[roe] (2) roe agreement

Catalog

One 、ROE structure

1.1 summary

1.2 topology

1.3 The underlying network （ Information ）

1.4 ROE Functional units

 1.4.1 Ethernet link

1.4.2 RoE mappers/RoE de-mappers

1.4.3 CPRI port

1.4.4 Subtype mapping object

1.5 ROE Transaction type

1.5.1 ROE General frame header

Two 、 Timing and synchronization

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This section mainly describes RoE Encapsulate the transport format , as well as ：

1. RoE framework
2. Encapsulate and unpack functions and locations
3. RoE Mapper function and location
4. Support roe The basic settings of the network

One 、ROE structure

1.1 summary

RoE Interfaces carry three types of transactions over physical links , As shown in the figure below . These physical connections will contain the following ：

——LCc ： logical connection for control packets Logical connection of control package

——LCd ： logical connection for data packets Logical connection of packets

——LCt ： logical connection for timing packets Logical connection of sequential packets

         These three logical connections can be transmitted through the same physical link or through different physical links . This standard uses the terms node and RoE node , Both represent a support RoE The network entity , It is RoE The initiator or receiver of a communication link .RoE Nodes can be RoE The end of the traffic termination , It can also be a pass through endpoint that forwards traffic to the following nodes . A given node can support a mixture of termination traffic and transmission traffic . There may be zero or more intermediate network nodes , act as RoE Between endpoints RoE Transfer point , As shown in the figure below .

         This standard support will enable roe Of nodes connected to legacy CPRI Nodes and / Or an endpoint scene . Some of these scenes , Used with RoE Structure independent and right CPRI Structure has a perceptive mapper , Pictured 4 Shown . For the first two scenarios ,CPRI Flow by RoE Mapper maps to RoE, Then from RoE Demapper regenerate . In the third scenario , A serial CPRI A stream exists only at one end . At the other end there is a package based CPRI processor , It does not require serial CPRI flow .

1.2 topology

1. Single point to single point
2. Multipoint to multipoint
3. Single point to multipoint
4. Chain type
5. Ring
6. Tree shape

1.3 The underlying network （ Information ）

To make RoE Work successfully , The underlying network needs to be properly configured . Although the need for time sensitive networks is clear , But this RoE The specification does not specify how to implement this configuration . Generally speaking , The underlying network needs to meet the following requirements ：

        a) The network includes bridging and point-to-point Ethernet links .

        b) This standard does not specify the actual links and the number of nodes , But the frame transmission delay (FTD) And frame delay change (FDV) It should meet the requirements of the application .

        c) The network will need to FTD and FDV Management of .

        d) Managed networks should not be over configured ( At least for RoE identical / For higher priority transactions ） The network needs to have enough bandwidth to carry all RoE Business . Peak bandwidth 、 Delay and FDV I knew it in advance .

        e) Support ToD Distribute .

        f) Both transmitting and receiving endpoints need to share pairs ToD The same understanding , In order to provide information at the desired time .

        g) Don't execute RoE Retransmission of transactions .

        h) The maximum one-way transfer time needs to meet the requirements of the application , Need to be less than RoE orderInfo The field represents the time or the amount of time represented by the serial number .

        i） The Ethernet network needs to maintain the frame source address (SA) And the destination address (DA).

1.4 ROE Functional units

        a)Ethernet link： Ethernet link . Each pair has a unique SA/DA Yes , And for all RoE At least one implementation is required .

        b)RoE mappers/RoE de-mappers：RoE mapper /RoE Demapper .RoE The mapper packages the data , and RoE The demapper parses the data . Both of these are for all RoE Implementation is required . chart 6 Shows and RoE mapper /RoE Demapper related objects .

        c)CPRI port ：CPRI port . Structure known and structure unknown RoE The mapper needs to use CPRI port .

notes ： For structure unknown pattern , Even if mapped / The resolved protocol is not CPRI, The term... Is also used CPRI（ Or class CPRI） port .

 1.4.1 Ethernet link

         In this standard , The Ethernet link is defined to be associated with a specific SA and DA The connection of . One RoE The node shall have at least one Ethernet link . An Ethernet link can accept and provide data from multiple networks flow and RoE Mapper packets . Ethernet links are considered bidirectional ; However , This standard does not exclude the option of using only one direction .

1.4.2 RoE mappers/RoE de-mappers

        RoE Mapper is a way to convert other transport framework formats to ROE The function of frame format / Program , and RoE The demapper performs the opposite function . This specification describes different types of RoE mapper . The structure is known and Native RoE The mapper separates the control data and sample data into different channels . The control data input is referred to in this specification as “ Control procedures ” The block .RoE The main function of the mapper is to stream data from the input ( for example , One CPRI port ) Select the appropriate input data , And then packet it .RoE The mapper can also generate or select control information .

         Structure unknown RoE The mapper does not control packets , Because the whole data flow （ Including control information ） Encapsulated as a single LCD Data channel .

1.4.3 CPRI port

        CPRI（ Or similar CPRI Of ) Ports are physical connections . In mapping patterns with known and unknown structures ,RoE Nodes have CPRI( Or similar CPRI Of ) port . hypothesis CPRI( Or something like CPRI Of ) Ports are bidirectional .

