This document discusses techniques for achieving good quality of service (QoS) in computer networks. It describes factors that affect QoS like error rates, bit rate, throughput, transmission delay, reliability, and jitter. It discusses how reliability, delay, and jitter impact different applications differently. It also covers approaches like over-provisioning networks, traffic shaping using mechanisms like leaky buckets and token buckets, and using buffers to reduce disk I/O and improve performance for retrieving multimedia data.

1. TECHNIQUES OF
ACHIEVING GOOD
QUALITY OF SERVICE
SATYA PRAKASH JOSHI

2. QOS
• Quality of service (QoS) is the overall
performance of a telephony or computer
network, particularly the performance seen by
the users of the network.
• QoS considered, such as error rates, bit
rate, throughput, transmission delay, relaibilty,
jitter, etc.

3. RELIABILITY
• Lack of reliability means losing a packet or
acknowledgement, entails retransmission.
• How ever sensitivity of all application program
not same. i.e email, file transfer, and internet
access have reliable transmission than
telephony and audio conferencing.

4. DELAY
• Source to destination delay is another flow
characteristics.
• In this case telephony, audio conferencing,
video conferencing, and remote login need
minimum delay While in file transfer or email Is
less importance.

5. JITTER
• Jitter is the variation in delay for packets
belonging to the same flow. High jitter means
the different between delays is large; low jitter
means the variation is small.

6. OVER-PROVISIONING
• An alternative to complex QoS control
mechanisms is to provide high quality
communication by generously over-
provisioning a network so that capacity is
based on peak traffic load estimates.
• This approach is simple for networks with
predictable peak loads. The performance is
reasonable for many applications.

7. • This might include demanding applications
that can compensate for variations in
bandwidth and delay with large receive
buffers, which is often possible for example in
video streaming.

8. TRAFFIC SHAPING
• It is the mechanism to control the amount and
the rate of the traffic sent to the network.

10. • The rate at which water leaks from a bucket
does not depend on the rate at which the
water is input to the bucket
• The input rate varies but the output remains
constant, similarly, network can smooth out
burst traffic.

12. TOKEN BUCKET
• Leaky bucket does not taken into account idle host,
if a host is not sending for a while , it’s buckets
becomes empty
• If the host has bursty data, leaky buckets allows
only average rate.
• Token bucket takes into account the idle time with
each clock tick the token are added to bucket,
when the data needs to be send, it collects token
from bucket and then send the data packets
consisting of data = no of tokens.

13. BUFFRING
• Multimedia data are large in size and reside on disks.
• When users retrieve large multimedia data, in-memory
buffers are used to reduce the number of disk I/Os,
since memory is significantly faster than disk. The
problem to be studied is to efficiently make use of
buffers in the multimedia system to reduce the number
of I/Os in order to get a better performance when
multiple users are retrieving multiple multimedia data
simultaneously.
• Existing works on multimedia data buffering focus on
either the replacement algorithms to lower the number
of cache misses or the buffer sharing algorithms when
many simultaneous clients reference the same data item