This week’s topic is about switch, routers, and firewalls. In a cooperation, there are core routers which are connected to many different servers, while for personal use, there is a home router. After a router, there is a switch, and after that is a firewall, and then the network.

There are different types of storage media:
– ROM: read only memory, contain things that cannot be changed (e.g. OS, factory configuration.
– NVRAM: while RAM is volatile memory that use electrical to store memory in the media, NVRAM is non volatile, data is still stored inside even if there is no electrical.
– DRAM: common memory that is used in computer
– CAM: content addressable memory, used in application that need to be regularly used and fast
– hard disk

Switches is in OSI layer 2, it contain the physical address (MAC address) in hexa code, the code is important, just a few characters in the code can help identify which device are being used in the network, however, people can fake their MAC address. By using ARP, it is possible to convert the MAC address to IP address, it will request the DHCP server to give the IP address, however, in a limited time. By providing the lease time, it will be able to help identify the device used in the attack of a network, (e.g. which devices are being used during the lease time). Switch use CAM to track the countless traffics in the network.

Routers is in OSI layer 3, main difference between routers and switch is router can make routing but switch are not able to. Routing is used to make a connection between different network, while switch is only used in a more internal network.

Firewalls, contain information such as successful/failure of connection attempts, the protocols used in the network, and the application used in the network. There are several capabilities that firewalls have:
– NAT, DHCP, VPN tunneling
– load balancing
– fragmentation reassembly
– stateful filtering, performance monitoring
– HW upgrades