Network 01

MAC

• Media access control (MAC) addresses are identifiers uniquely assigned to network interfaces.
• first 3 octets refer to the Organizationally Unique Identifier (OUI) which can help identify manufacturers

IP

• IP addresses are means of identifying devices connected to a network under Internet Protocol.
• In IPv4 we can partition a block of addresses into a subnet.
• The number that comes after the slash (/) is the subnet mask.
• This represents how many bits are in the network address, the remaining bits identify a host within the network.

ARP

• Address Resolution Protocol (ARP) is a protocol used to resolve IP addresses to MAC addresses.
• unicast: unicasting a frame means to send that frame to exactly one MAC address.
• broadcast: broadcasting a frame by sending it to the broadcast address means the frame should be sent to every device on the network.

DNS

• DNS is a system that maps a domain name like google.com to its IPs.
• DNS Records
  • A records name = hostname, value = IP address
  • NS records name = domain, value = name of dns server for domain
  • CNAME records name = alias, value = canonical name
  • MX records The record used by mail service.

TCP

• Transmission Control Protocol (TCP)
• TCP is a stateful stream oriented protocol that ensures reliable transport.
• Guarantees that information arrives wholly intact and in order at the destination.
• TCP is a connection oriented protocol which means it must first establish a connection before sending any data.
• A TCP connection begins with something known as the TCP handshake.
• The TCP handshake consists of setting certain flags in the TCP header of packets exchanged between sender and receiver.
  • Client, SYN, a packet with the SYN flag set.
  • Server, SYN-ACK, a packet with both the SYN and ACK flags set
  • Client, ACK
• TCP then begins transmitting data and if it successfully arrives on the other end of the connection then an ACK is issued.
• TCP also has a procedure to close connections. For a graceful termination:
  • Clinet, FIN
  • Server, respond by sending a FIN and an ACK
    • If Server only sends a ACK the connection persist and additional data can be sent until an FIN is sent.
  • Once Client has received a FIN and an ACK it sends one last ACK to signal the connection termination.

UDP

• User Datagram Protocol (UDP)
• UDP is stateless connectionless protocol.
• UDP focuses on sending messages in datagrams.
• Being connectionless UDP also doesn’t incur the overhead of the TCP handshake and termination.