Implementing Integrated Services in Network Simulator

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Implementing Integrated Services in Network Simulator

Author: Yaohui Li

Supervisor: Raimo Kantola

Instructor: Lic.Sc. Mika Ilvesmäki

Table of Contents• Overview of Integrated Services

• Overview of NS2(Networking Simulator version 2)

• Tasks definition

• Tools

• Modeling designing and implementation

• Testing and results

• Conclusion

Overview of IntServ (1)• Internet only offers a best effort service,

which can meet the traditional non-real-time Internet traffics.

• For real-time traffic, it needs a new scheme to make reservation for the traffic.

• IntServ(Integrated Services) can provide resource allocation to meet the requirement of real-time application.

• IntServ is per-flow service.

Overview of IntServ (2)• IntServ Implementation Framework

Input Traffic

RoutingProtocols

ReservationProtocol

AdmissionControl

ManagementAgent

Traffic ControlDatabase

Routing Table

ClassifierPacket

Scheduler

QoS Queue

Best-effort Queue

ForwardingTable

•packet classifier: maps each incoming packet into corresponding class.

•packet scheduler: implements resource allocation.

•Admission control: determines a new reservation request is allowed or denied.

Overview of IntServ (3)• IntServ Service Models

– Best efforts (BE) no any guarante

– Controlled Service(CL) (RFC2211)provides service intended to predictive or delay-adaptive

real-time class, or better than BE.

– Guaranteed Service(GS) (RFC2212)provides a deterministic bound of end-to-end delay and

bandwidth guarantee

Overview of IntServ (4)• Before a network entity

can be enable to invoke or select a specific service, it needs a set of parameter:

• Traffic Specification (TSpec)– describes the traffic characteristics

for which the service is being requested. for example: it can be a token bucket filter.

– GS and CL needs it

Overview of IntServ (5)

• RSpec (request specification)– describes the quality of service that application

wishes to request from the network.– GS needs RSpec, but as for CL: no RSpec is

requested.


• The Resource Reservation Model– RSVP is one of the protocols to implement the

purpose. – It is a signalling protocol – be responsible for install and maintain

reservation state in each router by transferring the parameters.

– Receiver oriented.– Soft state.


• RSVP Messages

R1

R2

R3

D1

S1

D3

D2

Path

Path

Path

Path

Path

Path

R1

R2

R3

D1

S1

D3

D2

Resv Resv

Resv

Resv

Resv

Resv

Other message types include reservation confirmation messages,error report messages and reservation and path teardown messages.


• RSVP object Classes• A Path message contains the following important

objects: RSVP Header, INTEGRITY, SESSION,

RSVP_HOP, TIME_VALUES, POLICY_DATA, SENDER_TEMPLATE, SENDER_TSPEC and ADSPEC.

• A Resv message contains the following objects: RSVP Header, INTEGRITY, SESSION,

RSVP_HOP, TIME_VALUES, RESV_CONFIRM, SCOPE, POLICY_DAT, STYLE, FLOWSPEC and FILTER_SPEC.

Overview of NS-2 (1)

Network simulator version 2• Simulates various networking

models, used for researches for example: simulation in TCP, routing, and multicast protocols, mobile networks, satellite networks, and so forth.

Hierarchy of NS2

•OTcl: Object-oriented support

•tclcl: C++ and otcl linkage

•Discrete event scheduler

•Data network (the Internet) components

Overview of NS2 (2)• Ns2 is writtten in two programming languages C++

and Tcl • C++: Detailed protocol simulations require systems

programming language – byte manipulation, packet processing, algorithm implementation– C++ is fast to run so that it is used in the core of ns2. – Turn around time (run simulation, find bug, fix bug, recompile, re-run)

is slower

• Tcl: Simulation of slightly varying parameters or configurations– OTcl is a scripting language as a front-end or interface in ns2. – quickly exploring a number of scenarios– iteration time (change the model and re-run) is more important

• In sum, C++ is for data, aiming at per packet action; tcl is for control, aiming at periodic or triggered action.

Overview of NS2 (3)• NS2 package stucture

Overview of NS2 (4)

• The binding of member variables from C++ to OTcl.

