TP/TCP/UDP

In the past two weeks, I continue to learn the SCPS-TP protocol located at the lower position of the transport layer in the CCSDS protocol stack, and have reviewed the TCP and UDP protocols in the TCP/IP system, by studying and comparing the two systems of agreement, I have deepened my understanding and understanding of SCPS-TP protocol.

We know that the transmission layer is very important in both the TCP/IP and CCSDS protocols. It provides reliable transmission performance to the upper layer, these Transmission Performances include Error Control, congestion control, and retransmission mechanism. Especially in the CCSDS system, the data link layer and the network layer cannot have similar protocols such as ARQ as in the TCP protocol system. That is to say, in the CCSDS protocol system, the underlying protocols below the transport layer only provide unreliable and fast transmission performance to the upper layer (this is closely related to the CCSDS protocol environment, I mentioned previously that CCSDS is mainly used for spatial transmission, including ground base stations and satellites, and between satellites. Their transmission latency is very high ). Therefore, the task of providing reliable transmission to the application layer lies in the transmission layer, and the TP protocol is a key link in the CCSDS transmission layer.

In the last summary, I only described some impressive points after the read-through protocol. This time I will explain the overall TP protocol. The TP protocol mainly describes the TCP and UDP protocols in the TCP system. From the perspective of the article, the TP protocol mainly targets the TCP protocol, which has only one page. First of all, I will give a brief introduction to the TP-UDP protocol, the UDP protocol in CCSDS, but also for the non-connection unreliable protocol, the protocol provides a fast transmission mode, it inherits all the features and methods in all TCP-UDP protocols. In addition, the TP-UDP protocol is also extended for the TCP-UDP protocol, added the priority management mechanism (through the network layer service primitive execution, that is, the network layer NP Protocol needs to provide priority management for the upper layer of the business ). Next, we will introduce the TCP protocol. In the TP protocol, we emphasize at the beginning that the TP protocol inherits the features of most TCP Protocols, the Protocol environment of the CCSDS protocol is modified to obtain the TP protocol. The most important points are:

1) connection management: As we all know, TCP is a connection-oriented transmission protocol. Therefore, a connection should be established before reliable end-to-end transmission, the connection is closed after the transmission is complete. Here, the TCP protocol implements a three-way handshake mechanism, while the TP protocol only performs a simple answer mechanism for connection management, that is, two-way handshake. In addition, when sending the initial sequence SYN, the TP Protocol adds extended functional domains, which can better serve in different environments.

2) data transmission: This section describes to readers how the TP Protocol processes out-of-order and wrong frames during data transmission, retransmission and other issues (the text cannot be found in the standard TCP protocol, that is, the content modified for the TCP protocol ). The basic content is to add several limit parameters in the transmission process. These parameters work with the system timer (R1, R2, be1, Be2 ).

3) error recovery: the content of the TCP protocol is basically the same. Some congestion control algorithms all inherit the TCP protocol. However, in some special cases, the algorithm is improved.

4) Others: Includes SCPS-TP Header Compression: Describes some Header Compression content and formats in the TP Protocol (to save transmission bandwidth and time ). Multi-transmission forward correction and snack option content (this content is not fully understood, and I don't know what it is .)

 

 

In the next two weeks, we also need to compare and analyze the key content of the TP Protocol: connection management, data transmission, and error recovery through the relevant content of the TCP protocol. Deepen understanding.

 

Turn: Zhang Yu

TP/TCP/UDP