EQ-BGP: an efficient inter-domain QoS routing protocol

Andrzej Bęben

(abeben@tele.pw.edu.pl)

Institute of TelecommunicationsWarsaw University of Technology,

Poland

Outline

Introduction

EQ-BGP protocol

Performance of EQ-BGP

Summary

Introduction (1)Providing end-to-end Quality of Service in IP

networks still remains a challenging task: Different types of traffic and QoS objectives: VoIP,

VTC, Multimedia Streaming, high throughput data,.. Different network technologies: LAN, WLAN, xDSL,

UMTS, IP core, etc.

Recognised approaches: single domain network: DiffServ, IntServ, MPLS – currently

deployed in GENAT, Q-BONE, AQUILA, ...

multi-domain network: Concept of end-to-end classes of service (e2e CoS) – ITU-

T, IETF, IST EuQoS (www.euqos.org) Path computation architecture (PCE IETF) „user probing” approach ...

e2e CoSs concept (1)The end-to-end Classes of Service :

represents a specific set of traffic requiring from network similar QoS guaranties, e.g. VoIP, multimedia, guaranteed throughput, ...are offered to the users as „Globally Well Known” servicesare mapped into local CoSs offered inside particular domains and on inter-domain links

Access 1 (WLAN)

Access 2 (UMTS)

Core

Telephony

RT Interact.

MM Stream.

High Thr. D.

Standard

RT

NRT

BE

Over - provisi oned

RT

NRT

BE

RT

NRT

BE

RT

NRT

BE

Telephony

RT Interact.

MM Stream.

High Thr. D.

Standard

e2e CoSs concept (2)

The QoS level offered by e2e CoSs depends on: QoS level offered by particular domains and inter-

domain links The routing between source and destination

However, BGP-4 establishes paths based on „AS path length” that may be not suitable

Solution: to enhance BGP-4 protocol with QoS features => EQ-BGP (Enhanced QoS Border Gateway Protocol)

EQ-BGP protocol (1)

Objective: to fix inter-domain routing paths that for

particular e2e CoS offer the most attractive QoS level, e.g. lowest delay, jitter, losses,...

AS – BGP Autonomous System

– BR routers

--- Best Effort link

--- QoS link

--- AS path

AS1AS6

AS2

AS5

AS4

AS3

RM

T31

AS – BGP Autonomous System

– BR routers

--- Best Effort link

--- QoS link

--- AS path

AS1AS6

AS2

AS5

AS4

AS3

RM

T31

EQ-BGP protocol (2)New entities of EQ-BGP:

New QOS_NLRI attribute of update messages, that carries information about e2e CoSs and values of QoS parameters, e.g. delay, jitter, losses, offered on a given AS path

QoS aware decision algorithm, that allows to select paths taking into account QoS objectives of e2e CoS

QoS assembling function, that calculates „aggregated” value of QoS parameters

Multiple routing tables, as e2e CoSs usually need disjointed paths

...,0max,0max

,..)2,1,...,2,1(22

2

11

1

qT

f

qT

fffQQDoP

RMARMB RMC

RM – Domain Resource Manager

EQ-BGP protocol (3)

AS A AS CAS B

QoSPathDestQoSPathDestQoSPathDest QoSPathDest

QC

QCASCASC

QoSPathDest

RMC provides EQ-BGP router information about QoS offered inside domain C (QC)

RMB provides EQ-BGP router information about QoS offered on inter-domain link B->C (QB->C)

QB->C

QBASBASB

QoSPathDest

RMB provides EQ-BGP router information about QoS offered on inter-domain link B->C (QB->C) and offered by domain B

QBQA->B

RMA provides EQ-BGP router information about QoS offered on inter-domain link A->B (QA->B)

EQ-BGP protocol (3)RMA

RMB RMC

AS A AS CAS B

QoSPathDestQoSPathDestQoSPathDest QoSPathDest

QC

QCASCASC

QoSPathDest

QB->C

QBASBASB

QoSPathDest

QBQA->B

Finally, all routers has information about QoS offered inside its domain and on inter-domains links. So, they start to exchange these information.

