Monday, January 05, 2015

Bandwidth allocation sizing


When trying to calculate bandwidth allocation for a particular protocol, you would need to understand what the size of the actual payload/data is, then calculate what the bottom layer headers would add as overhead. Also, you would need to know what a particular data/payload would measure on Data Links (Layer 2), e.g. Ethernet, Ethernet 801.1Q (VLAN), HDLC, PPP, Frame Relay, Fiber

The typical example is a G.729 voice packet. Just the payload of the packet is 8 kbits, then we add the overheads of the lower layers:

Overhead Byes/sec Total
G729 20 20
Layer 5 RTP 12 32
Layer 4 UDP 8 40
Layer 3 IP 20 60
Layer 2 Ethernet 38 98


Some links I came across:
http://www.techrepublic.com/blog/linux-and-open-source/use-wireshark-to-inspect-packets-on-your-network/
http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080094ae2.shtml
http://sd.wareonearth.com/~phil/net/overhead/
http://aconaway.com/2011/01/10/network-protocol-overhead/


http://networkengineering.stackexchange.com/questions/2793/bandwidth-calculation-for-protocol-over-different-data-physical-links
http://networkengineering.stackexchange.com/questions/2789/wireshark-protocol-hierarchy-explanation

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