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HDBaseT Contribution: HD-CMP Company Name: Valens Semiconductor

Contribution Title: HDBaseT HD-CMP Protocol Date Submitted: 07/06/2010Source: Eyran LidaCompany: Valens Semiconductor

Abstract: The HDBaseT Control & Management Protocol (HD-CMP) is described.

Purpose: Agreement on the referencing methods for HDBaseT 2.0 specification. Release: Confidential under Section 16 of the HDBaseT Alliance Bylaws. Contributed Pursuant to Section 3.2 of the HDBaseT Alliance IPR policy .

HDBaseT Contribution

HDBaseT Contribution: HD-CMP Company Name: Valens Semiconductor2

• PDMEs, SDMEs and CPMEs are communicating using HD-CMP

• HD-CMP messages shall be transmitted over Intra Links using Ethernet packets identified by the HD-CMP EtherType

• HD-CMP messages shall be transmitted over Edge Links using HLIC or Ethernet packets according to the end node choice

• HD-CMP is being used in two different ways:

– Sub Network Propagation Message (SNPM) – Intra HDBaseT Sub Network restricted, T-Network direction aware, loop protected, message sent by each PDME/Edge SDME to its, directional neighbors, PDMEs/SDMEs according to the HDBaseT physical topology

• Downstream SNPM (DSPM) – The message propagates to downstream neighbors

• Upstream SNPM (USPM) – The message propagates to upstream neighbors

• Mixpath SNPN (MXPM) – The message propagates to all neighbors

– Normal - unicast and broadcast communication according to the Ethernet active topology (as determine by the RSTP protocol)

• Unicast messages may use HLIC on the edge links

Management & Control

HDBaseT Contribution: HD-CMP Company Name: Valens SemiconductorValens Confidential

3

HD-CMP Over Ethernet- Ethernet Fields

• HD-CMP messages are encapsulated within Ethernet packets identified by the HD-CMP EtherType

• When sending a unicast HD-CMP message, the Destination MAC Address field (DA) conveys the unique identifier MAC address of the target SDME/PDME/CPME and the message is switched according to the DA along the Ethernet active topology

• When sending/propagating SNPMs towards intra network, HDBaseT links, the DA field may contain 802.1D single LAN, reserved multicast MAC address (such as the LLDP_Multicast) to indicate that the link partner is the destination

• By using this special address the message can be sent according to the HDBaseT network topology overriding the Ethernet active topology

• The Source MAC Address field (SA) conveys the unique identifier MAC address of the source SDME/PDME/CPME

Destination MAC Address

Source MACAddress

Type: HD-CMPEtherType

HD-CMP Payload

6 Bytes 6 Bytes 2 Bytes Variable Length

Eth CRC

4 Bytes

Destination TPG

2 Bytes

Source TPG

2 Bytes


HD-CMP Over Ethernet – HD-CMP Fields

• Destination TPG conveys in combination with the Destination MAC address the Port and T-Group reference of the message target entity

• Source TPG conveys in combination with the Source MAC address the Port and T-Group reference of the message source entity

• The Destination and Source TPG fields also enable the sending management entity to send the Ethernet message according to the Ethernet active topology (not necessarily through the port appears in the source TPG) but the receiving entity will treat this message as if it was transmitted from the source TPG and received from the destination TPG

• Additional T-Adaptors referencing, using type masks, is done, if needed, as part of the HD-CMP payload depending on the type of the HD-CMP message

• The HD-CMP Op Code field conveys the type of this message and determine the format of the HD-CMP payload


Source MACAddress


HD-CMP Payload


Eth CRC

4 Bytes

Destination TPG

2 Bytes

Source TPG

2 BytesHD-CMP Op Code

2 Bytes


HD-CMP Over HLIC – Short Form

• Short Form HD-CMP messages are encapsulated within HLIC packets identified by Op Code = 32

