What is connection management?

Connection management in networking refers to the process of establishing, maintaining, and terminating connections between devices or systems within a network. In the web, connections typically refer to logical associations or pathways that enable communication between devices.

Connection management process include:

  • Connection Establishment: The process begins with initiating a request from one party (client) to another (server). This typically involve protocols such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) for establishing connections between hosts in a network, or protocols like HTTP (Hypertext Transfer Protocol) for establishing communication between clients and servers in web applications.

  • Handshake: Once the connection request is received, the server validates the request and responds with a handshake message to acknowledge and establish the connection. During the handshake, both parties may exchange additional information required for secure communication, such as cryptographic keys.

  • Data Transfer: With the connection established, data can be transmitted between the client and server. This may involve multiple rounds of data exchange, depending on the communication protocol and application requirements.

  • Data Transmission Monitoring: Throughout the lifespan of the connection, both parties monitor its status to ensure continued reliability and performance. This may involve periodic checks, heartbeats, or other mechanisms to detect and handle failures or timeouts.

  • Connection Termination: when the data exchange is complete or either party wishes to end the connection, a termination sequence is initiated. This involves sending a termination request or notification, followed by the ACK: acknowledgment of closure.

  • Resource Management: efficient allocation and utilization of resources, such as network bandwidth, memory, and processing power, to support multiple concurrent connections without compromising performance or stability.

  • Error Handling and Recovery: communication protocols and networking software implement error detection, correction, and recovery mechanisms to handle various issues that may arise during connection establishment or data transfer, such as packet loss, network congestion, or hardware failures.

Connection management process chart sheme
Visualization of connection management process

Connection management is a important part of network architecture.

Connection troubleshooting - Common Errors - FAQ

  • Connection timeouts: Awaiting time refers to the period during which the system remains in this state, waiting for the connection to be established or the timeout to occur. A common procedure for managing timeout error involves setting a reasonable timeout period, typically in seconds (ie. 30s), to balance between allowing enough time for connections to be established and avoiding prolonged delays in case of failure.

  • Connection refused: Occurs when the server actively rejects the connection request, often due to being overloaded or misconfigured.

  • Connection reset: Happens when an established connection is terminated abruptly by one of the parties involved, usually due to network issues.

  • Connection dropped: The connection is terminated unexpectedly without proper closure, leading to data loss or corruption.

  • DNS resolution failure: The system is unable to resolve the domain name to an IP address, preventing connection establishment.

  • Too many connections: When the server reaches its limit for accepting new connections, causing subsequent attempts to fail.

  • Firewall or security restrictions: Connections are blocked or restricted by firewall rules or security settings, preventing successful communication.

  • Incorrect credentials: Authentication failure due to providing incorrect login credentials or authorization tokens.

  • Server unavailability: The server is offline or inaccessible, preventing any connection attempts from being successful.

  • Network congestion: Heavy traffic or network issues lead to delays (ping) or failures in connection establishment.

Connection management in the transport layer

Connection management in the transport layer is a critical function that ensures reliable data transfer between devices over a network. This process includes establishing, maintaining, and terminating data transfers, primarily handled by the Transmission Control Protocol (TCP).

1. Connection Establishment

Three-Way Handshake: The process of establishing a connection in TCP and other communication protocols involves a three-way handshake:

  1. SYN (Synchronize) The client sends a SYN packet to the server to initiate a connection. This packet includes an initial sequence number (ISN) chosen by the client.

  2. SYN-ACK (Synchronize-Acknowledge) The server responds with a SYN-ACK packet. The SYN part contains the server's initial sequence number. The ACK part acknowledges the client's SYN packet by incrementing the client's ISN by one.

  3. ACK (Acknowledge) The client sends an ACK packet back to the server. This acknowledges the server's SYN-ACK by incrementing the server's ISN by one.

After the three-way handshake, a connection is established, and data transfer can begin.

2. Data Transfer Procedures

  • Sequencing TCP assigns sequence numbers to each byte of data to ensure correct order delivery.

  • Acknowledgments (ACKs) The receiver acknowledges received data by sending ACKs back to the sender.

  • Flow Control TCP uses a sliding window protocol to manage the amount of data that can be sent before receiving an acknowledgment.

  • Error Detection and Retransmission If a segment is lost or corrupted, the sender retransmits the data after a timeout or upon receiving duplicate ACKs.

