Page 815 - 5G Basics - Core Network Aspects

Transport aspects 2

16
5
12
b) the remainder of the division by the generator polynomial x + x + x + 1, of the product of
16
k–2
k–1
1
x (m0×x + m1×x + … + mk–2×x + mk–1), where m0…. mk–1 are the bits of the eoc packet: m0 is
the LSB of the byte 1 of the eoc packet and mk–1 is the MSB of the last byte (byte P – 2) of the last
eoc message in the eoc packet, inclusive.
The computed value of the FCS:
15
14
fcs(x) = fcs0×x + fcs1×x + … + fcs14×x + fcs15 is the FCS polynomial where fcs0 is the LSB of the high byte
of the FCS field and fcs15 is the MSB of the low byte of the FCS field, and x is the delay operator.
The arithmetic in this clause shall be performed in the Galois Field GF(2).
NOTE – The FCS is defined in accordance with [b-ISO/IEC 13239].
11.2.1.2 eoc message format

The eoc message format is presented in Figure 11-4.

Byte MSB LSB
1 OPCODE (message type)
2 Message name
3 Message body byte 1
... ....
S + 2 Message body byte S

Figure 11-4 – eoc message format

Each eoc message is a command, a command segment, a response or a response segment. The first byte of
a message is the type (command and response type) indicated by an OPCODE. The second byte is name of
the command or the response associated with the given message type. The rest of the bytes carry the
management data associated with the command or response.
For message types that can exceed the set maximum value of P, the message segmentation protocol shall
be applied as defined in clause 11.2.2.3.
11.2.1.3 eoc transmission protocol

An FTU invokes eoc communication with the peer FTU at the other end of the link by sending an eoc
command message. The responding FTU, acting as a slave, shall acknowledge a command it has received
correctly by sending a response, unless one is not required for the particular command type. Furthermore,
it shall perform the requested management function.
Both the FTU-O and FTU-R shall be capable of sending eoc commands and responding to received eoc
commands. The same eoc packet format described in clause 11.2.2.1 and eoc message format described in
clause 11.2.2.2 shall be used in both transmission directions. To send commands and responses over the
line, the FTU originates eoc messages. For transmission, each eoc message shall be submitted to the TPS-
TC_MGMT interface using the eoc message format defined in clause 11.2.2.2. If an eoc packet is received
with an FCS error, all messages carried by this packet shall be considered as received in error and discarded.
Each command and the corresponding response are associated with a priority level specified in
clause 11.2.2.2. To maintain priorities of eoc commands when sent over the link, the FME shall submit eoc
messages to the TPS-TC_MGMT interface in accordance with the priority levels of the commands
(responses) carried by these messages, as specified in Table 11-2.

805