Suleyman Demirel University 2012 EXPLORATION 1 Chapter 7

Suleyman Demirel University, 2012 EXPLORATION 1, Chapter 7 OSI Data Link Zhamanov Azamat

Suleyman Demirel University, 2012 Upon completion of this chapter, you will be able to: • Explain the role of Data Link layer protocols in data transmission. • Describe how the Data Link layer prepares data for transmission on network media. • Describe the different types of media access control methods. • Identify several common logical network topologies and describe how the logical topology determines the media access control method for that network.

Suleyman Demirel University, 2012 Upon completion of this chapter, you will be able to: • Explain the purpose of encapsulating packets into frames to facilitate media access. • Describe the Layer 2 frame structure and identify generic fields. • Explain the role of key frame header and trailer fields, including addressing, Qo. S, type of protocol, and Frame Check Sequence.

Suleyman Demirel University, 2012 Data Link Layer

Suleyman Demirel University, 2012 Data Link Layer performs two basic services: Data Link Services Allows the upper layers to access the media using techniques such as framing Controls how data is placed onto the media and is received from the media using techniques such as media access control and error detection

Suleyman Demirel University, 2012 Different Frames

Suleyman Demirel University, 2012 Data Link – Creating a Frame Unique Combinations of bits For Start of Frame and End of Frame

Suleyman Demirel University, 2012 Connecting Upper Layer Services to the Media

Suleyman Demirel University, 2012 Data Link Sublayers Logical Link Control (LLC) Media Access Control (MAC)

Suleyman Demirel University, 2012 Logical Link Control • Logical Link Control (LLC) places information in the frame that identifies which Network layer protocol is being used for the frame. This information allows multiple Layer 3 protocols, such as IP and IPX, to utilize the same network interface and media.

Suleyman Demirel University, 2012 Media Access Control • Media Access Control (MAC) provides Data Link layer addressing and delimiting of data according to the physical signaling requirements of the medium and the type of Data Link layer protocol in use.

Suleyman Demirel University, 2012 Data Link Layer • Prepares network data for the physical network • Provides a means for exchanging data over a common local media • The Data Link is responsible for controlling the transfer of frames across the media

Suleyman Demirel University, 2012 Data Link Sublayers

Suleyman Demirel University, 2012 DATA LINK LAYER - STANDARDS

Suleyman Demirel University, 2012 Data Link Standards International Organization for Standardization (ISO) Institute of Electrical and Electronics Engineers (IEEE) American National Standards Institute (ANSI) International Telecommunication Union (ITU)

Suleyman Demirel University, 2012 PLACING DATA ON THE MEDIA

Suleyman Demirel University, 2012 Media Access Control • No Control • Control Based

Suleyman Demirel University, 2012 No Control

Suleyman Demirel University, 2012 With Control Mechanism

Suleyman Demirel University, 2012 Two basic media access control methods Media Access Control Methods Controlled Contention. Based

Suleyman Demirel University, 2012 Controlled • When using the controlled access method, network devices take turns, in sequence, to access the medium. • This method is also known as scheduled access or deterministic.

Suleyman Demirel University, 2012 Controlled

Suleyman Demirel University, 2012 Contention - Based • Also referred to as non-deterministic, contention-based methods allow any device to try to access the medium whenever it has data to send.

Suleyman Demirel University, 2012 Contention - Based

Suleyman Demirel University, 2012 Question • Duplex?

Suleyman Demirel University, 2012 Answer • Duplex commonly means double or twofold. • Example: Duplex Printing, double-sided printing

Suleyman Demirel University, 2012 Duplex in Computer Network Duplex Types Full Duplex Half Duplex

Suleyman Demirel University, 2012 Full Duplex

Suleyman Demirel University, 2012 Half Duplex

Suleyman Demirel University, 2012 LOGICAL TOPOLOGY VS PHYSICAL TOPOLOGY

Suleyman Demirel University, 2012 Logical Topology • This arrangement consists of virtual connections between the nodes of a network independent of their physical layout.

Suleyman Demirel University, 2012 Logical Topologies

Suleyman Demirel University, 2012 Physical Topology • The physical topology is an arrangement of the nodes and the physical connections between them. • The representation of how the media is used to interconnect the devices is the physical topology. These will be covered in later chapters of this course.

Suleyman Demirel University, 2012 Logical PPP Topology

Suleyman Demirel University, 2012 Physical PPP Topology

Suleyman Demirel University, 2012 Multi-Access Topology

Suleyman Demirel University, 2012 Ring Topology

Suleyman Demirel University, 2012 FRAMING

Suleyman Demirel University, 2012 Role of the Header

Suleyman Demirel University, 2012 Frame Trailer

Suleyman Demirel University, 2012 Data Link Layer Protocols – The Frame

Suleyman Demirel University, 2012 Frame Structure

Suleyman Demirel University, 2012 FOLLOW DATA THROUGH AN INTERNET

Suleyman Demirel University, 2012 Follow Data Through an Internet

Suleyman Demirel University, 2012 MAC Address • Is divide into two parts • OUI , Organizationally Unique Identifier, 24 bits • Rest 24 bits are belong to identify device in the organization • Stored in ROM (Read Only Memory) • MAC Address consist of 48 bits, it is 2^48 or 281 474 976 710 656 addresses. • By evaluation of IEEE this range is enough till 2100 year. • Example • 01: 23: 45: 67: 89: ab

Suleyman Demirel University, 2012 Q/A