Questions tagged [latency]

For questions about network latency. For instance: the propagation of your network traffic, where the transmission medium can be defect or the processing of packets by a network device has slowed down.

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22
votes
4answers
8k views

Does physical distance affect download speed?

I just had an argument with a colleague of mine and thought I'd just reach out to the experts on this. Here's the scenario. We were using a website that measures your connection's speed. We tested ...
16
votes
12answers
34k views

What would cause high latency anytime there is traffic on WAN?

I have a network that has been experiencing slow internet speeds. After a great deal of troubleshooting, I have determined that any streaming content/downloads will cause the latency of WAN traffic to ...
15
votes
2answers
2k views

Serialization and serialization times in 40G/10G and 100G/25G Ethernet

I've recently been involved in discussions about lowest-latency requirements for a Leaf/Spine (or CLOS) network to host an OpenStack platform. System architects are striving for the lowest possible ...
14
votes
4answers
12k views

What's the difference between `Latency` and `Round Trip Time`?

Golang community provide a HTTP/2 demo website to compare the performance between HTTP 1.1 and HTTP/2. We can choose different latency, e.g. 0s latency, 30 ms latency, 200ms latency. Is latency a ...
13
votes
6answers
3k views

Network latencies between opposite ends of the Earth

This is just out of curiosity. I'm currently in South-east asia, and when I pinged domains such as bbc.co.uk and google.com (in California), I get latencies of around 5ms as below: 64 bytes from 151....
13
votes
4answers
57k views

How to find the source of increased latency?

I've got monitoring setup on several devices in our office. The ping response time to small access switches is commonly 1-4ms... As of 3AM this morning, this has sky-rocketed to 300ms on average. ...
12
votes
7answers
3k views

Accurate strategy for measuring point-to-point link performance?

I have a requirement to provide an accurate means to demonstrate line performance over a flat layer2 1Gb point-to-point Ethernet circuit, approx 100 miles apart that seemingly goes through a number of ...
12
votes
5answers
2k views

Do faster segments of a network mean faster flow rate or lower latency?

This is another one of those hypothetical questions. I've been trying to figure out whether or not having a faster 'segment' of a network in between host A and host B will translate into a faster flow ...
12
votes
2answers
16k views

Is daisy chaining switches increasing latency?

This is a general question not related to specific hardware. If we have the following configuration of daisy chained switches: internet ---- core network ----- switch 1 ----- switch 2 ----- switch 3 -...
10
votes
2answers
2k views

Does bridging add delay?

If I use a bridge to perform traffic sniffing like man in the middle will the bridge add a delay? And what word should I use delay or latency?
10
votes
2answers
552 views

Ultra-Fast Querying Using UDP Packets

I am implementing a system where one device on a network queries at a very high frequency (hundreds or thousands of queries per second) through sending a small UDP packet with 8 or so bytes of data. ...
10
votes
1answer
2k views

measure one-way latency/jitter/packet-loss

I'm getting increased latency and StDev due to route congestion and packet loss, but the forward and reverse paths go over distinct networks (e.g. one being init7.net, the other one being he.net), so, ...
9
votes
4answers
2k views

Measuring per-link latency/jitter/packet-loss

I need to measure the latency, jitter and packet-loss per link in a network, as opposed to end-to-end, e.g. like this: s1-eth0 <--> s2-eth0 (~ 20µs avg. latency, standard derivation 10µs, 57 % ...
9
votes
4answers
366 views

Recording latency between a controlled startpoint and uncontrolled endpoint

This might be a very basic troubleshooting question, but it's worth asking to make sure I'm testing things the correct way and interpreting results effectively. I have a controlled start point (a ...
9
votes
4answers
3k views

High latency during downloads

I am having the same issue on my business connection 5Mbps as in another posting on this site. As soon as any computer starts a download the latency on the first hop past our DFG provided by our ISP (...
8
votes
5answers
4k views

Can you reduce RTT by increasing the bandwidth on a link?

Does increasing the bandwidth on a link from, let's say, 1mb to 30mb reduce the RTT? I have found one answer saying no. Can someone please explain? Also, what are the best mechanisms to reduce RTT?
6
votes
3answers
4k views

What is a reasonable latency for a L2 1G leased line between 2 sites, about 420km apart?

