ELSA Documentation


Encapsulation-table

Association of encapsulation types (frame types) to the layer-2 protocols in the network.

A WLAN can only transfer packets in accordance with the 802.3 standard. Other encapsulation types such as Ethernet_II can be converted to 802.3 using the Subnetwork Access Protocol (SNAP) to permit them to be transferred via the WLAN. A SNAP header is added to the packet when entering the WLAN. This SNAP header is removed again when transferring to the LAN or WAN, restoring the 802.3 packet to its original Ethernet_II packet format.

Some layer-2 protocols such as AppleTalk already create a SNAP header for transfers in the LAN. In the case of packets using these protocols, care must be taken not to remove the SNAP header when transferring them from the WLAN to the LAN, as this protocol is also a precondition for the LAN. The LANCOM devices continuously observe the network traffic and check the protocols used for their encapsulation types to ensure the correct handling of the packets when transferring them from the LAN to the WLAN.

The details of the encapsulation table:

Protocol Hexadecimal identifier of the layer-3 protocol as per RFC 1010, see lower table
Encapsulation Recognized or selected encapsulation type for the protocol.
'Eth_II' shows packets of the Ethernet_II type that receive a SNAP header when entering the WLAN and which must be removed when leaving the WLAN.
'SNAP' are originally Ethernet_II packets that have already been given a SNAP header and converted to 802.3 format for transfer in the WLAN and which must remain unchanged when exiting the WLAN.

The hexadecimal identifiers for the most important layer-3 protocols as per RFC 1010:

0800 Internet Protocol - IP (IPv4)
0806 Address Resolution Protocol (ARP)
8035 Reverse ARP
809B AppleTalk
80F3 AppleTalk Address Resolution Protocol (AARP)
8137 NetWare IPX (old, with 'ECONFIG E' option)
8138 NetWare IPX


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