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Latency and TTL

Dear Experts,

can somebody explain me what is latency and ttl. Please dnt give defination for them. Which i can find in all websites. And is good latency and what is bad latency . Better tests to check them. I am asking this cos we have slow application performance issue i am trying to figure it out.
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Dave BaldwinFixer of Problems
Most Valuable Expert 2014

Details might make it possible to answer your question.  You say "we have slow application performance issue" and you put it in the networking zones.  Why do you think it is a networking problem?  And what have you compared it to?
greg wardSenior Systems Engineer

TTL is time to live
a packet starts life with a limit on the number of hops (routers) it can pass through. This is set depending on the routing protocol and the admin policy.
For example RIP has a max of 15.
The default for EIGRP is 100 and can be as much as 220.
When the packet runs out of life it is discarded.
Latency is time lost in the system, this is often when the router is waiting for something to happen, ie waiting for a whole packet to arrive before it sends to the next router.
Top Expert 2010

>And is good latency and what is bad latency
On a LAN, WAN, or the Internet (Dialup, PPP, PPPoA, T1, Ethernet, cable, etc)?
What protocol is your application using?
What is the average size of the data payload?
What is the current bandwidth utilization of you LAN, WAN or Internet that his application is using?
As Dave has pointed out, we need more information; Also, typically, asking what something is will come in a form of a definition; do you need clarification on Latency and TTL?

A traceroute tool is as important to a network engineer as a screwdriver is to an electrician. All networks have latency (Good or Bad) and a traceroute tool is used to analyze the performance and latency end to end across a communication path; however, using ICMP that is destined to a Internet router (Hop by Hop) is not very reliable as typically you can get undesired results that are normal operation for a Internet router that will seem like there is an issue (300 ms a one hop is not a sign of an issue, typically if the latency continues from that hop to the final destination can indicate an issue, but also not in the direction that you think [You also have to consider the return path as well]). Troubleshooting latency is a skill that comes with years of experience of understanding TCP/UDP, BDP, router architecture (ASICs, Fabrics, data plane, control plane, ICMP rate limit, queuing, propagation delay, etc and in some cases, it is even obvious where the issue is and not as complex as I described).

So please detail in why you think latency is the cause for your application to operate "slowly".

Top Expert 2005

Thank heavens for people like DavBaldwin and deepdraw "cos" even though you can not understand the plethora of definitions of TTL and Latency on the web  they step in and try to help.

If you do not understand the definitions of those terms, why would you ask us for the same?  Is a paraphrase going to be as detailed and accurate as a posted definition?
Latency and TTL may have absolutely nothing to do with your "slow application performance issue."

"cos" = nnob speak for because, and "i" means "I" if I understand your posted question.

"cos" you speak that way and because "Please dnt give defination for them." should written "Please don't give me a definition for them" leaves me little confidence that you are capable of discovering the actual problem, "cos" you do not understand the definitions of Latency and TTL, nor do you know if these have any bearing of the "slow application performance issue."

At the very minimum you are too lazy to write correctly, so I do not have confidence you will be able to follow the advice given, or to do so without taking shortcuts, "cos" that's the way you come across in your post.

Firefox has a spell checker. Maybe you should first change browsers so we know what you are trying to say.



Dear Experts,

I am sorry for not being clear with my question.

Latency its on Wan connection MPLS link.
What protocol is your application using? We are capturing data i will share that with you.
What is the average size of the data payload? After test only i will come to know.
What is the current bandwidth utilization of you LAN, WAN or Internet that his application is using?
Lan side there is no problem. Wan its 21 mbps mpls line. Its not fully utilized. We upgraded bandwidt also still no performance improved.

Due to corprate policy i am unable to share much data.

Regarding TTL i know it is used to avoid packet travelling unlimitted path.  I need some clarification on that
1) On what basic the TTL changes when i ping some destination.
2) Does TTL effects performance.

Coming to Latency as far i understand latency describes how much time does a packet takes to reach its detination. Clarification  i need is.

If my latency is around 214 over wan mpls link does that effect the download speed. Cos this application downloads data from far site.

I understand without proper information inconvience is caused. But this is not rite way to pin point others. If your expert its not fair to expect others also to be like you.
I understand my English is not that great. For your kind information i am not native english speaker.
I dont expect any help also from you.


greg wardSenior Systems Engineer

TTL depends on the routing protocols you are using.
TTL will only effect performance if the packet dies. If you ping something using the dos command and it says you have a TTL of more than 5 you dont need to worry about it.
latency is only part of the equation.
You also need to look at packet size (mtu) and windowing.
Basic networking guide below, alway good to follow the OSI model for troubleshooting.
Top Expert 2010
> If my latency is around 214 over wan mpls link does that effect the download speed. Cos this >application downloads data from far site.

It can, and is the reason for the questions that I asked:
I wrote an article on the issue; http://www.experts-exchange.com/articles/Networking/Network_Management/Network_Analysis/Understanding-Network-and-Internet-Latency.html?sfQueryTermInfo=1+30+latenc+understand

it might help or it might not as already stated Latency is only part of the equation.




I have gone through your article. I should say there is lot difference between this and from normal internet one. This how an experienced expert explains. I could not follow it completely i will read it once again and again until i understand. I really appreciate your patience and your passion towards networking.