1. Network Access Layer: Introduction
Rick Graziani
Cabrillo College

2. Interacts with the network application software
Transforms data into a recognizable format for the application layer
Data/Stream
Controls the dialogues (connections) between devices
Responsible for any reliability, flow control and error control
Segment
Responsible for message being sent from original sender to final destination
Packet
Responsible NIC-to-NIC communications on the same network
Frame
Responsible transmitting the bits over the physical medium (wired or wireless)
Bits
Note
These layers and protocols, and the relationship between them will become more evident as you learn about each of the layers and its protocols

3. Network Interface Cards (NICs) connect a device to the network.
Section
Network Interface Cards (NICs) connect a device to the network.
Ethernet NICs are used for a wired connection whereas WLAN (Wireless Local Area Network) NICs are used for wireless.

4. Network Access Layer: Introduction
Rick Graziani
Cabrillo College

5. Physical Layer: Introduction
Rick Graziani
Cabrillo College

6. Physical Layer
Section
The OSI physical layer provides the means to transport the bits that make up a data link layer frame across the network media.

7. Purpose of the Physical Layer Physical Layer Media
Section
The physical layer produces the representation and groupings of bits for each type of media as:
Copper cable: The signals are patterns of electrical pulses.
Fiber-optic cable: The signals are patterns of light.
Wireless: The signals are patterns of microwave transmissions.

8. Purpose of the Physical Layer Physical Layer Standards
Section
Upper OSI layers are performed in software designed by software engineers and computer scientists.
TCP/IP suite are defined by the Internet Engineering Task Force (IETF) in RFCs

9. Purpose of the Physical Layer Physical Layer Standards
Standard organization
Networking Standards
ISO
ISO 8877: Officially adopted the RJ connectors (e.g., RJ-11, RJ-45)
ISO 11801: Network cabling standard similar to EIA/TIA 568.
EIA/TIA
TIA-568-C: Telecommunications cabling standards, used by nearly all voice, video and data networks.
TIA-569-B: Commercial Building Standards for Telecommunications Pathways and Spaces
TIA-598-C: Fiber optic color coding
TIA-942: Telecommunications Infrastructure Standard for Data Centers
ANSI
568-C: RJ-45 pinouts. Co-developed with EIA/TIA
ITU-T
G.992: ADSL
IEEE
802.3: Ethernet
802.11: Wireless LAN (WLAN) & Mesh (Wi-Fi certification)
802.15: Bluetooth
Section

10. Fundamental Principles of Layer 1 Physical Layer Fundamental Principles
Media
Physical Components
Frame Encoding Technique
Signalling Method
Copper cable
UTP
Coaxial
Connectors
NICs
Ports
Interfaces
Manchester Encoding
Non-Return to Zero (NRZ) techniques
4B/5B codes are used with Multi-Level Transition Level 3 (MLT-3) signaling
8B/10B
PAM5
Changes in the electromagnetic field
Intensity of the electromagnetic field
Phase of the electromagnetic wave
Fiber Optic cable
Single-mode Fiber
Multimode Fiber
Lasers and LEDs
Photoreceptors
Pulses of light
Wavelength multiplexing using different colors
A pulse equals 1.
No pulse is 0.
Wireless media
Access Points
Radio
Antennae
DSSS (direct-sequence spread-spectrum)
OFDM (orthogonal frequency division multiplexing)
Radio waves
Section

11. Fundamental Principles of Layer 1 Physical Layer Fundamental Principles
Section
Encoding or line encoding - Method of converting a stream of data bits into a predefined "codes”.
Signaling - The physical layer must generate the electrical, optical, or wireless signals that represent the "1" and "0" on the media.

12. Physical Layer: Introduction
Rick Graziani
Cabrillo College

13. Bandwidth and Throughput
Rick Graziani
Cabrillo College

14. Fundamental Principles of Layer 1 Bandwidth
Section
Bandwidth is the capacity of a medium to carry data.
Typically measured in kilobits per second (kb/s) or megabits per second (Mb/s).

15. Fundamental Principles of Layer 1 Throughput
Section
Throughput is the measure of the actual transfer of bits across the media over a given period of time limited by latency, delay and other factors.
Due to a number of factors, throughput usually does not match the specified bandwidth in physical layer implementations.

16. Bandwidth and Throughput
Rick Graziani
Cabrillo College

17. Data Link Layer: Introduction
Rick Graziani
Cabrillo College

18. The Data Link Layer NIC to NIC communications on the same network.
Section
NIC to NIC communications on the same network.

