The document discusses the TCP/IP protocol suite, which is composed of four layers: physical/data link layer, network layer, transport layer, and application layer. The network layer uses IP and four supporting protocols to enable internetworking. The transport layer uses UDP for non-reliable delivery and TCP for reliable, connection-oriented delivery. TCP/IP addressing includes physical, IP, port, and special purpose addresses.

1. Lecture#04
Computer Communications
& Networks CS-576

2. TCP/IP Protocol Suite
 Transmission Control Protocol/internetworking Protocol
 Developed Prior to OSI Model
 Widely used in the Internet Today
 Layers in TCP/IP Protocol Suite
i. Physical and Data Link Layer
ii. Network Layer
iii. Transport Layer
iv. Application Layer

3. TCP/IP Protocol Suite

4. Physical and Data Link Layer
 TCP/IP does not define any specific protocol.
 It supports all the standard and proprietary
protocols
 Network can be LAN or WAN

5. Network Layer
 TCP/IP support the internetworking Protocol.
 IP uses 4 supporting protocols: ARP, RARP, ICMP and IGMP.
 ARP(Address Resolution Protocol).
 Used to find physical address of the node when its internet address is known.
 RARP(Reverse Address Resolution Protocol).
 It allows host to discover its internet address when its physical address is known.
 ICMP (Internet Control Message Protocol).
 Used by host and gateways to send notification of error to sender. It sends query and
error reporting message .
 IGMP (Internet Group Message Protocol).
 It facilitates group messages to no. of recipients.

6. Transport Layer
 TCP/IP in transport layer works through 2 protocols:
UDP, TCP
 UDP (User Datagram Protocol)
 Process-to-process protocol
 It adds port address, checksum error control and length information to the
data.
 TCP (Transmission Control Protocol)
 TCP is reliable and connection oriented protocol.
 It divides data packets into smaller data segments, include sequence number,
collects frames and record transmission.

7. SCTP(Stream Control Transmission Protocol)
 It is combination of best features of UDP and TCP.
 It supports for newer applications such as Voice Over The
Internet.

8. Application Layer
 It is equivalent to combined session, presentation
and application layer of OSI model.
 Several protocol are defined in this layer.

9. Addressing
 There are four levels of addressing:
i. Physical Addresses (Link): address length vary depending on the
network
ii. Logical Addresses (IP): 32-bit address
iii. Port Address (port): 16-bit address
iv. Specific Addresses (Special purpose): emails & URLs

10. Relationship of layers & Addresses