OS purposes Abstract the hardware Both for convenient and portability Multiplex Of applications Isolation Between applications Sha...

What is multicast Imagine this scenario: An example of network topology for multicast Now A wants to send same packets to address group containing B, C, E, and X. It can simply send packets ove...

Routers RIP enable conf t[erminal] router rip [version 2] net[work] <ip-address-1> # Declare connected network net[work] <ip-address-2> net[work] ...

What happened My systemd service clash won’t start on boot, which is under user mode. What I’ve done: In [Unit], Change After=network.target to After=default.target. This is because that...

End-to-end routing Approaches Flooding. As its name, packets go anywhere (it may form loops). Sourcing routing. Source router put the full path (from source to destination) in packets. For...

Introduction Network address translation (NAT) is a gate between local network and the Internet. It translates/rewrites internal IP address to external IP address When packet is sent from interna...

User Datagram Protocol (UDP) Checksum includes pseudo header Transport Control Protocol (TCP) Automatic Repeat reQuest (ARQ) There are three ARQ protocols as follows: Stop and Wait prot...

Data switching There are three data switching methods: Circuit switching: 建立连接，独占资源，类似管道。 Message switching: 一次性发送整个报文到相邻节点。 Packet switching: 把报文分割为多个组，分别发送到相邻节点。 Delays in Computer Net...

DNS (Domain Name System) DNS uses port 53 to communicate, and can be implemented by both TCP and UDP. (Usaully UDP) Except when: Secondary name server syncs with primary servers, T...

Introduction There are many kinds of networks, like private, public, reserved, and loopback. Address space IPv4 Private networks include the following addresses: 10.0.0.0/8 172.16.0.0/12 ...