19. Reminder of encapsulation/decapsulation
Data Link Header
IP Header
TCP Header
HTTP Header
Data Link Trailer
Data
Data Link Header
Data Link Header
Data Link Trailer
Data Link Trailer
IP Packet
IP Packet
Data Link Header
Data Link Header
Data Link Trailer
Data Link Trailer
IP Packet
IP Packet
Data Link Header
Data Link Header
Data Link Trailer
Data Link Trailer
IP Packet
IP Packet
Data Link Header
IP Header
TCP Header
HTTP Header
Data Link Trailer
Data

20. Layer 2 Addresses

21. Purpose of the Data Link Layer Data Link Sublayers
Network
Data Link
LLC Sublayer
MAC Sublayer
Physical
Ethernet
802.3
802.11
Wi-Fi
Bluetooth
802.15
Section
Data Link layer has two sublayers (sometimes):
Logical Link Control (LLC) – Software processes that provide services to the Network layer protocols (IPv4, IPv6).
Media Access Control (MAC) - Media access processes performed by the hardware.
Provides Data Link layer addressing and framing of the data according to the protocol in use.

22. Data Link Layer: Introduction
Rick Graziani
Cabrillo College

23. Data Link Layer: Accessing the Media
Rick Graziani
Cabrillo College

24. Topologies Controlling Access to the Media
Section

25. Media Access Control
Media Access Control - Regulates the placement of data frames onto the media.
The method of media access control used depends on:
Media sharing
Do more than two nodes share the media?
If so, how? (Switches, hubs, etc.)

26. Point-to-Point vs multi-access
Point-to-Point networks
Only two nodes
Protocols: PPP, HDLC, Frame Relay
Multi-access networks (LANs)
Multiple nodes
Subnets mask range depends upon the number of hosts (nodes)
Protocols: Ethernet, (wireless), Frame Relay Multipoint

27. Multi-access Topology
A logical multi-access topology - Enables a number of nodes to communicate by using the same shared media.
Ethernet LANs – Connected by Ethernet switches (legacy hubs)
“Every node “may” see all the frames that are on the medium.
Data Link Destination Address denote which device the frame is for.

28. Multi-access Addressing
2222
4444
6666
3333
5555
6666
2222
Multi-access networks require an address to specifically identify the destination.
Much more when we discuss Ethernet

29. Point-to-Point topology
A point-to-point topology connects two nodes directly together.
The media access control protocol can be very simple.
Frames from one devices are for the device at the other end.
Point-to-point topologies, with just two interconnected nodes, do not require special addressing.

30. Data Link Layer: Accessing the Media
Rick Graziani
Cabrillo College

31. Rick Graziani Cabrillo College graziani@cabrillo.edu
Full and Half Duplex
Rick Graziani
Cabrillo College

32. Duplex Transmissions Simplex Transmission: One way and one way only.
Half-duplex Transmission: Either way, but only one way at a time.
Ethernet hubs use half-duplex
Full-duplex Transmission: Both ways at the same time.
Ethernet NICs and switches use full-duplex by default
Most serial links are full-duplex
More later with Ethernet

33. Rick Graziani Cabrillo College graziani@cabrillo.edu
Full and Half Duplex
Rick Graziani
Cabrillo College

34. Data Link Layer: Frame Structures
Rick Graziani
Cabrillo College

35. Data Link Layer Layer 2 Frame Structure
Section

36. Data Link Frame Fields Data Link frame header fields may include:
Start Frame field - Indicates the beginning of the frame
Source and Destination address fields - Indicates the source and destination nodes on the media
Priority/Quality of Service field - Indicates a particular type of communication service for processing
Type field - Indicates the upper layer service contained in the frame
Logical connection control field - Used to establish a logical connection between nodes
Physical link control field - Used to establish the media link
Flow control field - Used to start and stop traffic over the media
Congestion control field - Indicates congestion in the media

37. Framing- The Trailer The signals on the media could be subject to:
Interference
Distortion
Loss
This would change the bit values that those signals represent.
The trailer is used to determine if the frame arrived without error.
Error detection.
The Frame Check Sequence (FCS) field is used to determine if errors occurred in the transmission and reception of the frame.

38. Cyclic Redundancy Check
Cyclic redundancy check (CRC) is commonly used.
Sending node includes a logical summary of the bits in the frame.
Receiving node calculates its own logical summary, or CRC.
Compares the two CRC values.
Equal – Accepts the frame
Different – Discards the frame

39. Ethernet Protocol for LANs
Ethernet is a family of networking technologies that are defined in the IEEE and standards.
Uses 48 bit addressing (Ethernet MAC addresses) for Source and Destination
More later!

40. Point-to-Point Protocol for WANs
Point-to-Point Protocol (PPP) is a protocol used to deliver frames between two nodes.

41. Wireless Protocol for LANs
is an extension of the IEEE 802 standards.
It uses the same 48-bit addressing scheme as other 802 LANs.
Contention-based system using a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)

42. Data Link Layer: Frame Structures
Rick Graziani
Cabrillo College