This chapter explains the terms used in this guide. If you encounter unfamiliar concepts while reading, you can quickly find their definitions and detailed explanations here.
Flow
A flow refers to a complete network session transmitted from the source to the destination, where data is transmitted and processed between various network nodes (clusters, virtual machines, switches, physical hosts, etc.).
The traffic visualization feature provided by the observability service supports monitoring of TCP, UDP, and ICMP flows, presenting the key information such as protocol type, traffic direction, data size, number of packets, source and destination, helping you monitor flows in the network, improve troubleshooting efficiency and enhance security monitoring.
Connection
A connection refers to the communication path between two communicating endpoints, providing a reliable and ordered data transmission channel. The establishment of a connection usually goes through a handshake process to ensure the reliability and order of communication.
The connections mentioned in this manual specifically refer to TCP connections, including full connection and half-open connection.
Full connection: Refers to the state where both parties have completed the three-way TCP handshake process and successfully established a connection. The three-way handshake includes the client sending a connection request (SYN packet) to the server; the server replying with a SYN + ACK response, indicating that the server has received the client's request and agrees to establish the connection; finally, the client replies with an ACK response, completing the connection establishment. In a full connection state, data can be reliably and orderly transmitted between the communicating parties. In a full connection state, data can be reliably and orderly transmitted between the communicating parties.
Half-open connection: Refers to the state where the client has sent a connection request to the server, but the server has not responded, and the two parties have not fully established a connection. This state is called a half-open connection.
Packet
A packet is the basic unit of data transmission in computer networks. It is a data structure that divides data into small blocks and adds necessary information (such as source address, destination address, checksum, etc.) for effective transmission. Data packets are transmitted across the network, traversing various network devices before ultimately reaching their intended destination address.
Traffic
In network communication, traffic refers to the packets transmitted through the network. The existence of traffic depends on whether there is actual packet transmission, not just on the existence of a connection. Therefore, there may be situations where there is a flow but no connection.
RTT
RTT (Round-Trip Time) refers to the time it takes for data to be sent from the sender to the receiver, and then for the response data from the receiver to return to the sender. RTT is an important metric for measuring network latency and response time. Smaller RTT means the lower the network communication delay and the higher the communication efficiency.
System service
System services refer to services that run as virtual machines to provide management and other advanced functions for the cluster, such as Arcfra Operation Center (AOC), Arcfra Network Service (ANS), Backup service, Replication service, Arcfra File Storage (AFS) service, etc. This Version of observability currently supports association with AOC, ANS, Arcfra Backup and Disater Recovery (ABDR), and AFS, providing monitoring and alerting functions for them.
