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Network Protocol Overhead

Here are some packet overhead numbers for a few popular protocols to help with doing bandwidth requirement calculations. This may be another add-as-we-go post, so please comment with additions or corrections.

Ethernet : 20 bytes
Frame Relay : 4 – 6 bytes
PPP : 6 bytes
MLPPP: 10 bytes
MPLS : 4 bytes

IP : 20 bytes

TCP : 20+ bytes
UDP : 8 bytes
GRE: 4 – 20+ bytes

IPSec : 50 – 57 bytes
ESP : 20+ bytes
AH : 16+ bytes
L2TP : 24 bytes
RTP : 12 bytes

Bonus: A voice packet is always 40 bytes + data link since it will always (?) use RTP + UDP + IP.

Sources

CCNA Voice Official Exam Certification Guide (640-460 IIUC)

Protocol Overhead

Generic Routing Encapsulation

IP Authentication Header

Encapsulating Security Payload

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