We need a dual gigabit connection to one of our customers and for the time being one of the lines has been brought online. The connection is between our DC and the customer's HQ, it's a L2 connection. ...
5
votes
2answers
6k views

What is the difference between data rate and latency?

Both attempt to measure the speed of a network. If data rate is the thing that is commonly measure in Mbps and latency is the thing that is measured in milliseconds, what are their similarities and ...
5
votes
2answers
3k views

Switch Buffer Sizing

What is the relationship between a switches buffer size and the effect it has on latency? I am aware of the bufferbloat issue and understand that buffers that are too large in networks of slower BW (i....
5
votes
2answers
2k views

How to reduce latency on ASA 5510 WAN link?

I have a Cisco ASA 5510 connecting our office via 2Mbit/s Internet. When Internet link fills up, latency to a well-connected host on Internet goes from 5-8 ms to 500-800 ms. With ping, it may look ...
4
votes
3answers
4k views

Network Latency issues with Cisco AP

This question involves network latency as opposed to bandwidth. I have a small remote office with a single Cisco 881W Integrated Services Router (Ethernet WAN). The WAN modem is an AdTran NetVanta ...
4
votes
2answers
686 views

does the DSL distance really add more latency

I've been using dsl internet for quite a while and having a ping from Algeria to France of about 90 ms , after trying to ping some locations in Algeria , i am getting about 50 ms, ping to my gateway ...
4
votes
2answers
12k views

How to find out TCP/UDP latency of your network?

Many people often suggest you to use ping command to find out your network latency. But it is false and a myth you often find in articles on Internet. ICMP ping was never designed to find out latency ...
4
votes
2answers
2k views

Cisco - MtR alternatives

I trying to establish if there is a function within IOS somewhere that can provide the same results of MTR , i know it can be run from Juniper devices / *Nix & Windows devices. Goal is to ...
4
votes
1answer
270 views

Latency in P2P Circuit

I have one P2P Circuit from our HQ to a secondary office. the distance between them is approx 2kms. Earlier when the Circuit was delivered at that time we were having an RTT of 3-4ms. It is a 10Mbps ...
4
votes
1answer
21k views

Initial estimated round trip time in the RTT formula

I was reading about Round Trip Time (RTT) and then I came across this formula EstimatedRTT = 0.9 * PreviousEstimatedRTT + 0.1 * Sample RTT What is the value of PreviousEstimatedRTT when it is ...
4
votes
2answers
515 views

High Jitter and Data Loss on Cisco Meraki Z1

Our office is running a Cisco Meraki Z1 Security Appliance and recently (March 5th) the internet has been dropping out intermittently. The appliance remains online but the internet either doesn't work ...
4
votes
1answer
2k views

Basic Link Aggregation scenario with high ping latency

Resume: I'm have a really basic network cenario with some new switches that I just bought. After configuring a LAG (without LACP) between them, I started to have ping losses and high latency. I also ...
4
votes
1answer
872 views

Cisco C891F-K9 ISR latency?

What is the multicast routing latency of Cisco C891F-K9 ISR? Please cite references for your answer. I think it's store-forward type and isn't one of the fastest models (given its price!). I've ...
3
votes
2answers
263 views

How fast can information travel through various media?

I'm working on compiling some information about network latency and designing tests to help our support folks troubleshoot problems. In order to do this, I need some basic information that I don't ...
3
votes
2answers
67 views

are the RTTs additive?

By using the ping, I calculate the RTT between A and B. I calculate the RTT between A and C. I calculate the RTT between C and B. Is it possible to compare the RTT of topological link A->B with the ...
3
votes
1answer
444 views

What is the relationship between throughput and latency

Looking at the structure of a TCP packet, such as discussed here: What is the internal structure of a mobile phone call packet/datagram?, this indicates that a TCP packet size is 192 bytes excluding ...
3
votes
1answer
2k views

What is the value of EstimatedRTT at first time?

