Medium Access Control (MAC) and Physical Layer (PHY) - CISE

4-June-07 P1901_PRO_016_r0
If PCF is set to 1, this indicates that PCP contains a valid BPL service class.
For packets received through a non-BPL interface, PCF = 0. For packets received through a BPL interface PCF
must be left unchanged.
BPL service class can be calculated then by the QoS function (see 8.2).
6.2.4 PB Field
This field are used to avoid loops with broadcast packets.
Broadcast packets can be sent in two ways through the BPL network:
- Using the broadcast port. The broadcast packet is sent using the broadcast port and all nodes that have
negotiated ports with the sender will receive it.
- Using unicast ports. The broadcast packet is sent once per each negotiated port, except the port where it was
received in the case it was a BPL port.
In the case when a broadcast packet is sent using the broadcast port, these fields are used to avoid loops. In the other
case, they are not necessary. In any case, they shall always be present in all packets.
The meaning of the field (defined in 6.2) is the following:
- PB: Previous Bridge ID. It shall contain the MAC address of the previous node that has transmitted this
packet.
When a packet enters the BPL network Previous Bridge ID shall be set to 0.
In any retransmission, the Previous Bridge ID shall be filled with the ID of the last unit that transmitted the packet.
When receiving a packet it shall be discarded when its Previous Bridge ID is equal to the MAC address of the node
that has received the packet, because this indicates that the node has already received the packet before..
6.2.5 Octet alignment
The bytes from IEEE Std 802.3 are stored in 32 bits words in the following way:
Byte
3
Byte
2
Submission page 169 UPA-OPERA
Byte
1
Byte
0
Figure 65 Byte order