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Multimedia Wireless Networks: Technologies, Standards, and QoS Chapter 3. QoS Mechanisms

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(sometimes called Out-of-traffic mechanisms) are mechanisms ... E.g. CSMA/CD. Service level can be improved by: Over-provisioning or. Adding a priority scheme ... – PowerPoint PPT presentation

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Title: Multimedia Wireless Networks: Technologies, Standards, and QoS Chapter 3. QoS Mechanisms


1
Multimedia Wireless Networks Technologies,Standa
rds, and QoSChapter 3. QoS Mechanisms
  • TTM8100
  • Slides edited by Steinar Andresen

2
QoS Mechanisms
3
Traffic handling mechanisms
  • (sometimes called In-traffic mechanisms) are
    mechanisms that classify, handle, police, and
    monitor the traffic across the network. The main
    mechanisms are
  • classification,
  • channel access,
  • packet scheduling, and
  • traffic policing.

4
Bandwidth management mechanisms
  • (sometimes called Out-of-traffic mechanisms) are
    mechanisms that manage the network resources
    (e.g., bandwidth) by coordinating and configuring
    network devices' (i.e., hosts, base stations,
    access points) traffic handling mechanisms. The
    main mechanisms are
  • resource reservation signaling and
  • admission control.

5
Classification
6
Classification Techniques related to OSI layers
OSI layer Classification Techniques
Application
User/Application Identification
Transport
Flow (5 tuplet IP Address)
Network
IPTOS, DSCP
Data Link
802.1p/Q Classification
Physical Layer
7
Data Link Classification (ref. 3- bits field
IEEE 802 header)
8
Network Layer Classification
  • Network layer, or Layer 3 classification is
    using Layer 3 header.s Layer 3 classification
    enables service differentiation in Layer 3
    network.
  • An example of Layer 3 classification is IPTOS
    (Internet protocol type of service
  • IPv4 and IPv6 standard defined a prioritization
    field in the IP header RFC 1349 defined a TOS
    field in IPv4 header. The type of service field
    consists of a 3-bit precedence subfield, a 4-bit
    TOS subfield, and the final bit which is unused
    and is set to be 0. The 4-bit TOS subfield
    enables 16 classes of service. In IPv6 header
    there is an 8-bit class of service field
  • and DSCP (Internet protocol differential service
    code point).
  • Later IETFs differentiated services working
    group redefined IPv4 IPTOS to be DSCP,. DSCP has
    a 6-bit field enabling 64 classes of service.

9
Structure of IPTOS and DSCP in IPv4
DSCP
6-bit DSCP
2-bit Unused
0 7
3-bit Precedence
4-bit TOS
0
IPTOS
0 31
16-bit total length (in bytes)
4-bit header l
4-bit version
8-bit TOS
16-bit identification
3-bit flag
13-bit fragment offset
8-bit TTL
8-bit Protocol
16-bit header checksum
32-bit source IP address
32-bit destination IP address
DATA
10
Structure of IPTOS and DSCP in IPv6
0 31
Flow Label
4-bit version
8-bit traffic class
Payload Length
Next Header
Hop Limit
Payload Length
Payload length
11
Transport Layer Classification
  • A 5-tuplet IP header
  • source IP,
  • destination IP,
  • source port,
  • destination port, and
  • protocol IP)
  • can be used for transport layer classification.

12
Transport Layer Classification
  • A 5-tuplet IP header can uniquely identify the
    individual application or flow. This
    classification provides the finest granularity
    and supports per-flow QoS service.
  • Limitations
  • OK at the EDGE, but NOT Suitable to CORE
  • Problems when passing firewalls using NAT

13
Application or User Classfication
  • The users or applications can be uniquely
    identified by an ID and a central agency in the
    network can be made responsible to
  • allow or reject
  • requests for new sessions, depending on the
    traffic situation. Normally each session also
    will be given a unique ID number.

14
Channel Access Mechanisms
  • There is two options to channel access control
  • Collision based access and
  • Collision-free channel access
  • Collision based access needs a MAC protocol that
    tries to avoid and resolve collisions (in the
    case they occur). E.g. CSMA/CD. Service level
    can be improved by
  • Over-provisioning or
  • Adding a priority scheme

15
Collision-Free Channel Access
  • Polling
  • TDMA - illustrated here -static or dynamic

16
Packet Scheduling Mechanisms
  • Hierarchical
  • or
  • - Flat Packet scheduling

17
FIFO Packet Scheduling
18
Strict Priority Packet Scheduling
19
Weight Fair Queue (WFQ)
20
Traffic Policing Mechanisms
(A) Incoming traffic with rate R which is less
than the bucket rate r. The outgoing traffic
rate is equal to R.In this case when we start
with anempty bucket, the burstiness of the
incoming traffic is the same as the burstiness
of the outgoing trafficas long as R lt r.
21
Traffic Policing Mechanisms
(B) Incoming traffic with rate Rwhich is
greater than the bucket rate r. The outgoing
traffic rate is equal to r (bucket rate).
22
Traffic Policing Mechanisms
(C) Same as (B) but the bucket is full.
Non-conformant traffic is eitherdropped or sent
as best effort traffic.
23
Token Bucket Mechanism (A)
The incoming traffic rate is less than the token
arrival rate. In this case the outgoing traffic
rate is equal to the incoming traffic rate.
24
Token Bucket Mechanism (B)
The incoming traffic rate is greater than the
token arrival rate. In case there are still
tokens in the bucket, the outgoing traffic rate
is equal to the incoming traffic rate.
25
Token Bucket Mechanism (C)
If the incoming traffic rate is still greater
than the token arrival rate (e.g., long traffic
burst), eventually all the tokens will be
exhausted. In this case the incoming traffic has
to wait for the new tokens to arrive in order to
be able to send out. Therefore, the outgoing
traffic is limited at the token arrival rate.
26
Resource Reservation Signaling Mechanisms
  • Provision of resource reservation signaling that
    notifies all devices along the communication path
    on the multimedia applications' QoS requirements.
  • Delivery of QoS requirements to the admission
    control mechanism that decides if there are
    available resources to meet the new request QoS
    requirements.
  • Notification of the application regarding the
    admission result.

27
Resource Reservation Signaling Mechanisms
28
Admission Control
  • Explicit admission control This approach is
    based on explicit resource reservation.
    Applications will send the request to join the
    network through the resource reservation
    signaling mechanism. The request that contains
    QoS parameters is forwarded to the admission
    control mechanism. The admission control
    mechanism decides to accept or reject the
    application based on the application's QoS
    requirements, available resources, performance
    criteria, and network policy.
  • Implicit admission control There is no explicit
    resource reservation signaling. The admission
    control mechanism relies on bandwidth
    over-provisioning and traffic control (i.e.,
    traffic policing).

29
QoS Architecture
  • Applications with quantitative QoS requirements
    mostly require QoS guaranteed services.
    Therefore, explicit resource reservation and
    admission control are needed, also require strict
    traffic control (traffic policing, packet
    scheduling, and channel access).
  • Applications with qualitative QoS requirements
    require high QoS levels but do not provide
    quantitative QoS requirements. We can use
    resource reservation and admission control. They
    also require traffic handling which delivers
    differentiated services.
  • Best effort There is no need for QoS guarantees.
    The network should reserve bandwidth for such
    services. The amount of reserved bandwidth for
    best effort traffic is determined by the network
    policy.

30
QoS Architecture for Infrastructure based
Wireless Networks
31
QoS Architecture for Ad Hoc Wireless Networks
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