This document discusses quality of service (QoS) in converged networks. It defines QoS and explains why it is important for networks carrying voice, video, and data. It describes different QoS models including best effort, Integrated Services (IntServ), and Differentiated Services (DiffServ). The DiffServ model is now commonly used as it is more scalable. The document outlines steps to implement QoS which include identifying traffic classes, assigning requirements, and applying mechanisms like classification, marking, queuing and policing. Command-line interface and Modular QoS CLI methods are presented.

1. RED1PROYDESA
L ATA M
S D LU
L
TID N L E A R NING S . SERVI CES
FUNDACION
PROYDESA
PROYECTOS Y
DESARROLLOS
ARGENT I NOS

2. Using the Medium

3. Introducción de QoS
Comprendiendo la necesidad de QoS

4. QoSDefinición

5. Before Converged Networks
Traditional data traffic characteristics:
– Bursty data flow
– First-come, first-served access
– Mostly not time-sensitive – delays OK
– Brief outages are survivable

6. Después de las redes convergentes
Características tradicionales del tráfico de datos:
 Flujo de datos en ráfagas
 Acceso por orden de llegada
 La mayoría de las veces no es sensible al
tiempo, si hay retrasos no hay problema
 Se puede sobrevivir a breves interrupciones

7. Redes convergentes: problemas de calidad
– Llamada Telefónica: “I cannot understand you;
your voice is breaking up.”
– Teleconferencia: “The picture is very jerky.
Voice not synchronized.”
– Casa de Bolsa: “I needed that information two hours
ago. Where is it?”
– Call Center: “Please hold while my screen refreshes.”

8. Requisitos de tráfico de QoS: Datos
•
Diferentes aplicaciones tienen
diferentes características de
tráfico.
Diferentes versiones de la misma
aplicación puede tener diferentes
características de tráfico.
Clasifique los datos en un modelo de
prioridad relativa con no más de
cuatro a cinco clases:
•
•
– Apps de misión crítica: aplicaciones
críticas definidas localmente
– Transaccional: tráfico interactivo,
servicio de datos preferido
– Mejor esfuerzo: Internet, correo
electrónico, tráfico no especificado
– Menos que el mejor esfuerzo
(Scavenger): Napster, Kazaa,
aplicaciones de igual a igual
Suave o ráfaga
Benigno o codicioso
Insensible a las caídas
Insensible al retraso
Retransmisiones de TCP

9. QoS Traffic Requirements: Voice
•
•
•
•
Latency < 150 ms*
Jitter < 30 ms*
Loss < 1%*
17-106 kbps guaranteed
priority bandwidth
per cal–
l
150 bps (+ Layer 2
QoS
ve
T
rh
ra
e
fa
fid
c)Requirements: Voice
guaranteed bandwidth for
voice-control traffic per call
•
*one-way requirements
Fluido
Benigno
Sensible a las Caídas
Sensible a Demoras
Prioridad UDP

10. QoS Requirements: Videoconferencing
• Latency ≤ 150 ms*
• Jitter ≤ 30 ms*
• Loss ≤ 1%*
• Minimum priority bandwidth
guarantee required is:
– Video stream + 20%
– For example, a 384 kbps
stream would require 460
kbps of priority bandwidth
*one-way requirements
Ráfaga
Ávido
Sensible a las Caídas
Sensible a Demoras
Prioridad UDP

11. Converged Networks:
Quality Issues (Cont.)
– Lack of bandwidth: Multiple flows compete for a limited amount of
bandwidth.
– End-to-end delay (fixed and variable): Packets have to traverse many
network devices and links that add up to the overall delay.
– Variation of delay (jitter): Sometimes there is a lot of other traffic, which
results in more delay.
– Packet loss: Packets may have to be dropped when a link is congested.
Video Lacking
Proper QoS

12. – Best-Effort: No QoS is applied to packets.
– IntServ: Applications signal to the network that they require special QoS.
– DiffServ: The network recognizes classes that require special QoS.

13. Best-Effort Model
Llegará ahí cuando llegue.
– Internet initially based on a best-
effort packet delivery service
– The default mode for all traffic
– No differentiation between types
of traffic
– Like using standard mail

14. Best-Effort Model (Cont.)
+ Benefits:
• Highly scalable
• No special mechanisms required
Drawbacks:
• No service guarantees
• No service differentiation
–

15. IntServ Model
– Some applications have special
bandwidth or delay requirements
or both
– IntServ introduced to guarantee a
predictable behavior of the
network for these applications
– Guaranteed delivery:
no other traffic can use reserved
bandwidth
– Like having your own private
courier plane
It will be there by 10:30 a.m.

16. IntServ Model (Cont.)
– Provides multiple service levels
– Requests specific kind of service
from the network before sending
data
– Uses RSVP to reserve network
resources
– Uses intelligent queuing
mechanisms
– End to end

17. – RSVP QoS services
•
•
Guaranteed-rate service
Controlled-load service
– RSVP provides policy to QoS mechanisms
IntServ Model (Cont.)

18. IntServ Model (Cont.)
+ Benefits:
•
•
Explicit resource admission control (end to end)
Per-request policy admission control (authorization object, policy
object)
Signaling of dynamic port numbers (for example, H.323)
•
– Drawbacks:
•
•
Continuous signaling because of stateful architecture
Flow-based approach not scalable to large implementations such as
the public Internet (can be made more scalable when combined with
elements of the DiffServ model)

19. DiffServ Model
– Network traffic identified by class
– Network QoS policy enforces
differentiated treatment of traffic
classes
– You choose level of service for
each traffic class
– Like using a package delivery
service
• Do you want overnight delivery?
Do you want two-day air
• delivery?
• Do you want three- to seven-day
ground delivery?

