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
1
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
2
Goals of this presentation
• To find out the broadcast traffic trend
• To study the effectiveness of VLAN in broadcast
isolation
3
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
4
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
5
LAN Traffic (hourly)
6
LAN Traffic (busiest hour)
7
LAN Traffic (by minutes)
8
LAN Traffic (Peak to mean ratio)
9
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
10
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)
11
Type of Packets Detected
•
•
•
•
•
ARP request
Spanning Tree Frame (hello frame)
Netbios
SAP
IP Multicast Solicitation
12
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
13
Traffic Statistic (no IP Multicast)
Broadcast traffic (no IP Multicast)
Bit per second
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
1
2247
4493
6739
8985 11231 13477 15723 17969 20215
Second
14
Traffic Statistic (no IP Multicast)
Broadcast traffic (no ip mcast)
4000
3000
2500
2000
1500
1000
500
955
902
849
796
743
690
637
584
531
478
425
372
319
266
213
160
107
54
0
1
Bit per second
3500
Second
15
Traffic Statistic (no IP Multicast)
Broadcast traffic (no IP Multicast)
2500
1500
1000
500
97
91
85
79
73
67
61
55
49
43
37
31
25
19
13
7
0
1
Bit per second
2000
Second
16
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
17
Traffic Statistic with IP Multicast
application
Traffic Statistic with IP Multicast Application
160000
140000
120000
100000
80000
60000
40000
20000
222
209
196
183
170
157
144
131
118
105
92
79
66
53
40
27
14
0
1
Bit per second
180000
Second
18
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.
19
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
20
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
21
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
22
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.
23
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
24
Question ??
Question can be forwarded to
wkchan@mmu.edu.my
25