Networking Basics CCNA 1 Chapter 2

Networking Basics and Terminology A Brief History of the Networking Universe Earliest commercial computers were large mainframes, run by computer scientists Terminals were invented, allowing users to interact with the computers Eventually (1960s), some terminals were located to allow remote access

Networking Basics and Terminology A Brief History of the Networking Universe By late 1960s minicomputers entered marketplace “Mini’s” were smaller, less powerful and less expensive than mainframes Mid 1970s – First personal computers (PCs) built by researchers

Networking Basics and Terminology A Brief History of the Networking Universe 1977 – Apple introduces the Apple-II 1981 – IBM introduces its first PC Mid 1980s – Computer users with standalone computers start sharing data through the use of modems connecting to another computer (dialup, point-to-point)

Networking Basics and Terminology The Need for Networking Protocols and Standards 1960s to 1980s – Each vendor set its own proprietary protocols and standards Equipment from different vendors would not interoperate Eventually, open standards were agreed upon Open standards allow more competition, which increases speed of development

Networking Basics and Terminology Popular Network Standards Organizations

Networking Basics and Terminology Ethernet LANs and LAN Devices Ethernet LANs originally used coaxial cable (similar to Cable TV cable) Network Interface Cards (NICs) would attach to a length of cable called a segment

Networking Basics and Terminology Ethernet LANs and LAN Devices In early Ethernet LANs, all devices sent their data on one wire All other devices on the segment received the signal These types of Ethernet are said to be “broadcast” media, because any signal sent by one device is received by all other devices

Networking Basics and Terminology Characteristics of Early Ethernet LANs Limited to a relatively small geographic area Allows multiple devices access to high-speed media Administrative control rests within a single company Provides full-time connectivity Typically connects devices that are close together

Networking Basics and Terminology Cisco Networking Device Icons

Networking Basics and Terminology Ethernet Repeaters When a signal is sent over a wire, it degrades 10BASE5 limited a single segment to 500 meters; 10BASE2 to a little less than 200 meters (185 meters) – hence their names (the 5 and the 2; the 10 is for 10Mbps) To extend the distance of LANs, repeaters were developed

Networking Basics and Terminology Features of Ethernet Repeaters Typically had two ports connecting two different Ethernet segments Interpreted the incoming signal on one port as 1’s and 0’s Sent a regenerated clean signal out the other port

Networking Basics and Terminology Repeated Ethernet Signal See Conceptual View on next slide Betty sends a clean signal The signal degrades by the time it reaches the repeater The repeater regenerates a new, clean signal and sends it out its other port

Networking Basics and Terminology Repeated Ethernet Signal

Networking Basics and Terminology Ethernet Hubs and 10BASE-T Coax cables were expensive and difficult to work with If the cable broke, everyone on the LAN had problems Lead to the creation of 10BASE-T

Networking Basics and Terminology Ethernet Hubs and 10BASE-T The 10 means it runs at 10Mbps The T means that it uses twisted-pair cable The cable is Unshielded Twisted-Pair (UTP), which is cheaper than coax cable Smaller diameter than coax cable Terminated with RJ-45 connectors

Networking Basics and Terminology 10BASE-T with a Hub – Star Topology

Networking Basics and Terminology Functions of a Hub Provides RJ-45 jacks so cables with RJ-45 connectors can be attached Repeats any incoming signal out all other ports Was originally called a “multiport repeater”

Networking Basics and Terminology Ethernet Bridges Examine incoming signal, interpret signal as 0’s and 1’s, find the destination MAC address listed in the frame If destination MAC address is reachable via a different interface than the one on which it was received, then clean, regenerate and forward the frame out that interface If the destination is reachable on the same interface on which it was received, discard the frame (this is called “filtering”)

Networking Basics and Terminology A Bridge Making a Filtering Decision

Networking Basics and Terminology A Bridge Making a Forwarding Decision

Networking Basics and Terminology Ethernet Frames An Ethernet frame is the data sent by an Ethernet NIC or interface The first bits sent are the header; contains info such as the destination and source MAC addresses Includes headers from other protocols, such as IP

Networking Basics and Terminology Conceptual View of an Ethernet Frame

Networking Basics and Terminology Unicast and Broadcast Ethernet Frames and Addresses Before the introduction of bridges, the LAN acted as a broadcast medium The term unicast MAC address identifies a single NIC or Ethernet interface Sometimes a computer needs to send a frame that will reach all devices on the LAN; it uses a broadcast address: FFFF.FFFF.FFFF All devices must process data sent to this address

