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Apricot2001 Effectiveness of VLAN Chan Wai Kok (wkchan@mmu.edu.my) Faculty of Information Technology Salim Beg (salim@mmu.edu.my) Faculty of Engineering Multimedia University. The benefit of VLAN. Simplify the process of add, moves and changes
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Apricot2001Effectiveness of VLAN Chan Wai Kok (wkchan@mmu.edu.my)Faculty of Information TechnologySalim Beg (salim@mmu.edu.my) Faculty of EngineeringMultimedia University
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 • To find out the broadcast traffic trend • To study the effectiveness of VLAN in broadcast isolation
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) • 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
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 • 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 • ARP request • Spanning Tree Frame (hello frame) • Netbios • SAP • IP Multicast Solicitation
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 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
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 • 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 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
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
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.
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
Question ?? Question can be forwarded to wkchan@mmu.edu.my