Transport Layer (7Eh) and (7Dh)

OSI: Transport Layer

Keywords: Connection/-less network, flow control, reliable transport service, low communication overhead, sensors, internet of things, embedded systems, sensor networks

Scope

The scope of this project is to define the Isotropic Sensor Network Transport layer for broadcast and peer to peer connection in distributed sensor area network, wired or wireless, low and high data rate devices, battery powered devices, short-range devices with short operational space, low-cost devices to support trivial sensors, besides the fully featured devices.

Purpose

The purpose of this specifications is to provide a standard for low complexity, low cost, and low power (aware) consumption devices (sensors) to provide a connection-less and reliable connection-oriented network in combination with a Sensor Frame layer.

Key features

  • Adds Logical Ports and Sequence Counters

  • Basic Hand-Shaking

  • Low-Cost and Compact Implementation

Definitions, Acronyms and Abbreviations

device

An entity containing this protocol implementation. Also referred as sensor device or just sensor or device.

frame

The format of aggregated bits that are transmitted together in time.

packet

The format of aggregated bits that are transmitted together in time across the physical medium.

LSB

least significant byte/bit

MSB

most significant byte/bit

Packet Formats

Protocol defines short and long frame formats:

  • short frame format supports connection-less network, with up to 64 logic ports and 2 pending transactions

  • long frame format supports connection-oriented network, with up to 256 logic ports, 8 pending transactions, and flow-control acknowledge bits

Both protocol can be nested to address larger space and more complex structures.

Short Frame Format (16-bits)

Fields

Protocol ID

Port

Counter

Payload

Bits

8

6

2

N

Value

0x7E

0-63

0-3

user

Protocol ID:

defines the unique protocol identification number

Port:

logical port 0..31

Counter:

packet counter 0..3

User Payload:

of arbitrary length, typically defined by upper or nested Frame Layer (80h+)

Long Frame Format (24-bits)

Extends the Short Frame format and adds optional hand-shaking with two acknowledge bits.

Fields

Protocol ID

Port

Counter

Ack

Payload

Bits

8

8

14

2

N

Value

0x7D

0-255

0-16383

user

Protocol ID:

defines the unique protocol identification number

Port:

logical port 0..255

Counter:

packet counter 0..16383

User Payload:

of arbitrary length, typically defined by upper or nested Frame Layer

Opening and Closing Port

Opening a port starts with a first message from or to selected port and non-empty message.

Any side may close the port by sending an empty message, a message which does not contain any user payload.

Packet Counter

In general counter is incremented after every transmission of a packet,

Acknowledge Bits

To be revised.

Document Changes

Date

Release

Changes

January 17, 2015

Initial specifications.

February 21, 2016

1.0

Public version of Renewed Sensor Transport Layer

September 15, 2018

1.x

Reviewing in progress

References