Ch.2 – Networking Fundamentals Getting past some basics… CIS 81 and CST 311 Cabrillo College and CSUMB Rick Graziani Fall 2005

Ch.2 – Networking FundamentalsGetting past some basics…

CIS 81 and CST 311

Cabrillo College and CSUMB

Rick Graziani

Fall 2005

Rick Graziani [email protected] 2

Overview

Remember, we are just beginning to herd the cats.Much of this will become clearer LATER!The more we learn, the more all of this will come into focus!


What is Networking?

Networking - the interconnection of workstations, peripherals, terminals and other devices.

Whatis.com: “In information technology, networking is the construction, design, and use of network, including the physical (cabling, hub, bridge, switch, router, and so forth), the selection and use of telecommunication protocol and computer software for using and managing the network, and the establishment of operation policies and procedures related to the network.”


The Evolution of Data networks

• Peer-to-peer: Enabling communications between two computers, without relying on a computer server (client/server).

• LANs (Local Area Networks): Enabling communications between groups of computers and other devices within an office, company, etc., including servers and printers.

• WANs (Wide Area Networks): Enabling communications between individual computers, computers on different LANs, etc.


Network Media Symbols

The Serial connection symbol usually represents some sort of WAN connection such as leased line (T1), ISDN, Frame Relay, ATM, asynchronous dial-up (modem), etc.

Usually a LAN connection

Becoming obsolete


Symbols for Networking Devices


Network topologies


Network topologies

• Network topology defines the structure of the network. • Physical topology: Actual layout of the wire or media.

– Bus– Star, Extended Star– Ring

• Logical topology: Defines how the media is accessed by the hosts for sending data. – Broadcast or multi-access – Token passing


Bus Topology

“A bus topology uses a single backbone segment (length of cable) that all the hosts connect to directly.”


Other Bus Topologies


In the 70’s I was usually working on my bus topology…


Ring Topology

• “A ring topology connects one host to the next and the last host to the first.

• This creates a physical ring of cable.”

• Becoming less common.


Token Ring

• Ring topologies use a token passing (logical topology).

• Token Ring NIC and Hub (or MAU)

• Token Ring networks are becoming obsolete and not part of this curriculum.


Star Topology

• “A star topology connects all cables to a central point of concentration.

• This point is usually a hub or switch, which will be described later in the chapter.”


Extended Star Topology

• “An extended star topology uses the star topology to be created.

• It links individual stars together by linking the hubs/switches.

• This, as you will learn later, will extend the length and size of the network.”


Mesh Topology

• A mesh topology is used when there can be absolutely no break in communications, for example the control systems of a nuclear power plant.

• Each device has its own connections to all other hosts.

• This also reflects the design of the Internet, which has multiple paths to any one location.”

• There are also full mesh and partial mesh topologies, both physical and logical, which will be discussed in later courses.

Circuit and Packet Switched networks could be full or partial mesh.


Full Mesh and Switched Telephone Lines


Network protocols

• Protocol - Set of rules and conventions that govern a particular aspect of how devices on a network communicate. – Including: format, timing, sequencing, and error control in data

communication.

• Protocol suites are collections of protocols that enable network communication from one host through the network to another host.

• Without protocols, the computer cannot make or rebuild the stream of incoming bits from another computer into the original format.

010010100111000111010011100101001000111101 ...


Network protocols

Examples:• Ethernet• TCP/IP protocol suite

– IP– TCP– UDP– ARP


Network Technologies

LANs

MANs

WANs


Local-area networks (LANs)

Some common LAN technologies are:

• Ethernet

• Token Ring

• FDDI


Wide-area networks (WANs)

Some common WAN technologies are: • Modems (Asynchronous) • Integrated Services Digital Network (ISDN) • Digital Subscriber Line (DSL) • Frame Relay • US (T) and Europe (E) – T1, E1, T3, E3 • Synchronous Optical Network (SONET)


Metropolitan-area networks (MANs)

• A MAN is a network that spans a metropolitan area such as a city or suburban area.

• A MAN usually consists of two or more LANs in a common geographic area.

• For example, a bank with multiple branches may utilize a MAN.


Importance of bandwidth

• Bandwidth - The amount of information that can flow through a network connection in a given period of time.

• Available at http://www.thinkgeek.com


Analogies


Measurement

• In digital systems, the basic unit of bandwidth is bits per second (bps).

