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Community Member

(HElP) How to reduce latency in ISP network

Hi netpro's

i have build a network powered by cisco routers and switches and everything ip wise is fine, as thir is communication and customers can brose the internet etc.

However, i am suspecting that i ahve a huge latency issue betwoeen my customers and the internet. The roudntrip produced by ping and traceroute indicate more than 1000ms from the internet to my customers router via my network.

I would like to reduce this latency so my customers can run thier VPN's and other traffic without much latency and with atleast a minimum of less than 600ms rounftrip from pings.

What advice to you guys give me so that i can improve delay and latency.

What shoudl i configure on my core routers and switches to achieve this.

I will appreciate all the feedback.


Re: (HElP) How to reduce latency in ISP network

Even if the link is heavily congested, u may experience latency in response.

If the traffic pattern is normal but latency is still there, then u may have to check for errors.

Have you observed these 2, before considering for config modification.

Community Member

Re: (HElP) How to reduce latency in ISP network

Hi bro,

actually i get some errors but they are transmission errors that norammly occur and they are minimal.

My major concern is i would like to reduce the round trip it take to reach a clines network from the internet or a remote site via my network.

Say one of my customers has a VPN tunnel from a remote site in USA to him office which is within my network.

The VPN is betwen the customers router via my ISP network , iwant to improve the speed and reduce latency so that they can have no packet losses.

Some sort of Qos i guess.

Any idea's


Hall of Fame Super Gold

Re: (HElP) How to reduce latency in ISP network

Try to find first where the "bottleneck" is, that is your circuits to the internet or any other interface where queue builds up and worst case packet drops. On this interface you would apply a service policy with priority od bandwidth to packets having some value of DSPC set what you will tag at your customer ingress.

Also check if your interface to customer is ever congested in which case you would a apply service policy there too.

If you have no interface that falls in the category above, there isn't anything that you can be because the delay lies elsewhere.

Hope this helps, please rate post if it does!

Community Member

Re: (HElP) How to reduce latency in ISP network

I have check all the interface for congestiona and everything seems ok.

However, here is the senarionagain, one customer has a mail server locally and they can send mails and recieve. However, they only receive email from one of their braches in framce but they can recieve emails from other branches in japan,usa, mexico etc.

Is this something to do with latency in my ISP network that this other locations cant send emails to this customers exchange server.

Why would only one remote branch send emails to this mail server and the rest not.

Please advice, it is getting to my nerves and i might loose this customer because he believes the cause in my network but if it was whay would they only recieve from one branch.

thanks for your opinions.

Hall of Fame Super Gold

Re: (HElP) How to reduce latency in ISP network


have you checked that customer's server have complete connectivity to mentioned branches ?

Is their VPN under your supervision? If something doesn't work there, is not your fault.

Community Member

Re: (HElP) How to reduce latency in ISP network

Hi again,

Actually this custostomer says,thru his previous providers network, all him remote branches could send and recieve emails via their vpns thru the same exchange server and that when they transfer their mail server to my public ip and network, only one of thir branches would work.

So basically, it it a little wierd even if i give them a better speed thn thir previous provider.

They can telnet the pubic ip address of their server which i allocated them on port 25 and that mean smtp is open but why do they say other brances cant reach their mail server but only one.

Man this is driving me crazy.

hope to get more opinions.


Re: (HElP) How to reduce latency in ISP network


there can be because of either link utilization with provider or by the customer or due to some network element . Check the link settings such as duplex and speed settings ,check the CPU utilization . Try trace the delay from one end point to other and try to find out the bottle neck and work on that

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