WiNG5_VoWLAN_Best_Practices

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VoWLAN Best Practices

Vik Evans

Systems Engineer

Enterprise Networking and Communications

WiNG 5

22

VoWLAN Best Practices: Topics

Planning

Design

Implementation

Configuration

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Planning

Starts with project information gathering

Determine client info

Manufacturer(s) / Model(s)

Specs (Tx pwr, receive sensitivity, protocols)

# of clients to support

Manufacturers recommendations

Device Certifications & latest drivers

Applications to support on network

Understand possible segmentation

Understand voice requirements (capacity)

Push-to-talk? Broadcast / multicast concerns

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Planning (cont.)

Know the wired infrastructure - audit

What data switches

Port densities for AP’s

PoE or no PoE – if so, which standard

Uplink capacity – 1Gbps, LAG

Identify for design phase

Logical Landscape

Flat or Tiered network & what changes may be needed

Existing IP scope – room for growth

VLAN existence / structure

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Planning (cont.)

QoS Planning

Is there any prioritization currently?

Will there be any traffic tunneling?

If so, what IP header markings will be needed?

Note boundaries (firewall / router)

Will ACL Priority marking be necessary?

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Planning

Design

Implementation

Configuration

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Design

Starts with logical integration

How will wired network accommodate WLAN

Plan Application separation (VLAN’s)

Plan service level enforcement (QoS)

802.11e / WMM (L2) / DSCP (L3) - prioritization

WLAN and LAN

Physical integration

Resilience planning

LAN uplinks

WLAN core (controller redundancy)

Cell / neighbor coverage

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Design (cont.)

For multi-site, individually large installs, interviews are a huge help.

Site IT contact

Example: Individual schools for entire district

Predictive Modeling

1st recommendation; minimum

Garbage in / garbage out –modeling elements are extremely important

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Design (cont.)

Site Survey highlyrecommended

Spectrum analysis minimum

Use for reference of existing environment.

May be revisited post-implementation to verify install

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Design (cont.)

Voice concerns

Capacity planning

What 802.11 protocols will be used (b only / g / a)

What voice codecs? Will contribute to per-call BW

Expected number of simultaneous calls

Push-to-talk? - multicast

Wireless concerns

Coverage is a combination of cell boundaries and channel overlap

“% of overlap” – what does this mean? Not a good guideline.

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Design (cont.)

Wireless concerns (cont.)

Use min/avg RSSI values for coverage

Channel capacity as metric, not AP capacity

Co-channel interference affects channel capacity

Expected number of simultaneous calls

AP power – plan cell coverage that doesn’t support lower data rates; meaning higher density

To avoid power-asymmetry, AP power should be comparable to client device Tx power

Industry rule is -65 to -67 dBm to maximize throughput and minimize co-channel

Utilize Smart-RF for fine-tuning; establish base parameters.

AP Choice – is support for legacy protocols necessary

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Planning

Design

Implementation

Configuration

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Implement / Configure

Traffic segmentation - VLANs

Segment voice clients from other traffic

IP address space conservation

Voice client protection

Simplifies QoS configuration & troubleshooting

Segmentation required on wired as well as wireless

Data VLAN(s)

Voice VLAN

Voice WLANs mapped here

Other

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Implement / Configure (cont.)

Wireless Voice general rules

-65 to -67 dBm avg RSSI

5.5mbps min. data rate

AP power: start at 17dB; likely to work down

5GHz operation for voice clients preferred

More channels = higher capacity

Consider UNII-1 & 3 only – no requirement for DFS / TPC

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Utilize QoS mechanisms of WiNG 5

Radio QoS Policies – QoS on AP radios

Admission Control

QoS has little effect when AP’s are over-subscribed

Use AP profiles to set per radio MU limits

WLAN QoS Policies – QoS on WLAN

Create separate WLAN’s for data and voice hosts

Enable QoS on wired Network

QoS needs to be implemented on network, end-to-end

DiffServ / IP TOS (L3), Queuing methods - wired

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Client Considerations

Push-to-Talk clients

Can IGMP Snooping be used?

Will lower overhead for broadcast traffic, sending only to AP’s with registered clients

May further segment PTT from other voice clients at WLAN

Legacy clients

May not support WMM; segment from newer client devices

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Verify post-install with a site survey

Include stairwells, cafeterias, etc.

Do not limit survey to purpose-built app. Use same network applications that users will

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Conclusion

For more resources on WiNG 5 configuration for voice, see the EWLAN Sales Enablement Pages:

http://compass.mot-solutions.com/web/wlan/Guides

http://compass.mot-solutions.com/web/wlan/How To Videos







Documents

WiNG5_VoWLAN_Best_Practices