Chapter 2. Protocol Architecture, TCP/IP, and Internet-Based Applications

What is the Protocol?

• Network protocols are formal standards and policies compriesed of rules, procedures and formats that define communication between two or more devices over a network
• Network protocols govern the end-to-end processes of timely, secure and managed data or network communication.

What is Protocol Architecture?

This is a layered structure of hardware and software which supports the exchange of data between systems.

The key features of a protocol are:

• Syntax : Format of data blocks
• Semantics : Control information for coordination and error handling
• Timing : Speed matching and sequencing

Functions of Protocol Architecture

: OSI (Open System Interconnection) 7 Layers

1. Application layer: message format, human-machine interfaces
2. Presentation layer: encryption, compression
3. Session layer: authentication, permissions, session restoration
4. Transport layer: end-to-end error control
5. Network layer: network addressing, routing or switching
6. Data-link layer: error detection, flow control on physical link
7. Physical layer: physical medium

* All People Seem To Need Data Processing

* Please Do Not Tell Secret Passwords Anytime

1. Physical Layer

• Bit representation: Encode bits into electrical or optical signals
• Transmission rate: The number of bits sent each second
• Physical characteristics of transmission media
• Synchronizing the sender and receiver clocks
• Transmission mode: Simple, half-duplex, full-duplex
• Physical topology: How devices are connected (E.g., ring, star, mesh, bus)

2. Data Link Layer

• Framing: Divides the stream of bits received from network layer into manageable data units called frames
• Physical Addressing: Add a header to the frame to define the physical address of the source and the destination machines
• Flow Control: Control rate at which data is transmitted
• Error Control: Adds mechanisms to detect and re-transmit damaged or lost frame. This is achieved by adding  trailer to the end of a frame

3. Network Layer

• Routing
• Provide mechanisms to transmit data over networks that are linked together
• Add the header which includes addressing information

4. Transport Layer

• Segmentation and reassembly
• Divide message into smaller segments, number them and transmit
• Reassemble these messages at the receiving end
• Error control
• Adding header which includes error checking information
• Make sure that the entire message arrives without errors (else retransmit)

5. Session Layer

• Session control
• The session layer provides the mechanism for opening, closing and managing a session between end-user application processes
• It means that this layer creates and destroys the sessions (e.g., TCP/IP session)
• Synchronization
• It provides synchronization points in the stream of exchanged messages
• It allow information of different streams to be properly combined or synchronized
• It adds checkpoints (synchronization points) into stream of data
• Session checkpointing and recovery

6. Presentation Layer

• Translation
• Different computers use different encoding system (bit order translation)
• Convert data into a common format before transmitting
• Compression
• Reduce number of bits to be transmitted
• Encryption
• Transform data into an unintelligible format at the sending end for data security
• Decryption
• At the receiving end

7. Application Layer

Responsible for this layer are:

• Contains protocols that allow the user to access the network.
• Does not include application programs such as email, browsers, etc
• Protocols contain utilities and network-based services that support email via SMTP, Internet access via HTTP, file transfer via FTP, etc

The OSI 7 Layers and protocols

Layer	Name	Protocols
7	Application Layer	HTTP, FTP, SSH
6	Presentation Layer	SSL, TLS
5	Session Layer	NetBIOS, PPTP, SOCKETS
4	Transport Layer	TCP, UDP
3	Network Layer	IP, ARP, ICMP, IGMP
2	Data Link Layer	PPP, Ethernet
1	Physical Layer	Coax, Fiber, Wireless, Bluetooth

TCP/IP Layers

TCP/IP model is also a layered model but it is a four-layer model.

1. Application Layer: HTTP, FTP, Telnet ( Combined 5, 6, and 7 layers in the OSI model )
2. Transport Layer: TCP, UDP
3. Internet Layer: IPv4, IPv6
4. Network Access Layer: Ethernet ( Encompasses the data link and physical layers of the OSI model )

Transmission Control Protocol (TCP)

• TCP is the transport layer protocol for most applications
• TCP provides a reliable connection for transfer of data between applications
• A TCP segment is the basic protocol unit
• TCP tracks segments between entities for duration of each connection in order to regulate the flow of segments and to recover from lost or damaged segments

3-way Handshaking in TCP

• The TCP three-way handshake is the method used by TCP set up.
• TCP's three way handshaking technique is often referred to as "SYN-SYN-ACK" (or more accurately SYN, SYN-ACK, ACK) because there are three messages transmitted by TCP to start a TCP session between two computers

* SYN: SYNchronize

* ACK: ACKnowledge

User Datagram Protocol (UDP)

• UDP is a simple message-oriented transport layer protocol
• UDP provides no guarantees to the upper layer protocol for message delivery
• UDP layer retains no state of UDP messages once sent
• It does not guarantee delivery, preservation of sequence, or protection against duplication
• It enables a procedure to send mesages to other procedures with a minimum of protocol mechanism
• It includes a checksum to verify that no error occurs in the data alternative to TCP

TCP vs. UDP

Item	TCP	UDP
Stands For	Transmission Control Protocol	User Datagram Protocol
Protocol	Connection Oriented	Connectionless
Security	Makes Checks For Errors And Reporting	Makes Error Checking But No Reporting
Data Sending	Slower	Faster
Header Size	20 Bytes	8 Bytes
Segments	Acknowledgement	No Acknowledgement
Typical Applications	Email	VoIP

Traditional Internet-Based Applications

• Simple Mail Transfer Protocol (SMTP)
• Provides a mechanism for transferring messages among separate hosts
• File Transfer Protocol (FTP)
• Used to send files from one system to another under user command
• Both text and binary files are accommodated
• Secure Shell (SSH)
• Provides a secure remote logon capability

Multimedia Terminology

• Media
• Refers to the form of information and includes text, still images, audio, and video
• Multimedia
• Human-computer interaction involving text, graphics, voice and video
• Streaming media (e.g., Youtube)
• Refers to multimedia files, such as video clips and audio
• It begins playing immediately or within seconds after it is received by a computer from the Internet or Web.
• Thus, the media content is consumed as it is delivered from the server rather than waiting until an entire file is downloaded

Multimedia Technologies

• Compression
• Communications / networking
• Protocols
• RTP (Real-Time Transport Protocol)
• SIP (Session Initiation Protocol)
• Quality of service (QoS)
• Can deal with priority, delay, constraints, delay, variability, constraint, and other similar requirements