• Bandwidth is the measure of how much information, or bits, can flow from one place to another in a given amount of time, or seconds.

• Later – The size of a bit!


Limitations

• Bandwidth varies depending upon: – Type of media – Type of technology and protocol (LAN, WAN, wireless,

etc.)• The physics of the media account for some of the

difference.


Throughput

• Throughput - The amount of data transferred from one place to another or processed in a specified amount of time. (wikopedia.com)

• Often far less than the maximum possible digital bandwidth of the medium that is being used. Internetworking devices

The following are some of the factors that determine throughput: • Type of data being transferred • Network topology • Number of users on the network • User computer • Server computer • Power conditions


Digital versus Analog

GOLDMAN: DATACOMM FIG.02-14

DTE DCE

DTE DCE

Modulation

Demodulation

digital analog

digital analog

PSTN Dial-up network

PSTN Dial-up network

Digital Signals

• A signal whose state consists of discrete elements such as high or low, on or off

Analog Signals

• A signal which is “analogous” to sound waves

• telephone lines are designed to carry analog signals


Digital and Analog Bandwidth

Bandwidth = The width or carrying capacity of a communications circuit.

Digital bandwidth = the number of bits per second (bps) the circuit can carry

• used in digital communications

• measure in bps

Analog bandwidth = the range of frequencies the circuit can carry

• used in analog communications such as voice (telephones)

• measured in Hertz (Hz), cycles per second

• voice-grade telephone lines have a 3,100 Hz bandwidth


Sound Waves


ISO and the OSI Model

• The International Organization for Standardization (ISO) released the OSI reference model in 1984, was the descriptive scheme they created.

• “ISO. A network of national standards institutes from 140 countries working in partnership with international organizations, governments, industry, business and consumer representatives. A bridge between public and private sectors.” www.iso.ch

http://www.iso.ch/


ISO and the OSI Model

• “According to ISO, "ISO" is not an abbreviation. It is a word, derived from the Greek isos, meaning "equal", which is the root for the prefix "iso-" that occurs in a host of terms, such as "isometric" (of equal measure or dimensions) and "isonomy" (equality of laws, or of people before the law).

• The name ISO is used around the world to denote the organization, thus avoiding the assortment of abbreviations that would result from the translation of "International Organization for Standardization" into the different national languages of members.

• Whatever the country, the short form of the organization's name is always ISO.” www.whatis.com

http://www.whatis.com/


OSI Model

• It breaks network communication into smaller, more manageable parts.

• It standardizes network components to allow multiple vendor development and support.

• It allows different types of network hardware and software to communicate with each other.

• It prevents changes in one layer from affecting other layers.

• It divides network communication into smaller parts to make learning it easier to understand.


OSI Model

• OSI (Open Systems Interface) was released as a suite of protocols to be used as the Internet standard.

• However, TCP/IP became the de facto standard.

• The OSI reference model is the primary model for network communications.

• Although there are other models in existence, most network vendors, today, relate their products to the OSI reference model, especially when they want to educate users on the use of their products.


OSI Model

• The OSI reference model allows you to – view the network functions that occur at each layer – a framework that you can use to understand how information

travels throughout a network. – understand, visualize, and troubleshoot the sending and receiving

data on a network– visualize how information, or data packets, travels from application

programs, through a network medium (e.g. wires, etc.), to another application program that is located in another computer on a network, even if the sender and receiver have different types of network media

• Note: The Application Layer of the OSI model refers to networking applications, and not user applications.

The use of this model can be confusing and will become clearer later!


OSI layers


OSI layers

Usually not referred to.Usually not referred to.


OSI Layer 1 – Physical Layer

• The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems.

• Signals, network media (cables, wireless, …), layer 1 devices

• Layer 1 devices include:– Repeaters– Hubs


OSI Layer 1 – Physical Layer

• Determines how are the bits to be transferred over the physical medium.


Repeaters

• Signals can only travel so far through media before they weaken, and become garbled.

• This weakening of signals is called attenuation.

• Attenuation increases when:• Media distances are lengthened• Nodes are added to the media

Medium Max Distance

Twisted Pair 100 meters

Coaxial Cable 185/500 meters

Fiber Optic 2+ kilometers


The Repeater

• Repeaters are Layer 1 internetwork devices used to combat attenuation.