• These messages do not convey a reference to the source and destination entities and they are useful since some frequent HD-CMP messages, such as periodic SNPMs are sent between link partners with no need to specify their source and destination entities

• Short Form HD-CMP payload, over HLIC, max length is limited to 509 bytes

• The initiator of the HLIC transaction mark it as a request and the responder should send a reply according to the HLIC protocol

•

Length Op Code

Request

/ Reply

Flag

1 0 0 0 0 0 HD-CMP Op Code

HD-CMP Payload

2 Bytes

CRC-32

4 BytesVariable Length


HD-CMP Over HLIC – Full Form

• Full Form HD-CMP messages are encapsulated within HLIC packets identified by Op Code = 36

• These messages convey a Port and T-Group reference of the source and destination entities

• Full Form HD-CMP payload, over HLIC, max length is limited to 493 bytes

• The initiator of the HLIC transaction mark it as a request and the responder should send a reply according to the HLIC protocol

•

Length Op Code

Request

/ Reply

Flag


HD-CMP Payload

2 Bytes

CRC-32


DestinationDevice ID : TPG

Source Device ID : TPG

8 Bytes 8 Bytes


Mapping HD-CMP Over Ethernet to Full Form HD-CMP over HLIC


Source MACAddress


HD-CMP Payload


Eth CRC

4 Bytes

Destination TPG

2 Bytes

Source TPG

2 BytesHD-CMP Op Code

2 Bytes

Length Op Code


HD-CMP Payload

2 Bytes

CRC-32


DestinationDevice ID : TPG

Source Device ID : TPG

8 Bytes 8 Bytes


• Each T-Adaptor identifies its connected native edge device, collect its capabilities, using various methods according to the T-Adaptor type and reports to its local PDME/SDME

• Each PDME generates periodic Edge SNPMs, on behalf of all its T-Groups and their associated T-Adaptors, towards its connected edge SDME

• Each edge SDME generates periodic intra SNPMs towards its intra ports, on behalf of all the end nodes, directly connected, to the same switch device, via edge links and on behalf of all the integrated T-Adaptors/T-Groups in the switch device

• Each SDME propagates SNPMs which it receives through its intra ports towards its other intra ports according to the SNPM propagation rules

• The periodic SNPMs allow each SDME to know/store which T-Adaptors exists in the T-Network, what are their capabilities and directional connectivity from this SDME

• Each edge SDME generates periodic edge SNPMs towards its edge ports notifying its connected PDMEs its knowledge about all the other, directionally connected, T-Adaptors in the T-Network

Making Of The HDBaseT Sub Network Using HD-CMP Periodic SNPMs


• Each PDME/SDME informs each of its associated T-Adaptors all the needed information regarding other T-Adaptors, considering the directional connectivity and type of those other T-Adaptors for example:

• IR source T-Adaptor does not need any information regarding other T-Adaptors in the T-Network

• USB Host T-Adaptor needs information regarding all USB dev/hub T-Adaptors

• HDMI Sink T-Adaptor needs information regarding all HDMI sources T-Adaptors which are upstream connected to it

• SDMEs are also using those periodic SNPMs to build switching table, marking which entities are accessible, per direction, through which port devices of the switch, with how many hops and with what available BW/ number of T-Streams

• On stand by mode, Switch ports shall support LPPF #2 (HDSBI + Ethernet) and use HD-CMP over Ethernet while end node ports do not have to support Ethernet and may use HD-CMP over HLIC over HDSBI in LPPF #1

Making Of The HDBaseT Sub Network (continue)


• Only SNPMs, received from Intra Ports are propagated

• SNPMs are propagated only towards Intra Ports

• Bi-Directional ports are consider as downstream input and downstream output

• Downstream SNPM (DSPM): When received from a downstream input, propagates to all other downstream outputs and propagates as a MXPM to all other downstream inputs

• Upstream SNPM (USPM): When received from a downstream output, propagates to all other downstream inputs and propagates as a MXPM to all other downstream outputs

