single flat switch connected to the encrption device on each side. Site A has servers. Site B has workstations. ...
4
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1answer
268 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 ...
2
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6answers
5k 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 ...
38
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7answers
11k 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 ...
1
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3answers
996 views

How to optimize Windows Server 2008 TCP Latency?

I 'm designing a distributed system and I deploy it on 1Gb cluster of Windows Server 2008 R2 But I have issue with the latency, the normal Ping takes 0.270ms and I believe this is too much, since all ...
1
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2answers
1k views

Troubleshooting intermittent network “drops”

We do most of our work on colocated servers in a datacenter over SSH. This means that we're connected to the boxes almost all day, 5 days a week. Intermittently, we'll see a lag between typing on the ...
4
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2answers
207 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 ...
2
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4answers
3k views

What kind of latency numbers are reasonable for a corporate network?

I am a software developer and I sometimes want to work from home but to write code over on a VPN is just tortuously slow. I have tried several different things to try and make it more reasonable. On ...
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1answer
1k views

what is the latency for an 8K transfer of Fibre Channel? (NFS vs FC) [closed]

I've heard it said that a 512byte data transfer over fibre channel is 10us so would an 8k (16x the data) take 160us? or is much of that 10us one time transmit overhead? I'm interested in comparing ...
3
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1answer
258 views

different ACK behaviors (slowing down throughput?)

I'm running netio (http://freshmeat.net/projects/netio/) on one machine (opensolaris) and contacting two different Linux machines (both on 2.6.18-128.el5 ), machine A and machine B. Machine A has a ...
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1answer
60 views

Measuring latency to a firewalled server

The firewall in front of this server is blocking ping requests. Is is still possible to measure latency to this system? If so, how?
2
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5answers
192 views

Measuring Site to Site Latency for Video Conferencing

We are currently looking at doing some international video conferencing, and before we go ahead and buy a system we need to measure Site to Site Latency & bandwidth objectively. I can't see any ...
0
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1answer
285 views

Slow upload to Server 2008 DC, Downloads work as expected

I have a Windows Server 2008 Domain Controller that I run as a do-it-all server. It has a GbE connection to the network and to every machine on the network. Downloads from the server file shares work ...
3
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2answers
9k 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 ...
4
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1answer
2k views

low latency TCP settings on windows 2008 R2

I am running a third party software on a W2008 server. This client connects to a server via TCP. The average ping times between the two are 1ms. However, when I check the tcp connection in resource ...