CS 447 Network & Data Communication

QoS Implementation for the InternetIntServ and DiffServ

Department of Computer ScienceSouthern Illinois University Edwardsville

Fall, 2013

Dr. Hiroshi FujinokiE-mail: hfujino@siue.edu

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Two existing QoS implementations for the Internet

QoS implementationin the Internet

IntServ (Integrated Service)

DiffServ (Differentiated Service)

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IntServ

IntServ controls QoS parameters by reserving resources at routers

• It is a virtual-circuit approach on top of datagram Internet

• By using a new add-on protocol, RSVP (developed by Intel)

(RSVP = Resource Reservation Protocol)

• Combination of admission control & traffic policing

• “flow-oriented” QoS control (“per-flow QoS control”)

Router Router Router Router

RSVP request forreserve resources Reserve

resources

Reserveresources

Reserveresources

Reserveresources

PositiveACK

HTTP

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IntServ

• “flow-oriented” QoS control

• A logical pipe must be created for each flow

• After the mid 90’s, user population in the Internet started exploding

• After the mid 90’s, many different types of network applications were introduced

• Huge number of pipes must be managed by each IntServ router

(scalability problem)

• IntServ uses a strict policing

Network traffic that violates its promise is all dropped

IntServ was not easy to use

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DiffServ

• Datagram approach (“packet-based QoS control”)

No admission control

No new QoS protocol is needed

(because IP network (the Internet) is a datagram packet switching network)

(no signaling)

- Extends “TOS” filed in the IP header

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TCP Datagram (TCP packet)

TCP Header

(implemented on top of TCP)

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DiffServ

• Not “flow-oriented” QoS control

• Datagram approach

- No admission control

- No new QoS protocol is needed

(because IP network (the Internet) is a datagram packet switching network)

- DiffServ routers classify on-going traffic to groups of network traffic that has similar QoS requirements

• Mainly implemented by classifier, policing, shaping and scheduler at each router

• Many router venders, such as CISCO, implement DiffServ

(no signaling)

- Extends “TOS” filed in the IP header

TCP

DeviceDriver

IP

DiffServ

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Internal organization of DiffServ

DeviceDriver

NIC Routing Classifier

Device Queue(managed by OS)

NIC

(FIFO Queue)

PolicingShaping

PolicingShaping

PolicingShaping

DiffServ Queues(managed by Diffserv)

Scheduler

- Traffic shaping & policing- Queues & scheduler- Buffer (queue) management

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Traffic Shaping & Policing

Packet Marker + Buffer Manager

Token Bucket + Buffer Manager

Perform traffic policing only

Perform both traffic shaping and policing

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Packet Marker + Buffer Manager

Tra

ffic

Loa

d (

in b

ps)

Time

TMin

All marked as “BLUE”

All marked as “RED”

All marked as “YELLOW”

TMaxImmediately drop

TAcceptable

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Packet Marker + Buffer Manager

Classifier Marker

DiffServ Queue

When the DiffServ queue becomesfull, what should be done?

Buffer Manager

• If there are multiple packets of the same color (only one color),

• If there is no red packet, drop one yellow• If there is no red or yellow packet, drop one blue

• If there is a red packet, drop one red

(from tail, or top or middle of the queue)

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Token Bucket + Buffer Manager

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Global Synchronization and RED Queue

Classifier Marker

DiffServ Queue

When the DiffServ queue becomesfull, what should be done?

Queue Length MaxPac

ket

Dro

p P

rob

abil

ity

1.0(100%)

Is this bad?

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Global Synchronization and RED Queue

Router Router Router Router

The queuebecomes full

TCP detectsa packet loss

TCP detectsa packet loss

TCP detectsa packet loss

TCP detectsa packet loss

DiffServ Queue

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Global Synchronization and RED Queue

Router Router Router Router

The queuebecomes full

DiffServ Queue

I slowdown!

I slowdown!

I slowdown!

I slowdown!

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Global Synchronization and RED QueueA

ggre

gate

d T

hrou

ghpu

tof

a D

iffS

erv

queu

e (i

n bp

s)

Time

the bufferbecomes full

Globalsynchronization

Everyone hasbacked off

TCP slow-startin progress

Average queuethroughput

Available Txbandwidth

Wasted transmission bandwidth

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RED (Random Early Detection) Queue

Queue Length MaxPac

ket

Dro

p P

rob

abil

ity

1.0(100%)

Queue Length MaxPac

ket

Dro

p P

rob

abil

ity

1.0(100%)

Min

RED Queue

RED (Random Early Detection) Queue

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Router Router Router Router

Someone’s packetBEFORE queue

becomes full!

DiffServ Queue

I am OK!

I slowdown!

I am OK!

I am OK!

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ggre

gate

d T

hrou

ghpu

tof

a D

iffS

erv

queu

e (i

n bp

s)

Time

the bufferbecomes full

Globalsynchronization

Everyone hasbacked off

TCP slow-startin progress

Average queuethroughput

Available Txbandwidth

Wasted transmission bandwidth

the bufferbecomes full

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RED (Random Early Detection) Queue