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

4-June-07 P1901_PRO_016_r0
- Single Validity – 4 bits. It is expressed in slots (each slot is composed of 16 symbols). The Single Validity is
an indication from the master on the validity that may be assigned for individual transmission. This
information is only used as an example of how to distribute the token validity. However, the receiving node
does not have to follow that distribution. In that case the receiving node may change the Single Validity to a
new value, according to the validity that it assigns in the Data Token. Individual transmission means the
transmission from a TDR to a CPE or a CPE to its TDR. This field is not used by CPEs. The relevant field
for CPEs is the Validity. The Single Validity includes all symbols transmitted after the TA. The minimum
Single Validity is 1.
- Validity – 12 bits. From Master to Slave. This indicates the maximum validity that the slave will be
allowed to use before returning the token. It is expressed as a number of symbols. The master shall start a
timer after the transmission of the Token Announce by the slave with the duration of the Validity it has
assigned, and expect to receive the token back before this timer expires. If the slave is a repeater, the
Validity includes the time needed for the repeater to communicate with its slaves.
- Destination Port – 7 bits. Local Port assigned to the intended receiver of the Data Token. See 9.1.4 for more
information on the Port Solver protocol.
- Session Id – 8 bits. Identify a specific flow reserved by the CAC protocol that should have priority over
other flows registered or best-effort traffic.
- Frame Service class – 8 bits. Only used from slave to master. The Frame Service class field in the token is
used to convey the information of the service classes that have been transmitted within the frame, when the
token is directed towards its master node and also all the service classes detected in the previous upstream
transmissios. CPEs use this field to indicate the service classes sent in their transmission and TDRs gather
the service class information of their slaves and the service class information from their own transmissions.
Therefore, the HE has the information of all the priorities transmitted in the network. When the token is
transmitted towards slave nodes, this field is not used. If bit X is equal to 1, there is at least one packet in
this frame with service class X.
- Unused frame symbols - 13 bits. Unused symbols in the current frame, compared to the Validity indicated
in the token announce of the same transmission frame.
- Received words - 16 bits. The Received Words Field is used to communicate to the token receiver the
number of 32-bit words that have been received from that destination since the last time, so that the
bandwidth limitation algorithm can respond. Counting shall be performed over complete received packets
when they are passed to the Convergence Layer.
- Number of Downstream Nodes – 8 bits From a CPE to its master, the Number of Downstream Nodes is
equal to 0. From a TDR to its master, the Number of Downstream Nodes is equal to the number of nodes in
its BPL subtree minus 1.
- Maximum Number of Hops – 4 bits. From a CPE to its master, the Maximum Number of Hops is equal to 0.
A TDR will set the Maximum Number of Hops as the maximum value of number of hops amongst those
received by the nodes hanging from it plus 1.When this field is set to 31 means that there are 32 hops or
more.
- Distributor Sequence Number – 3 bits. Identifier of the current Distributor Token when this Data Token
belongs to an scheduded chain of transmissions generated by a Distributor Token.
Submission page 116 UPA-OPERA