Illustration of packets and frames
This figure shows an example of an IP packet with the naming conventions used for the different parts of the packet and the frame.
The figure in Illustration of packets and frames also shows where the various encapsulation fields are located:
- ISL encapsulation of a MAC frame is done by inserting an ISL header in front of the MAC header and an ISL CRC after the MAC CRC.
- VLAN tags can be inserted inside the MAC header by using a 0x8100 or 0x88A8 length/type value. The last VLAN tag holds the protocol type of the packet.
- MPLS labels can be inserted after the MAC header (or after the last VLAN tag) by using a 0x8847 or 0x8848 length/type value. If a frame is MPLS-encapsulated, the packet is assumed to be an IP packet.
Note: In this document inner layers, inner fragments, inner packets, inner hash keys and so on refer to the first tunnel discovered. Deeper tunnels are not decoded.