Virtualization 4 of 4 – Networking

Virtual LAN (VLAN) Although VLAN emerged before virtualization and is not part of virtualization topic. I’d just like to start from here as a refresher. Suppose we have computers from finance department and computers from sales department all connected to a single layer-2 switch. There are at least three problems: 1) too many devices on … Read moreVirtualization 4 of 4 – Networking

Docker network

Reading notes of “Docker DeepDive” Docker networking is backed by libnetwork, which is an implementation of Container Network Model (CNM), an open-source pluggable architecture designed to provide networking to containers. Libnetwork also provides native service discovery and basic container load balancing solution. Docker networking also involves some drivers that extend the CNM model with specific … Read moreDocker network

Capture filter and Display filter in Network Analyzer

Capture filter is set before collecting packets. It is applied at the time of data acquisition and it impacts the size of the capture. It does not have as many variations as display filter and is usually not aware of protocols above TCP/UDP layer. A common form of capture filter is BPF (Berkerly Packet Filter) … Read moreCapture filter and Display filter in Network Analyzer

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

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