This slide contains fundamental concept about Quality of Service (QoS) technolog, according to the latest version of Cisco books (CCIE R&S and CCIE SP) and i taught it at IRAN TIC company.In the next slide, i upload advanced topic about this attractive technology.

1. Quality of Service(QoS)
By : Reza Farahani

2. QoS BASICS
 What is QoS and main Idea of this?
 QoS features affect a network by manipulating the following
network characteristics:
 Bandwidth
Delay
 Jitter
Packet Loss

3. QoS Parameters : B.W
The term bandwidth refers to the number of bits per second that can reasonably
be expected to be successfully delivered across some medium.
Difference between bandwidth and speed ?
BANDWIDTH RESERVATION Methods:`

4. QoS Parameters : Delay

5. QoS Parameters : Delay

6. QoS Parameters : Delay
Other Types of Traffics Delay for example :
Video Traffic’s Delay :
 Codec Delay
 Compression Delay
Voice Traffic Delay :
 Packetization Delay
 De-jitter Buffer Delay

7. QoS Parameters : Delay
 Delay RESERVATION Methods :

8. QoS Parameters : Loss
Packet loss occurs when one or more packets of data travelling across a
computer network fail to reach their destination.
Cause of Packet loss ?  channel or waiting in buffer and etc.
Loss RESERVATION Methods :
 Increase Queue buffer size
 Using RED (Random Early Detection)
 Using WRED (Weighted RED )
What is benefits of RED and WRED methods?
What kind of packets are appropriate for drop ?

9. QoS Parameters : Jitter
Jitter is defined as a variation in the arrival rate (that is, variation in delay through
the network) of packets that were transmitted in a uniform manner.
 It’s very important for voice traffic

10. Types of QoSComplexity
199619941992 1998 2004…2002
Best
Effort
Integrated
Services
(RSVP)
Differentiated
Services
(Per-Hop)
MPLS/VPN
QOS
Auto/Template
QOS
QOS for
Security

11. IP PRECEDENCE & DSCP
The ToS byte was intended to be used as a field to mark a
packet for treatment with QoS tools.
The ToS byte itself was further subdivided, with the high-
order 3 bits defined as the IP Precedence (IPP) field.

12. IP PRECEDENCE & DSCP

13. IP PRECEDENCE & DSCP
A series of RFCs collectively called Differentiated Services
(DiffServ) came along later
The ToS byte was renamed the Differentiated Services
field ,and IPP was replaced with a 6-bitfield called the
Differentiated Services Code Point (DSCP) field.

14. IP PRECEDENCE & DSCP
Explicit Congestion Notification (ECN).

15. IP PRECEDENCE & DSCP
RFC 2475 defines a set of DSCP values and Per-Hop Behaviors (PHBs),
called Class Selector (CS) PHBs that provide backward compatibility with IPP
The CS PHB simply states that packets with larger CS DSCPs should be
given better queuing preference than packets with lower CS DSCPs.

16. IP PRECEDENCE & DSCP

17. ASSURED FORWARDING PHB
The Assured Forwarding (AF) PHB defines four classes for queuing purposes,
along with three levels of drop probability inside each queue.
The AF DSCPs name format: AF xy
Where x implies one of four queues and y implies one of three drop priorities.

18. IP PRECEDENCE & DSCP
The AF PHB suggests that the higher the value of x in the DSCP name AF
xy, the better the queuing treatment a packet should get.
For example, packets with AF11 DSCPs should get worse queuing
treatment than packets with AF23 DSCP values.
Additionally, the AF PHB suggests that the higher the value of yin the
DSCP name AF xy, the worse the drop treatment for those packets.

19. IP PRECEDENCE & DSCP

20. IP PRECEDENCE & DSCP
The first 3 bits of the binary DSCP values designate the queuing
class, and the next 2 bits designate the drop preference.
Queuing tools that operate only on IPP can still react to the AF
DSCP values.
RFC 2598 defines the Expedited Forwarding (EF) with AF46

21. IP PRECEDENCE & DSCP
 What is Starvation problem in IPP and?
 How DSCP can solve starvation problem?

22. ETHERNET LAN CLASS OF SERVICE

23. WAN MARKING FIELDS

24. MODULAR QoS CLI (MQC)
Internet
F0/0 S0
Class-Map1 Class-Map2 Class-Map3
Policy-Map1 Policy-Map2
InOut

25. MQC
MQC separates the classification function of a QoS tool from the action (PHB)
that the QoS tool wants to perform.

26. MQC

27. Classification
Inspecting one or more aspects of a packet to see what that packet is carrying
Marking
Writing information to a packet to classification decision
MQC

28. Trust Boundary
MQC

29. MQC

30. USING MULTIPLE MATCH
COMMANDS

31. USING MULTIPLE MATCH
COMMANDS

32. NBAR
Network base Application Recogniation
Use for matching tool
Use for statistical Result
Use for search inside of payload or header
NBAR classifies packets that are normally difficult to classify.

33. CB Marking Example

34. CB Marking Example

35. CB Marking Example

36. CB Marking Example

37. CB Marking Example

38. CB Marking Example

39. CB MARKING OF CoS AND DSCP
Example of configuration for CB Marking when an attached LAN switch is
performing QoS based on CoS:

40. CB MARKING OF CoS AND DSCP

41. CB MARKING OF CoS AND DSCP

42. Power of NBAR

43. Power of NBAR

44. CB MARKING DESIGN CHOICES

45. QoS PRE-CLASSIFICATION
If we encapsulate traffic inside a VPN tunnel, the original headers and
packet contents are unavailable for inspection.
The only thing we have to work with is the ToS byte of the original
packet, which is automatically copied to the tunnel header when the packet
is encapsulated.
But features like NBAR are broken when we are dealing with
encapsulated traffic.

46. QoS PRE-CLASSIFICATION
The issue that arises from this inherent behavior of tunnel
encapsulation is the in ability of a router to take egress QoS
actions based on encrypted traffic.

47. QoS PRE-CLASSIFICATION
Solution ?  buffering