Building Reliable Campus H'323 Videoconferencing Networks

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Building Reliable Campus H.323 Videoconferencing
Networks
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VTAS document which aims to provide

• guidance on the H.323 traffic profile and how it
  differs from some other IP traffic
• details of common network issues that can
  potentially effect videoconferences
• advice on Network Engineering and its application
  to H.323 traffic
• advice on Traffic Engineering and its application
  to H.323 traffic
• examples of topologies and configurations for
  sample equipment

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H.323 traffic profile - metrics

• Packet loss (bandwidth)
• 0.25 MAX with MCU
• 0.5 MAX without MCU
• Latency
• True end to end
• Compression
• Transmission
• Network Delay (equipment plus transport)
  lt50/100ms
• Reception
• Decompression
• Jitter (inter Packet Delay Variation)
• lt 30ms normally

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H.323 traffic profile required bandwidth
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H.323 traffic profile required bandwidth
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H.323 traffic profile required bandwidth
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H.323 traffic profile required bandwidth
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Network Issues common campus complaints

• General traffic profile
• Rises 9am, small peaks during lecture changeover,
  large peaks at break and lunchtime, falls at 5pm
• Network logon, web email access
• Broadcast Traffic
• More hosts more broadcasts
• Worst case broadcast storm faulty
  NIC/switch/bad configuration
• but can also be 5 10 of network bandwidth
  (100Mbps with some 10Mbps links?)
• Spanning Tree Updates
• Disable on switch ports connected to hosts - or
  traffic floods until MAC/port tables rebuilt

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Network Issues common campus complaints

• Speed and Duplex mismatches
• Surprisingly common
• Break most voice and video apps others run
  slowly
• Always set BOTH ENDS of a link manually for VC
  equipment and preferably for most other core
  equipment/servers etc. Make sure auto is set both
  ends for hosts.
• Look for Collision Errors on ports
• Firewalls and NAT
• Support is getting better for H.323 in FW and NAT
• See some oddities conferences drop after 30
  minutes etc
• Sometimes better to get native IP support to
  end-points if possible depending on topology.
  Especially an issue with School and corporate
  networks.

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Network Engineering

• Network Engineering uses physical, topological
  separation of links to provide dedicated, high
  quality network links to facilities such as
  videoconferencing studios. Frequently, with the
  advent of structured cabling, the provision of
  separate topologies for certain types of
  equipment can be simpler, and more effective,
  than the use of more advanced techniques.

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Network Engineering
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Network Engineering
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Traffic Engineering

• Traffic Engineering uses logical differentiation
  between network traffic to provide separation
  between different traffic flows, or better
  treatment for one class of traffic over another.
  It relies on the use of Virtual LANs and priority
  queuing techniques.

