Indeed [?] On Thu, May 3, 2012 at 1:00 PM, Jimmy Thuo <jimmy.thuo@gmail.com> wrote:

Thats a good read brian.

On Thu, May 3, 2012 at 11:50 AM, Brian Ngure <brian@pixie.co.ke> wrote:

...

http://rescomp.stanford.edu/~cheshire/rants/Latency.html

On Thu, May 3, 2012 at 11:49 AM, Dennis Kioko <dmbuvi@gmail.com> wrote:

...

A question to network gurus: Which is the faster network, one with

higher

...

speeds or one with lower latencies? -- with Regards:

blog.denniskioko.com

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-- Regards

Brian Ngure

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-- Best Regards Jimmy Thuo _______________________________________________ Skunkworks mailing list Skunkworks@lists.my.co.ke ------------ List info, subscribe/unsubscribe http://lists.my.co.ke/cgi-bin/mailman/listinfo/skunkworks ------------

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-- Regards Brian Ngure

This is an anomalous question. Latency is the inverse of throughput so it

...

generally follows that a higher throughput network will have lower latency.

I doub't , since you suggest that at 10 Mbps, on the same network, you get a lower latency compared`````````````` to one at 1 Mbps

Why do you doubt it? I suggest exactly that. Assume I have 10 Mb to send over two ideally *identical* networks of capacity 10Mbps and 1 Mbps. The time for transmission over the 10 Mbps link is 1 sec while it's 10 sec over a 1 Mbps link. If I'm interested in the last byte of the transmission I'll wait 10x longer if the data is communicated over the 1 Mbps link -- i.e. data transmission latency is higher. I suspect you're confusing minimum communication latency with transmission latency. The minimum communication latency is the minimum time required to transfer a byte across a link. In this regard, given two *otherwise* ideally *identical* networks, the determining factor is the length of the link. So, for the example above, if both networks were for example, point-to-point fibre and the 1 Mbps link was 1 m long while the 10 Mbps link was 300*10^3 KM long, a single byte transmitted over both links at the same time would take 0.00 sec to get across the 1 Mbps link and 1.00 sec to get across the 10 Mbps link (determined by the speed of propagation of light). However, note that transmission latency of the 1 Mbps link is lower than the 10 Mbps link, so if you were to start transmission of 10 Mb over both these networks at the same time you would receive the last byte of the transmission in 1 second over the 10 Mbps link and 10 seconds over the 1 Mbps link. The link with the higher minimum communication latency still wins.

Sohan, just to be sure that we are on the right page, here is the Wikipedia entry on Latency http://en.wikipedia.org/wiki/Latency_(engineering)

Kioko, I genuinely fail to see how the generic Wikipedia entry on Latency relates to your question and am confused at your response. If you feel I'm wrong I would appreciate a correction. One is always looking to learn.

On Sun, May 6, 2012 at 7:47 AM, Stephen Munguti <kamitu.sm@gmail.com> wrote:

Throughput of a network (Which i presume is what you are referring to as speed) depends on

Your presumption is erroneous. When I mentioned speed I was explicitly clear to mention it is the speed of propagation of light and not the maximum attainable bandwidth of the network.

latency, the application (e.g TCP/IP window sizes) and bandwidth (Maximum packets one can send across a link under ideal conditions)

Which is why you will notice I go to great pains to highlight the fact that I assume otherwise "identical" networks. This serves to encompass and abstract away everything else apart from the parameters in question (link BW and length)

The concepts form a lengthy explanation, but you cannot separate throughput and latency

Which was my exact point two emails back. So either the point of this email was to agree with me or I have misunderstood. Given your initial sentences I don't think it was the former. Please elucidate further. With kind regards

For the record, I agree with rsohan. Picking up from Mr Okoth, Assuming I'm transferring 10 Mbps. On a 1Mbps link, over one second, I can only put 1 Mb of data on the wire, however, for the 10Mb link, I can put 10 Mb of data on the wire. Hence the 10Mb link will be approximately 10x faster. Of course in reality though, other factors such as protocol choice eg TCP vs UDP, window size, packet size, propagation delay, cable length, transimssion media etc will have their effect. A good way to look at how latency affects throughput, is to think from the TCP point of view; The device has to wait for an acknowledgement before putting more data on the wire. = wasted time if the acknowledgement is not so important.= Lower throughput. If my packet is too large, the first hop has to receive the full packet before it can start transmitting it to the second hop.= wasted time =lower throughput. If I halve the packet size, the first hop can receive the first packet and start transimtting it before receiving the second packet.= cumulatively saved time = higher throughput. But only to a certain point before the overheads become a limiting factor. ( Think ATM cell size). It really is a complicated but interesting topic. IMHO :-) On Mon, May 7, 2012 at 8:36 AM, Gregory Okoth <gregory.okoth@gmail.com>wrote:

@Sohan,

In your earlier example, some factors were varying. I would like you to give an explanation, keeping all factors constant i.e

- Lenght of cable is same, - Identical physical x-tics of the tramission media, and - a similar data size being transmitted across

expect of course for the link capacities which will be a comparison for 1Mbps and a 10Mbps link.

Would the same explanation suffice?

On Sun, May 6, 2012 at 1:59 PM, rsohan@gmail.com <rsohan@gmail.com>wrote:

...

On Sun, May 6, 2012 at 7:47 AM, Stephen Munguti <kamitu.sm@gmail.com>wrote:

...

Throughput of a network (Which i presume is what you are referring to as speed) depends on

Your presumption is erroneous. When I mentioned speed I was explicitly clear to mention it is the speed of propagation of light and not the maximum attainable bandwidth of the network.

...

latency, the application (e.g TCP/IP window sizes) and bandwidth (Maximum packets one can send across a link under ideal conditions)

Which is why you will notice I go to great pains to highlight the fact that I assume otherwise "identical" networks. This serves to encompass and abstract away everything else apart from the parameters in question (link BW and length)

...

The concepts form a lengthy explanation, but you cannot separate throughput and latency

Which was my exact point two emails back. So either the point of this email was to agree with me or I have misunderstood. Given your initial sentences I don't think it was the former. Please elucidate further.

With kind regards

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-- Regards, Greg -------- Life is not a rehearsal, you only live once!

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On Mon, May 7, 2012 at 11:37 AM, Dennis Kioko <dmbuvi@gmail.com> wrote:

Sohan,

The idea here is that networks are different. The way they are set up, 2 ISPs sharing the same building in Nairobi will take different periods of time to access content in a server abroad.

The question is, Say ISP A has a 1 Mbps link, and a 200 MS latency, while ISP B gave you a 2 Mbps link, with 350 Mbps latency. What would be the effect on both networks, while say, watching a YouTube video , or playing Counter Strike on Valve

So, in this scenario: Playing CS means exchanging lots of small packets for synchronisation, assuming both networks meet the BW requirements of the program pick the one with the smaller latency. For YouTube, personally I would pick the the 2 Mbps link even though it has a higher latency. I will wait an additional 150ms for the data to reach my device but the higher throughput capacity means I'm less likely to suffer from buffer underrun