SOME/IP Transport Protocol

Overview

RAPIDSEA supports SOME/IP Transport protocol as explained in the SOME/IP Protocol page. This module is used by both SOME/IP Clients and SOME/IP Servers when message payload size exceeds the single-frame limit. Messages smaller than 1400 bytes are directly transmitted via UDP socket communication. For payloads exceeding this limit, the SOME/IP layer delegates data to the TP layer. The TP layer then segments the data into smaller chunks (typically 1392 bytes each) and transmits them sequentially to the socket layer. On the receiver side, the socket delivers incoming segments to the SOME/IP layer.If the message is identified as a large payload, it is passed to the TP layer for reassembly before being returned to the application layer. The APIs provided by this module abstract the TP handling so that upper layers can seamlessly send and receive large messages.

The below diagram captures the block level diagram of the SOME/IP TP and how it interfaces with other modules.

Application Interface

The module ensures reliable transport of large payloads by providing mechanisms for: - Splitting outgoing messages into multiple transport PDUs. - Reassembling incoming segmented PDUs into a complete SOME/IP message. - Managing transmit and receive message buffers. - Queueing and releasing message buffers after use. - Registering user callbacks for transmission and reception events.The RAPIDSEA SOME/IP Transport protocol clearly defines API functions that are essential for the user to use/implement.

The below table captures the function that are to be called from the application logic.

API Functions
Function	Description
rs_someip_tp_set_config	To set TP configuration
rs_someip_tp_open	To initialize the SOME/IP Transport Protocol instance and configuration.
rs_someip_tp_set_tx_msg_buf	To set up the transmit message buffers for the SOME/IP TP communication.
rs_someip_tp_set_rx_msg_buf	To set up the receive message buffers for the SOME/IP TP communication
rs_someip_tp_get_rx_assembled_msg_buf	To get the fully assembled received message after segmentation reassembly
rs_someip_tp_process	To process the SOME/IP Transport Protocol state machine, including message, segmentation, reassembly, and transmit/receive handling.
rs_someip_tp_close	To close the SOME/IP Transport Protocol instance and release all allocated
rs_someip_tp_transmit	To initiate the transmission of a SOME/IP message using the Transport Protocol layer. Handles message segmentation and enqueues the message for sending.
rs_someip_tp_rx_indication	To indicate the reception of a SOME/IP message fragment or complete message to the Transport Protocol module for further processing or reassembly.

SOME/IP TP Configuration Parameter:

TP Configuration
Function	Description
tp_rx_timeout	Timeout (in milliseconds) for receiving the next segment of a TP message.
tp_tx_separation_time	Minimum separation time (in microseconds) between consecutive TP segments during transmission.
burst_size	Maximum number of consecutive TP segments that can be sent in a single transmission burst before applying the separation delay

Implementation Guide

Initialize instance using rs_someip_tp_open.
Configure TX and RX buffers via rs_someip_tp_set_tx_msg_buf and rs_someip_tp_set_rx_msg_buf.
Periodically call rs_someip_tp_process for internal state handling.
Handle incoming PDUs via rs_someip_tp_rx_indication.
Release message buffers after transmission or reception using appropriate release APIs.
Close the instance using rs_someip_tp_close during shutdown.

High level flow chart is depicted below:

The below diagram captures the Initialization of SOME/IP TP associated with the application layer.

The below diagram captures the high level sequence of operations associated with the SOME/IP stack layer.

SOME/IP TP Stack Memory Usage

ROM/RAM Consumption (Stack only)
Platform	Memory	Size
Micro controller (iMXRT)	ROM	4KB
Micro controller (iMXRT)	RAM	0KB

SOME/IP TP Stack Memory Details

The SOME/IP Transport Protocol (SOME/IP-TP) layer is responsible for segmentation and reassembly of large SOME/IP messages that exceed the standard Ethernet MTU. It ensures reliable end-to-end data delivery for payloads that cannot fit within a single SOME/IP frame.

Each SOME/IP-TP instance allocates dedicated transmit (TX) and receive (RX) buffers to handle segmented message transfers. By default, a single TX or RX buffer is sized at approximately 5 KB. However, the total TP memory usage dynamically scales with the number of transmit and receive message contexts configured within the TP message manager.

The TP layer defines two key configuration parameters:

num_tx_msg – Number of TX messages supported by the TP instance.
num_rx_msg – Number of RX messages supported by the TP instance.

TP buffer size must always equal SOME/IP buffer size for consistent data flow.
Increasing message counts enables higher concurrency but increases RAM consumption.
Reducing these counts may limit simultaneous segmented transfers.
All memory used by TP is statically allocated during initialization, ensuring predictable runtime behavior.
As per Autosar, TCP is not applicable for SOMEIP Transport Protocol layer.