20. Descripción general
R1 R2

21. QoS for Converged Networks

22. Step 1:
Identify Traffic and Its Requirements
– Network audit
• Identify traffic on the network
– Business audit
• Determine how each type of
traffic is important for
business
– Service levels required
• Determine required response
time

23. Step 2:
Divide Traffic into Classes

24. Classification
– Classification is the identifying and splitting of traffic into different classes.
– Traffic can be classed by various means, including the DSCP.
– Modular QoS CLI allows classification to be implemented separately from
policy.

25. Calificación
– Marking, also known as coloring, marks each packet as a member of a
network class so that the packet class can be quickly recognized throughout
the rest of the network.

26. Differentiated Services Model
– The Differentiated Services model describes services associated with
traffic classes.
– Complex traffic classification and conditioning is performed at the network
edge, resulting in a per-packet DSCP.
– No per-flow state in the core.
– The core only performs simple “per-hop behaviors” on traffic aggregates.
– The goal is scalability.

27. DSCP Encoding
– DiffServ field: The IP version 4 header ToS octet or the IPv6 traffic class
octet, when interpreted in conformance with the definition given in RFC
2474
– DSCP: The first six bits of the DiffServ field, used to select a PHB
(forwarding and queuing method)

28. DiffServ Model (Cont.)
+ Benefits:
• Highly scalable
• Many levels of quality possible
– Drawbacks:
•
•
No absolute service guarantee
Complex mechanisms

29. QoS for Converged Networks

30. QoS Mechanisms
– Classification: Each class-oriented QoS mechanism has to support some
type of classification.
– Marking: Used to mark packets based on classification, metering, or
both.
– Congestion management: Each interface must have a queuing
mechanism to prioritize transmission of packets.
– Congestion avoidance: Used to drop packets early to avoid congestion
later in the network.
– Policing and shaping: Used to enforce a rate limit based on the metering
(excess traffic is either dropped, marked, or delayed).
– Link Efficiency: Used to improve bandwidth efficiency through
compression, link fragmentation, and interleaving.

31. Classification
– Classification is the identifying and splitting of traffic into different classes.
– Traffic can be classed by various means, including the DSCP.
– Modular QoS CLI allows classification to be implemented separately from
policy.

32. Marking
– Marking, also known as coloring, marks each packet as a member of a
network class so that the packet class can be quickly recognized throughout
the rest of the network.

33. Congestion Management
– Congestion management uses the marking on each packet to
determine in which queue to place packets.
– Congestion management uses sophisticated queuing technologies,
such as WFQ and LLQ, to ensure that time-sensitive packets such as
voice are transmitted first.

34. Congestion Avoidance
– Congestion avoidance may randomly drop packets from selected queues
when previously defined limits are reached.
– By dropping packets early, congestion avoidance helps prevent bottlenecks
downstream in the network.
– Congestion avoidance technologies include random early detection and
weighted random early detection.

35. Policing
– Policing drops or marks packets when a predefined limit is reached.

36. Organización
– Shaping queues packets when a predefined limit is reached.

37. Compression
– Header compression can dramatically reduce the overhead associated with
voice transport.

38. Link Fragmentation and Interleaving
– Without link fragmentation and interleaving, time-sensitive voice traffic can
be delayed behind long, non-time-sensitive data packets.
– Link fragmentation breaks long data packets apart and interleaves time-
sensitive packets so that the time-sensitive packets are not delayed.

39. Applying QoS to Input and
Output Interfaces

40. Methods for Implementing QoS Policy
– CLI
– MQC
– AutoQoS VoIP (voice QoS)
– AutoQoS Enterprise (voice, video, and data QoS)
– QPM

41. Implementing QoS with CLI
interface Multilink1
ip address 10.1.61.1 255.255.255.0
ip tcp header-compression iphc-format
load-interval 30
custom-queue-list 1
ppp multilink
ppp multilink fragment-delay 10
ppp multilink interleave
multilink-group 1
ip rtp header-compression iphc-format
!
– Traditional method
– Nonmodular
– Cannot separate traffic
classification from policy
definitions
– Used to augment, fine-tune
newer AutoQoS method

42. Implementing QoS with MQC
•
• A command syntax
for configuring QoS
policy
• Reduces configuration steps
and time
• Configure policy, not
“raw” per-interface
commands
• Uniform CLI across major
Cisco IOS platforms
• Uniform CLI structure for all
QoS features
• Separates classification
engine from the policy
•
•
•
•
•
• class-map VoIP-RTP
match access-group 100
class-map VoIP-Control
match access-group 101
• !
•policy-map QoS-
Policy class VoIP-RTP
•priority 100
class VoIP-Control
bandwidth 8
class class-default
fair-queue
• !
• interface serial 0/0
• service-policy output QoS-Policy
• !
• access-list 100 permit ip any any
precedence 5 access-list 100 permit ip any any
dscp ef
• access-list 101 permit tcp any host 10.1.10.20
range 2000 2002
• access-list 101 permit tcp any host 10.1.10.20
range 11000 11999

43. Implementing QoS with AutoQoS
[trust] option is used to trust DSCP marking
– AutoQoS VoIP supported both in
the LAN and WAN environments
– AutoQoS Enterprise supported
on WAN interfaces
– Routers can deploy Enterprise
QoS policy treatment for voice,
video, and data traffic
– Switches can deploy QoS policy
treatments for voice by a single
command

44. Comparing Methods for
Implementing QoS