For example: In C++

TcpAgent::TcpAgent(){

Bind(“window_”, $wind_)

}

In Otcl : Agent/TCP set window_ 100

• The correspondence of member functions between C++ and OTcl:

• In C++ and Otcl

•OTcl to call C ++ : command(), tcl.result()

•C++ to call otcl: tcl.eval()

Thesis Task Definition

In current Ns2

• there are very few modules for IntServ

only control load service was implemented, by using simple three-way handshake algorithm for signalling and a simple priority queue with two kinds of services (BE and CL)

• The task is Adding Guaranteed Service module into NS2 by making use of RSVP as a signalling protocol

Tools used in the work

• Design language: UML

• Programming language: C++ and OTcl

• NS2 package NS-2.1b9a on the Solaris platform

• CVS

Modeling designing and implementation(1)

• Preconditions and assumptions in GS implementation– To use RSVP as the signalling protocol to set up

reservations.– We have to assume that every service element (a router,

or a subnet, etc) in the path supports GS or mimics GS. However, this requirement does not mean that GS must be deployed throughout the Internet.

– Routing protocols or other network management functions are outside the scope of this implementation.

– The network elements must ensure that the service to be implemented approximates the “Fluid Model Service”.


• The new architecture of IntServ implementation in ns-2

AdmissionControl

SignalingSupport(SimpleRSVP)

DelayLink

Measurementfor class 1

Estimator1

Measurementfor class 2

CL

GS

Best Effort traffic

Estimator2

SchedulerWFQ for GS

Classifier1packets

SimpleScheduler

for CL

Classifier2

Modeling designing and implementation(3) The relationship of classes to be implemented between C++ and OTcl

Agent GSSAAgent

Connector GSSAChecker

GSSAmessage

GSSAObject

FILTER_SPEC

FLOWSPEC

ERROR_SPEC

GSSA_HOP

SENDER_TEMPLATE

SENDER_TSPEC

SESSION

STYLE

TIME_VALUES

RESV_CONFIRM

SENDER_ADSPEC

Queue WFQ Queue/WFQ

TclClass PacketHeaderClass

Agent/GSSA

GSSAChecker

SALink GSSALink GSSALink

C++ OTcl

WFQClass WFQClass


• the class diagram of signaling part implementation

• RSB(Reservation State Block)

• TCSB (Traffic Control State Block)

• PSB (Path State Block)

SENDER_ADSPEC

ERROR_SPEC

FILTER_SPEC

FLOWSPECRESV_

CONFIRMGSSA_HOP

SENDER_TSPEC

STYLE SESSIONTIME_

VALUESSENDER_

TEMPLATE

GSSAObject GSSAmessage

TCSB RSB PSB

session

Agent

GSSAAgent RNG

Modeling designing and implementation(5)• The extended class diagram in NS2

GSSALink

Connector

ADC

MeasureModGSSAChecker

Param_ADC

Queue

WFQ

SALink

MS_ADCHB_ADCACTO_ADC

WFQClass

Hashtable

Estimator

Estimator_Timer

GSSAAgent


• Signalling module (GSSA GS signalling)

PacketClassifier

GSSADeamon

AdmissionControl

PacketScheduler

Senders(source)

Receivers(sink)

GSSA MessageGenerator

PATH

RESV

PATH

RESV

Control plane

Data plane

Modeling designing and implementation(7) The signalling process and the role of each participator

Sender: the initiation state of sender

• Sender: the waiting state diagramof sender

Sender_Idle

Set t;

Path_msg

Init

Wait_Ack

Wait_Ack

Resv_msg

Reset t;

A connection setup and send

data

Sender_Idle

Path_Tear Sender ends processor timeout

ResvConf

Modeling designing and implementation(8) For the intermediate router (complex)

• path message processing • Resv message processingRouter_Idle

Path_message

Exists session(dest, fid)?

exists PSB(session, sender)?

Create newsession

(dest, fid)

Update theold PSBstate andforward it

Forward tonext router

Create anew PSBstate andforward it

Router_Idle

No

Yes

No Yes

Router_Idle

Resv

Exists session(Dest, fid)?

Exists PSB(session, sender)

Resv_Err

Router_Idle

Update theold RSBstate andforward it

Exists Resv_conf

CopyResv_Confinto RSB

Create anew RSBstate andforward it

Updatetraffic_control

Router_Idle

No

Yes

No

Yes

Yes

No

LOOP

Resv_Err

Exists RSB(session, Flowspec)

No Yes

Flowspec is null?


