TCP/IP (Transmission Control Protocol/Internet Protocol)

TCP/IP

(Transmission Control Protocol/Internet Protocol)

OSI Seven Layer Model

This will present TCP/IP communications starting from Layer 2 up to Layer 4 (TCP/IP applications cover Layers 5-7)

• IP Addresses
• Data Link Layer
• Network Frames
• Address Resolution Protocol
• Network Layer
  • Internet Protocol
  • IP Routing
  • ICMP Error Reporting
• Transport Layer
  • User Datagram Protocol
  • Transmission Control Protocol
• Session through Application Layers
  • Domain Name System
• Final example tracing DNS transaction through a router

Definitions:-

• Physical network - a collection of computers, communications devices, wiring, etc. that communicate directly with one another (e.g., Ethernet, Token Ring)
• Host - A computer, connected to a physical network, that exchanges information with another computer via TCP/IP
• Gateway - A computer that interconnects two or more physical networks and that routes TCP/IP information among those networks (accurately referred to as a router)

IP Addresses

• Are unique, 32-bit addresses
• correspond to connections, not hosts (generally, move connection ==> change IP address)
• are referenced by humans via dotted decimal (or dotted quad) notation, one number per 8 bits (1 octet or byte), e.g., 128.192.6.7
• consist of three primary classes A, B, and C (class D is for multicast) of the form [Net ID, Host ID]

Class formats:-

Subnet Mask (netmask):-

• 32-bit value
• Generally used to subdivide (subnet) a given IP class network into smaller (sub)networks
• Netmask determines which portion of an IP address is the network address and which is the host address
  • An IP address bit is a network address bit if the corresponding net mask bit is 1
  • An IP address bit is a host address bit if the corresponding netmask bit is 0
• "Natural netmask" has all netid bit locations = 1 and all hostid bit locations = 0 (e.g., 255.0.0.0, 255.255.0.0, and 255.255.255.0 for class A, B, and C networks, respectively)

Net ID and host ID conventions:

• Network addresses have hostid with all bits = 0 (e.g., 128.192.0.0 with netmask=255.255.0.0 and 128.192.6.0 with netmask=255.255.255.0)
• Directed broadcast addresses have host ID with all bits = 1 (e.g., 128.192.255.255 with netmask=255.255.0.0 and 128.192.54.255 with netmask=255.255.255.0)
• "Limited" broadcast has all bits = 1 (e.g. 255.255.255.255)
• Loopback address 127.xxx.yyy.zzz used for internal testing, no traffic generated (typically 127.0.0.1)

IP network ranges by class:

• Class A ==> 1.0.0.0 - 126.0.0.0
• Class B ==> 128.xxx.0.0 - 191.xxx.0.0
• Class C ==> 192.xxx.yyy.0 - 223.xxx.yyy.0
• Class D ==> 224.xxx.yyy.zzz - 239.xxx.yyy.zzz (multicast IP)

Hosts with multiple IP addresses per interface and/or on multiple interfaces are called multi-homed hosts.