• Mix Path SNPM (MXPM): When received from a port propagate to all other ports

SNPM Propagation Rules


• Only edge SDMEs generate Intra SNPMs

• Edge SDMEs generate intra SNPMs towards their intra ports:

– DSPMs are generated towards all downstream outputs conveying information “learned” from previous edge DSPMs

– USPMs are generated towards all downstream inputs conveying information “learned” from previous edge USPMs

– MXPMs are generated towards each port conveying all information “learned” from previous edge SNPMs which was not already sent to that port in DSPMs or USPMs

– Each edge SDME shall also reports in these SNPMs its embedded T-Adaptors, the internal connectivity between the T-Adaptors and the switching function can be treated according to the switch device choice it can be treated as DS/US/Bi-Dirc so this T-Adaptors information will be reported accordingly

Intra SNPM Generation Rules


End Node PDME Generating Edge SNPMs - Example

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E8

USPM: E2

USPM: E1

DSPM: E

3 DSPM: E4

USPM: E6

USPM: E7

S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port

E1 End Node device without Ethernet Termination

4


Edge Switch Generating Intra SNPM - Example

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

USPM: E1, E2

MXPM: E8

DSPM: E3, E4

DSPM: E3, E4

USPM: E7, E6

MXPM: E7, E6

DSPM: E5

MXPM: E5

MXPM: E5

This is an HDMI Source T-Adaptor

S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4


Propagating Intra DSPM Example Step 1: Generated

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E3, E4


S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4


Propagating Intra DSPM Example Step 2: First Propagation

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E3, E4


S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4

DSPM: E3, E4

DSPM: E3, E4

MXPM: E3, E4


Propagating Intra DSPM Example Step 3: Second Propagation

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E3, E4


S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4

DSPM: E3, E4

DSPM: E3, E4

MXPM: E3, E4

DSPM: E3, E

4

MXPM: E3, E4

MXPM

: E3,

E4

Will be dropped by loop protection


Propagating Intra DSPM Example Step 4: Third Propagation

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E3, E4


S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4

DSPM: E3, E4

DSPM: E3, E4

MXPM: E3, E4

DSPM: E3, E

4

MXPM: E3, E4

MXPM

: E3,

E4

Will be dropped by loop protection

DSPM: E3, E4

MXPM: E3, E4

MXPM: E3, E4


Edge Switch Generating Edge SNPMs - Example

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E8, E3, E4, E5

MXPM: E2, E7, E6

DSPM: E8, E3, E4, E5

MXPM: E1, E7, E6

USPM: E1, E2

MXPM: E3, E4, E5, E7, E6

DSPM: E3, E4, E5

MXPM: E1, E2, E8, E6

DSPM: E3, E4, E5

MXPM: E1, E2, E8, E7

USPM: E1, E2, E7, E6

MXPM: E4, E5, E8 USPM: E1, E2, E7, E6

MXPM: E3, E5, E8

S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4


Path Description Section (PDS)

Valens Confidential

19

Periodic SNPM HD-CMP Payload Format

HD-CMPMsg OpCode

Network Path Availability

Device xxxxxxInfo

2 Bytes 8 bytes Variable Length

…Device zzzzzz

Info

Variable Length

0x0001 – Periodic downstream SNPM

0x0002 – Periodic upstream SNPM

0x0003 – Periodic mix path SNPM

PDS Entries Max Count: N

1 BytePDS Entries Occ Count

1 BytePDS Entry

N

10 BytesPDS Entry

1 …

10 Bytes

Devices Info Section

• HD-CMP Op Code – Specify which type of SNPM it is

• Path Description Section (PDS) – each SNPM carries a list of Path Description Entries conveying devices unique identifiers and port ids, marking the devices it already passed on its network path, using that, SDMEs can eliminate loops in the network

• Network Path Availability – each SDME mark in this section the availability of the next hop in terms of free throughput and number of packet streams