Networking Basics and Terminology LAN Switches Like a hub, a switch provides a large number of ports/jacks to plug in cables Forms a physical star topology When forwarding a frame, the switch regenerates a clean signal Like bridges, switches use the same filtering/forwarding logic on a per-port basis

Networking Basics and Terminology A Switch Making a Forwarding Decision

Networking Basics and Terminology Wide-Area Networks (WANs) Cover a large geographic area WAN Technologies: Modems Integrated Services Digital Network (ISDN) Digital Subscribe Line (DSL) Frame Relay T1 or E1 leased lines – T1, E1, T3, E3, etc. Synchronous Optical Network (SONET) – synchronous transport Level 1(STS-1) optical carrier [OC]-1, STS-3 (OC-3), etc.

Networking Basics and Terminology Point-to-Point Leased Lines A point-to-point leased line extends between two locations The line is not owned by the user; it is leased from a service provider The service provider is often a telephone company (telco) Often, the term link is used to describe a point-to-point leased line

Networking Basics and Terminology Point-to-Point Leased Lines: Leased lines are drawn like lightning bolts

Networking Basics and Terminology Routers and Their Use with LANs Routers perform a basic but very important forwarding process in which they receive data packets and then forward the packets toward the destination Routers can send and receive traffic on most any kind of physical networking media Routers are the perfect device to connect a LAN to a WAN

Networking Basics and Terminology Metropolitan Area Networks (MANs) A medium-sized network geography, perhaps city-wide Usually very high speed Optical media used between routers can move data at 10 Gbps or even 40 Gbps

Networking Basics and Terminology High-Speed City-Wide MAN

Networking Basics and Terminology Storage-Area Networks (SANs) Allow computers to communicate with storage devices Features of SANs: Performance: concurrent access of disk or tape arrays Availability: used to back up data to offsite locations Scalability: easy relocation of backup data, operations, file migration, and data replication between systems

Networking Basics and Terminology Typical SAN Used by a Server Farm

Networking Basics and Terminology Virtual Private Networks (VPNs) Companies can use the Internet to send data between sites, instead of using leased lines Often less expensive than leased lines Can be less secure than leased lines

Networking Basics and Terminology Virtual Private Networks (VPNs)

Networking Basics and Terminology Intranet VPNs Packets are encrypted before they leave for the Internet Not practical for a hacker to break the encryption Intranet VPNs are used inside a single organization

Networking Basics and Terminology Intranet VPN

Networking Basics and Terminology Comparing Intranet VPNs to Extranet and Access VPNs Intranet VPN – A VPN between sites of a single organization Extranet VPN – A VPN between sites of different organizations Access VPN – A VPN between individual users and an enterprise network, allowing access while working from home or traveling

Networking Basics and Terminology Extranet and Access VPNs

Networking Basics and Terminology Physical Network Topologies

Networking Basics and Terminology Physical Bus Topology 10BASE2 and 10BASE5 use a bus topology Looks like a city street where each of the computers is a bus stop A frame sent by one device is received by all other devices

Networking Basics and Terminology Physical Star Topology 10BASE-T Ethernet connects with a hub The hub is the device at the center, so it resembles a start The actual physical layout of the cable may not be in a star pattern

Networking Basics and Terminology Logical Bus Topology “Logical” refers to how the network operates, not where the cables run 10BASE-T is a logical bus, because all devices see any signal sent by other devices on the network

Networking Basics and Terminology Physical versus Logical Topology Physical Topology – The topology is determined by the physical layout of the cabling and transmission media Logical Topology – The topology is determined by the media access control logic and how the devices collectively send traffic over the network

Networking Basics and Terminology Typical Modern LAN and Its Similarities to a Star Topology

Networking Basics and Terminology Typical Modern LAN Design for a Single Building

Networking Basics and Terminology Ring Topologies Cable is installed from first device to second device, second device to third device, and so on, until the last device connects to the first device Each device cleans up the signal, so fewer repeaters are needed Can have single or dual rings

Networking Basics and Terminology Ring Topology R1 and R2 detect that cable between them is cut R1 and R2 loop the primary ring to the backup ring using circuitry in the routers One ring still works, assuring connectivity

Networking Basics and Terminology Hierarchical and Extended Star Topologies A central device or site connects to several other sites Much like a star topology The other sites then connect to still more sites Extended star topologies have the same features as a hierarchical topology, but are not drawn in a hierarchy

