Developing delay requirements

1. Unit - II
DEVELOPING DELAY
REQUIREMENTS

2. Delay
 A period of time by which something is
late or postponed.

3. DELAY REQUIREMENTS
 Measuring the delay in the network we
use
 – end-to-end delay,
 – round-trip delay,
 – delay variation
◦ as measures of delay in the network.

4.  End-to-End delay:
◦ Refers to the time taken for a packet to be
transmitted across a network from source
to destination.

5.  Round-Trip Delay (RTD):
◦ Also called Round-trip time (RTT).
◦ It is the time required for a signal pulse or
packet to travel from a specific SOURCE
to a specific DESTINATION and back
again.
 It is the length of time it takes for a
signal to be sent and the length of
time it takes for an acknowledgment of
that signal to be received.

6.  End-to-End & Round Trip Delays are composed of many sources
 including
◦ Propagation :
 how long it takes one bit (Unit of information : 0 and1) to travel
from one end to another.
◦ Queuing:
 A queue consists of a number of packets.
 It is a collection of data packets waiting to be transmitted by a
network device using a pre-defined structure methodology.
◦ Transmission:
 The process of sending and propagating an analogue or digital
information signal over a physical medium(wired/wireless)
◦ I/O:
 It is the communication between an information processing
system.
◦ Switching :
 groups all transmitted data – regardless of content, type, or
structure into suitable size.

7. Delay Variation:
◦ Also called packet delay variation (PDV)
◦ It is the difference in end-to-end (or) one-
way delay between selected packets in a
flow with any lost packets being ignored.
◦ It is often coupled with end-to-end or round-
trip delay to give an overall delay
performance.
◦ The effect is sometimes referred to as jitter.
◦ Examples :`
 Video(buffering)
 Audio(signal loss)
 Telemetry information(due to power failure)

8.  Begin by introducing some useful
general
thresholds and limits for delay:
◦ Interaction Delay(INTD),
◦ Human Response Time(HRT),
◦ Network Propagation Delay(NPD).

9.  These thresholds and limits are helpful
in distinguishing low- and high-
performance delay requirements for
your network.

10.  Interaction delay (INTD) is an estimate
of how long a user is willing to wait for
a response from the system during an
interactive session.
 The interaction delay depends on
◦ user behavior,
◦ the user’s environment, and
◦ the types of applications.

11.  Human response time (HRT):
 It is an estimate of the time threshold
at which users begin to understand
delay in the system.
 A good estimate of HRT, based on
experience and observation, is
approximately 100 ms.

12.  Network propagation delay is an estimate of how
long it takes for a signal to cross a physical
medium/transmission medium or link.
Ex:
Physical transmission media :
Use wire, cable, and other physical materials to
send communication signals.
 This provides a lower limit to the end-to end and
round-trip network and system delays.
 Propagation delay is dependent on distance and
technology.

15. THANK Y OU