© JNU College Presentation End-to-End Quality of Service in IP Networks © JNU College Presentation Chetan Kumar S [email protected] Wipro Technologies

©JNU College Presentation

End-to-End Quality of Service in IP

Networks


Chetan Kumar S [email protected]

Wipro Technologies29th March 2003


Organization of the talk

Introduction

QoS definition

What do End-to-End mean

Discussion on QoS at various levels

Some Recent Advancements in QoS

Discussion


Need for Communication


How do people communicate today

Internet


IP Networks

Current day network is IP based, no options ? !!

IP provides a best effort service, it takes care of data transfer from sender to receiver, not how !!

Ideally a loosely knitted network of hosts, routers and switches

Build for flexibility and robustness


What it is IP networks are built with statistical parameters

Reason, to get advantage of statistical-gain

Reduce the operational costs, can pump more data.

IP networks are built mainly to exchange data not voice/movie

Initial IP network by DARPA was to exchange information between computers


Further.. IP networks grew enormously, making it not just to share data across computers.

Now, one wants IP networks to service all type of services

Many human-centric applications, voice, video

As a consequence one needs to think more than just data transfer, needs to look at how data is transferred.


IP network for future

1968 First transit node by BBN on DDP 316ARPANET was born with 4 transit nodes1969

1974 TCP/IP for inter networking

ARPANET has 200 transit nodes1983ANSNET from MERIT, MCI, IBM1990

Internet as you know it 1995

2000Internet 2 ??

??Something really fast

ATM, QoS,RVSP, DiffServ,IPv6, MPLS…


What do you want your network to do - today !!

INTERNET


Internet What it is

IP based Network


But in reality

Technology basedRegion based, Politics based,

Economy based


So What ??Now experts say we cannot assume things for granted

Need to define services and how they are serviced and a parameter to measure them.

Did we ever think of QoS in telephone ??

Yes, but the parameters were much different.

MOS, Call blocking, Call dropping.. etc.

To large extent this is different that what we see today in IP networks

The reason, telephone networks are based on deterministic parameters


Quality of Service

Defines a set of parameters to measure and define the service provided by an entity

Could be host, Router, subnet

End-to-End, definition based on

End host to End host

End Application to End Application

Producer to Consumer

We normally restrict to host to host here.


QoS Parameters

Data Rate: The transfer bit rate of the flow, also called throughput.

End-to-End Delay: Elapsed time between the generation of the data and consumption of the data

Packet Loss Rate: percentage of packets that are dropped due to lack of buffer space in the network

Delay Jitter: Variation of End-to-End delay


QoS Parameters

Data Rate is not bandwidth, remember Shanon's theorem

Data rate=bandwidth*ln(1 + SNR)

Depends on the link, and how the link shared across flows

End-to-End Delay is sum total of propagation delay, switching delay and queueing delay

Since propagation delay is under control, we try to achieve better queueing delay

Delay variance is due to change in the network statistics


End-to-End QoS

So End-to-End QoS is measure of these parameters end-to-end

All the elements of the Internet, hosts, routers, link and network should be tuned.

Providing QoS at various points involves various issues

What works on host may not work on network

Mangoes != Oranges


Various Aspects

Scheduler

Resource Manager

Admission Controller

Signalling

Provisioning


End-to-End QoS involve

Internet

Subnet Subnet Subnet

Routers Routers Routers

Desktops Desktops Desktops Desktops


Desktop QoSInvolves stream synchronization, use of resources like sound device, monitor and mic/cam

Sharing is simple, no multi-user contention for resources

Comparatively simple

Resource is at abundance, memory is cheap, CPU prices are slashed regularly

The are good OSs out there that can be customized to do pretty nice jobs

And main thing is what ever you do, you need not have to interoperate

• Really not much work gone into this– No killer application


End-to-End QoS

Internet





Router opened

IP packet

IP packet

Filter Action

Forwardingtable

Routingagent

IP input processing IP output processing

IP packet

Packet scheduler

IP output processing

IP packet

Packet scheduler

Routers forward the IP packets, do you need more explanation ??


