Re: [Codel] Latency vs Delay

Re: [Codel] Latency vs Delay

[David Collier-Brown]

On 03/14/2015 03:00 PM, divya singla asked
> Hi Members,
> is there anybody who can explain me difference between latency and delay?
In queuing, latency is the time between the send and the first byte of 
the reply, and (total) response time is the time between the send and 
the last byte of the reply. The time between first and last byte is the 
transfer time. Both are stated as if they were being observed by a 
client, either nearby or remote.

Delay, on the other hand, is the time the job spends sitting in a queue 
waiting to start work. Service time is the time it takes to do the work. 
Both are specifically at the server, or "queuing center"

If you draw a diagram, they overlap inconveniently (;-))

--dave



-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb@spamcop.net           |                      -- Mark Twain

Re: [Codel] Latency vs Delay

[David Collier-Brown]

On 03/14/2015 10:05 PM, David Collier-Brown wrote:
> On 03/14/2015 03:00 PM, divya singla asked
>> Hi Members,
>> is there anybody who can explain me difference between latency and
>> delay?
> In queuing, latency is the time between the send and the first byte of
> the reply, and (total) response time is the time between the send and
> the last byte of the reply. The time between first and last byte is
> the transfer time. Both are stated as if they were being observed by a
> client, either nearby or remote.
>
> Delay, on the other hand, is the time the job spends sitting in a
> queue waiting to start work. Service time is the time it takes to do
> the work. Both are specifically at the server, or "queuing center"
>
> If you draw a diagram, they overlap inconveniently (;-))
>
> --dave
>
>
>

For example, in

\
  |- queue delay
  |- service time
/|- more service time
  |
/

The latency is the time from \ to the first /, and it contains the 
network time, the queuing delay and all the service time required to get 
to the first byte of the reply.

The transfer time is from the \ to the last /, and includes and 
additional service time to get to the last byte of the reply

--dave


-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb@spamcop.net           |                      -- Mark Twain

[Codel] Latency vs Delay

[divya singla]

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Hi Members,

is there anybody who can explain me difference between latency and delay?

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Re: [Codel] Latency vs Delay

[Jonathan Morton]

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They mean the same thing, for most practical purposes. However, you could
(when writing your own papers) usefully define latency as the total RTT,
and delay as only the avoidable components of that. The speed of light,
etc, mean that some latency is unavoidable in any communication.

- Jonathan Morton

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