Broadband Communic

ation Lab.

Asymmetric Path Detection in BGP Routing

29 January, 2004

Eun Mi, ParkKorea Univ.

Dept. of Electronics and Computer Engineeringeun@widecomm.korea.ac.kr

Broadband Communic

ation Lab.

2KESG / APAN

Contents

IntroductionRouting Area GoalSystem Architecture & Visualization systemData Analysis for BGP messagesAsymmetric Paths In/out of KORENApproaches in KESG ProjectAsymmetric Path DetectionAPD system ApproachIssues

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Introduction

Improving international link resource utilization

Develop BGP analysis system to analyze and improve international link

Collaborations with KOREN members, JP members

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Goal in BGP Routing Area

1st YearFramework for improve international network performance & for detect abnormal routing informationfinding & collecting asymmetric pathsBGP monitoring & visualization system

2nd YearDetecting asymmetric pathsLoad balancing of the international links

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System Architecture (1)

Seoul XP

Busan XP

BGPview Analyzer VisualizerDataBase

2nd year major

Measurement Area BGP Routing Area

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System Architecture (2)

Korea

Pusan

Taejon

Seoul

TO:APII linkTEIN linkH-G link

BGPviewVisualizationAnalysissystem

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Brief Overview

APAN-JP

APAN-JP

RENATER3SINGAREN

BGP ViewBGP View

Web based interfaceWeb based interface

DB

Visualization systemVisualization system

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Implementing Visualization System

The purpose is to report BGP table & update message status visuallyFrom modified BGPview agent

Query from DBReal time report from BGPview

User can see not only BGP status, but also full message formatIn abnormal state such as abnormal updates, user can see the routing entry to removeMessage ID searching functionMessage information, message Prefix information, full message information

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Web based Visualization

Total Message Information

Prefix Information

Full Information

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Data Structure for Visualization

Field name Field Type Contents

date Date Message date

time Time Exact time for message

total long Total number of the message

update long Number of the updated message

notification long Number of the notification message

open long Number of the OPEN message

keepalive long Number of the KEEPALIVE message

prefix long Number of the prefix in a receiving packet

withdraw longNumber of the withdraw message in a

receiving packet

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Categorization

PEERSneighbor : BGP router IP addressremote_as : BGP router AS numberlocal_as : default AS numberholdtimer : for Hold timer adjust to manage the KEEPALIVE message

MESSAGE_INFOFor total message number

ROUTER_TTFor keep connection with the peer router

DUMMYINFOTo check BGPview’s condition

ROUTE_INFOROUTE_HISTORY

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Message Analysis

Total Received Message

0

200

400

600

800

1000

1200

1400

1600

1 191 381 571 761 951 1141 1331 1521 1711 1901 2091 2281 2471 2661 2851 3041 3231

Time (Minute)

Num

ber

of M

essa

ge

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Data Analysis

All message is update messageOPEN : WITHDRAW = 89% : 11%Only 1 OPEN messageKEEPALIVE MESSAGE = (3msg./1min.)NO Notification MessageAbout 12Mbyte/1day

7660(APAN-JP)2200(RENATER3)2523(APAN-JP)

7610(SingaREN)

Entries in the International Links

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Asymmetric Paths

KOREN

User 1

User 2

User 3

JAPAN

SingaREN

TEIN

Inside of the KOREN…

CommercialNetwork??

CommercialNetwork??

Outside of the KOREN…

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APs in International Links

KORENAS9270

JAPANAS7660

APII 8Mbps

G-H 1Gbps #1

G-H 1Gbps #2

Others???

TO JAPAN

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APs in International Links

KORENAS9270

USASTARTAP

HPCnet 45Mbps

TransPAC 155Mbps * 2

Others???

TO USA

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Asymmetric Path Detection

Basically, {traceroute} is the only to find exact asymmetric pathsWe can guess the APs by collecting routing information

Match next hop, routing table

If the path is outside of the KORENBy collecting routing table & BGP table

IF the path is inside of the KORENBy PMI APD system

For International PathInternational collaboration must be needed

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PMI Approach

Router

MonitoringServer

DataBase

2. 라우팅 테이블 목록을 가져옴

1. RSH “Show ip bgp”

5. 데이터베이스에 서 요청 정보를 검색

4. 사용자가 필요정보를

요청

6. 검색된 결 과를 웹 서버 에 전송

7. 전송되온 정보 정보 표시

Web Interface

3. 라우팅 테이블 목록 ,에서 필요 데이터 추출

데이터베이스에 저장

computercomputer

APDAgent APDAgent

APDServer

2. Interface IP list from each router

1. RSH “show ip aliases”3. User selects APDAgent IP

7. Show result of APD

4. RSH“traceroute execute”

4. RSH “traceroute execute”

5. Store router interface IP and measured IP 6. Sends result which is compared

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Measurement Area Approach

Netflow data based, inbound & outbound traffic analysisMake set of SRC AS Number of inbound traffic and DST AS Number of outbound trafficAS(in, seoul) = {AS1, AS2, … }

AS(out, seoul) = {AS3, AS4, … }

AS(in, daejeon) = {AS5, AS6, …}

AS(out, daejeon) = {AS7, AS8, …}

Ex. ASn ∈ AS(in,seoul) and ASn ∈ AS(out,daejeon)

the path with ASn is asymmetirc

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APD System Approach

All table must be gatheredSeoul, Daejeon, Suwon, Kwangju…PMI system + measurement area data

Implementing Matching function in AnalyzerAnalyzer will be added in modified BGPview system in 2nd yearAlgorithm must be developed for address/AS PATH matching

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Conclusion

After Asymmetric Path Detection, What is the Next?

Asymmetric Paths are not abnormal…Basic Information for load balancing

For International APD…Way to International collaboration

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Thank you