quality of service (qos)-based management of preempted traffic in mpls networks eng. ayman maliha...

Quality of Service (QoS)-Based Quality of Service (QoS)-Based Management of Preempted Management of Preempted Traffic in MPLS NetworksTraffic in MPLS Networks

Eng. Ayman MalihaElectrical & Computer Engineering Department

The Islamic University of Gaza

Contents

• Introduction

• Preemption in MPLS (MNS-2)

• Thesis Statement

• Proposed Preemption Technique

• Simulation Results

• Conclusion and Future Work

• MPLS & Traffic Engineering• MPLS & Traffic Engineering

OSI Reference Model

Application

Presentation

Session

transport

Network

Data link

Physical

Application

Presentation

Session

transport

Network

Data link

Physical

Network

Data link

Physical

Source node Destination node

Intermediate node

Signals

Packets

Bits

Frames

OSI Reference Model

* Functionality: + Implement the desired procedure. + Provide the user interface

* end-to-end error recovery and flow control

* Provide host to host link

* Provide physical connection to the net

ROLE

* Provides for reliable transfer of information across the physical layer.

LAYER

7. Application

4. Transport

3. Network

6. Presentation

5. Session

2. Data Link

1. Physical

* Provide enhanced services (Control structure for communication between applications.)

OSI Reference Model


Application

Presentation

Session

transport

Network

Data link

Physical

Application

Presentation

Session

transport

Network

Data link

Physical

Network

Data link

Physical

Intermediate nodeSignals

OSI Reference Model

AL-Hdr Application Layer Msg

PL-Hdr Presentation Layer Msg

SL-Hdr Session Layer Msg

TL-Hdr Transport Layer Msg

NL-Hdr Network Layer Msg

DLL-Hdr Data Link Layer Msg

PL-Hdr Physical Layer Msg

Presentation

Session

Transport

Network

Data Link

Physical

Application7

6

5

4

3

2

1

Network A Node

OSI Reference Model

Application

Presentation

Session

transport

Network

Data link

Physical

Application

Presentation

Session

transport

Network

Data link

Physical

Network

Data link

Physical


Intermediate nodeSignals

TCP/IP Reference Model

Transport

3. Internet

TCP/IP

Not Present

Not Present

Application

OSI

7. Application

4. Transport

3. Network

6. Presentation

5. Session

2. Data Link

1. Physical

2. Data Link

1. Physical

Internet Today

• Internet today

Exceeding the delays and jitter boundaries causes problems to real-time applications.

- Provides “best effort” data delivery

- Complexity stays in the end-hosts

- Network core remains simple

- As demands exceed capacity, service degrades gracefully (increased jitter etc.)

Quality of Service (QoS)

• Definition

• Goal

A set of service requirements to be met by the network while transporting a flow.

Provide some level of predictability and control beyond the current IP “best-effort” service.

QoS Metrics

- Bandwidth

- Jitter

- Delay (or latency)

- Loss rate

Vary according to Service Level Agreement (SLA)

QoS Protocol Classification

•QoS can be achieved by :–- Resource reservation (integrated services)–- Prioritization (differentiated services)

QoS can be applied :–- Per flow (individual, uni-directional streams)–- Per aggregate (two or more flows having

something in common)

QoS Protocol

IETF

- Integrated Service (IntServ)

- Differentiated Services (DiffServ)

- Multi Protocol Labeling Switching (MPLS)

Integrated Service (IntServ)

• Philosophy BehindRouters have to be able to reserve resources

to provide special QoS for specific user packet streams.

• Four components of IntServ Model• The signaling protocol (e.g. RSVP)• The admission control routine• The classifier• The packet scheduler

• Four components of IntServ Model• The signaling protocol (e.g. RSVP)• The admission control routine• The classifier• The packet scheduler

IntServ Components

IntServ Components

Sender sends a PATH Message to the receiver specifying the characteristics of the traffic

The receiver responds with a RESV Message to request resources for the flow

The receiver responds with a RESV Message to request resources for the flow

Every intermediate router along the path can reject or accept the request of the RESV Message

Every intermediate router along the path can reject or accept the request of the RESV Message

•The signaling protocol•The signaling protocol

IntServ Components

• Admission controlDecide whether a request for resources can be granted

• ClassifierWhen a router receives a packet, the classifier will perform classification and put the packet in a specific queue based on the classification result