Networking Basics and Terminology Hierarchical Network Design

Networking Basics and Terminology Mesh: Full and Partial Most often refers to WAN topologies Full mesh: all devices connect to all other devices – highly reliable – Frame Relay is an example Partial mesh: Each device connects to many, but not all, other devices

Networking Basics and Terminology Mesh: Full and Partial

Names and Units of Digital bandwidth: Bandwidth: Number of bits per second that can be sent by a device across a particular transmission medium Names and Units of Digital bandwidth:

Bandwidth LAN and WAN Bandwidth Actual speed is limited by 3 factors: cabling, cable length, and the speed at which the devices on the end of the cable try to send data Ethernet standards call for Category 5 (Cat 5) UTP cabling, for speeds of 10, 100 and even 1000 Mbps The cable can handle higher speeds, but is hardware limited

Bandwidths for Various Ethernet Standards and Cables

Bandwidth WAN Bandwidths Vary significantly, as do LAN bandwidths Engineers need to worry about details such as cable length restrictions and required equipment Customers need to worry about how fast the WAN link is, how much it costs, and the type of technology used

WAN Bandwidth Standards

WAN Bandwidth Standards (continued)

Throughput Versus Bandwidth Throughput is how many bits are actually transferred between two computers in a given time Two points to consider when comparing throughput to bandwidth: Throughput rate may vary over time due to network conditions; bandwidth does not vary over time Bandwidth defines the speed of a single link; throughput measures the speed of the end-to-end connection

Two Examples of Throughput Bandwidth Two Examples of Throughput

Bandwidth is What You Pay for, Throughput is What You Get Factors That Affect Throughput Networking devices in the route being used Type of data being transferred Protocols used to transfer the data Topology of the network Congestion level in the network Speed and current workload of the computers Time of day (# of active concurrent users)

Calculating Data Transfer Time: Two Methods Bandwidth Calculating Data Transfer Time: Two Methods

Bandwidth Calculating Data Transfer Time: Four Examples from the “Two Examples of Throughput” Slide

Bandwidth Analog Bandwidth In the analog world, a number of consecutive frequencies (a “band of frequencies”) defined how much information could be sent with an analog signal The wider the band of frequencies, the more information could be sent With digital transmission, the range of frequencies does not affect the speed, but the term “bandwidth” is still used to describe the speed of the bits across a link

Analog Bandwidth (continued) Analog transmission requires a set frequency band to work The figure below shows a 3-hertz signal

Planning for Bandwidth Neither LAN nor WAN bandwidth is free On enterprise networks, WAN costs can be 30-40% of the total budget LAN links cost money, due to wiring costs and the costs of networking devices such as switches Bandwidth is not infinite, and it costs money to upgrade

Planning for Bandwidth (continued) Four reasons why bandwidth is important: Bandwidth is finite Bandwidth is not free Network engineers need to plan for bandwidth Bandwidth demand is ever-increasing

The OSI and TCP/IP Networking Models Networking models define a related set of standards and protocols When used together, these protocols and standards allow the creation of a working network The two most commonly used models are the Open Systems Interconnection (OSI) model and the Transmission Control Protocol/Internet Protocol (TCP/IP) model

The OSI and TCP/IP Networking Models In the 1960s, vendors each used their own set of standards and protocols These proprietary networking models would not allow equipment from one company to work with equipment from another company To overcome this problem, the OSI model was developed beginning in 1984

The OSI and TCP/IP Networking Models The OSI Model Goal was to be the one open networking model that all vendors would implement The term “open” means that all vendors have access to the protocols and rules for building products Most vendors worked toward adopting the OSI model in the late 1980s and early 1990s Many vendors and networking professionals adopted the OSI terminology to hold meaningful conversations about different networking models, making those conversations a little easier

The OSI and TCP/IP Networking Models The OSI Model (continued) The OSI model might have been the final standard for networking, but TCP/IP proved to be more widely accepted Computers today rarely implement the OSI model as their model for networking Why use OSI? The terminology is still used, and it is useful in troubleshooting networking problems

The OSI and TCP/IP Networking Models The OSI Layers General networking functions are defined in layers: Allows better standardization of different components Opens up competition in marketplace Standardizes components Standardizes interfaces between different layers, allowing companies to focus on one layer Prevents changes in one layer from affecting other layers Breaks network communication into smaller components

The OSI and TCP/IP Networking Models The OSI Layers

The OSI and TCP/IP Networking Models Memorizing the Order of the OSI Layers Starting with Layer 1: Please Do Not Take Sausage Pizza Away Pew! Dead Ninja Turtles Smell Pretty Awful Starting with Layer 7: All People Seem To Need Data Processing

