* The TCP/IP protocol suite usually refers not only to the two most well-known

protocols called TCP and IP but also to other related protocols such as UDP, ICMP, HTTP, TELNET and FTP.

* Basic structure of TCP/IP protocol suite is shown in above figure.

* Protocol data unit (PDU) exchanged between peer TCP protocols is called segments.

* Protocol data unit (PDU) exchanged between peer UDP protocols is called datagrams.

* Protocol data unit (PDU) exchanged between peer IP protocols is called packets.

* In the above figure an HTTP GET command is passed to the TCP layer, which

encapsulates the message into a TCP segment.

* The segment header contains an ephemeral port number for the client process and well known port 80 for HTTP server process.

* The TCP segment is passed to IP layer where it is encapsulated in an IP packet.

* The IP packet contains source and destination network address.

* IP packet is then passed through network interface and encapsulated into PDU of underlying network.

* In the network interface, the IP packet is encapsulated into an Ethernet frame, which contains physical addresses that identify the physical endpoints for the Ethernet sender and receiver.

* IP packets transfer information across Internet

* Host A IP → router→ router…→ router→ Host B IP

* IP layer in each router determines next hop (router)

* Network interfaces transfer IP packets across networks

* Internet Names

* Each host has a unique name

o Independent of physical location

o Domain Name will facilitates memorization by humans

* Host Name

o Name given to host computer

* User Name

o Name assigned to user

Internet Addresses

* Each host has globally unique logical 32 bit IP address

* Separate address for each physical connection to a network

* Routing decision is done based on destination IP address

* IP address has two parts:

* netid and hostid

* netid unique

* netid facilitates routing

* Dotted Decimal Notation is used for representation:

Ex: - int1.int2.int3.int4

128.100.10.13

DNS(Domain Name Service) resolves IP name to IP address

Physical Addresses

* LANs (and other networks) assign physical addresses to the physical attachment to the network

* The network uses its own address to transfer packets or frames to the appropriate

destination

* IP address needs to be resolved to physical address at each IP network interface

* Example: Ethernet uses 48-bit addresses

o Each Ethernet network interface card (NIC) has globally unique Medium Access Control (MAC) or physical address

o First 24 bits identify NIC manufacturer; second 24 bits are serial number

o 00:90:27:96:68:07 12 hex numbers