• Devices Info Section – this section is built by the generator of the SNPM describing end nodes devices with their T-Groups and T-Adaptors. This section travels intact through the whole network path

HDBaseT Contribution: HD-CMP Company Name: Valens SemiconductorValens Confidential

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Periodic SNPM Path Description Section (PDS)

HD-CMPMsg OpCode


Device xxxxxxInfo


…Device zzzzzz

Info

Variable Length






1 BytePDS Entry

N

10 BytesPDS Entry

1 …

10 BytesPath Description Section (PDS) Devices Info Section

• Max Count: Path Description Max Number Of Entries – The sender of the SNPM specifies how many entries are pre allocated in the PDS

– Non Occupied entries contains zero value

– Periodic Edge SNPM shall contain max entries count of zero and Occ count of zero with no PDS entries, since these messages are not propagated throughout the network

– Periodic Intra SNPM shall contain max entries value of 7

– Future propagating SDME may add more entries to the PDS so propagating SDME shall not assume these numbers (0 and 7)

• Occ count: Number of Occupied Path Description Entries – the current number of occupied entries in the PDS


Path Description Section (PDS)-2

• Each PDS entry contains the following fields:

– Device ID: unique identifier 6 bytes MAC address of the device which the message passed

– Input Port ID: The Port ID (TPG field with T-Group ID = 0) with in this device where the message was received from

– Output Port ID: The Port ID with in this device where the message was propagated to

• This list of PDS entries define a path on the network where per device on the path the input port and output port are listed so this path defines one flow direction from input port to output port and the opposite flow direction from “output” port to “input” port

• PDS is used in several HD-CMP messages not just periodic SNPM it is used as a general way to collect / discover a path and to describe / set a certain network path

HD-CMPMsg OpCode


Device xxxxxxInfo


…Device zzzzzz

Info

Variable Length






1 BytePDS Entry

N

10 BytesPDS Entry

1 …


Device IDInput

Port IDOutput Port ID

2 Bytes 2 Bytes6 Bytes


Periodic SNPM Path Description Section (PDS)-3

• Each Intra SNPM generating device allocates PDS at the proper size, set max count accordingly, init PDS entries to zero, fill up the first PDS entry (with its device id, zero input port and output port id) and set number of occupied entries to one

• Upon the reception of Periodic SNPM, each propagating SDME checks the PDS:

– If the max entries count already reached (max count = occ count), the Spec 2.0 propagating SDME shall accept/”learn” the info in this SNPM but shall not propagate it (edge SNPMs are an example for this case)

– If the SDME identifies its own unique identifier MAC address, in a previous entry of the PDS it means that a loop is detected, it shall discard this SNPM and shall not accept the info conveys in this SNPM

• When propagating a SNPM, each SDME fill up the next available PDS entry and advances the number of occupied entries field

