Quick Bandwidth Calculation

Total packet size Total bandwidth requirement

Payload size Nominal bandwidth requirement

Total packet size = All headers + payload

Payload size Nominal bandwidth requirement

Total packet size = All headers + payload

Parameter

Value

Layer 2 header

6 to 18 bytes

IP + UDP + RTP headers

40 bytes

Payload size (20-ms sample interval)

20 bytes for G.729, 160 bytes for G.711

Nominal bandwidth

8 kbps for G.729, 64 kbps for G.711

Example: G.729 with Frame Relay:

Total packet size * nominal bandwidth requirement

Example: G.729 with Frame Relay:

Total packet size * nominal bandwidth requirement

Total bandwidth requirement payload size (6 + 40 + 20 bytes) * 8 kbps --= 26.4 kbps

20 bytes

A quick way to calculate total bandwidth requirement for a voice packet is to remember that the ratio of the total bandwidth requirement to the nominal bandwidth for the payload is the same as the ratio of total packet size to payload size.

The payload size is dependent on the sample interval and the codec used and is usually 20 bytes for G.729 and 160 bytes for G.711, assuming a 20-ms sample interval.

The headers are always 40 bytes for the IP, UDP, and RTP headers, plus the Layer 2 header size. This size might be 6 bytes for Frame Relay or PPP or 18 bytes for Ethernet, for example.

To calculate the total bandwidth, find the total packet size, including all the headers plus payload and divide by the payload size. Multiply the result by the nominal bandwidth for the codec, and the result will be the total bandwidth requirement.

Note At http://tools.cisco.com/Support/VBC/do/CodecCalc1.do, you can try to calculate the bandwidth using the Voice Codec Bandwidth Calculator. Access to the URL requires a valid Cisco.com account.

2-62 Optimizing Converged Cisco Networks (ONT) v1.0 © 2006 Cisco Systems, Inc.

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Readers' Questions

  • alicia
    How to calculate bandwidth requirements?
    1 month ago
  • To calculate bandwidth requirements, you need to consider the following factors:
    1. Determine the types and number of devices: Calculate the number of devices that will be connected to the network, including computers, smartphones, tablets, IoT devices, etc.
    2. Identify the usage patterns: Determine the type of activities that will be conducted on the network, such as web browsing, video streaming, file downloads, online gaming, etc. Different activities require varying amounts of bandwidth.
    3. Calculate the average bandwidth per user: Based on the usage patterns, determine the average bandwidth required per user. For example, if you have 10 users and the total bandwidth required is 100 Mbps, each user will need around 10 Mbps.
    4. Account for peak usage times: Determine the peak usage periods when the network will be most active, such as during office hours or evening entertainment. You may need to allocate more bandwidth during these periods to avoid congestion.
    5. Consider future growth: Take into account potential future growth in terms of the number of users and their bandwidth requirements. It is advisable to plan for scalability and ensure your network can handle increased demands over time.
    6. Calculate total bandwidth requirement: Multiply the average bandwidth required per user by the number of devices/users to calculate the total bandwidth requirement. Additionally, add any extra bandwidth needed for peak usage periods or future growth.Remember, these calculations are estimates, as actual bandwidth usage can vary based on network conditions, the efficiency of network protocols, and the quality of the network infrastructure. It is recommended to consult with a network professional or ISP to get more accurate calculations based on your specific requirements.
    • Isabella
      How to calculate bandwith?
      1 month ago
    • Bandwidth can be calculated using the following formula: Bandwidth = (8 x Data size) / Time Where, - Data size is the amount of data being transferred (in bytes) - Time is the time taken to transfer the data (in seconds) For example, if you have transferred a file of 10 megabytes (10,000,000 bytes) in 5 seconds, the bandwidth would be: Bandwidth = (8 x 10,000,000) / 5 = 16,000,000 bytes per second = 16 megabits per second (Mbps) Note that data needs to be converted to bits from bytes, as bandwidth is typically measured in bits per second.
      • tewelde
        How is bandwidth calculated?
        8 months ago
      • Bandwidth is calculated by measuring the throughput of data over a given period of time. This measurement is usually in megabits per second (Mbps) or kilobits per second (kbps). Bandwidth is usually calculated by taking the rate of data transfer over a defined period of time, such as a day, a week, a month, or a year.