Strata Net IP and IPT Bandwidth Requirements

Top Previous Next

Most Visited: Toshiba's All New IP5000 Series Phones | CIX40i: Big Features for Small Businesses and Branch Offices | Toshiba eManager FAQ | Toshiba CIX Business Phone Systems Product Line

The amount of bandwidth required for communications over a particular IP network segment depends on the number of voice channels supported, the anticipated call setup traffic, and how much other data network traffic is present.

The quality of service (Excellent, Good, Fair, and Poor) provided by Strata Net IP channels and IP telephones depends heavily on the LAN parameters as shown in Table 46. This table shows the amount of bandwidth required for each Strata Net IP voice call (without data traffic) based on the interval and the CODEC.

Table 46 Strata Net IP and IPT Quality of Service

IP Network Quality Parameters		Speech
IP Network Quality Parameters		Excellent: No one perceives delay.1	Good: Very few people perceive delay.'	Fair: Some people may perceive delay.'	Poor: Many people may perceive delay.' IPT is usable even with a “Poor” rating if delay is acceptable.
Latency (Round trip delay)2		20ms or less	50ms or less	100ms or less	200ms or less
Jitter2		20ms or less (-10 ms ~ +10ms)	50ms or less (-25ms ~ +25ms)	50ms or less (-25ms ~ +25ms)	50ms or less (-25ms ~ +25ms)
Packet loss2		1×10-3 or less	1×10-3 or less	1×10-3 or less	1×10-3 or less
Packet error2		1×10-4 or less	1×10-4 or less	1×10-4 or less	1×10-4 or less
Speech quality dependency on CODEC parameters		Speech quality as the combination of the above network environment and the CODEC parameters.
CODEC and packet interval in mschannel	Bandwidth per channel (Single direction, control included)
G.711 at 20ms i Prg 250-07 Prg 152-01	88kbps3	Excellent	Good	Fair	Poor
G.711 at 40ms i Prg 250-07 Prg 152-01	76kbps3	Excellent	Good	Fair	Poor
G.729A at 40ms Prg 250-07 Prg 152-01	20kbps3	Good	Good	Fair	Poor
G.729A at 80ms Prg 250-07 Prg 152-01	14kbps3	Good	Fair	Poor	Poor

1.	Ratings of Excellent, Good, Fair, Poor were based on the tester in a quiet room and the tester could not see the other call party.

When selecting router equipment, the Latency, Jitter, Packet loss and Packet error conditions above should be considered as well as the bandwidth. Bandwidth can be calculated with the CODEC and packet size. For better results, more bandwidth may be required, depending on the amount of overall data traffic. For more details on QoS refer to “A Handbook for Successful VoIP Deployment: Network Testing, QoS, and More” by John Q. Walker, NetIQ Corporation on www.netiq.com.

3.	Use this number to estimate the bandwidth needed for the CODEC and IP headers required to achieve an expected Quality of Service (Excellent, Good, etc.). When planning you should allow extra bandwidth, especially when mixing voice and data.

Appendix — Specifications Strata Net IP and IPT Bandwidth Requirements

When sharing voice and data on the same network segment, the data will cause some jitter in voice communications, especially on slower segments. Table 47 shows calculations of the amount of

jitter assuming a worst case data packet size of 1500 bytes (Maximum Transmission Unit (MTU) = 1500) based on a segment’s bandwidth. This also requires that the routers connecting the segment through the WAN support Diffserv.

Note A router that doesn’t support Diffserv may stack multiple data packets together increasing the jitter perhaps indefinitely. And the voice quality will be indeterminate.

Table 47 Strata Net IP Jitter on Mixed Voice and Data WAN

No. of B-Channels of WAN	Bandwidth (kbps)	Time to transmit max. MTU (ms)	Expected Jitter (ms)	Class
2	128	93.75	100	Poor
4	256	46.88	50	Fair
6	384	23.44	30	Fair
8	512	15.63	20	Good
24	1536	1.00	1	Excellent

Class definition categories are shown in Table 48.

Table 48 Strata Net IP Class Definitions

Class	Delay (ms)		Jitter (ms)
Excellent	<	20	<	10
Good	<	50	<	20
Fair	<	100	<	50
Poor	<	200	<	100

Table 49 shows the amount of bandwidth required for setting up and tearing down calls independent of the amount of voice traffic.

Table 49 Strata Net IP Bandwidth Required for Call Setup

Traffic Rate (BHCA1)	Required Bandwidth
1000	6
2000	12
4000	23
6000	36

1. BHC = Busy Hour Call Attempts

So the amount of bandwidth that is required on a segment to support a specific number of calls is the sum of the number of channels multiplied by the bandwidth for the selected CODEC and

interval, plus the bandwidth required for the selected number of busy hour call attempts. And the jitter is determined by the bandwidth of the WAN segment.

Example: If you want to support 4 calls using the G.7 11 CODEC with a 20 msec. interval, this requires 4 x 88 kbps = 352 kbps of bandwidth. In addition, to support 1000 busy hour call

attempts, 6 kbps must be added for a total of 358 kbps. If only voice is going to be carried on the segment, then a 384 kbps segment (6 B-channels) is sufficient.

If voice and data are going to be mixed on the segment, then at least 25% (89.5 kbps) should be

added, or more, based on the amount of data traffic desired. In this case, a total of 447 kbps will be required which would best be supported by a 512 kbps segment (8 B-channels). This would result in an expected jitter of 20 ms in the voice traffic.

When using the MEGACO+ protocol with IPT telephones, keep alive packets are exchanged between the IPU and the phones. This traffic amounts to 3 kbps per phone.

Appendix — Specifications

Strata CIX Software License Requirements

KTS CUSTOMER USER GROUP RESOURCES | TOSHIBA CIX PHONE SYSTEMS
Sponsors Web Site | http://www.ip-office-telephone-systems.com
Telephone Number | (888) 4-TOSHIBA
Telephone Equipment Service Area By California County:
Los Angeles, Orange, Riverside, San Bernardino, San Diego
Site Managed By | ABCI Web Marketing