Although this question might be marked as duplicated! I'm asking again because other question's answers like this couldn't help me. So please consider the case and don't mark it as duplicate and ...
3
votes
2answers
380 views

Network latency and network bandwidth correlation

Today I was pinging random websites, and I decided to ping a website, from which I was downloading at the speed of 2mb/s, and the ping(latency) was 10 ms. My question is, if the answer from the ...
3
votes
1answer
1k views

What is the latency of IP over Infiniband compare with 10Gbps fibre network?

What is the latency of IP over Infiniband compare with 10Gbps fibre network? 10Gbps network is something like a Solarflare low latency NIC card. How well does IP over IB perform not just throughput ...
3
votes
2answers
179 views

Transmission Rate in terms of distance

If the transmission rate of a physical link, such as ethernet cable, between a sender and receiver is set to be 100Mbps, does it imply that the receiver will receive 100Mb of data in each second? What ...
3
votes
2answers
849 views

POST duration over https vs ping time? [closed]

I'm trying to get a first-order evaluation of how network latency / Round Trip Time (RTT) T, as characterized by ping time, will affect the duration of consecutive sequential POST requests over an ...
3
votes
1answer
1k views

When should a transparent clock or boundary clock be used when designing a network supporting clock synchronization? [closed]

When designing a network incorporating IEEE-1588 (PTP), packet-delay variation (PDV) is a significant source of timing error. Both boundary clocks (network nodes which act as a slave clock to upstream ...
2
votes
3answers
3k views

Why can insufficient bandwidth reduce latency?

In this article, it is stated that latency does not affect bandwidth, but insufficient bandwidth can reduce latency. Can someone explain me the latter part of the statement? How would insufficient ...
2
votes
3answers
373 views

How can I determinte the reason of server-to-server latency in my network? [closed]

We have a proplem with server-to-server latency. How can I determine the reason for it? These servers are connected to different Cisco switches. Althought the reason for this problem might not be ...
2
votes
8answers
263 views

What are the concerns other than latency for network tuning?

Everywhere I keep finding "to achieve low latency" or "latency is of concern", do this! So, I don't really get what are the other concerns other than latency. I mean who doesn't want low latency? Or ...
2
votes
2answers
4k views

What's the difference among bandwidth, ping, ping rate and latency?

All these terms are quite related but I couldn't understand when to use which. I often hear that some networks have low bandwidth and high ping rate for online gaming. I thought they might be ...
2
votes
3answers
10k views

What causes packet loss when using full bandwidth from ISP?

We have a small, local ISP that is having some networking issues and I'm trying to understand the cause to better communicate with their network guys. I work with a number of companies with different ...
2
votes
2answers
315 views

Dynamically generate OSPF/BGP routes based on Internet latency

Scenario Three Offices with 2 ISPs each - utilizing static routing to the ISP. Each office has a VPN and leased point-to-point circuits connecting the offices in a ring. A VPN is also connecting the ...
2
votes
2answers
593 views

On a Layer 3 switch, what part does the CPU play in forwarding packets?

I am a Systems Administrator at a small firm. We are latency sensitive. When forwarding packets, what protocols use the CPU and which use the ASICs? We have mostly Arista 7124's (for the most latency ...
2
votes
1answer
148 views

Loosely speaking, at any given moment, how much of the internet is buffered?

When we ping a major web site, we're roughly measuring the delay between our device and the geographic location of the server that the site has chosen to send us to. It really could be anywhere. but ...
2
votes
2answers
1k views

Difference in latency between public and internal IP addresses

Should there be a difference in latency when accessing resources by their public IP address versus their private, internal IP address? And if there is, would (mis)configuration be to blame? My ...
2
votes
2answers
798 views

What are the differences between TCP iRTT and ICMP Ping?

I’m attempting to estimate latency between my PC and any servers/clients it interacts with. I don’t want to use Ping for various reasons (requires both ends to allow it, would require additional ...
2
votes
1answer
65 views

Setting policy on a Steelhead Mobile Controller (SMC) for “Latency-based location awareness”

When setting policy on an SMC with reference to Location Awareness - > Latency-based location awareness -> Optimize over adapters specified below if latency to SteelHead is more than: <#> ms: ...
2
votes
1answer
155 views

Estimating latency via distance and betweenness

I want to compute the relationship between delay (latency) with distance and betweenness. More specifically, if I know (let's assume) that the distance and betweenness values for two different ...