RoutersThere are multiple flows that are flowing through the router, and each contend for resource

Need to share the output link

Need to share the buffer space

Also router works on packets from other routers, so need to interoperate


SchedullingThis is main component of a packet based box/router

Define the time a packet get on the output link, inturn the bandwidth

Can also define the packet delay and delay jitter, based on the priority

Kinds of scheduler:Flat and Hierarchical scheduler

If the delay and bandwidth are linked or independent

Various flavours available• Round Robin, WRR, Priority, GPS, PGPS


Scheduling - QueueingDefines how the packets are queued on the ingress point

Also defines what to do when the queue is filled up

Drop tail, Drop Head, Priority Drop etc..

A complex design issue to decide the queue length

Queue length can not be infinite, this may give rise to large delay

Various approaches available• Shared queue, per class queue & etc..


Resource Manager

Does the book keeping of various resources on the router

Interacts with the system to get the resources avialable

Give inputs to the admission controller

Fairly simple and a passive component in a router


Admission ControllerThe router need to make sure if it can serve a flow

So accept only those call, do not over-stuff

Accept only these many type of services

Various types of admission controller– Measurement based, parameter based

– For CBR, Best Effort, VBR, VBR peak etc..

• Really a complex operation, often has two contradictory goals

– Reject as less calls as possible

– Make sure all the QoS parameters are satisified

– An LP model is proposed and worked upon.


Admission Controller

Class I

Class II


SignallingOne of the Complex entities sitting in the router

Why do we need this? - to inform routers about the resource requirements and data one is sending

Signalling could be inband OR out of band

Needs standardization, since need for interoperability

IETF is proposing standards

– Int-serv: Flow based, out-of-band signalling

– Diff-serv: Discreate, inband signalling.


Int Serv

Service differentiation in the Internet

Focuses on individual packet flows

Each flow requests specific levels of service from network

Levels of service quantified as a minimum service rate, or a maximum tolerable end-to-end delay or loss rate

Network grants or rejects the flow requests, based on availability of resources and the guarantees provided to other flows

• Best effort service• Real time service• Controlled link sharing


Int Serv

Application

Packet schedulerPacket classifier

Signalling protocolPolicy Control

AdmissionControl

Data


Diff Serv

Based on a model where traffic entering a network is classified , possibly conditioned at the boundaries of the network, and assigned to different service classes

• Here, we avoid complexity and maintenance of per-flow state information in core nodes and push unavoidable complexity to the network edges

• Things are based on PHB, per hop beheviour


Diff Serv

Classifier

Meter

MarkerShaper/Dropper

Packet In Packet Out


Provisioining

How to setup resources on the interfaces of the routers

How configure the router box, which flow to be what resources

Also defines the admission control ploicy and queue management policy

Fairly simple, since need to address only on the node we are looking at, i.e router

Normally one can use management tools with assistance of LDAP and databases.


QoS Router


End-to-End QoS

Internet





Subnet - Level

Need to share various flows across various links

Need to find a path for the flow with the associated resource

Need to setup these paths

Provisioning of these paths

Observe, we move higher the chain, we have move towards management and aways from working stuff


Path setup scenario

E4 E3

Ec

E2

Ea Ee

Ingress

Egress


Resource Management

Scheduling has little meaning here

One need to manage resource subnet wide

The resource data based is normally called TE database

OSPF and ISIS is extended to support new LSA to exchange these resource information

These routing protocols also maintain the TE database to be used by CSPF


Admission Control

Need to find if a new path can be setup in the network

If yes, which is the path to be taken

• CSPF, a proprietary route computing algorithm is used to find the path

– Various algorithms are around in the field

– K shortest path, Delay constrained least cost, Multi Constrained path.. etc

• Fairly complex stuff, no standard and works well within a subnet


Traffic Engineering

Data is routed through the network, based on the management view.Map the demand on to the network topology.

i.e., demand driver paradigm rather than topology driver.

DEM

AN

D !!