1.4.4 Subtype mapping object

         The subtype mapping object is a table , Subtypes for maintaining and allocating mappings （ As shown in the table 2 It is specified in ） To a specific organization unique identifier (OUI) Or company identifier (CID) Entities and their specified subtypes / Payload structure .RoE The node handles the subtypes of the mapping 、 Corresponding payload structure , And by OUI or CID Entity specified seqNum Optional reserved bits in .OUI or CID Value can be passed through IEEE Register to obtain . Implementations can pre populate the mapping table with implementation specific default values . That is not used / Unmapped OUI/CID The subtype is set to ALL_ONES.

1.5 ROE Transaction type

        RoE Frames are encapsulated in Ethernet frames , Pictured 7 Shown . For this standard ,SA、DA And frame check sequence (FCS) Implicitly to all RoE package .RoE  ethertype Value specified as 0xFC3D（ As mentioned in the background of the previous article ）. This standard mainly focuses on RoE Header and RoE Fields in payload fields .

 

1.5.1 ROE General frame header

General purpose RoE The frame format has the following header fields ：

 

• subType : 8 bits

8 The bit subtype field is used to define RoE Subtypes and RoE What the packet carries flow The type of .

Subtype Binary value	function	describe
0000 0000b	ROE Control subtypes	Control or manage information
0000 0001b	R1	Retain
0000 0010b	ROE Unknown structure	ROE Public head + Structure unknown load
0000 0011b	ROE The structure is known	ROE Public head + The structure is known CPRI  I/Q data
0000 0100b	Native ROE	ROE Direct encapsulation
0000 0101b	Slow signaling CPRI subtypes	ROE Public head + The structure is known CPRI   Slow signaling
0000 0110b- 0000 1111b	R2	Retain
notes ： Different versions of the protocol are for subtype The binary corresponding function of is slightly different , The newer the version, the finer the definition

• flowID  : 8 bits

flowID Identify a specific flow between two endpoints . The endpoint is defined as the Ethernet framework in the context of this specification SA and DA Yes . The flowID Allow reuse between two endpoints up to 255 A specific stream .

flowID The identifier has no routing function , Interpreted only by endpoints . The identified flow can include multiple subflows （ Group flow ）. The interpretation of the traffic content and possible subflows is controlled only by the endpoint .

FlowID Binary value	function	describe
0000 0000b- 1111 1110b	flowID	flowID
1111 1111b	ALL_ONE flowID	be used for ROE Control pack

• length  : 16 bits  

Although Ethernet network interface controller (NIC) The length of the packet can be determined by the low-level encoding feature , However, these length fields cannot be used implicitly at the high-level layer or when packets are sent through other transports .RoE Packets should follow an internet protocol similar to IPv6 The plan , And contains a length field , Where the value of length is in the public RoE The total number of bytes after the header . The length does not include Ethernet FCS byte . That is, pure payload The length of .

Although the length field is 16 position , But the highest 2bit Reserved by this standard for future use .

because roe Based on Ethernet , So the length requirement is the least 64 byte .

• orderInfo : 32 bits

Sorting information is assigned to each stream , And expressed in one of two ways ： Serial number .seqNum Or timestamp timestamp.

When used, it is given by flow Parameters in （.orderInfoType) Definition ：0 To express with .seqNum,1 To express with timestamp.

—— .seqNum

         The sequence number field is used to identify the sequence of successive packets . To allow additional flexibility , There can be two independent counters , for example , One for the number of superframes (HFN), The other one is for nodes B frames (BFN).

The serial number field consists of RoE Mapper generates , It consists of three fields of independent size , Its size depends on two variables ,p and q. As shown in the figure below ：

 0 ≤ p < 32

0 ≤ q ≤ p and (if q = p, q-counter non-existent )

The other two fields may be based on p and q Value . Each with a serial number RoE Every stream should have its own p The counter and q Counter entity . When using the serial number for the first time , Each field is initialized to a known value . Please note that , stay RoE During the service life of the flow , Its value should remain unchanged .

—— timestamp

         The timestamp field is defined by RoE Mapper generates . It is 32 position , And provide the frame start mark 、 Compress the sequence number and the absolute time when the parser presents the packet information at the receiving endpoint .

Bit[    0]：SOF, Frame start marker , Set to 1 It means that this load is the beginning of the wireless frame .

Bit[2 ：1]：seqNum,p Counter low 2bit

Bit[26：3]： Time stamp , Integral part , Company ns

Bit[31：27]： Time stamp , Fraction part , Company ns

The entire timestamp can represent approximately 17ms Time for .

• RoE Payload

         Contents of the payload field 、 Structure and size are specific to RoE Subtypes and their definitions . The payload may contain for a single antenna carrier (AxC) Or a group AxC Of I/Q Sample stream . Both single content and group content pass through two RoE Flow between nodes ID To mark .

        RoE The payload should consist of full bytes .

        RoE The minimum payload is 64 Bytes .

Two 、 Timing and synchronization

         To make RoE Interface work , Both ends of the link need to know the time . In order to meet the requirements of radio signals , The presentation time of radio signals needs to be strictly controlled .

 ROE presentation time：

        RoE Indicates that time is used for phase alignment RoE Data transfer between endpoints . Indicates that the time is from RoE The sender calculates , Express RoE Packet data payload from RoE Time from receiving packet buffer to data consumer .

         The picture above shows RoE A measuring plane that represents time . When RoE The sender calculates at RoE Time at the receiver , It has to take into account RoE The entire end-to-end delay between the sender and receiver reference planes . End to end FTD Including network delay （ Transmission time ）、 Processing delay and sufficient buffer time , To compensate for the FDV.