Dependency

This stack depends on the below RAPIDSEA interfaces that can be obtained or custom implemented.

SOME/IP Client Stack

SOME/IP Server Stack

Socket Interface

SOME/IP TP Header Details

Documentation from the relevant header as follows:

SOME/IP TP Module.

This file contains the APIs for using defined SOME/IP TP Module

Author: Embien RAPIDSEA Team
Copyright: Embien Technologies India Pvt. Ltd.

Defines

RS_SOMEIP_TP_E_UNINIT: SOME/IP TP module not initialized.

RS_SOMEIP_TP_E_PARAM_POINTER: Null pointer has been passed as an argument.

RS_SOMEIP_TP_E_PARAM: Unknown parameter has been passed.

RS_SOMEIP_TP_E_INIT_FAILED: Invalid configuration set selection.

RS_SOMEIP_TP_E_MESSAGE_TYPE: The TP-Flag (of Message Type) was set to ’0’

RS_SOMEIP_TP_E_INCONSISTENT_SEQUENCE: Inconsistent subsequent segment received.

RS_SOMEIP_TP_E_INCONSISTENT_HEADER: Inconsistent header received.

RS_SOMEIP_TP_E_DISASSEMBLY_INTERRUPT: Disassembly Interrupt due to the upper layer.

RS_SOMEIP_TP_E_ASSEMBLY_INTERRUPT: Assembly Interrupt due to the upper layer.

RS_SOME_TP_RX_MSG_MGR_STATE_FREE: TP RX State machine status is free.

RS_SOME_TP_RX_MSG_MGR_STATE_INPROGRESS: TP RX State machine status is inprogress.

RS_SOME_TP_RX_MSG_MGR_STATE_DONE: TP RX State machine status is done.

RS_SOMEIP_TP_MSG_STATUS_FREE: Message is unused.

RS_SOMEIP_TP_MSG_STATUS_IN_USE: Message is used.

RS_SOMEIP_TP_MSG_STATUS_READY_FOR_TX: Message is ready to be transmitted.

RS_SOMEIP_TP_MSG_STATUS_RX_ASSEMBLY_DONE: Message is assembled and ready to be received.

RS_SOMEIP_TP_MSG_STATUS_DISCARD: Message is to be discarded.

RS_SOMEIP_TP_RX_MSG_MGR_SIZE: Size of SOME/IP TP RX message manager.

Typedefs

typedef struct tag_rs_someip_tp_rx_msg_mgr rs_someip_tp_rx_msg_mgr_t: Contains information about SOME/IP RX Message Manager.

typedef struct tag_rs_someip_tp_msg_mgr rs_someip_tp_msg_mgr_t: Contains information about SOME/IP TP message manager.

typedef struct tag_rs_someip_tp_config rs_someip_tp_config_t: Contains information about SOME/IP TP configuration.

typedef struct tag_rs_someip_tp_instance rs_someip_tp_instance_t: Contains information SOME/IP TP Instance.

Functions

rs_ret_val_t rs_someip_tp_set_config(rs_someip_tp_config_t *ptr_config, uint32_t u32_rx_timeout, uint32_t u32_sep_time, uint32_t u32_burst_size)

Function to set TP configuration.

This function called to set TP configuration

Parameters:

ptr_config – [out] - Pointer to the SOME/IP TP configuration
u32_rx_timeout – [in] - TP RX Timeout
u32_sep_time – [in] - Time between two segments
u32_burst_size – [in] - Number of segments to send without separation time

Returns:

0 for success.

rs_handle_t rs_someip_tp_open(rs_someip_tp_instance_t *ptr_instance, rs_someip_tp_config_t *ptr_config)

Initialize the SOME/IP TP instance structure with initial values.

This function initialize the SOME/IP TP instance structure with initial values.

Parameters:

ptr_instance – [in] - Pointer to the SOME/IP TP instance
ptr_config – [in] - Pointer to the SOME/IP TP configuration

Returns:

Handle of the SOME/IP instance information

rs_ret_val_t rs_someip_tp_set_tx_msg_buf(rs_handle_t handle, rs_someip_msg_t *ptr_tx_msgs, uint16_t u16_num_msg)

Set up the transmit message to be used for the SOME/IP TP.

This function sets up the transmit buffer to be used for SOME/IP TP

Parameters:

handle – [in] - Handle of SOME/IP TP instance information
ptr_tx_msgs – [in] - Pointer to TX message
u16_num_msg – [in] - Number of RX messages in array

Returns:

Zero or negative error code

rs_ret_val_t rs_someip_tp_set_rx_msg_buf(rs_handle_t handle, rs_someip_msg_t *ptr_rx_msgs, uint16_t u16_num_msg)

Set up the receive message to be used for the SOME/IP TP.

