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Chapter 3 - Network Protocols and Communications

3.0 Network Protocols and Communications

3.0.1 Introduction >3.0.1.1 Introduction

Upon completion of this learner you will be able to:

  • Explain why protocols are necessary in communication
  • Explain the purpose of adhering to a protocol suite
  • Explain the roles of standards organizations in establishing protocols for network interoperability
  • Explain how the TCP/IP and the OSI model are used to facilitate standardization in the communication process.
  • Explain why RFC's became the process for establishing standards.
  • Describe the RFC process
  • Explain how data encapsulation allows data to be transported across the network.
  • Explain how local hosts access local resources on a network
  • Explain how local hosts access remote resources on a network

3.0.1 Introduction >3.0.1.2 Class Activity - Designing a Communication System

The image on this page shows the following common standards organizations:

  • The Electronic Industries Alliance (EIA)
  • The Internet Engineering Task Force (I ETF)
  • The Internet Assigned Numbers Authority (IANA)
  • The Institute of Electrical and Electronics Engineers (IEEE)
  • The Internet Corporation for Assigned Names and Numbers (I CANN)
  • The International Telecommunication Union (ITU)
  • The Telecommunications Industry Association (TIA)

The description given for this image is " Network Protocols and Standards make network communication easier."

Objectives

Explain the role of protocols and standards organizations in facilitating interoperability in network communications.
In this activity, you will determine ways to communicate when standards are not present or agreed upon. You will also resolve a communication issue by establishing standards for communication.

3.1 Rules of Communication

3.1.1 The Rules >3.1.1.1 what is Communication?

Figure 1 on this page is an animation of a conversation taking place between two people. This shows that in order for successful communication there needs to be:

  • A message, the words that the person wants to tell the other
  • A transmitter, the speaking person
  • A medium in which to transmit the message, the air carrying the voice
  • A receiver, the ears of the person being spoken to
  • A message destination, the person being spoken to

Figure 2 on this page is an animation of a conversation taking place between two computers. This shows that in order for successful communication between computers there also needs to be:

  • A message, a data packet
  • A transmitter, the network card of the source computer
  • A medium in which to transmit the message, network cables
  • A receiver, the network card of the destination computer
  • A message destination, the destination computer

3.1.1 The Rules >3.1.1.2 Establishing the Rules

Figure 1 on this page is a box displaying the following two sentences used to represent the importance of establishing rules for communication:

  • The first sentence is a long sentence that does not have any spaces between the words, which makes it difficult to read.
  • The second sentence is written in Spanish, and could be hard to understand if the receiver doesn’t speak the language.
There is a Translate button that the learner can activate that will add the spaces between the words and also translate form Spanish to English.

Figure 2 on this page is a star diagram with the word protocols in the center and the following branches:

  • Message encoding
  • Message formatting and Encapsulation
  • Message size
  • Message timing
  • Message delivery Options

3.1.1 The Rules >3.1.1.3 Message encoding

Figure 1 on this page is an animation of the communication process between two people. A woman is thinking of a message, she formulates the message and transmits it to a man who receives the message. This is used to demonstrate the communication process.

Figure 2 on this page is an animation of the communication process between two computers. A data packet is formed on a computer and then the message is transmitted to a receiving computer.

3.1.1 The Rules >3.1.1.4 Message formatting and Encapsulation

Figure 1 on this page is an animation used to demonstrate the rules used in communication. The figure shows an envelope that has a recipient address and a return address on it.

The components of the letter represent the following:

  • The recipient address represents the location address of the recipient.
  • The return address represents the location address of the sender of the message.
  • The letter inside represents the message being sent.
  • The greeting such as “Dear” on the message aligns with the start of message indicator.
  • The name following Dear such as “Jane” represents the identity of the recipient.
  • The contents of the letter represent the encapsulated data.
  • The signing of the letter is the source identifier.
  • The stamp represents transmitting the message.

Figure 2 on this page illustrates the format and contents of a frame. This encapsulation has the frame addressing on one end, made up of Destination (physical/hardware address) and Source (physical/hardware address), the encapsulated message in the middle, made up of Start Flag (start of message indicator), Recipient (destination identifier), Sender (source identifier) and Encapsulated Data (bits). At the end is the End of Frame (end of message indicator).

