Figure 54.2: PPPoE packet format
Each field meanings in the following:
Type field (2 bytes) of Ethernet II frame: The protocol sets type field value of PPPoE protocol
packet as 0x8863 (include 5 kinds of packets in PPPoE discovery stage only), type field value of
session stage as 0x8864.
PPPoE version field (4 bits): Specify the current PPPoE protocol version, the current version
must be set as 0x1.
PPPoE type field (4 bits): Specify the protocol type, the current version must be set as 0x1.
PPPoE code field (1 byte): Specify the packet type. 0x09 means PADI packet, 0x07 means
PADO packet, 0x19 means PADR packet, 0x65 means PADS packet, 0xa7 means PADT packet.
PPPoE session ID field (2 bytes): Specify the session ID.
PPPoE length field (2 bytes): Specify the sum of all TLV length.
TLV type field (2 bytes): A TLV frame means a TAG, type field means TAG type, the table is
as follows.
TLV length field (2 bytes): Specify the length of TAG data field.
TLV data field (the length is not specified): Specify the transmitted data of TAG.
Tag Type Tag Explanation
0x0000 The end of a series tag in PPPoE data field, it is saved for ensuring the version
compatibility and is applied by some packets.
0x0101 Service name. Indicate the supplied services by network.
0x0102 Server name. When user receives the PADO response packet of AC, it can obtain
the server name from the tag and select the corresponding server.
0x0103 Exclusive tag of the host. It is similar to tag field of PPPoE data packets and is
used to match the sending and reveiving end (Because broadcast network may
exist many PPPoE data packets synchronously).
0x0104 AC-Cookies. It is used to avoid the vicious DOS attack.
0x0105 The identifier of vendor.
0x0110 Relay session ID. PPPoE data packet can be interrupted to other AC, this field is
used to keep other connection.
0x0201 The error of service name. When the requested service name is not accepted by
other end, the response packet will take this tag.
0x0202 The error of server name.
0x0203 Common error.
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