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

4-June-07 P1901_PRO_016_r0
Packet fragments shall only appear at the beginning or the end of the burst. Once a fragment of a packet is sent in a
burst, the rest of the packet shall be sent before any other packet to the same Local Port (regardless of service class).
Packets with the same destination port and same service class shall be transmitted in order. Within the same
destination port, packets are transmitted according to their service class, with highest service class packets first (see
8.2).
The inter-packet header has the following structure:
7 6
Part of
Packet
Version
- Preamble – 8 bits. Set to 0x5D
5
4
Unfinished Last Packet ACK Req Packet Id [11:8]
Length [5:0]
5D
Reserved
Submission page 155 UPA-OPERA
3
Packet Id [7:0]
Fragment Number
CRC – 16 bits
Figure 58 Inter-packet header
2
1
Length [8:6]
0
Padding Last Word
- Part of Packet – 1 bit. The first fragment in the burst is part of a previous packet. This field shall only be
checked by the receiver in the first inter-packet header.
- Unfinished – 1 bit. The last fragment in this burst is unfinished. To be set to one in the last inter-packet
header if it is not a complete packet.
- Last Packet – 1 bit. This is the last fragment or packet inside this burst.
- ACK Req – 1 bit. The transmitter is waiting an ACK about this packet to free it. When it is set to 0, the
transmitter frees this packet when this packet is sent and the receiver can not request retransmissions about
it.
- Packet Id – 12 bits. Unique identification of each packet.
- Version – 2 bits. Version is set to 0.
- Fragment number – 3 bits. Each packet could be divided into 6 fragments. This is the identification of each
fragment: from 0 to 5.
- Length – 9 bits. Length of the packet or fragment in words.
Octet
1
2
3
4
5
6
7
8