3.1.1 The Rules >3.1.1.5 Message size

Figure 1 on this page is an animation of the following communication process between two people, specifically on the message size:

  1. A woman is thinking of a message
  2. She formulates the message and transmits it to a man very quickly with no spacing between the words
  3. The man cannot process the information in this manner and has to ask for it to be re-sent in a slower and organized fashion.
  4. The woman complies and this time the man can understand the information.

This represents segmenting of data.

Figure 2 on this page is an animation of the following communication process between two computers:

  1. The data is sent from one computer to another very quickly and with no breaks
  2. The receiving computer cannot process the data.
  3. The sending computer repeats sending data and the second time it segments the message
  4. The data can then be processed by the receiving computer.

3.1.1 The Rules >3.1.1.6 Message timing

Figure 1 on this page shows a woman calling a man on the phone and each is asking the other a question at the same time. Neither one can understand the other. This represents access method.

Figure 2 on this page shows the woman asking if the man can hear her, and the man doesn’t answer because he cannot understand the woman. This represents the need for flow control.

Figure 3 on this page shows the man not answering her, so she repeats the question. This is representing the response timeout of a communication.

3.1.1 The Rules >3.1.1.7 Message delivery Options

Figure 1 on this page shows the following three ways of sending a message:

  • A woman is talking towards a group of people and is speaking only to one person in the group, this is a unicast.
  • When she speaks to more than one member of the group, but not the whole group she is sending a multicast message.
  • Lastly when she speaks to the group as a whole she is sending a broadcast message.

Figure 2 on this page shows a computer sending a message to a switch that has four other computers connected to it. The different processes are:

  • The unicast message is delivered to one specific host.
  • The multicast message is delivered to two of the four computers.
  • The broadcast message is delivered to all of the other computers.

3.2.1 Protocols >3.2.1.1 Protocols: Rules that Govern Communication

The figure on this page illustrates the following example of a communication session between two people. One person is asking another person where the cafeteria is:

  1. The question is the content layer
  2. The rules layer consists of the following conversation protocol suite rules:
    • The use of a common language
    • Waiting ones turn to speak
    • Signalling when finished.
  3. The physical layer is represented by speaking.

3.2.1 Protocols >3.2.1.2 Network Protocols

Figure 1 on this page shows the role of protocols in data transfer as follows:

  1. A P C decides " I will send this message across the network using an IP v 4 header."
  2. The Router decides "I can forward this message because I understand the I P v 4 header."
  3. The Server decides "I can accept this message because I understand IP v 4"

Figure 2 on this page shows routers sharing information about pathways to other networks as follows:

  1. Network devices decide "Let us all agree that if one of our pathways is down, we will notify all connected devices."
  2. Path A is down. All network devices are notified.

It is common for routers to share information.

Figure 3 on this page shows routers communicating with each other regarding a slow path due to another path that is down as follows:

  1. Network devices decide "Let's all agree that error messages will have a unique ID number."
  2. Path A is down. All network devices are sent the error message "Error 1001: Path A is down."
  3. Path B is slow. All network devices are sent the error message "Error 1002: Path B is slow."

This sharing of information is critical to a network.

Figure 4 on this page shows the setup and termination of a data transfer session between a host and a server as follows:

  1. APC sends the following message to a server " I would like to set up a virtual connection with you so we can exchange information."
  2. The Server replies "I agree. We can now send and receive information between us."

3.2.1 Protocols >3.2.1.3 Interaction of Protocols

The figure on this page depicts the protocol stack interaction during a web server and a web client communication as follows:

  1. This communication begins with the hypertext transport protocol (HTTP)
  2. It is then passed to the Transmission Control Protocol (TCP)
  3. From here it is passed to the Internet Protocol (IP) layer
  4. Lastly it is passed to a network access protocol such as Ethernet.