HD-CMPMsg OpCode


Device xxxxxxInfo


…Device zzzzzz

Info

Variable Length






1 BytePDS Entry

N

10 BytesPDS Entry

1 …


Device IDInput

Port IDOutput Port ID

2 Bytes 2 Bytes6 Bytes


PDS in Intra DSPM Example Step 1: Generated

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E3, E4


S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4Device Input

PortOutput

Port

S3 0 1

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

Max Count: 7 Occ Count: 1

PDS

E3


PDS in Intra DSPM Example Step 2: First Propagation

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E3, E4


S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4Device Input

PortOutput

Port

S3 0 1

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0


PDS

DSPM: E3, E4

PDS

E3

Device Input Port

Output Port

S3 0 1

S2 4 3

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0


E3


PDS in Intra DSPM Example Step 3: Second Propagation

S1

S2

S3 S4

S5

E1E2

E3

E5

E4

E6

E7E8

2

12

34

1

2

34

1 2

13

1

2

3

3

4

4

DSPM: E3, E4


S1

S1

1

1

E1

E1

Edge Switch

Intra Switch

Edge Port

Intra Port

End Node device

Embedded T-Adaptors

Edge Link

Intra Link

1 Virtual Edge Port


4Device Input

PortOutput

Port

S3 0 1

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0


PDS

DSPM: E3, E4

E3

Device Input Port

Output Port

S3 0 1

S2 4 3

S4 2 1

0 0 0

0 0 0

0 0 0

0 0 0


PDS

E3

Device Input Port

Output Port

S3 0 1

S2 4 3

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0


MXPM: E3, E4

PDSE3

S3 will drop this message since its device ID already appears in

the PDS


Periodic SNPM Network Path Availability

…

• Available Throughput – The generating device sets this field according to the available throughput at the proper direction, on the link where the SNPM is transmitted. The propagating device when propagating to another link updates this field only if the next link have less throughput at the proper direction than what is represented by this field value

• HighTh/MidTh/LowTh packet streams number – represents the accumulated numbers of active High/Mid/Low Throughput packet streams along the path per direction. The generating device sets these fields according to the link where the SNPM is transmitted. The propagating device when propagating to another link updates these fields only if additional packet streams are active on the next link

Available Throughput

HighTh Packet Streams Number

MidTh Packet Streams Number

LowTh Packet Streams Number

1 Byte 1 Byte 1 Byte 1 Byte

DS Path Availability

US PathAvailability

4 bytes 4 bytes

HD-CMPMsg OpCode


Device xxxxxxInfo


…Device zzzzzz

Info

Variable Length






1 BytePDS Entry

N

10 BytesPDS Entry

1 …



Periodic SNPM Device Info Section

Device MAC:xxxxxx

6 Bytes

Device Status

1 ByteT-Groups Number

1 ByteTPG 1

Info

Variable Length

…TPG Last

Info

Variable Length

TPG ID

2 BytesT-Adaptors Type Mask

2/4 BytesT-Adaptor 1

Info

Variable LengthT-Adaptor 2 Optional Info

Variable Length

…T-Adaptor Last

Optional Info

Variable Length

Rest of Info Length In Bytes

1 ByteT-Adaptor Type Code

2/4 BytesT-Adaptor

Specific Info

Variable Length

Info Length:7

1 ByteT-A Type Code:

0x0001

2 BytesHDMI Source

Type

1 ByteHDMI Source

Status

1 ByteCEC PreferredLogical Addr

2 BytesCEC Device

Type

1 Byte

Example of HDMI Source T-Adaptor Info

T-Adaptor Info Format

T-Group Info Format

Device Info Format

If ‘Rest of Info Length’ is zero -> end of T-Group infoContent parsing only by target T-Adaptor and supported CP (transparent to the switch)

Info of a device which contains T-Groups

HD-CMPMsg OpCode


Device xxxxxxInfo


…Device zzzzzz

Info

Variable Length






1 BytePDS Entry

N

10 BytesPDS Entry

1 …



T-Adaptor to T-Adaptor Direct Communication

• Using the Periodic SNPMs each T-Adaptor can build a data base containing all other T-Adaptor which are “interesting” for this T-Adaptor, for example HDMI sink T-Adaptor can list all the active HDMI sources in the network

• The data base may contain full reference for the other T-Adaptor in what T-Group it is associated with, what is the info it publish with the periodic SNPMs

• The T-Adaptor/CPME may now send a HD-CMP unicast message to the other T-Adaptor and interact with it in ways that the SDMEs in the T-Network are not aware of

• This unicast message is delivered using the Ethernet active topology directly to the destination entity, on the edge links this message may be sent using full form HD-CMP over HLIC while the edge switches will “translate” it from Ethernet encapsulation to HLIC encapsulation and vice versa


Unicast SNPM (U_SNPM)

• The motivation for U_SNPM is to query / search a network path between two management entities and /or to collect information from / configure the devices along the path

• This type of functionality is needed for example for session creation

• In Unicast SNPM the SDMEs are propagating the message to their link partners in a similar way as in Periodic SNPM with additional restrictions according to the HD-CMP Op Code