  • Congestion Control TCP implements algorithms like Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery to manage network congestion and optimize throughput.

3. Connection Termination

Four-Way Handshake: The process of terminating a TCP connection involves a four-way handshake:

  1. FIN (Finish) The client or server sends a FIN packet to terminate its side of the connection.

  2. ACK (Acknowledge) The receiving end acknowledges the FIN packet with an ACK packet.

  3. FIN (Finish) The receiver sends a FIN packet to close its side of the connection.

  4. ACK (Acknowledge) The initiator of the termination acknowledges the receiver's FIN packet with an ACK.

After these steps, the connection is fully terminated.

4. Resetting Connections

RST (Reset Command): A TCP connection can be reset using the RST packet, which immediately terminates the connection. This is typically used to handle errors or when one side wants to abort the connection abruptly.

Key Concepts in Connection Management:

  • Full-Duplex Communication: Both ends can send and receive data simultaneously.

  • Half-Open Connections: If one side terminates or crashes, the other side may still think the connection is open. TCP handles such scenarios with timeouts and retransmission mechanisms.

  • State Management: Both the client and server maintain states (e.g., SYN_SENT, ESTABLISHED, FIN_WAIT) to manage the connection lifecycle.

  • Timeouts and Retransmissions: TCP uses timeouts to detect lost packets and triggers retransmissions to ensure reliable delivery.

Connection management in the transport layer, primarily implemented by TCP, involves:

  • Establishing connections using a three-way handshake.

  • Ensuring reliable data transfer with sequencing, acknowledgments, flow control, and error handling.

  • Terminating connections using a four-way handshake.

  • Managing connection states and handling errors with mechanisms like resets.

Commands for network management

Managing network connections involves a variety of commands specific to operating system used by admin. Below are some of the most important commands categorized by most popular operating systems like Windows, Linux, and macOS.

Windows Connection Commands

  1. ipconfig Displays network configuration details such as IP address, subnet mask, and default gateway.

    • Common usage:

      ipconfig /all

  2. netsh Configures and manages network interfaces, protocols, and firewall settings.

    • Example:

      netsh interface ip set address "Local Area Connection" static

  3. ping Tests connectivity between devices by sending ICMP Echo Request messages.

    • Example:

      ping google.com

  4. tracert Traces the route packets take to a destination.

    • Example:

      tracert google.com

  5. nslookup Queries DNS to obtain domain name or IP address mapping.

    • Example:

      nslookup google.com

  6. netstat Displays active TCP connections, listening ports, and network statistics.

    • Example:

      netstat -an

  7. route Displays and modifies the IP routing table.

    • Example:

      route print

  8. arp Displays and modifies the ARP (Address Resolution Protocol) cache.

    • Example:

      arp -a

Linux/macOS Connection Commands

  1. ifconfig (Linux/macOS) Configures network interfaces. Note: Deprecated in some Linux distributions in favor of ip

    • Example:

      ifconfig eth0 netmask

  2. ip (Linux) Configures network interfaces, routing, and tunnels.

    • Example:

      ip addr show

  3. ping (Linux/macOS) Tests connectivity between devices.

    • Example:

      ping google.com

  4. traceroute (Linux/macOS) Traces the route packets take to a destination.

    • Example:

      traceroute google.com

  5. dig (Linux/macOS) Queries DNS servers for information about host addresses and other DNS records.

    • Example:

      dig google.com

  6. netstat (Linux/macOS) Displays network connections, routing tables, interface statistics, masquerade, and multicast memberships.

    • Example:

      netstat -tuln

  7. route (Linux) Displays and modifies the IP routing table.

    • Example:

      route -n

  8. ss (Linux) Displays socket statistics and more detailed information than netstat

    • Example:

      ss -tuln

  9. nmcli (Linux) Command-line client for NetworkManager, used to manage network connections.

    • Example:

      nmcli device status

  10. iwconfig (Linux) Configures wireless network interfaces.

    • Example:

      iwconfig wlan0 essid "network_name" key s:password

  11. systemctl (Linux) Manages services, including network services.

    • Example:

      systemctl restart network.service

  12. scutil (macOS) Manages system configuration parameters from the command line.

    • Example:

      scutil --dns

Other names for connection management:

  1. Network communication control

  2. Web/Network session management

  3. Connection handling/control

  4. Session handling

  5. Communication protocol management

  6. Network connectivity

For more informations please visit PubNub connection management technical documentation