Unit A - Connecting to the Network - SLCtech.orgjpichie/game100/classnotes/game100-networking... ·...

© 2007 Cisco Systems, Inc. All rights reserved. Cisco PublicITE PC v4.0Chapter 1 1

Unit A - Connecting to the Network

ITE PC v4.0Chapter 1 2© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

What is a network?

� The ability to connect people and equipment no matter where they are in the world.

– telephone

– computers

– television

� How does your body work as a network?


Networking and Its BenefitsA CONVERGED NETWORK!!!


Networking and Its Benefits

� SOHO Network– Small Office/Home Office

– sharing of resources

• Internet

• Printer


Networking and Its Benefits

Schools, Corporations

Internet


Networking and Its Benefits� Define the components of an Information network

� Hosts– PCs

– send and receive information across the network

–connected to a network device

� Peripherals– not directly connected to the network, but connected to hosts

� Network devices– hub, switch, router

� Network media– used to connect hosts/devices


Networking and Its Benefits� Clients and servers

– software installed determines the role of a client or a server

� Server software– enables the server to provide information to other hosts

� Client software– enables the client to request and display information from the server

– Example: Internet Explorer


Networking and Its Benefits� Build computer peer-to-peer network and verify

� The ability to act as both a client and server


Network Topologies� Physical topology

– created to record where each host is on the network

– shows how each host is connected (media, devices, etc)


Network Topologies� Logical topology

– how the host uses the network

– host names, addresses, groups, applications


Communication Protocols� Primary purpose of a network – to communicate

� Elements of communication– Sender (source)

• has a need to communicate

– Receiver (destination)

• receives message and interprets it

– Channel

• pathway for information to travel


Successful delivery of the message

� Rules (protocols) must be followed:– Identification of the sender and/or receiver

– Channel in which to communicate (face-to-face)

– Mode of communication (written or spoken)

– Language

– Grammar

– Speed or timing


Communication Protocols� Encoding vs. Decoding

� Encoding – Humans

• converting thoughts into language, symbols, or sounds

– Computers

• messages converted into bits by the sending host

• each bit encoded into sound, light, or electrical impulses

• destination host then decodes the signal

� Decoding– reverse of encoding


Communication Protocols� Message formatting and encapsulation

� Message needs a specific format

� Compare to parts of a letter– Identifier (recipient)– Salutation– Message– Closing– Identifier (sender)

� Encapsulation– placing the letter into the envelope

� De encapsulation– letter removed from the envelope


Communication Protocols� Messages have size restrictions depending on the

channel used

� If the message is broken into smaller pieces, it is easier to understand

� If the message is too long or too short, will be considered undeliverable.


Communication Protocols

� Timing– when to speak; how fast or how slow– how long to wait for a response

� Access Method– determines when someone is able to send a message– can speak when no one else is talking, otherwise a COLLISONoccurs

� Flow Control– timing for negotiations– sender might transmit messages faster than the user can handle

� Response Timeout– how long should you wait for a response and what action to take

� Acknowledgment– may be required to ensure message was delivered


Communication Protocols� Message Patterns

� Unicast – single destination

� Multicast – same message to a group

� Broadcast – all hosts need to receive the message


Communication Protocols

PROTOCOLS = RULES TO FOLLOW


Communication Across a Local Ethernet Network� Computers must speak the same language in order to

communicate!!


Standards in technology

� Standards – rules by which equipment from different vendors operate

� Benefits of standards:– Facilitate design– Simplify product development– Promote competition– Provide consistency– Facilitate training– More vendor choices for customers


Communication Across a Local Ethernet Network� IEEE (Institute of Electrical and Electronic Engineers)

– maintains networking standards

– 802.3 – Ethernet standard

� A breakdown of terminology– 100 Base-T

– 100 = Speed in Mbps

– Base = Baseband transmission

– T = Twisted Pair


Communication Across a Local Ethernet Network� Physical addressing

� MAC address (Media Access Control)

� Ethernet communication– each interface has a MAC address

– each device may look at the data that has been transmitted, but only the interface that matches the destination MAC will respond


MAC Addresses by another Name

Other names for a MAC address include:

� physical address

� hardware address

� Ethernet address

� burned-in address

� data-link layer address (7-layer model)

� Layer 2 address (of 7-layer model)


The Ethernet Frame

� Preamble – beginning of the timing

� SFD (Start Frame Delimiter) – marks the end of the timing, but beginning of the frame

� Destination MAC

� Source MAC

� Length/Type– Length – tells which protocol receives the data– Type – number of bytes of data

� Encapsulation – packet of information

� FCS (Frame Check Sequence) – used to check for damaged frames

46-1500


Example Ethernet Type Values

� EtherType value of 0x0800 signals that the frame contains an IPv4 frame.

� EtherType of 0x0806 indicates an ARP frame

� EtherType of 0x8100 indicates an IEEE 802.1Q frame-Used with Virtual Lans (vlans)

� EtherType of 0x86DD indicates an IPv6 frame.


Cisco 3-layer Networking Model

� Cisco has defined a hierarchical model known as the hierarchical internetworking model.

� This model simplifies the task of building a reliable, scalable, and less expensive hierarchical internetwork because rather than focusing on packet construction, it focuses on the three functional areas, or layers, of your network:

� Access

� Distribution

� Core


3-layer Networking Model� Core layer: This layer is considered the backbone of the network and

includes the high-end switches and high-speed cables such as fiber cables. This layer of the network does not route traffic at the LAN. In addition, no packet manipulation is done by devices in this layer. Rather, this layer is concerned with speed and ensures reliable delivery of packets.