• Packet schedulerSchedule the packet accordingly to meet its QoS requirements

• Admission controlDecide whether a request for resources can be granted

• ClassifierWhen a router receives a packet, the classifier will perform classification and put the packet in a specific queue based on the classification result

• Packet schedulerSchedule the packet accordingly to meet its QoS requirements

IntServ Problems

•Problems– Not scalable

• Huge storage and processing overhead on the routers

• The amount of state information increases proportionally with the number of flows

– Requirement on routers is high

• All routers must implement RSVP, admission control, classification, and packet scheduling

DiffServ

- Description Applied on flow aggregates Services requirements are classified Classification is performed at network ingress points A predefined per-hop behavior (PHB) is applied to every service class Traffic is smoothed according to PHB applied

DiffServ functional elements

• edge functions:– packet classification

– packet marking

– traffic conditioning

• core functions:– forwarding based on per-hop behavior (PHB) associated with packet’s class

DiffServ - Traffic Classes


• packet classification Classifier selects packets based on values in packet header fields and steers packet to appropriate marking function

• Meter Calculates the traffic level, which is compared against the customer’s contract/Service Level Agreement (SLA) profile.


• Marker The packets are marked by setting the DS value to a correct codepoint as needed

• Shaper The shaper Polices traffic by delaying packets as necessary so the that the packet does not exceed the traffic rate specified in the profile for that class


• Dropper Drops the packets when the rate of packets of a given class exceeds that specified in the profile for that class

• Per-hop behavior (PHB) defines differences in performance among classes.

DiffServ - Traffic Classes

Two traffic classes are available : –Expeditied Forwarding (EF)

• Minimizes delay and jitter• Provides the highest QoS • Traffic that exceeds the traffic profile is

discarded–Assured Forwarding (AF)

• 4 classes, 3 drop-precedences within each class

• Traffic that exceeds the traffic profile is not delivered with such high probability

DiffServ - Advantages

• Advantage– Scalable

• Edge routers maintain per aggregate state• Core routers maintain state only for a few traffic

classes

– Easy implementation• Incremental deployment is possible for Assured

Forwarding

DiffServ - Disadvantages

• Disadvantage– Provide weaker service than InteServ– per hop behavior cannot guarantee end-to-end QoS.

Multiprotocol Label Switching (MPLS)

3- Multiprotocol Label Switching (MPLS)

MPLS is a technology that integrates label-swapping paradigm with network-layer routing within Label Switching Routers (LSRs).

It is proposed to be a combination of the better properties of ATM and IP.

A short fixed-length “label” results in high-speed switching.

MPLS

Forwarding:Label Swapping

Control:

IP Router Software

Control:

IP Router Software

Forwarding:Longest-match Lookup

Control:

ATM Forum Software

Forwarding:Label Swapping

IP Router MPLS ATM Switch

Contents

• Introduction







IP Traditional Routing

• Choosing the next hop Open Shortest Path First (OSPF) to populate the

routing table Route look up based on the IP address Find the next router to which the packet has to be

sent Replace the layer 2 address

• Each router performs these steps

IP Routing Table

47.1

47.247.3

Dest Out

47.1 147.2 2

47.3 3

1

23

Dest Out

47.1 147.2 2

47.3 3

Dest Out

47.1 147.2 2

47.3 3

1

23

1

2

3

Build IP routing table

IP Traditional Routing

47.1

47.247.3

IP 47.1.1.1

Dest Out

47.1 147.2 2

47.3 3

1

23

Dest Out

47.1 147.2 2

47.3 3

1

2

1

2

3

IP 47.1.1.1

IP 47.1.1.1IP 47.1.1.1

Dest Out

47.1 147.2 2

47.3 3

Traditional IP forwarding

Disadvantages

• Header analysis performed at each hop

• Increased demand on routers

• Utilizes the best available path

• Some congested links and some underutilized links!Degradation of throughputLong delaysMore losses

• No QoSNo service differentiationNot possible with connectionless protocols

• Header analysis performed at each hop

• Increased demand on routers

• Utilizes the best available path

• Some congested links and some underutilized links!Degradation of throughputLong delaysMore losses

• No QoSNo service differentiationNot possible with connectionless protocols

MPLS & Traffic Engineering

• MPLS Components1- Label Switching Based Router (LSR & LER)

A high-speed router device that participate in the establishment of LSP.