3.2.2 Protocols suites

3.2.2 Protocols suites >3.2.2.1 Protocol Suites and Industry standards

The figure on this page is a table that illustrates the four different protocol suites as follows:

TCP/IPISOAppleTalkNovell Netware
HTTP
DNS
DHCP
FTP
ACSE
ROSE
TRSE
SESE
AFPNDS
TCP
UDP
TP0 - TP1
TP2
TP3 - TP4
ATP - AEP
NBP - RTMP
SPX
IP v 4 - IP v 6
I CMP v 4
I CMP v 6
CONP/C MNS
CLNP/CLNS
AARPIPX
Ethernet PPP Frame Relay ATMW LAN

3.2.2 Protocols suites >3.2.2.2 Creation of the Internet and Development of TCP/IP

The figure on this page is a timeline that shows the evolution of the Internet starting from 1965. A few highlights in time are as follows:

  1. October 29, 1969, the first message is transmitted from an SDS Sigma 7 mainframe computer at University of California, Los Angeles (UCLA) to an SDS 940 mainframe computer at Stanford Research Institute.
  2. 1970, ALOHAnet becomes operational, the first packet radio network, developed by Norman Abramson, University of Hawaii.
  3. 1972, Telnet specification was written (RFC 318). Larry Roberts writes the first email management program. Ray Tomlinson chooses the @ sign to signify the recipient's destination.
  4. 1981, the TCP and IP protocols are formalized (RFC 793 and RFC 791).
  5. 1982, the Exterior Gateway Protocol (EGP) is developed to allow routers to exchange network information (RFC 827).
  6. 1984, the Domain Name Service (DNS) is introduced.
  7. 1985, the File Transfer Protocol (FTP) is documented (RFC 765).
  8. 1986, Cisco launched its first routing innovation, the AGS multiprotocol router.
  9. 1988, The Internet Relay Chat (IRC) is developed by Jarrko Oikarinen.
  10. 1991, Tim Berners-Lee and Robert Cailliau release the specifications for WWW.
  11. 1993, the first web browser, MOSAIC, is developed by Marc Andreessen at the University of Illinois, Champaign-Urbana.
  12. 1995, the first specifications for IP v 6 (the eventual successor to IP v 4) released (RFC 1883).
  13. June 8, 2011, the first World IP v 6 day, many websites and Internet service providers around the world, including Google, Facebook and Yahoo! participated with more than 1000 other companies for a worldwide trial of IP v 6.

3.2.2 Protocols suites >3.2.2.3 TCP/IP Protocol Suite and Communication Process

Figure 1 on this page lists the many TCP/IP protocols organised in layers using the TCP/IP protocol model.

  1. Application layer:
PurposeProtocolDescription
Name systemDNS: Domain Name System (or Service)Translates domain names, such as cisco.com, into I P address.
Host configBOOT P: Bootstrap Protocol* Enables diskless workstations to discover its own IP address, the IP address of a BOOT P server on the network, and a file to be loaded into memory to boot the machine.
* BOOT P is superseded by DHCP
Host configDHCP: Dynamic Host Configuration Protocol* Dynamically assigns IP address to client stations at start-up
* Allows the address to be reused when no longer needed.
EmailSMTP: Simple Mail Transfer protocol* Enables clients to send emails to a server
* Enables servers to send email to other servers.
EmailPOP: Post Office Protocol version 3(POP3)* Enables client to retrieve email from a mail server
* Downloads email from the mail server to desktop.
EmailI MAP: Internet Message Access Protocol* Enables clients to access email stored on a mail server
* Maintains email on the server.
File transferFTP: File Transfer Protocol* Sets rule that enable a user on one host to access and transfer files to and from another host over a network.
* A reliable, connection oriented, and acknowledged file delivery protocol.
File transferTFTP: Trivial File Transfer Protocol* A simple, connectionless file transfer protocol
* A best effort, unacknowledged file delivery protocol
* Utilizes less overhead than FTP
WebHTTP: Hypertext Transfer ProtocolSet of rules for exchanging text, graphic, video, sound and other multimedia files on the World Wide Web.
  1. Transport Layer:
ProtocolDescription
UDP: User Datagram Protocol* Enables a process running on one host to send packets to a process running on another host
* Does not confirm successful transmission
TCP: Transmission Control Protocol* Enables reliable communication between processes running on separate hosts
* Reliable, acknowledged transmissions that confirm successful delivery.
  1. Internet Layer:
PurposeProtocolDescription
 IP: Internet Protocol* Receives message segments from the transport layer
* Packages messages into packets.
* Addresses the packet for end-to-end delivery over an Internetwork.
 NAT: Network Address TranslationTranslates IP addresses from the private network into globally unique public IP addresses
IP supportICMP: Internet Control Message ProtocolProvides feedback from a destination host to a source host about the errors in the packet delivery.
Routing ProtocolsOSPF: Open Shortest Path First* Link-state routing protocol
* Hierarchical design based on areas
* Open standard interior routing protocol
Routing ProtocolsEIGRP: Enhanced Interior Gateway Routing Protocol* CISCO proprietary protocol
* Uses composite metric based on bandwidth, delay, load and reliability.
  1. Network Access Layer:
ProtocolDescription
ARP: Address Resolution ProtocolProvides dynamic address mapping between an IP address and a hardware address.
PPP: Point-to-Point protocolProvides a means of encapsulating packets for transmission over a serial link.
EthernetDefines the rules for wiring and l standards of the network access layer.
Interface driverProvides instruction to a machine for the control of a specific interface on a network device.

