Apricot2001 Effectiveness of VLAN Chan Wai Kok ([e-mail]) Faculty of Information Technology Salim Beg ([e-mail]) Faculty of Engineering Multimedia University

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Apricot2001 Effectiveness of VLAN Chan Wai
Kok (wkchan_at_mmu.edu.my)Faculty of Information
TechnologySalim Beg (salim_at_mmu.edu.my) Faculty
of EngineeringMultimedia University
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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

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Goals of this presentation

• To find out the broadcast traffic trend
• To study the effectiveness of VLAN in broadcast
  isolation

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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

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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

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LAN Traffic (hourly)
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LAN Traffic (busiest hour)
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LAN Traffic (by minutes)
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LAN Traffic (Peak to mean ratio)
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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 its effect the broadcast plus multicast
  traffic in the IP subnet.
• Make some conclusions on the result

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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)

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Type of Packets Detected

• ARP request
• Spanning Tree Frame (hello frame)
• Netbios
• SAP
• IP Multicast Solicitation

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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

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Traffic Statistic (no IP Multicast)
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Traffic Statistic (no IP Multicast)
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Traffic Statistic (no IP Multicast)
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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

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Traffic Statistic with IP Multicast application
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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.

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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 gt 350 times
• 20 IP addresses - at least 1 hour per connection
• 70 IP addresses - average 1 min per connection

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IP Multicast Application

• Over 4.5 year
• 20 of users joined MBone more than 1 day
• 5 of users joined gt 300 hours
• A total of 33,545 unique IP is seen in 4.5 year
• Jan 1998 - 10,600 unique IP seen
• ( gt 20,000 IP didnt joined any multicast session
  for more than 1 year)
• Jan 1999 - 5,000 unique IP seen

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Conclusion

• 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

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Conclusion

• 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.

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References

• http//imj.ucsb.edu/publications.html
• BGPK. Almeroth, "A Long-Term Analysis of Growth
  and Usage Patterns in the Multicast Backbone
  (MBone)", IEEE INFOCOM '00, Tel Aviv, ISRAEL,
  March 2000
• http//www.patents.ibm.com
• http//www.argreenhouse.com/papers/wel/
• 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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Question ??
Question can be forwarded to wkchan_at_mmu.edu.my