TRAFFIC

ENGINEERIN

G

To achieve maximum network utilization.•To engineer to the network to provide a guaranteed QoS.•To provide policy based network.


Signalling/Provisioning

Need to signal path in the network

Need some special tools like source routing, explicit paths, routing pinning etc..

MPLS with TE support as been proposed by IETF for signalling paths

Two signalling protocols, CR-LDP and RSVP-TE


CR-LDP

RSVP-TE and CR-LDP provides mechanisms for establishing explicitly routed Label Switched Paths (LSPs).CR-LDP (Constrained Routing LDP) is extension to basic LDP protocol.CRL-LDP has a special set of messages that can be used to signal ER LSP.Initiated by ingress to set-up end-to-end ER-LSP.CR-LDP allow dynamic modification of LSP attributes.


RSVP-TE

RSVP-TE protocol is extended to establish LSP tunnels along a explicit route.

Associates a labels to RSVP flow.

Path messages are sent from ingress LSR to Egress LSR to initiate LSP

Resv messages are sent from egress LSR to ingress LSR with a label binding.


MPLS TE

Supports demand driven LSP set-up.

Ability to set-up LSP based on the ER-Hop, similar to source routing.

The network can also set-up LSP based on the constraints in the CR-LDP.

Frequency, Negotiation, Route-Pinning and traffic parameters are powerful parameters for traffic engineering.

Both Diff-serv and Int-Serv based.


End-to-End QoS

Internet





Internet Level

Need for path setup accross networks that span multiple service providersMost of the issues involved are in signalling and provisioningMuch of these are cost specific

Leama 1.1: As go up $$ is what matters

Need to define how the resources are allocated and how is costing done

Much more complex since there are more unknown parameters involved,

SP do not share every thing with others


Signalling/Provisioning

Need to manage domain specific resource

Also need to aggregate this and have inter domain specific resource

One approach is BRBP, Border Gateway Reservation protocol

Aggregate all the reservation from intra domain

Do reservation across multiple domains

BRGP Agents reside on BGP router at the area border

BRGP use PROBE, GRAFT and REFRESH messages to exchange the resource and reservation issues.


BRGP


Recent Advancements

Hot topic is how do I signal resource for every connection

Can I user RSVP for one phone call

The answer is NSIS, Next Step in Signalling by IETF

Lot of work is still on in inter domain QoS, including bandwidth broker and BRGP

Agent based network and reservation based on this.


Recent Advancements

European Union's Experements on Interdomain QoS AquilaTeauilaCadenus


Argument

Bandwidth Over Provisioning Vs QoS


BOP v/s QoSBOP: Generous approach

Simple and brute force method, want to run video ?? I will give 10 Mbps

The essence is to give twice or more the requirements so that customer will not crib

When is bandwidth is becoming cheap, what is the issues. Maintenance of QoS is more costly for SP

SP: “Let me get back money for the link, do not want install more resources”


BOP v/s QoSQoS: Conservative Approach

Clever way of doing things, give customer what he wants and exactly what he wants

Essence is manage the network cleverly

Bandwidth may be cheap, but not as cheapConsider Indian popolation, 1 Billion, so if 10 percent want to talk over the IP phone, humungous numbers !!!!

Morse law of bandwidth does not yet exist

Giving value added services can be new revenue generating proposition


BOP v/s QoS

Each has its advantages and dis-advantagesArea of applicability may be a better parameter to judge the issuesThese are applicable both at core and edge, only the parameters considered will differ

And the argument continues.......... (Have a coffee bite)


For Further InformationEnd-to-End Working Group. Discussion forum on end2end research.

http://www.postel.org/mailman/listinfo/end2end-interest

An Engineering Approach to Computer Networking

S Keshav, AWL publication.

IETF Working Groups

IEEE Communication Magazine, January 2003, Vol 41 No. 1

Europian Union Projectswww.ist-tequila.org

www.ist-aquila.org

www.ist-cadneus.org


Thanks !!

Documents

© JNU College Presentation End-to-End Quality of Service in IP Networks © JNU College Presentation Chetan Kumar S [email protected] Wipro Technologies