Figure 2 on this page is an animation that depicts the protocol encapsulation process involved when a web server sends a web page to a client across a network. A detailed description is in the page notes.

Figure 3 on this page is an animation that depicts the protocol de-encapsulation process involved when a web client receives a web page from a web server across a network. This is the reverse of figure 2.

3.2.2 Protocols suites >3.2.2.4 Activity-mapping the protocols of the TCP/IP suite

The figure on this page displays the following list of TCP/IP protocols:

  • Ethernet
  • POP
  • Interface Drivers
  • TCP
  • DNS
  • UDP
  • HTTP
  • EIGRP
  • IP
  • SMTP
  • OSPF
  • DHCP
  • I MAP
  • ICMP
  • FTP
  • BOOT P

A 4 column table is also displayed with the following column headings representing various layers of the TCP/IP model:

  1. Application
  2. Transport
  3. Internet
  4. Network Access

The user is asked to match each of the TCP/IP protocols with the corresponding layer of the TCP/IP model.

3.2.3 Standards Organizations >3.2.3.1 Open Standards

The image on this page shows common standards organizations including:

  • The Electronic Industries Alliance (EIA)
  • The Internet Engineering Task Force (IETF)
  • The Internet Assigned Numbers Authority (I NA)
  • The Institute of Electrical and Electronics Engineers (IEEE)
  • The Internet Corporation for Assigned Names and Numbers (ICANN)
  • The International Telecommunication Union (ITU)
  • The Telecommunications Industry Association (TIA)

3.2.3 Standards Organizations >3.2.3.2 I SOC, IAB and IETF

The figure on this page shows the organizational chart for the Internet Society (ISOC). The Internet Architecture Board (IAB) is the only branch off of the Internet Society, and it has two branches, the Internet Engineering Task Force and the Internet Research Task Force.

3.2.3 Standards Organizations >3.2.3.3 IEE

The figure on this page lists many IEEE 8 0 2 working groups and study groups as follows:

  • 8 0 2.1: Higher Layer LAN Protocols Working Group
  • 8 0 2.3: Ethernet working Group
  • 802.11: Wireless LAN Working Group
  • 8 0 2.15 Wireless Personal Area Network (W PAN) Working Group
  • 8 0 2.16: Broadband Wireless Access Working Group
  • 8 0 2.18: Radio Regulatory TAG
  • 8 0 2.19: Wireless Coexistence Working Group
  • 8 0 2.21: Media Independent Handover Services Working Group
  • 8 0 2.22: Wireless Regional Area Networks
  • 8 0 2.24: Smart Grid TAG

3.2.3 Standards Organizations >3.2.3.4 ISO

The figure on this page shows the symbol for the International Organization for Standardization, also known as the ISO.