2- Label Switching Path (LSP)

A sequence of LSRs that is to be followed by a packet.

3- Labeled Packets

A packet into which a label has been encoded.

MPLS & Traffic Engineering - (LSP)

IntfIn

LabelIn

Dest IntfOut

3 0.40 47.1 1

IntfIn

LabelIn

Dest IntfOut

LabelOut

3 0.50 47.1 1 0.40

47.1

47.247.3

12

3

1

2

1

2

3

3

Mapping: 0.40

Request: 47.1

Mapping: 0.50

Request: 47.1

MPLS & Traffic Engineering - (LSP)

IntfIn

LabelIn

Dest IntfOut

3 0.40 47.1 1

IntfIn

LabelIn

Dest IntfOut

LabelOut

3 0.50 47.1 1 0.40

47.1

47.247.3

1

2

1

2

3

3

IntfIn

Dest IntfOut

LabelOut

3 47.1 1 0.50

IP 47.1.1.1

IP 47.1.1.1

1

2

3

MPLS Switching

MPLS & Traffic Engineering - (ER-LSP)

IntfIn

LabelIn

Dest IntfOut

3 0.40 47.1 1

IntfIn

LabelIn

Dest IntfOut

LabelOut

3 0.50 47.1 1 0.40

47.1

47.247.3

12

31

2

1

2

3

3

IntfIn

Dest IntfOut

LabelOut

3 47.1.1 2 1.333 47.1 1 0.50

IP 47.1.1.1

IP 47.1.1.1

MPLS & Traffic Engineering - Labels

• A short, fixed length identifier (32 bits)

• Sent with each packet

• Local between two routers

• Can have different labels if entering from different routers

• A short, fixed length identifier (32 bits)

• Sent with each packet

• Local between two routers

• Can have different labels if entering from different routers

Label Value Exp . S TTL

8320 1

20-bits : Label value used for lookup 8-bits : Time-To-Live

1-bit : Bottom of Label Stack

3-bits : Reserved

MPLS & Traffic Engineering - Labels

•ATM: Label VPI/VCI(w/shim)

•Frame Relay: Label DLCI(w/shim)

•Ethernet: Label Shim

•PPP: Label Shim

•ATM: Label VPI/VCI(w/shim)

•Frame Relay: Label DLCI(w/shim)

•Ethernet: Label Shim

•PPP: Label Shim


PPP Header

LAN MAC Header

ATM Cell Header

PPP Header

LAN MAC Header

ATM Cell Header

Layer 3 Header PPP HeaderLabel

Layer 3 Header MAC HeaderLabel

DATA HEC CLP PTI VCI VPI GFC

Label


TE Definition An iterative process of network planning and network optimization

TE Objectives - High service quality

- Efficiency

- Survivability

- Cost

The established path must fulfill some requirements to deliver the required QoS and it should satisfy the network capacity and policy.

MPLS & Traffic Engineering.

• TE Attributes of Traffic Trunks

- Traffic parameter attribute i.e. peak rates, burst size, etc..

- Policing attribute

- Path selection and management attribute

- Priority attribute

- Preemption attribute

- Resource attribute

Preemption

Definition Preemption is the premature suspension or termination of an activity in order to permit some other activity to proceed.

Preemption attribute determines whether a traffic trunk can preempt another traffic trunk from a given path.

Preemption attribute

It is an action that is taken by a system element when the demand for the resources exceeds the available supply.

Adaptive Real-time Traffic

Adaptive or Controllable real-time applications can adjust their data rates to the available bandwidth e.g. videoconferencing (CIF, MPEG-I).

Such applications could be treated at lower QoS level that depends on the available bandwidth.

Contents


• Introduction

• Preemption in MPLS (MNS-2)• Proposed Preemption Technique




Thesis Statement

Bandwidth allocation is an important issue in network management dealing with guaranteed bandwidth policy. The ability of an application to maintain its bandwidth depends on its precedence attribute within the network. Preemption allows guaranteed bandwidth for high priority traffic.

Harsh solution for the preempted traffic, which loses its resources.

Thesis Statement

Real-time traffic• Advantageous for the preemptor traffic.

• Disastrous for the preempted traffic

Upon preemption, network needs to consider:

• Reservable bandwidth

• traffic type• priority

Adaptive real-time traffic needs to be treated differently when preempted i.e. serving it at lower bit rate if the reservable bandwidth meets the new rate.

