Network Access Layer: Introduction Rick Graziani Cabrillo College graziani@cabrillo.edu

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

Network Interface Cards (NICs) connect a device to the network. Section 4.1.1.2 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.

Network Access Layer: Introduction Rick Graziani Cabrillo College graziani@cabrillo.edu

Physical Layer: Introduction Rick Graziani Cabrillo College graziani@cabrillo.edu

Physical Layer Section 4.1.2.1 The OSI physical layer provides the means to transport the bits that make up a data link layer frame across the network media.

Purpose of the Physical Layer Physical Layer Media Section 4.1.2.2 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.

Purpose of the Physical Layer Physical Layer Standards Section 4.1.2.3 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

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 4.1.2.3

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 4.1.3.1

Fundamental Principles of Layer 1 Physical Layer Fundamental Principles Section 4.1.3.1 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.

Physical Layer: Introduction Rick Graziani Cabrillo College graziani@cabrillo.edu

Bandwidth and Throughput Rick Graziani Cabrillo College graziani@cabrillo.edu

Fundamental Principles of Layer 1 Bandwidth Section 4.1.3.2 Bandwidth is the capacity of a medium to carry data. Typically measured in kilobits per second (kb/s) or megabits per second (Mb/s).

Fundamental Principles of Layer 1 Throughput Section 4.1.3.3 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. http://www.speedtest.net/ http://ipv6-test.com/speedtest/

Bandwidth and Throughput Rick Graziani Cabrillo College graziani@cabrillo.edu

Data Link Layer: Introduction Rick Graziani Cabrillo College graziani@cabrillo.edu

The Data Link Layer NIC to NIC communications on the same network. Section 4.1.2.1 NIC to NIC communications on the same network.

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

Layer 2 Addresses

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 4.3.1.2 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.

Data Link Layer: Introduction Rick Graziani Cabrillo College graziani@cabrillo.edu

Data Link Layer: Accessing the Media Rick Graziani Cabrillo College graziani@cabrillo.edu

Topologies Controlling Access to the Media Section 4.4.1.1

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.)

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, 802.11 (wireless), Frame Relay Multipoint

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.

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

Point-to-Point topology 11111111 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.

Data Link Layer: Accessing the Media Rick Graziani Cabrillo College graziani@cabrillo.edu

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

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

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

Data Link Layer: Frame Structures Rick Graziani Cabrillo College graziani@cabrillo.edu

Data Link Layer Layer 2 Frame Structure Section 4.3.2.1

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

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.

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

Ethernet Protocol for LANs Ethernet is a family of networking technologies that are defined in the IEEE 802.2 and 802.3 standards. Uses 48 bit addressing (Ethernet MAC addresses) for Source and Destination More later!

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

Wireless Protocol for LANs 802.11 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)

Data Link Layer: Frame Structures Rick Graziani Cabrillo College graziani@cabrillo.edu