3.2.3 Standards Organizations >3.2.3.5 Other Standards Organisations

The figure on this page shows common standards organizations as follows:

  • Internet Engineering task force (IETF)
  • Telecommunications Industry Association (TIA)
  • Internet Assigned Numbers Authority (IANA)
  • The International Telecommunications Union - Telecommunication Standardisation Sector (ITU-T)
  • Internet Corporation for Assigned Names and Numbers (ICANN)
  • Electronic Industries Alliance (EIA)

3.2.3 Standards Organizations >3.2.3.6 Lab - Researching Networking Standards

See Lab Descriptions.

3.2.3 Standards Organizations >3.2.3.7 Activity - Standards Body Scavenger Hunt

On this page, links are displayed to the six standards organisations that are responsible for creating, developing and monitoring many of the protocols/standards used in today's communications world. The links are:

A 7 column table is also displayed. The first column lists the following descriptions or functions:

  1. Manages the DNS Root Zone standards and the .int registry.
  2. Creates standards for worldwide cabling infrastructure.
  3. Defines policies describing how "names and numbers" of the internet operate.
  4. Official standards products are RFC documents, published free of charge.
  5. Standards are developed using a six stage lifecycle diagram.
  6. Uses communications standards to predict famines and global climate changes.
  7. Supports "bridge the digital divide" initiatives.
  8. Creates standards for wired & wireless technologies.
  9. Serves as the central repository for protocol name and number registries.
  10. Offers online tools and resources for standards and developers.
  11. Provides wireless standards for IPTV.
  12. Coordinates unique international Internet addresses for site names & IP addresses.
  13. Standardises the IP to applications protocol layers.
  14. Supports navigation and online maps via radio/satellite transmissions.
  15. Provides a space where Internet protocols are set and maintained.
  16. Manages the DNS, IP addresses and protocol identifier assignments.
  17. "Makes the Internet work better", using an engineering approach.
  18. Develops standards/protocols affecting cloud computing.
  19. Develops standards for homeland security/emergency response teams.

The remaining columns have the six organisation names as column headings.

The user is asked to read the page provided for each organisation and match the standards organisation to its description (or function).

3.2.4 Reference models >3.2.4.1 The Benefits of Using a Layered Model

The figure on this page shows the two competing networking models side by side, the seven layer OSI model and the four layer TCP/IP model. The main TCP/IP suite protocols are listed for each of the layers as follows:

  • The Application, Presentation and Session layers of the OSI model line up with the Application layer of TCP/IP model, which is made up of HTTP, DNS, DHCP, and FTP.
  • The Transport layers of both models align together and carry TCP and UDP.
  • The OSI Network layer aligns with the TCP/IP models Internet layer and carries IP v 4, IP v 6,

IC MP v 4 and ICMP v 6.

  • The OSI Data lLnk and Physical layers align with the TCP/IP models Network Access layer and some of the protocols here are PPP, Frame Relay and Ethernet.

3.2.4 Reference models >3.2.4.2 The OSI Reference model

The figure on this page lists the seven layers of the OSI model and the following brief descriptions of what each layer provides:

7. Application: The application layer provides the means for the end-to-end connectivity between individual in human network using data networks.
6. Presentation: The Presentation Layer provides for common representation of the data transferred between application layer services.
5. Session: The session layer provides services to the presentation layer to organize its dialogue and to manage data exchange.
4. Transport: The Transport Layer define services to segment transfer, and reassemble the data for individual communications between the end devices.
3. Network: The network layer provides services to exchange the individual pieces of data over the network between the identified end devices.
2. Data Link: The data link layer protocol describes the methods for exchanging the data frames between devices over a common media .
1. Physical: The physical layer protocol describes the mechanical,electrical,functional and procedural means to activate,maintain,d-activate physical connections for bit transmissions to and from a network device.

3.2.4 Reference models >3.2.4.3 The TCP/IP Protocol model

The figure on this page lists the four layers of the TCP/IP model and the following brief descriptions of what each layer provides:

ApplicationRepresents data to the user ,plus encoding and dialog control.
TransportSupports communication between diverse devices across diverse networks.
InternetDetermines the best path through the network.
Network AccessControls the hardware devices and media that make up the network.

