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Volodymyr Samotiy edited this page Sep 6, 2017 · 3 revisions

Port Breakout in SONiC

High Level Design Document

Rev 0.2

Table of Contents

List of Tables

Revision
Rev Date Author Change Description
0.1 Volodymyr Samotiy Initial version
0.2 Volodymyr Samotiy Update according to comments

About this Manual

This document provides general information about the Port Breakout feature implementation in SONiC.

Scope

This document describes the high level design of the Port Breakout feature.

Definitions/Abbreviation

Table 2: Abbreviations
Definitions/Abbreviation Description
API Application Programmable Interface
SAI Swich Abstraction Interface
JSON JavaScript Object Notation

1 Sub-system Overview

1.1 System Chart

Following diagram describes a top level overview of the SONiC Switch components:

1.2 Modules description

1.2.1 swssconfig

Reads prepared json-files with configuration and injects it into App DB.

1.2.2 App DB

Located in the Redis DB instance #0 running inside the container "database". Redis DB works with the data in format of key-value tuples, needs no predefined schema and can hold various types of data.

1.2.3 Orchestration Agent

This component is running in the "orchagent" docker container and is resdponsible for processing updates of the App DB and do corresponding changes in the SAI DB via SAI Redis.

1.2.4 SAI Redis

SAI Redis is an implementation of the SAI API which translates API calls into SAI objects which are stored in the SAI DB.

1.2.5 SAI DB

Redis DB instance #1. Holds serialized SAI objects.

1.2.6 syncd

Reads SAI DB data (SAI objects) and performs appropriate calls to Switch SAI.

1.2.7 SAI (Redis and Switch)

An unified API which represent the switch state as a set of objects. In SONiC represented in two implementations - SAI DB frontend and ASIC SDK wrapper.

2 Subsystem Requirements Overview

2.1 Functional requirements

Detailed description of the Port Breakout feature is here: Port Breakout and Speed.

Requirements are listed below.

  • User needs to provide port_config.ini for different port breakout mode.
  • Specify default speed in port_config.ini file for split ports.
  • Use the speed attribute in the minigraph to specify the speed of a port.
  • Assume that the user needs to restart the SWSS when he needs to change the port breakout mode.
  • Use create_port() and remove_port() SAI APIs, so SAI >= v1.0 is required.
  • Assume that there is no port breakout in SAI profile by default.

3 Modules Design

3.1 Modules that needs to be updated

3.1.1 Swssconfig

No update is needed to support Port Breakout.

3.1.2 App DB

No update is needed to support Port Breakout.

3.1.3 SWSS

3.1.3.1 Port SyncD

Current implementation parses port_config.ini file and creates new record in AppDB port table with the port_alias and hw_lanes info.

To add support of port breakout feature port_config.ini file should be updated in order to specify default speed for the port. It is needed because create_port() SAI API is used for creating new split port and it requires speed to be specified. So, when new split port will be created in HW, specified default speed will be set.

PortSyncD implementation also should be updated with the logic to get the speed value from the config file and then set new record in AppDB port table with the additional speed info. So, new record will specify the following info: (port_alias, hw_lanes, port_speed).

3.1.3.1.1 Example of port_config.ini

Below is an example of port_config.ini file without any changes.

# name          lanes
Ethernet0       0,1,2,3
Ethernet4       4,5,6,7
Ethernet8       8,9,10,11
Ethernet12      12,13,14,15
...

3.1.3.1.2 Example of port_config.ini with port breakout

Below is an example of new port_config.ini file, which specifies different port breakout modes and default speed values for the split ports.

# name          lanes             speed
Ethernet0       0,1               50000
Ethernet2       2,3               50000
Ethernet4       4,5               50000
Ethernet6       6                 25000
Ethernet7       7                 25000
Ethernet8       8                 25000
Ethernet9       9                 25000
Ethernet10      10                25000
Ethernet11      11                25000
Ethernet12      12,13,14,15
...

3.1.3.2 Orchestration Agent

PortsOrch should receive notification from App DB when new port is added with the following info: (port_alias, hw_lanes, port_speed). In class PortsOrch the following logic should be implemented to handle port breakout:

  • Check whether received port_alias or hw_lanes are already used.
  • If port_alias and hw_lanes are already present then do nothing.
  • If port_alias and hw_lanes are used, but with different mapping, then remove found port and create new port with the new hw_lanes.
  • Else, just create port with the specified port_alias and hw_lanes.

Port speed SAI attribute is mandatory on port creation, so when create new port, received in AppDB notification speed should be set as a default value. Default speed can be updated by the "Speed" attribute in minigraph configuration.

3.1.4 SAI Redis

No update is needed to support Port Breakout.

Listed below SAI APIs should be used to create and delete ports.

  • create_port()
  • remove_port()

3.1.5 SAI DB

No update is needed to support Port Breakout.

3.1.6 Syncd

No changes required to support Port Breakout.

3.1.7 SAI

No changes required to support Port Breakout.

4 Flows

4.1 Port breakout

5 Open Questions

  1. Port speed SAI attribute is mandatory on port creation, so what speed should be set by default, minimal supported?
  2. Do we want to have different speeds on the split ports?
  3. Minigraph generation procedure sets the same speed for all ports, how to handle in case of split ports?
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