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Traffic Engineering VLAN
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Traffic Engineering VLAN configuration
To configure a VLAN port on a 3COM 4400
switch Firstly, the VLAN must be explicitly
created Select Menu Option bridge vlan create
323 VIDEO-VLAN Here 323 is the VLAN ID and
VIDEO-VLAN is the text name of the VLAN Select
Menu Option Bridge vlan modify addport 323 12
untagged This adds VLAN 323 to port 12 (unit 1
port 2). The untagged keyword tells the switch
that a host will be connected to this port and it
is not a VLAN trunk.
To configure a VLAN port on a Cisco 2950
switch ! in Interface Configuration
mode Switch(config)int fa 0/3 Switch(config-if)s
witchport access vlan 323 Access VLAN does not
exist. Creating VLAN 323 Switch(config-if)int
fa0/4 Switch(config-if)switchport access vlan
323 Switch(config-if)CTRL-Z As can be seen, if
the VLAN does not currently exist the switch will
automatically create it as soon a port is put
into it. Showing the running configuration
gives ! interface FastEthernet0/2 ! interface
FastEthernet0/3 switchport access vlan
323 ! interface FastEthernet0/4 switchport
access vlan 323 !
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Traffic Engineering VLAN Trunks
To configure a VLAN trunk for all VLANs between
two Cisco switches Switch 1 (Cisco 3524) ! Port
0/24 is the link to the second switch Int
fa0/24 Switchport trunk encapsulation
dot1q Switchport mode trunk Switch 2 (Cisco
2950) ! Int fa0/24 Switchport mode trunk !
To configure a VLAN trunk for all VLANs between a
3COM 4400 and a Cisco 2950 switch The
configuration is the same as the configuration
detailed above. As the trunk is based on the
dot1q standard it will work between different
manufacturers equipment.
To configure a VLAN trunk for all VLANs between
two 3COM 4400 switches Select Menu Option
bridge vlan modify addport 323 124 tagged This
will add VLAN 323 to port 124 which is the link
port to the other switch. The tagged keyword
tells the switch that this is a VLAN trunk as
opposed to a single host connection.
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Traffic Engineering Inter VLAN traffic
Layer 3 VLAN commands on 6509 MSFC To create a
Layer 3 router VLAN interface interface vlan
323 description Video Conference Network ip
address a.b.c.d 255.255.255.0
Cisco 6509 Layer 2 VLAN commands To place switch
ports into VLAN 323 set vlan 323 2/5 To
configure a port as a dot1q VLAN trunk set trunk
2/2 on dot1q To set a VLANs name set vlan 323
name Video_Conference_Suite To disable Spanning
Tree on VLANs set spantree disable 323
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Traffic Engineering Layer 2 Prioritization

• QoS techniques can be applied at layer 2 allowing
  differentiated traffic to receive preferential
  treatment as it passes through network equipment.
  QoS at layer 2 is common in many voice and video
  networks. QoS at layer 3 is becoming more and
  more common.

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Traffic Engineering QoS steps

• Steps required to provide QoS
• Classification
• Selection of traffic for differentiated treatment
• Marking
• Setting DSCP (Differentiated Services Code Point)
  or Class of Service(CoS) value
• Policing
• Set a bandwidth limit for this class of traffic
• Queuing
• Configure queuing and select interfaces taking
  part in policy
• None or all of the above may be required!

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Traffic Engineering Cisco 3524

• Cisco 3524 has 2 queues
• Low CoS 0-3
• High CoS 4-7
• Default behaviour is to priority queue on
  outbound interfaces
• If you have a 3524 you ARE running QoS in your
  network now ?

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Traffic Engineering Cisco 2950

• !
• Class-map match-all VIDEO
• Match access-group 190
• !
• policy-map INCOMING
• class VIDEO
• set ip dscp 46
• police 20000000 4096 exceed-action drop
• !
• !
• interface FastEthernet 0/23
• service-policy input INCOMING
• !
• access-list 190 permit ip host 10.1.1.1 any

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Traffic Engineering 3COM 4400

• 4 queues mapped to 8 priority (CoS) values
• Priority Queue Index
• 0 1 (lowest)
• 1 1 (lowest)
• 2 1 (lowest)
• 3 2
• 4 2
• 5 3
• 6 4 (highest)
• 7 4 (highest)

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Traffic Engineering 3COM 4400

• Create a classifier
• Trafficqosclassifiercreate, number (323), name
  (VIDEO-CLASSIFIER), classifier type ipaddr
  (ipaddr and mask)
• From traffqosprofile
• Create (323), name (VIDEO-PROFILE)
• Remove 323 1 (remove the default traffic vlan 1
  - from this profile)
• Add to profile 323 classifier 323 service
  level number 5
• Assign to all appropriate switch ports
• Assign 11-24
• Conforming Used in
• Num Name Pri DSCP QoS Profile
• 1 Drop - - none
• 2 Best Effort 0 0 none
• 3 Business Critical 3 16 none
• 4 Video Applications 5 24 none
• 5 Voice Applications 6 46 (EF) 2,323
• 6 Network Control 7 48 none

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Steve Williams University of Wales
Swansea s.r.williams_at_swansea.ac.uk