Yes

No


• Path_Err message process • Resv_Err message process

Router_Idle

Path_Err

Existssession(Dest, fid)

Router_Idle

ForwardPath_Err

Makeerror_upcall

Router_Idle

No

Yes

Router_Idle

Resv_Err

Exists session(Dest, fid)

Router_Idle

ForwardResv_Err to next

router markedRSB

Makeerror_upcall

Router_Idle

No

Yes

LOOP

Filter_spec isNULL?

Marked RSB

Yes

No


• Path_Tear message process• Resv_Tear message process

Router_Idle

Path_Tear


Router_Idle

Router_Idle

No

Yes

Exists PSB(session, Dest)

Remove PSB


YesNo

Router_Idle

Router_Idle

Resv_Tear


ForwardResv_Tear

Router_Idle

No

Yes

Delete RSB

Updatetraffic_control

LOOP

Filter_specis null

Drop allRSBs

Yes

No

Rsb_listis null

Drop RSB forcorresponding

PSB

Rsb_listis null

Router_Idle

Yes

Yes

No

No


• Resv_Conf message process • the state diagram of receiver

Router_Idle

Resv_Conf_msg


Forward Resv_Conf tonext router marked

RSB

Makeconfirmation_

upcall

Router_Idle

No

Yes

IP address of routerexists in Resv_Conf msg

Yes

No

Receiver_Idle

Path_msg

Receiver computing anoptimum bandwidth usinginfo from Path message

Resv

Wait_Confirmand receive data

Resv_TearReceiver endsprocess or resv

timeout

Receiver_Idle

yes

no

Modeling designing and implementation(12)data structures

• session• PSB (Path State Block)

Modeling designing and implementation(13)data structures

• RSB • TCSB


• Scheduling module

Σ

Admission Control

Gu

ara

nte

ed

Se

rvic

es

Flo

ws

Be

st E

ffo

rts

Flo

ws

Ne

w F

low

s

WFQ

FIFO


• WFQ– one of the popular scheduling algorithms – IETF adopted it for IntServ networks– an approximation of GPS (generalized

processor sharing)


• Admission control

making use of measurement-based algorithm

It includes four control algorithms:– Measured Sum (MS). The MS algorithm admits a new flow if the sum of

the token rate of the new flow and the estimated rate of existing flows is less than a utilization target times the link bandwidth .

– Hoeffding Bounds (HB). The HB algorithm admits a new flow if the sum of the peak rate of the new flow and the measured equivalent bandwidth is less than the link utilization.

– Tangent at Origin (TO). The TO uses a tangent to the equivalent bandwidth curve at the origin to satisfy the specific formula if a new flow is admitted

– Tangent at Peak (TP). The TP is based on the tangent at the peak of an equivalent bandwidth curve computed form the Chernoff Bounds

Testing and Results (1)• The topology of simulation test

there are eleven CBR sources nodes n(1), n(2), n(3)…n(11) over UDP connection and their corresponding sink agents sink1, sink2, sink3 …sink(11).

The bandwidth of n12 and n13 is 2.8Mbps

The bandwidth of each source node n1—n11 to n12 is 1Mbps

We will guarantee that the traffic of source n(11) can be received at the sink whenever how many sources are added (best effort or controlled services traffics).

Testing and Results (2)• Before add GS module into ns2

Testing and Results (3)• test result after adding GS module into ns2

Testing and Results (4)• The simulation test after adding GS and CL into traffic nodes (the

same prerequisite)

Conclusion (1)

• The GS implementation makes use of RSVP as the signaling protocol, and takes advantage of the part of integrated services in ns2 as the skeleton which includes admission control algorithms, estimation and measurement methods.

• On the basis of the result of the test cases, some basic function of GS can almost be implemented in the ns2.

Conclusion (2)

However, there are still a lot of work to do for improving the implementation to realize the GS strictly according to [RFC2212] [RFC2205] and [RFC2210]. For example, in the RSVP, several objects which influence less to the implementation in ns2 were ignored, such as INTEGRITY, SCOPE AND POLICY_DATA.

Conclusion (3)

• Guaranteed services provide high-quality QoS.

• IntServ/GS is not likely to be the widely implemented QoS solution because of the well known reason:

the complexity in routers and limited scalability.

Questions?

Thanks for your attention!

Implementing Integrated Services in Network Simulator

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