• Repeaters take in weakened signals, clean them up, regenerate them, and send them on their way along the network.


Repeaters Extend Distances

By using repeaters, the distance over which a network can operate is extended.

Example: 10Base-T (a wiring standard) is allowed to run 100 meters. One repeater can double this distance to 200 meters!

NODE A REPEATER NODE B100 M 100 M

NODE A NODE B100 M


Repeater: Layer 1 Device

Repeaters are Layer 1 devices. They do NOT look at Layer 2, Data Link (MAC, Ethernet)

addresses or Layer 3, IP Addresses.

Signal come in … signal go out. (after I amplify

it)


Hub

Hub is nothing but a multiport repeater. Hubs are Layer 1 devices. Data that comes in one port is sent out all other ports, except for the port

it came in on.

Hubs are sometimes called Ethernet concentrators Multiport repeaters In Token Ring nets, Multi-station Access Units (MAU or MSAU)


Hub: Layer 1 Device

Hubs are Layer 1 devices. They do NOT look at Layer 2, Data Link (MAC, Ethernet)

addresses or Layer 3, IP Addresses.


Repeaters

• In the “old days”, repeaters were typically used to extend the size or length of a bus-topology network.

• Repeaters take a signal in on one end and regenerate that signal out the other end.

• In most networks (LANs), repeaters have been replaced by hubs, which have been mostly replaced by switches.

• MORE LATER!


Hubs

• Hubs allow computers and other network devices to communicate with each other, and use a star topology.

• Like a repeater, a hub regenerates the signal.

• Hubs have the same disadvantage as a repeater, anything it receives on one port, it FLOODS out all other ports.

• Wherever possible, hubs should be replace by switches.

• More LATER!


OSI Layer 2 – Data Link Layer

• The data link layer provides reliable transit of data across a physical link. In so doing, the data link layer is concerned with physical (as opposed to logical) addressing, network topology, network access, error notification, ordered delivery of frames, and flow control.

• Frames and Layer 2 protocols

• Layer 2 devices include:– Switches– Bridges


Switches

• Switches are the core devices in today’s modern LANs.• Switches are Layer 2 devices, like bridges.• Switches keep tables of MAC addresses.• Switches keep track of and examine Layer 2, Data Link addresses

(MAC addresses) – more later.• Switches learn about devices on each port and “decide” whether or not

it needs to forward the traffic: Flood or Filter.


Switches

• Switches filter or flood. – more later

• Switches can have a number of different “layer 2 features” and may cost anywhere from $50 to over $100,000

• What is a “layer 3 switch”? – Later, but it is nothing more than a switch with a router.

Etherfast 5-port 10/100 switch with one free nic$47.99 Click here for lease options! (Data Warehouse)


Switches

Switches will be discussed: More this semester More in CIS 83. More in course: Multilayered Switched Networks LAN design, media types, VLANs, VLAN Trunking Protocol, ISL,

802.1Q, Spanning Tree (802.1d), Inter-VLAN routing, Multilayer Switching, Flow Masks, HSRP, VACLs, Multicasting, and IGMP.


Switches

• Switches look a lot like hubs, but internally are much different.

• Switches can learn where devices are on the network, so they do not have flood information (frames), but can FILTER them so the information only goes out the port towards the destination device.

• Switches also uses a star topology.

Switch


Bridges

• A bridge is a two port switch.

• In the early days there were other types of bridges such as translation bridges that joined two different types of networks such as Ethernet and Token Ring.


Network Interface Card (NIC)




• www.whatis.com “A network interface card (NIC) is a computer circuit board or card that is installed in a computer so that it can be connected to a network. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or token ring. Network interface cards provide a dedicated, full-time connection to a network. Most home and portable computers connect to the Internet through as-needed dial-up connection. The modem provides the connection interface to the Internet service provider.’

• Data Link, Layer 2 Device

http://www.whatis.com/

http://searchebusiness.techtarget.com/sDefinition/0,,sid19_gci211746,00.html

http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212495,00.html



http://searchsystemsmanagement.techtarget.com/sDefinition/0,,sid20_gci212583,00.html






• Layer 2, Data Link Layer, device

• Connects the device (computer) to the LAN

• Responsible for the local Layer 2 address (later)

• Common Layer 2 NICs:

– Ethernet– Token Ring

• Common Bandwidth

– 10 Mbps, 10/100 Mbps, 10/100/1000 Mbps



Routers with Ethernet and Token Ring Interfaces also have NICs.