3.2.4 Reference models >3.2.4.4 Comparing the O S I Model with the TCP/IP Model

The figure on this page lines up the OSI Model and the TCP/IP Model side by side and shows the correlation between layers as follows:

  • The Application, Presentation and Session layers of the OSI model line up with the Application layer of TCP/IP model.
  • The Transport layers align together.
  • The OSI Network layer aligns with the Internet layer of TCP/IP.
  • The OSI Data link and Physical align with the TCP/IP Network Access layer.

The description given for this figure is "The key similarities are in the Transport and Network layers, however, the two models differ in how they relate to the layers above and below each layer."

3.2.4 Reference models >3.2.4.5 Activity - identify Layers and Functions

Figure 1 on this page lists the following 7 OSI layers:

7. Application
6. Presentation
5. Session
4. Transport
3. Network2. Data Link
1. Physical

The OSI layer functional descriptions are also listed as follows:

  1. Manages data exchange
  2. Exchanges frame between devices
  3. Data representation
  4. Provides a data path or route
  5. Bit transmission

The user is asked to match each layer with its functional description

Figure 2 on this page lists the following 4 TCP/IP layers:

  • Application
  • Transport
  • Internet
  • Network Access

The TCP/IP layer functional descriptions are also listed as follows:

  • Exchange frames between devices
  • Organises dialog - manages data exchange
  • Segments, transfers and reassembles data
  • Determines the best path through a network
  • Represents data to the user and controls dialogs

The user is asked to match each layer with its functional description.

3.2.4 Reference models >3.2.4.6 Packet Tracer - Investigating the TCP/IP and OSI Models in Action

Objectives

Part 1: Examine HTTP Web Traffic
Part 2: Display Elements of the TCP/IP Protocol Suite

3.2.4 Reference models >3.2.4.7 Lab - Researching RFC's

See Lab Descriptions

3.3 Moving data in the Network

3.3.1 Data Encapsulation >3.3.1.1 Communicating the messages

Figure 1 has two animations as follows:

  • The first animation depicts the process of segmenting a message. Segmentation is the breaking up of communication into pieces. In this animation a message is segmented into four segments and each one is transmitted.
  • The second animation depicts the multiplexing process where two computers share access to the network. Multiplexing is the interleaving of the pieces of communication as they traverse the media. Multiple communications are interleaved, giving each user a part of the bandwidth.

Figure 2 shows the labelling of segments to provide ordering and assembling of the segments as they are sent from the source and as they arrive at their destination.\ Multiple pieces are labelled for easy direction and re-assembly. Labelling provides for ordering and assembling the pieces when they arrive.

3.3.1 Data Encapsulation >3.3.1.2 Protocol Data Units (PDU's)

The figure on this page shows the data encapsulation process as a message is passed down the protocol stack as follows. The example is an e-mail and it starts as data at layer seven:

  1. The PDU is a segment when it acquires the transport layer header
  2. It becomes a packet when it receives the network header
  3. When the frame header and trailer are added the PDU becomes a frame
  4. As it moves to transmission across the medium it is in bits.

3.3.1 Data Encapsulation >3.3.1.3 Encapsulation

The figure on this page is an animation of protocol operations sending a message. In the animation a web page is being sent from a web server to a web client as follows:

  1. The data is passed from the application layer down to the transport layer where the data is encapsulated by the transport layer information, and here it is using TCP
  2. The segment is then passed to the Internet layer where it gets the IP addressing information
  3. The encapsulation continues as the packet is then passed to the data link layer where it is encapsulated within a frame header and trailer
  4. The bits are encoded onto the media by the server network interface card.

3.3.1 Data Encapsulation >3.3.1.4 De-encapsulation

The figure on this page is an animation of protocol operations receiving a message. In this figure the data is taken apart in the reverse order that it was encapsulated in as follows:

  1. The receiving computer removes the layer two header and trailer and checks the frame addressing
  2. The computer determines that it needs to read the data so it removes the IP address and reads the segment information
  3. The computer removes the segment header and then processes the data, which for a web client means displaying the web page.