Distribution layer: This layer includes LAN-based routers and layer 3 switches. This layer ensures that packets are properly routed between subnets and VLANs in your enterprise. This layer is also called the Workgroup layer.

Access layer: This layer includes hubs and switches. This layer is also called the desktop layer because it focuses on connecting client nodes, such as workstations to the network. This layer ensures that packets are delivered to end user computers.


The Hierarchical Design Structure (3-layer model)

� Smaller, more manageable groups allow traffic to remain local on the networks

� Divided into three layers– Access Layer

• connection to the hosts

– Distribution Layer

• interconnects smaller networks

– Core Layer

• high speed connection between

distribution devices (high-speed backbone > internet)



Logical Addressing� MAC vs. IP

� IP Address (Logical Address)– assigned based on where the host is located

– assigned by the administrator

� Parts of an IP address (Network and Host parts)– Network – same for all hosts connected to the LAN

– Host – unique to each host on the network


Access Layer Devices

� Most basic level

� Made up of:– host devices

– first line of networking devices

– hub, switch, workstations

Hub or switch


Access Layer Device – A HUB

� Accepts data signal from one port and sends it (regenerates) out all other ports

– multiport repeater

� Collisions– results in message being garbled and unreadable

– occur when two or more hosts send a message at the same time (undesirable in a network)

� NOT VERY SMART– a hub will not recognize there is a collision and sends it to all ports


Hubs And Collision Domains� Collision domain – area where the collision has

occurred.

� More collision domains = better performance

� How many collision domains exist in the graphic shown?


Access Layer Device – A SWITCH

� SMARTER THAN A HUB� dedicated bandwidth out each port

� no need to share with other ports (unlike a hub)

� Can forward messages to a specific host by looking in its MAC table

� If destination MAC is not in its MAC table, floods the network out all ports looking for a response

� Only the host with the correct MAC address will respond


More Stuff on Switches

� How does the MAC table get built?– keeps track of frames being sent between hosts

– records the information when there is a response

–-records the source MAC address of frames received

� Collision Domains– each port on a switch is its own collision domain

– 8 port switch = 8 collision domains


Broadcasts

� If there is only one destination MAC in a message, how can you contact everyone else?

– send a broadcast MAC

– hexidecimal digits

– FFFF.FFFF.FFFF (FF:FF:FF:FF:FF:FF)

� Useful when hosts need to send information but doesn't know what hosts are to receive it

� Switches and hubs send the broadcast out to everyone on their network. (Broadcast Domain)


ARP Request

� Sent when the sending host knows the destination IP, but not the MAC

� Will discover the MAC address of any local host on the network


Distribution Layer Devices and Communication Methods

� Responsible for making sure local traffic stays local on the network

� Traffic destined for other networks will be passed on.


Distribution Layer Devices—The Router

� Routers – directs traffic based on the destination IP address

� Routers build routing tables; switches build MAC tables

� Routers decode packets; switches decode frames

� Routers look at only the network portion of the IP address– finds the best path to take to get to the destination

� Routers do not forward broadcasts!!!


Default Gateway� Used when a host wants to send data to a host on a

different network.

� Must be set on the workstation connected to the routing device – the router interface connected to the PC


Routing Tables and ARP tables

� Used by routers to store information

The diagram to the right shows two networks connected together via a router. The router maintains an ARP table and ROUTING table with information similar to the tables shown above.


Types of Routing

� Dynamic – information is obtained from neighboring routers

� Static– manually entered by the network administrator

� What happens to a message that contains an IP destination address that does not exist in the routing table?

– It is dropped unless . . .

� A default route is set– “last resort” type of router– will send it to the router it thinks may have the destination IP


Distribution Layer Devices and Communication Methods

� LAN – Local Area Network

� Under the same administrative control


Plan, Implement and Verify a Local Network

� Consider the following before beginning:– Number and type of hosts

– Applications to be run on the network

– Data and devices to be shared

– Speed requirements (bandwidth)

– Level of security

– Reliability of the network

– Connectivity requirements


Building the Network� Physical environment

– temperature control– availability/placement of outlets

� Physical configuration– location of devices– how are devices connected– location/length of cable runs– hardware configurations (hosts, servers)

� Logical configuration– size of broadcast & collision domains– IP addressing scheme–Naming–Permissions–Sharing


Multifunction Devices

� Integrated routers– Linksys wireless router

– problem = single point of failure

� Cisco Integrated Services Router (ISR)– performs services of three different devices

• router

• switch

• wireless access point


Implement and Document the Network

� Develop a prototype– tests network design


Sharing Resources

� Main reason for networking – sharing resources– File sharing

– Print sharing

� Consider this before sharing:– security issues

– permissions granted

� Windows XP and Windows 7 users– use Simple File Sharing (default)


Simple file sharing in Windows 7� It is pretty easy and common

� It is to be used to share file/folder with other users that use Windows XP, Vista or 7 in the same workgroup.

� Other users are allowed to access the shared file/folder without doing authentication with username and password, and so we call it simple file sharing.

� However, please don’t enable this simple file sharing when your computer is connected to public network (at library, airport, restaurant, etc), because the other public users can also access the shared file/folder without authentication after you have enabled it.

� It’s not safe!


Summary� Information networks carry data using hosts as clients,

servers, or both.

� All computer communication involves a source, destination, and channel.

� Rules called protocols govern computer communications.

� Larger networks are divided into smaller, more manageable ones using a layered hierarchical design.

� Each network host needs both a physical MAC address and a logical IP address.

� Good network design requires a network plan.

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Unit A - Connecting to the Network - SLCtech.orgjpichie/game100/classnotes/game100-networking... ·...

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