Router C sends message to router B with information about QoS offered by domain C

QB-C

+QC

ASB

ASC

ASC

QoSPathDest

Router B writes new destination (ASC) to his routing table with QoS corresponding to cumulative value of QB->C and QC (denoted as QB->C+QC) using QoS NLRI attribute

QB->C+QC

Then, it advertises these information to RMB and peering router in domain B using iBGP with QoS NLRI attribute

QBASBASB

QB+

+QB-C

+QC

ASB

ASC

ASC

QoSPathDest

This peering router updates routing tabletaking into account QOS offered by domain B

QB+QB->C+QC

QA-B

+QB

ASA

ASB

ASB

QA-B

+QB+

QB-C+

+QC

ASA,

ASB

ASC

ASC

QoSPathDest

QA->B + QB+QB->C+QC

Finally, router A updates its routing table and informs RMA about

QoS towards domain C

Performance of EQ-BGP (1)

Objective: to analyse the impact of new EQ-BGP entities on network convergence

Methodology:We compare the performance of EQ-BGP with standard BGP-4 protocol based on convergence metrics:

Network convergence time – time elapsing from the occurrence of stressing event till the end of processing the last update message

Number of update messages that need to be exchanged

NS2 is used for simulation experiments

Performance of EQ-BGP (2)

Assumptions: Basic network stressing events:

Advertisement of a new route Withdrawal of the existing one

Each AS is represented by a single routerNetwork topologies:

Full mesh Ring Representative for the Internet

(B.Premore, SSFnet)

Different number of ASs

A single e2e CoS targeted for assurance „mean delay”

tree strategies for assigning QoSRepresentative Internet topology B.Premore,

SSFnet

Performance of EQ-BGP (3)

Convergence time after advertisement of new route: - randomly chosen AS advertises route - 100 simulation runs

EQ-BGP BGP-4 random increasing decreasing Network

type No. of ASs mean

[ms] max [ms]

mean [ms]

max [ms]

mean [ms]

max [ms]

mean [ms]

max [ms]

4 3.550,0 3.55 3.550,0 3.55 3.550,0 3.55 3.550,0 3.55 11 3.550,0 3.55 3.550,0 3.55 3.550,0 3.55 3.550,0 3.55

“Full mesh”

29 3.550,0 3.55 3.550,0 3.55 3.550,0 3.55 3.550,0 3.55

4 6,50,028 8,22 6,780,028 8,22 7,640,023 8,22 6,790,028 8,22 11 10,840,0 10,85 12,940,028 14,6 13,320,025 14,6 13,490,027 14,6 “Ring” 29 28,20,0 28,2 51,450,045 53,94 47,260,05 50,4 47,790,06 50,4

“Internet” 29 11,920,028 15,31 17,90,076 27,38 13,590,06 20,38 18,970,065 27,36

Conclusions:EQ-BGP gives stable routingFull mesh network converges independently from the applied protocolEQ-BGP protocol needs a bit more time to converge in case of ring and Internet topologies

Performance of EQ-BGP (4)

Convergence time after withdrawal of route: - randomly chosen AS withdraws route - 100 simulation runs

EQ-BGP BGP-4 random increasing decreasing Network

type No. of ASs mean

[ms] max [ms]

mean [ms]

max [ms]

mean [ms]

max [ms]

mean [ms]

max [ms]

4 16,750,03 18,47 16,830,03 18,47 17,040,03 18,47 12,490,0 12,49 “Full mesh” 11 18546,13 2077 717,24,21 1139 12753,5 1544 576,51,7 708,8

4 8,220,03 9,56 7,890,03 9,56 6,890,02 9,56 7,890,03 9,56 11 20,030,0 20,03 17,840,03 20,03 17,520,02 20,03 17,520,02 20,03 “Ring” 29 53,940,0 53,94 51,450,05 53,94 47,260,05 50,4 47,790,06 50,4

“Internet” 29 187213 2808 121265 1706 265423 4042 232826 5241

Conclusions:EQ-BGP gives stable routingEQ-BGP protocol converges faster then standard BGP-4

SummaryThe approach for providing e2e QoS in multi-domain network based on e2e CoSs was investigated

The Enhanced QoS BGP protocol (EQ-BGP) was proposed for supporting e2e CoS concept

Obtained preliminary simulation results confirm that: EQ-BGP gives stable routing Network convergence is similar to BGP-4

Further work: Evaluation of other stressing events, like link or node failure,

route flapping Evaluation of scalability in large networks Evaluation in test-bed