Contents



• Introduction





MNS Simulator

A simulation tool for MPLS network.

It is implemented as an extension of NS-2 simulator, which is an object-oriented Tcl script interpreter.

MNS-2 commands must be written in a Tcl script file, which defines the simulation scenario.

Preemption in MPLS

Total link BW

(1Mbps)

Time

Best-effort and signaling traffic (200 kbps)

Maximum Real-time bw fraction 800 (kbps)

Bandwidth allocation in MNS-2

CR-LSP1 300 (kbps)

CR-LSP2 400 (kbps)

Reservable bandwidth

Preemption in MPLS

Total link BW

(1Mbps)

Time


Bandwidth allocation for AD-RT in MNS-2

Reservable bandwidth (32 kbps)

Real-time bandwidth fraction (800 kbps)

CR-LSP1, bw 768 kbps

setupPrio 5 , holdprio 4.

CR-LSP1 768 (kbps)


setupPrio 3 , holdprio 2.CR-LSP2 (400 kbps)

CR-LSP1 768 (kbps)

CR-LSP1 768 (kbps)

Preemption in MPLS

Preempted traffic is served at best-effort level, and it becomes under the mercy of network load.

Real-time bandwidth fraction is not well utilized.

Preempted real-time traffic sharing other best-effort traffic resources, i.e. no dedicated resources remain for the preempted traffic.

Contents




• Introduction




Proposed Preemption Technique

Total link BW

(1Mbps)

Time


Bandwidth allocation for AD-RT in the proposed preemption mechanism.





CR-LSP1 768 (kbps)


setupPrio 3 , holdprio 2.CR-LSP2 (400 kbps)

CR-LSP1 (384 kbps)

CR-LSP1 (786 kbps)

reservable bw (16 kbps)

tt

Preemption time

Proposed Preemption Technique

Total link BW

(1Mbps)

Time


Bandwidth allocation for AC-RT in the proposed preemption mechanism.





CR-LSP1 500 (kbps)



No reservable bw

CR-LSP2 (400 kbps)

CR-LSP1 (400 kbps)

Reservablebandwidth

Reservablebandwidth

tt

Preemption time

Contents





• Introduction



Contents

Simulation results

0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

0 5 10 15 20 25 30 35 40 45 50 55 60

Time (sec)

Ban

dwid

th

( Mbi

t

)

Bandwidth allocation for two preempted traffics.

RT3AD-RT1

AD-RT2

Total link = 4 Mbit

RT- fraction = 3520 kbit

Reservable = 1320 kbit

Total link = 4 Mbit



Simulation results

0

0.5

1

1.5

2

2.5

3

3.5

0 5 10 15 20 25 30 35 40 45 50 55 60

Time (sec)

Ban

dwid

th

( Mbi

t

)

Bandwidth allocation for one real-time traffic when two traffics are preempted

RT3

AD-RT1

AD-RT2

Total link = 4 Mbit



Total link = 4 Mbit



Simulation results

0

5000

10000

15000

20000

25000

30000

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

Background data rate (kbps)

Thr

ough

put

Throughput for all traffic flows with different background data rates

AD-RT1

BET

RT1

• Throughput

Simulation results

0

2500

5000

7500

10000

12500

15000

17500

20000

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800


Thr

ough

put

( kbps

)

Throughput for all traffic flows with different background data rates

AD-RT1

RT2

BET

• Throughput

Simulation results

444648505254565860626466

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800


Del

ay

( ms

)• Delay

Simulation results

• Jitter

0

2

4

6

8

10

12

14

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

SBT data rate (kbps)

Jitt

er

Contents





• Introduction



Conclusion and future work

Allocating a dedicated bandwidth for traffic allows it to have stable behavior in terms of the throughput.

Better performance (jitter, delay) is achieved when serving the preempted traffic at lower QoS level.

Better network management can be achieved since the consumed resources in the network are known.

Better network bandwidth utilization is achieved.

Conclusion and future work

When a real-time traffic can not get the minimum requirement of recourses, Should it be served at:

1- Simple Best-effort level!

2- High best-effort level!

3- blocked!

A comparison study with different real-time applications to determine the criteria for each application is required.

quality of service (qos)-based management of preempted traffic in mpls networks eng. ayman maliha...

Documents

physical slide

node slide

physical connection

network core

common slide

present application

services qos

set of service requirements