1	Interconnecting Cisco Networking Devices Module 1 The OSI Model
2	Overview The “Big Picture” Why?! Encapsulation OSI vs. TCP/IP How to Remember It The 7 Layers How Cisco Refers to the Layers Where Physical Devices Reside Physical Cabling
3	The “Big Picture”
4	Why?! Allows developers to focus on a particular function Single point of reference One layer does not affect the other Platform independent
5	OSI Reference Model
6	Encapsulation
7	OSI vs. TCP/IP
8	How to Remember It Phew!! Dead Ninja Turtles Smell Pretty Awful!!! All People Seem To Need Data Processing Please Do Not Throw Sausage Pizzas Away
9	The 7 Layers Physical Data Link Network Transport Session Presentation Application
10	Layer 1: Physical 1s and 0s Defines voltage, wire speed and cable pin outs Moves bits between devices Examples: V.35, Ethernet, 802.11b
11	Layer 2: Data Link Combination of bits into bytes and bytes into frames MAC addresses Error detection and recovery Examples: HDLC, Frame Relay, ATM
12	Layer 3: Network Logical Addressing, which routers use for path determination Examples: IP, IPX, Appletalk
13	Layer 4: Transport Reliable or unreliable delivery Multiplexing Examples: TCP, UDP, SPX
14	Layer 5: Session Establishing and maintaining end-to-end bi-directional flows between end points Examples: RPC, SQL, NetBIOS names
15	Layer 6: Presentation How data is presented Special Processing, such as encryption Examples: JPEG, ASCII, GIF, MP3
16	Layer 7: Application Interface between network and application software Examples: Telnet, HTTP, FTP, WWW Browsers, SNMP
17	How Cisco Refers to the Layers Transport: Segment Network: Datagram Data Link: Frame Physical: Bit
18	Where Physical Devices Reside (L3) Network: IP Addresses -> Routers (L2) Data Link: MAC Addresses -> Switches (L1) Physical: bits -> Hubs
19	Ethernet Cables Straight Through Cable (Host to Switch) Pin 1 goes to Pin 1 Pin 2 goes to Pin 2 Cross Over Cable (Switch to Switch) Pin 1 goes to Pin 3 Pin 2 goes to Pin 6 Pin 3 goes to Pin 1 Pin 6 goes to Pin 2 Rolled Cable (Host to Router) Pin 1 goes to pin 8 Pin 2 goes to Pin 7 Pin 3 goes to Pin 6
20	Summary The “Big Picture” Why?! Encapsulation OSI vs. TCP/IP How to Remember It The 7 Layers How Cisco Refers to the Layers Where Physical Devices Reside Physical Cabling