OSI Layer 3 – Network Layer

• The network layer provides connectivity and path selection between two host systems that may be located on geographically separated networks.

• IP Addressing, routing and Layer 3 protocols

• Layer 3 devices include:– Routers


The Router

• The purpose of a router is to examine incoming packets, choose the best path for them through the network, and then switch them to the proper outgoing port.

• Routers work at Layer 3, the Network Layer.• Routers examine Layer 3 addresses IP (legacy technologies: IPX,

Appletalk, etc.)


Router

• Routers can also connect different Layer 2 technologies, such as Ethernet, Token-ring, and different serial technologies such as ISDN, PPP, etc.

• However, because of their ability to route packets based on Layer 3 information, routers have become the backbone of the Internet, running the IP protocol.


Router

• A router connects different networks or subnets.

• A router connects:– LAN to LANs– LANs to WANs– WANs to WANs

IMP (Interface Message Processor)

Juniper Router


Router

• Much more on routing:

• CIS 82: Routing theory, routing protocols, router configuration

• CIS 83: EIGRP, Single Area OSPF, classful and classless routing protocols

• CIS 185: Advanced Routing, multi-area OSPF, EIGRP, IS-IS, BGP, VLSM, CIDR, route redistribution, summarization and optimization.


Router

• A router is used to separate or segment one network from another network.

• This will make more sense LATER!


Devices and their layers

• Hosts and servers operate at Layers 2-7; they perform the encapsulation process.

• Routers: Layers 1 through 3, make decisions at layer 3

• Switches and NICs: Layers 1 and 2, make decisions at layer 2

• Hubs and transceivers: Layer 1, no decisions to make

Transceiver


Ethernet and TCP/IP

Ethernet & TCP/IP are the most pervasive LAN protocols, and are often used together.

Data Link Layer

Physical Layer

Network Layer

Session Layer

Transport Layer

Presentation Layer

Application Layer

TCP/IP

Ethernet



Peer-to-peer communications

• In order for data to travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination.

• This form of communication is referred to as peer-to-peer. • During this process, the protocols of each layer exchange information,

called protocol data units (PDUs). • Each layer of communication on the source computer communicates with a

layer-specific PDU, and with its peer layer on the destination computer as illustrated in Figure


TCP/IP model

• TCP/IP was developed as an open standard. • This meant that anyone was free to use TCP/IP. • This helped speed up the development of TCP/IP as a standard. • Although some of the layers in the TCP/IP model have the same name

as layers in the OSI model, the layers of the two models do not correspond exactly.


TCP/IP model

Some of the common protocols specified by the TCP/IP reference model layers. Some of the most commonly used application layer protocols include the following:

• File Transfer Protocol (FTP)

• Hypertext Transfer Protocol (HTTP)

• Simple Mail Transfer Protocol (SMTP)

• Domain Name System (DNS)

• Trivial File Transfer Protocol (TFTP)

The common transport layer

protocols include:

• Transport Control Protocol (TCP)

• User Datagram Protocol (UDP)

The primary protocol of the

Internet layer is:

• Internet Protocol (IP)


OSI and TCP/IP


Detailed encapsulation process

• All communications on a network originate at a source, and are sent to a destination.

• The information sent on a network is referred to as data or data packets.

• If one computer (host A) wants to send data to another computer (host B), the data must first be packaged through a process called encapsulation.


Detailed encapsulation process

Networks must perform the following five conversion steps in order to encapsulate data:

1. Build the data. 2. Package the data for end-to-end transport.3. Add the network IP address to the header. 4. Add the data link layer header and trailer.5. Convert to bits for transmission.


Application Header + data

Data Encapsulation Example

Let us focus on the Layer 2, Data Link, Ethernet Frame for now.

010010100100100100111010010001101000…

Application Layer

Layer 4: Transport Layer

Layer 3: Network Layer

Layer 2: Network Layer

Layer 1: Physical Layer


This will make much more sense later!

Ch.2 – Networking FundamentalsGetting past some basics…

CIS 81 and CST 311

Cabrillo College and CSUMB

Rick Graziani

Fall 2005

Documents

Ch.2 – Networking Fundamentals Getting past some basics… CIS 81 and CST 311 Cabrillo College and CSUMB Rick Graziani Fall 2005