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

Overview of vSphere

This post is a summary of VMware’s white paper Introduction to VMware vSphere. ESXi is the hypervisor (virtualization layer) on bare metal servers that abstracts processor, memory, storage and networking resources into multiple virtual machines. It was previously known as ESX and VMware discontinued ESX at version 4.1 so only ESXi is provided at and … Read moreOverview of vSphere

TCPdump and Wireshark configuration

This article explains how to troubleshoot TCP packet from Linux (CentOS) and Windows with TCP dump and wireshark. Both are important tools for troubleshooting. If you are troubleshooting a Windows server and have access to it to install Wireshark then there is nothing to worry about. Even if the server to troubleshoot is a Linux … Read moreTCPdump and Wireshark configuration