The OSI and TCP/IP Networking Models Functions of the OSI Layers Layer 7 (application layer) Provides services to end user’s applications Does not provide services to any other OSI layer Layer 6 (presentation layer) Ensures info from one system’s application layer can be read by another system Translates among multiple data formats Does encryption and decryption Handles graphics standards such as PICT, TIFF, JPEG, MIDI and MPEG

The OSI and TCP/IP Networking Models Functions of the OSI Layers (continued) Layer 5 (session layer) Establishes, manages and terminates sessions between two hosts Layer 4 (transport layer) Segments data given to it by the session layer into smaller chunks Defines error-recovery services

The OSI and TCP/IP Networking Models Functions of the OSI Layers (continued) Layer 3 (network layer) Provides connectivity and path selection between two host systems Concerned with logical addressing Layer 2 (data link layer) Provides transit of data across a physical link by defining the rules about how the link is used Concerned with physical addressing Layer 1 (physical layer) Defines electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems

The OSI and TCP/IP Networking Models Relationship of OSI Layers and Devices

The OSI and TCP/IP Networking Models The TCP/IP Networking Model Began as part of a research project for the US Dept. of Defense (DoD) in the 1970s. The structure remains the same today, but many new protocols have been added Can be easily compared to the OSI model; uses 4 layers instead of 7

The OSI and TCP/IP Networking Models The TCP/IP Reference Model Layers

The OSI and TCP/IP Networking Models Encapsulation Application headers are added Data is segmented IP address information is added Data link header and trailer are added Bits are transmitted

The OSI and TCP/IP Networking Models Segments, Packets, Frames, and PDUs Important to know the terminology for the group of bytes at each layer The generic term is protocol data unit (PDU)

The OSI and TCP/IP Networking Models De-encapsulation Physical layer interprets incoming electrical signal Contents of Ethernet header and trailer analyzed; IP packet extracted Network layer verifies IP header is okay, extracts contents of data field Segments are reassembled and error recovery performed Data is given to application

The OSI and TCP/IP Networking Models Layer Interactions Same layer interaction – creation of headers, and possibly trailers, by a protocol at one networking layer on one computer, with the goal of communicating to the same layer and protocol on another computer Adjacent layer interaction – On a single computer, the interaction of protocols that sit at adjacent layers of their networking model. Includes exchange of data during encapsulation and de-encapsulation, and how a lower layer protocol provides service to an upper layer protocol

Networking Fundamentals Summary Network devices (hubs, repeaters, bridges, switches, routers) connect host devices to allow them to communicate Protocols provide sets of rules for communication The physical topology is the actual layout of the wire or media Common physical topologies are bus, ring, star,extended star, hierarchical, and mesh A LAN is designed to work in a limited geographical area, providing multi-access to high-bandwidth media LANs are controlled privately under local administration LANs provide full-time connectivity to services and connect physically adjacent devices

Networking Fundamentals Summary WANs operate over large geographical areas WANs allow access serial interfaces that operate at lower speeds, provide full- and part-time connectivity to local services and connect devices separated over large areas A MAN is a network that spans a metropolitan area such as a city A SAN is a dedicated, high performance network used to move data between servers and storage resources SANs are scalable and have disaster tolerance built it A VPN is a private network constructed with a public network infrastructure such as the Internet The three main types of VPNs are access, intranet and extranet

Networking Fundamentals Summary Access VPNs provide mobile workers connectivity Intranet VPNs are only available to users who have access privileges to the internal network of an organization Extranet VPNs are design to provide applications and services to external users or enterprises Bandwidth equals number of bits per second (bps) that can theoretically be sent through a network connection Throughput is the amount of data that actually passes through a connection in a give time, and is constrained by the slowest link between the two end devices Analog bandwidth is a measure of how much of the electromagnetic spectrum is occupied by each signal Digital bandwidth is measured in bits per second

Networking Fundamentals Summary Layers are used to describe communication from one computer to another because it: Reduces complexity Standardizes interfaces Facilitates modular engineering Ensures interoperability Accelerates evolution Simplifies teaching and learning Two models are the OSI model and the TCP/IP model The OSI model has seven layers; the TCP/IP model has four – some layers have the same name but do not correspond exactly

Networking Fundamentals Summary Data is encapsulated with these steps: Images and text are converted to data Data is packaged into segments Each data segment is encapsulated in a packet with source and destination addresses Each packet is encapsulated in a frame with the MAC address of the next directly connected device Each frame is converted to a pattern of 1s and 0s and transmitted on the media