Latency on WAN link

[Zeeshan Siddiqui]

All can you please help with the following

Site A is connected to Site B using two 1 Gig LES lines the two site are physically 60 Miles apart.

When I ping Site B from Site A I can see delays of 5ms on the pings.

Is that normal ?

If yes can we make any config Changes or additional hardware to reduce the latency ?

If we have latency of 5ms whats the maximum Throughout we can have over a 1 Gig interface if we are coping a file from one server to another considering the server is not a bottle neck ?

Any help is much appreiciated

[paolo bevilacqua · Accepted solution]

May be telco has intermediate devices increasing latency, ask them.

You cannot do anything about it.

[Zeeshan Siddiqui]

Hi Paolo,

Many Thanks for your response

I have been in touch with the ISP and they confirmed these delays are normal for two SItes 60 miles apart.

Just wanted confirmation from experts on this Site.

I believe if we have latency backups will run slow between the two sites is there a way we can calulate the through put based on the LAtency we have

For me it is 5ms

Thanks in Advance

[vmiller · Accepted solution]

http://cisconet.com/traffic-analysis/throughput/104-tcp-throughput-calculation-formula.html

Good starting point for optimizing WAN utilization.

[Zeeshan Siddiqui]

Many Thanks  vmiller

[Joseph W. Doherty]

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Posting

5 ms for 60 miles - well fiber physical delay is about 5 us per Km, so 60 miles would be a little less than 100 Km, double for RTT and latency should be about 1 ms.  So, 5 ms ping seems a tad high.

If you're doing bulk file copies, you should be able to drive the link to gig capacity.  With standard size (1500) Ethernet and TCP, believe you should obtain close to 97% of link speed.  (Note: to obtain this TCP rate, your receiver needs to have RWIN large enough to support the BDP; and very, very few drops.)