This function sets up the transmit buffer to be used for SOME/IP TP

Parameters:

handle – [in] - Handle of SOME/IP TP instance information
ptr_rx_msgs – [in] - Pointer to RX message
u16_num_msg – [in] - Number of RX messages in array

Returns:

Zero or negative error code

rs_ret_val_t rs_someip_tp_get_rx_assembled_msg_buf(rs_handle_t handle, rs_someip_msg_t *ptr_out_rx_msg)

Called to get the assembled RX message from the array of messages.

This function is called to the assembled RX message from the array of messages

Parameters:

handle – [in] - Handle to the SOME/IP TP instance
ptr_out_rx_msg – [in] - Pointer to the SOME/IP message

Returns:

Length of the assembled message

rs_ret_val_t rs_someip_tp_transmit(rs_handle_t handle, rs_someip_msg_t *ptr_tx_msg)

Called to load the transmit message to message structure.

This function is called to load the transmit message and later handle it in process

Parameters:

handle – [in] - Handle to the SOME/IP TP instance
ptr_tx_msg – [in] - Pointer to the SOME/IP message

Returns:

0 for success.

rs_ret_val_t rs_someip_tp_close(rs_handle_t handle)

Called to free the instance from handle.

This function is called to free the SOME/IP TP instance from handle

Parameters:: handle – [in] - Handle to the SOME/IP TP instance
Returns:: 0 for success.

rs_ret_val_t rs_someip_tp_rx_indication(rs_handle_t handle, rs_someip_msg_t *ptr_tx_msg)

Called to indicate a TP message has been received.

This function called to indicate a TP message has been received

Parameters:

handle – [in] - Handle to the SOME/IP TP instance
ptr_tx_msg – [in] - Pointer to the SOME/IP message structure

Returns:

0 for success.

rs_ret_val_t rs_someip_tp_process(rs_handle_t handle)

Function to call the TP TX and RX process.

This function called to initiate the TP TX and RX process

Parameters:: handle – [in] - Handle to the SOME/IP TP instance
Returns:: 0 for success.

struct tag_rs_someip_tp_rx_msg_mgr

#include <rs_someip_tp.h>

Contains information about SOME/IP RX Message Manager.

Public Members

uint16_t session_id: Session ID.

uint16_t client_id: Client ID.

void *ptr_cur_rx_msg: Current RX msg in progress.

uint32_t curr_rx_offset: OFFSET Of the Current RX message.

uint32_t curr_rx_time: Current time of the RX message.

uint32_t expected_offset: Expected OFFSET Of the Current RX message.

uint8_t state: State.

uint8_t reserved1: Reserved1.

uint16_t rx_port: RX Port.

uint32_t last_rx_time: Last Receive Data time.

uint8_t rx_addr[RS_SOCKET_IP_ADDR_V6_LEN]: Source/Target address.

struct tag_rs_someip_tp_msg_mgr

#include <rs_someip_tp.h>

Contains information about SOME/IP TP message manager.

Public Members

uint8_t cur_rx_state: Current Receive state.

uint8_t cur_tx_state: Current Transmit state.

uint16_t curr_tx_len: Length of current transmit message.

void *ptr_cur_tx_msg: Current RX msg in progress.

rs_someip_msg_t *ptr_tx_msg: Pointer to the TX message buffers.

rs_someip_msg_t *ptr_rx_msg: Pointer to the RX message buffers.

uint16_t num_tx_msg: Number of total TX messages.

uint16_t num_rx_msg: Number of total RX messages.

rs_someip_tp_rx_msg_mgr_t rx_msg_mgr[RS_SOMEIP_TP_RX_MSG_MGR_SIZE]: RX Message Manager FIFO.

struct tag_rs_someip_tp_config

#include <rs_someip_tp.h>

Contains information about SOME/IP TP configuration.

Public Members

uint32_t tp_rx_timeout: TP RX Timeout time.

uint32_t tp_tx_separation_time: TP TX Separation time.

uint32_t burst_size: TP TX Burst size.

struct tag_rs_someip_tp_instance

#include <rs_someip_tp.h>

Contains information SOME/IP TP Instance.

Public Members

rs_someip_tp_config_t *ptr_tp_config: Pointer to the SOME/IP configuration.

rs_someip_tp_msg_mgr_t tp_msg_mgr: Structure of message manager.

uint32_t exp_rx_len: Num frame bytes expected.

uint16_t total_tx_frames: Num frame bytes transmitted.

uint16_t frame_cnt: Frame count of the current segment

uint32_t tx_last_time: Last TX time