Layer_Table
Interfaces and Buses / Networking / Layer_Table
Code File Location: VisualSim/Actor/lib/Layer_Table
o Used to describe the characteristics of the Layer_Protocol. One Layer_Table can be linked to multiple Layer_Protocol blocks.
o Multiple Layer_Table can exist in a model.
This block is used to define the chrateristics of the protocol layer. The Layer_Table block set the common parameters, configuring to execute the logic internal to the Layer_Protocol or use the external logic connected to the up_ext_out and dn_ext_out ports. Each Layer_Protocol must reference one Layer_Table block.
A single Layer_Table block can be used by multiple Layer_Protocol blocks in the model. A word of caution is that all Layer_Protocol blocks for the same protocol layer must have the same Layer_Number value. This will ensure that the correct amount of header and trailer bytes are added or removed. The Layer_Number is used to handle the retry also, as the retry will be return to the same level in the Source Node as the node where the retry was requested.
There are two sets of parameters: common upward/downward parameters, and individual upward and downward parameters.
Refer to the Retry Layer demo model to understand the block usage.
Parameter |
Explanation |
Type |
Example |
Layer_Table_Name |
This is the name of this Layer_Table. This is referenced by the Layer_Protocol blocks. One Layer_Table can be referenced by multiple Layer_Protocol blocks. |
String |
"LT_1" |
Layer_Number |
Layer number that corresponds to OSI layer number, or unique to layer position in the layer stack. Currently used to match the Source Node layer that must retransmit when another node layer triggers the transaction as a error. |
int |
1 |
Layer_MBytes_Sec |
Layer processing speed in MBytes per second. This is the delay toget the data across the Layer. If 'External_Delay' is set, this field is ignored. The delay is Task_Size/Layer_MBytes_Sec. If more detailed timing or logic is required, you can add it using the 'External Delay" configuration. |
double |
100.0 |
Layer_Frame_Size_Bytes |
The maximum frame size in bytes for a packet sent up or down this layer. Header and Trailer bytes are added to this frame size. For the purpose of the calculation, all Overhead bytes from previous layers are included. This parameter does not actually fragment the layers. It is used to add the overhead bytes. |
int |
64 |
Layer_Header_Trailer_Bytes |
Header and Trailer bytes. These bytes are added to Task_Size when going down the protocol stack and removed when going up the protocol stack. These Overhead bytes are also maintained in a separate field called Task_Overhead. |
int |
8 |
Layer_Queue_Size_Frames |
Queue length for the upward or downward flow. This is the number of packets that can be queued. In the case of UDP, this corresponds to the number of active sessions at any time. |
int |
32 |
Layer_Retry_Probability |
This is the probability that a message is retransmitted. The range 0.0 to 1.0 where 0.0 signifies no retry. |
double |
0.0 |
Up_Retransmissions |
Number of upward flow retransmissions that can be done for a packet before being dropped. |
int |
8 |
Up_Internal_Delay |
Internal (fixed) Delay for processing the entire packet (all fragments) going up to the next upper layer. This is added to the Task_Size/Layer_MBytes_Sec. |
double |
1.0E-06 |
Dn_Retransmissions |
Number of downward flow retransmissions that can be done for a packet before being dropped. |
int |
8 |
Dn_Internal_Delay |
Internal (fixed) Delay for processing the entire packet (all fragments) going up to the next lower layer or NODE. This is added Task_Size/Layer_MBytes_Sec. |
double |
1.0E-06 |
Layer_Configuration |
Pulldown to select where processing delays are computed. If Layer_Configuration is set to "External_Delay", the Up_Internal_Delay and Dn_Internal_Delay parameter values are ignored; and executed externally. The transfer delay (Task_Size/Layer_MBytes_Sec) is still executed. |
pulldown |
"Internal_Delay" or "External_Delay" |
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