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Apricot2001 Effectiveness of VLAN Chan Wai Kok ( Faculty of Information Technology Salim Beg ( Faculty of Engineering Multimedia University. The benefit of VLAN. Simplify the process of add, moves and changes

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The benefit of VLAN

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The benefit of vlan

Apricot2001Effectiveness of VLAN Chan Wai Kok ( of Information TechnologySalim Beg ( Faculty of EngineeringMultimedia University

The benefit of vlan

The benefit of VLAN

  • Simplify the process of add, moves and changes

  • Provide broadcast, multicast traffic isolation by grouping similar traffic types to a VLAN.

  • Provide some form of security

Goals of this presentation

Goals of this presentation

  • To find out the broadcast traffic trend

  • To study the effectiveness of VLAN in broadcast isolation

Why broadcast isolation is important

Why Broadcast isolation is important ?

  • On a 1 Gbps capacity backbone network

  • If 1% traffic is (broadcast + multicast + unknown unicast), all end stations with 10Mbps link may be congested (but backbone have more capacity!!!)

  • Broadcast frames will take up CPU resources. E.g On Pentium 120Mhz,

    • 1000 broadcast pps :- 15 % CPU resource

    • 3000 broadcast pps :- 28 % CPU resource

Related work will e leland daniel v wilson bellcore 1989 1990

Related Work(Will E. Leland & Daniel V Wilson Bellcore 1989 - 1990)

  • collected LAN traffic data for long time scale and analyzed the trend

  • Their showed that there is a great disparity in the values of peak to mean ratio for packet arrival rate. (73 to 861 for 5 sec to 5 milisec respectively)

  • LAN traffic is Bursty

  • Focus on behavior of total Ethernet traffic

Lan traffic hourly

LAN Traffic (hourly)

Lan traffic busiest hour

LAN Traffic (busiest hour)

Lan traffic by minutes

LAN Traffic (by minutes)

Lan traffic peak to mean ratio

LAN Traffic (Peak to mean ratio)

Analysis method

Analysis Method

  • Collect network traffic from few different IP Subnet and check the broadcast plus multicast traffic quantity.

  • Run an IP Multicast application

  • See how it’s effect the broadcast plus multicast traffic in the IP subnet.

  • Make some conclusions on the result

Network setup

Network Setup

  • A Pentium PC is used as a network analyzer

  • Traces are taken for a few days

  • Network consists of WinNT servers and Win95 PCs.

  • Each IP subnet consists of 60, 85 and 45 hosts respectively. 3 different labs.

  • Two Labs are is fully used during office hour.

  • Students accessing WinNT server to work

  • No Novell Server (future is IP)

Type of packets detected

Type of Packets Detected

  • ARP request

  • Spanning Tree Frame (hello frame)

  • Netbios

  • SAP

  • IP Multicast Solicitation

Traffic statistic

Traffic statistic

  • Average bandwidth (extremely low)

    • 1413, 1761, 1381 bps (office hour)

    • 809, 789, 406 bps (non office hour)

  • Maximum bandwidth (1 % of 10Mbps)

    • 31920, 125408, 130752 bps (office hour)

    • 29824, 70640, 38608 bps (non office hour)

  • Majority of the traffic is background traffic

  • Generally, broadcast traffic is very low

Traffic statistic no ip multicast

Traffic Statistic (no IP Multicast)

Traffic statistic no ip multicast1

Traffic Statistic (no IP Multicast)

Traffic statistic no ip multicast2

Traffic Statistic (no IP Multicast)

Traffic statistic with ip multicast application

Traffic Statistic with IP Multicast application

  • One IP Multicast Channel sending audio and text.

  • Average bandwidth :- 112 Kbps

  • Maximum Bandwidth :- 155 Kbps

  • Dramatic increased of (broadcast plus multicast) bandwidth when IP Multicast is ran.

  • Traffic isolation will required IP Multicast VLAN

Traffic statistic with ip multicast application1

Traffic Statistic with IP Multicast application

Ip multicast vlan

IP Multicast VLAN

  • Router will duplicate IP Multicast packet to all IP Subnet that joined in IP Multicast group

  • Some switch ports have multiple IP Subnet VLAN memberships. Therefore, may receive in duplicated IP Multicast packet

  • IP Multicast VLAN is patented by 3com US Patent No: 5,818,838

  • Term as IGMP spoofing

  • Dynamic filtering of IP Multicast group at switch port level.

  • Available in many commercial switches.

Ip multicast application

IP Multicast Application

  • Who is running IP Multicast at the 1st place ?

  • A 4.5 year studies on MBone traffic shows

  • 90% of users joined multicast group less than 74 times

  • top 1% joined MBone group > 350 times

  • 20% IP addresses - at least 1 hour per connection

  • 70% IP addresses :- average 1 min per connection

Ip multicast application1

IP Multicast Application

  • Over 4.5 year

  • 20% of users joined MBone more than 1 day

  • 5% of users joined > 300 hours

  • A total of 33,545 unique IP is seen in 4.5 year

  • Jan 1998 :- 10,600 unique IP seen

  • ( > 20,000 IP didn’t joined any multicast session for more than 1 year)

  • Jan 1999 :- 5,000 unique IP seen



  • When no IP Multicast application

  • Total Broadcast and multicast traffic is very low

  • problem of broadcast isolation does not arise at the first place

  • VLAN is of little use



  • When IP Multicast is deployed

  • Dramatic increase in mean bandwidth

  • VLAN is useful only when IP Multicast application is deployed

  • Make sure that current/future switch support IP Multicast VLAN

  • However, IP Multicast application is still not popular yet.

  • Studies have shown MBone is growing slowly and it uses is not widespread.




    • BGPK. Almeroth, "A Long-Term Analysis of Growth and Usage Patterns in the Multicast Backbone (MBone)", IEEE INFOCOM '00, Tel Aviv, ISRAEL, March 2000



    • Will E. Leland, Daniel V. Wilson, “High Time-resolution Measurement and Analysis of LAN Traffic: Implications for LAN Interconnection,” Proceedings IEEE Infocom 1991, Bal Harbour, Florida, April 1991, pp.1360-1366. building and forwarding


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