The OSI Model: Understanding the Layers and Protocols, Exams of Wireless Networking

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What does OSI stand for? ✔✔Open Systems Interconnect 7 Layers (Top to bottom) of the OSI Model ✔✔Application Presentation Session Transport Network Data Link Physical Layer of the OSI model that enables services to request network services. This layer uses protocols like HTTP, FTP, SMTP, IMAP and others. Proxies and firewalls also work on this layer. ✔✔Application Layer

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Layer of the OSI model that translates data into an intermediate form that both clients and servers can process. Encryption, compression, character sets, multimedia formats and more exist at this layer. Proxies and firewalls also work on this layer. ✔✔Presentation Layer Layer of the OSI model that establishes and controls data communication between two different devices. Regulates when each device can send and how much it can send at once. TCP and UDP port numbers exist at this layer. Firewalls also work on this layer. ✔✔Session Layer Layer of the OSI model that performs the actual establishment, maintenance, and tear-down of the connection. Can divide long communications into smaller segments, including error recognition and correction, and data receipt acknowledgments. TCP and UDP protocols work at this layer. Packet filtering routers, multi-layer switches, and firewalls work at this layer. ✔✔Transport Layer Layer of the OSI model that adds logical addressing and chooses the best route. IP, ICMP, IGMP exist at this layer. Routers, multi-layer switches, and firewalls work at this layer. ✔✔Network Layer

Layer of the OSI model that structures the data into a format appropriate for transmission. Adds physical address (MAC Addresses) or DLCI numbers. Has simple error checking. All WAN and LAN protocols exist at this layer including Ethernet, token ring, frame relay, Point-to-point protocol, and others. Switches and bridges work at this level. ✔✔Data Link Layer Layer of the OSI model that transmits bits from one device to another and regulates the transmission stream over a medium. Includes cabling, connectors, antennas, transceivers, baseband, broadband, signaling types, voltages, waveforms, modulation, frequencies, and clock rates. Network Interface Cards, hubs, and repeaters work at this layer. ✔✔Physical Layer The process of adding delivery information to the actual data transmitted on each layer. Takes place in the transmission end as data is passed down the layers. ✔✔Data Encapsulation HTTP, FTP, SMTP, IMAP... ✔✔Application Layer (protocols)

Encryption, compression, character sets, multimedia formats, MIME types, codecs... ✔✔Presentation Layer (protocols) TCP and UDP port numbers ✔✔Session Layer (protocols) TCP and UPD protocols ✔✔Transport Layer (protocols) IP, ICMP, IGMP ✔✔Network Layer (protocols) MAC Addresses, Ethernet, token ring, frame relay, PPP, HDLC, wireless access protocol, ATM, X.25... ✔✔Data Link Layer (protocols) Cabling, connectors, antennas, transceivers, baseband, broadband, signaling types... ✔✔Physical Layer (protocols) Proxies, firewalls ✔✔Application Layer (devices) Proxies, firewalls ✔✔Presentation Layer (devices)

Firewalls ✔✔Session Layer (devices) Firewalls ✔✔Transport Layer (devices) Multi-layer switches, routers, firewalls ✔✔Network Layer (devices) Switches, bridges, and access points ✔✔Data Link Layer (devices) Hubs, repeaters, patch panels, cables, and network cards. ✔✔Physical Layer (devices)