• Unicast SNPMs carry in their payload references, (Device ID : TPG), to the real source and final destination management entities of this message since the HD-CMP header is used for the propagation throughout the network similar to Periodic SNPM

• When a unicast SNPM reaches its final target device or the edge switch which is connected to this target device its propagation is stopped by the SDME

• Unlike Periodic SNPM, edge unicast SNPMs are also propagated by the SDMEs, it allows PDMEs to send U_SNPMs to other PDMEs

HD-CMPMsg OpCode


2 Bytes 8 bytesFinal Target Reference

8 BytesReal Source

Reference

8 Bytes

PDS

Variable Length

Per Op Code U_SNPM Body

Variable Length

0 0 0 0 0 0 0 1 DirMod

Session ID Query

1 or 33 Bytes


Unicast SNPM (U_SNPM) - OpCode

• In U_SNPM OpCodes the most significant byte value is 1, the least significant byte contains two bit Dir filed, two bits Mod field and 4 bits for 16 possible options of U_SNPM types

• The Dir field determines the directionality of the U_SNPM propagation within the sub network

• The Mod field determines the SDME directional propagation method:

– All Ports : Search all directional ports - propagate to all ports with the proper direction according to the type of the U_SNPM (U_DSPM, U_USPM and U_MXPM)

– With Path: Propagate to all directional ports with known path to the final target device

– Best Path: Propagate only to the directional port with the best path to the final target device

– By PDS: Propagate according to the PDS list delivered by this message

HD-CMPMsg OpCode



8 BytesReal Source

Reference

8 Bytes

PDS

Variable Length

00 – Not Used

01 – U_DSPM

10 – U_USPM

11 – U_MXPM

0 0 0 0 0 0 0 1 DirMod

00 – All Ports

01 – With Path

10 – Best Path

11 – By PDS


Variable Length

Session ID Query

1 or 33 Bytes


0 0 0 0 0 0 0 1 DirMod

31

More About Unicast SNPM (U_SNPM)

• Similar to Periodic SNPM the U_SNPM carries a PDS and each propagating SDME fill its PDS entry and provide loop protection

• When the op Code Mod field is ‘By PDS’ the propagation is done according to the PDS entries:

– PDS may or may not contain end node devices entries, (it may contain only SDMEs)

– The final edge SDME shall propagate to the final target according to the final target reference

– Occ Count field of the PDS mark in this case the current device on the PDS list

• Similar to Periodic SNPM the U_SNPM carries and maintains a Network Path Availability section

HD-CMPMsg OpCode



8 BytesReal Source

Reference

8 Bytes

PDS

Variable Length


Variable Length

Session ID Query

1 or 33 Bytes


0 0 0 0 0 0 0 1 DirMod

32

Unicast SNPM (U_SNPM) – Session ID Query (SIQ)

• The Session ID Query (SIQ) field is used to find out which are the active session ids along the network path:

– SIQ Length : One byte field specifying the length of the number of SIQ entries in bytes

• zero value represents that there are no SIQ entries and this message is not probing the session ids on the path

– SIQ Entries : Defined only when SIQ Length is equal 32, and holding a bit map of 256 bits (using 32 bytes) each bit represents a session id value for example the LS bit in the LS byte represents session id = 1 and the MS bit in the LS byte represents session id = 8

• When propagating U_SNPM, each SDME, per active session, passing through this SDME, set the proper bit in the SIQ entries such that at the end of the U_SNPM “journey” the SIQ entries bit map holds representation of all the active session ids along the network path

HD-CMPMsg OpCode



8 BytesReal Source

Reference

8 Bytes

PDS

Variable Length


Variable Length

Session ID Query

1 or 33 Bytes

SIQ Length SIQ Entries

1 Byte 0 or 32 Bytes LSB

hdbaset contribution - wikileaks · hdbaset contribution: hd-cmp company name: valens semiconductor...

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