Free tools for application high availability

High availability can be implemented through server clustering and load balancing. Clustering can be supported by corosync and pacemaker. On the load balancing side, there are dedicated hardware such as F5 which is expensive. Alternatively, there are three common ways to achieve load balancing with application, Linux Virtual Server (LVS), Nginx and HA Proxy. LVS … Read moreFree tools for application high availability

Networking Basics 3 of 3 – common network protocols and technologies

The 5 layer TCP/IP model (or its more rigorously defined alternative OSI model) leads to a whole world of network protocols. Understanding these new protocols requires one to map it out agains the network layers (e.g. at Layer 4 whether it is TCP or UDP, etc) . VPN is a whole family of technologies with … Read moreNetworking Basics 3 of 3 – common network protocols and technologies

Networking basics 2 of 3 – Layer 4 and common network configurations

Transport Layer Transport Layer handles multiplexing & de-multiplexing through ports. Port is more or less a virtual concept. Source port is usually ephemeral. Two dominant protocols are TCP and UDP. TCP relies on acknowledgement. TCP control flags are SYN, ACK, FIN, URG, PSH, RST, ECE, CWR. TCP connection is established by 3-way handshake and torn … Read moreNetworking basics 2 of 3 – Layer 4 and common network configurations

Networking Basics 1 of 3 – Layer 1 through Layer 3

What layer model works the best? Back in university my textbook was based on OSI 7-layer model. It is rigorously defined and often used in academics. When it comes to day-to-day operation, the 5-layer TCP/IP model is more useful. It combines Application, Presentation and Session layers in OSI model into a single Application layer. Physical … Read moreNetworking Basics 1 of 3 – Layer 1 through Layer 3