3.3.1 Data Encapsulation >3.3.1.5 Activity - Identify the PDU layer

The figure on this page lists the following 5 PDU's:

  • Packets
  • Bits
  • Frames
  • Data
  • Segments

The user is asked to organise the PDU's in the proper order in the stack to illustrate the order of the encapsulation process for sending a message.

3.3.2 Accessing Local Resources >3.3.2.1 Network Addresses and Data Link addresses

The figure on this page shows a Network addresses and data link addresses representation in each OSI layer as follows:

PhysicalData LinkNetworkTransportUpper Layers
Timing and synchronization bitsDestination and source physical addressesDestination and source logical network addressesDestination and source process number (ports)Encoded application data

3.3.2 Accessing Local Resources >3.3.2.2 Communicating with a Device on the Same Network

The figure on this page shows the source and destination MAC addresses being added to an Ethernet frame as follows:

  • PC1 is the source and has a MAC address of A A-A A-A A-A A-A A-A A.
  • The FTP server is the destination and it has a MAC address of C C-C C-C C-C C-C C-C C.

These two MAC addresses are placed into the frame header.

3.3.2 Accessing Local Resources >3.3.2.3 MAC and IP Addresses

The figure on this page is an animation showing the ARP process that occurs on a local area network. The sending computer is PC1 and it is sending data to an FTP server. The computer knows the IP address of the server, which is 192.168.1.9. However it does not have the server’s MAC address in its ARP cache, so it will send out an ARP request. This ARP request will ask for the device with a specified IP address to respond with its MAC address. The ARP request is sent to the switch which will broadcast it out to all ports. The device with the specified IP address will respond to the initiating device with its MAC address.

3.3.3 Accessing remote resources >3.3.3.1 Default Gateway

The figure on this page shows the process of a computer on a local network using its default gateway to send a message to a destination outside of the local network. In the network there are two computers and one FTP server all on the same segment. They all have the same IP address for a default gateway, which is 192.168.1.1, and this device is the closest router port to each of the devices.

3.3.3 Accessing remote resources >3.3.3.2 Communicating with a Device on a Remote Network

The figure on this page shows a computer communicating with a device on a remote network as follows:

  • PC1 has an IP address of 192.168.1.110 and a MAC address of A A-A A-A A-A A-A A-A A.
  • PC1 is sending data to a remote web server at IP address 172.16.1.99 and a MAC address of AB-CD-EF-12-34-56.
  • The server is on a remote network so PC1 has to send the data to the router to be sent across the network.
  • When PC1 forms the data frame the source IP and source MAC address are from PC1.
  • The destination IP is that of the server, but the destination MAC is that of the router, which is the default gateway. So in the figure that address is 11-11-11-11-11-11.

The point here is that the switch needs to send the data to the router to be routed, and it only knows the router by MAC address.

3.3.3 Accessing remote resources >3.3.3.3 Packet Tracer - Explore a Network

Objectives

Part 1: Examine Internetwork Traffic at Branch
Part 2: Examine Internetwork Traffic to Central
Part 3: Examine Internet Traffic from Branch

3.3.3 Accessing remote resources >3.3.3.4 Lab - Using Wireshark to View Network Traffic

See Lab Descriptions.

3.4 Summary

3.4.1 Summary >3.4.1.1 Activity - Guaranteed to Working

The figure on this page shows the two competing networking models side-by-side and lists some common TCP/IP protocols used at each layer.

The description given for this figure is "Using network protocols and standards facilitates quality data delivery in a timely manner."

Objectives

Explain the role of protocols and standards organizations in facilitating interoperability in network communications.
In this activity, the learner is asked to demonstrate how network communications can be compared to everyday activities using established procedures and standards.

3.4.1 Summary >3.4.1.2 Summary

The figure on this page shows the two competing networking models side-by-side, the seven layer OS I model and the four layer TCP/IP model.

The description given for this figure is "The key parallels are in the Transport and Network layers"

End of learner 3: Network Protocols and Communications.

Next - learner 4: Network Access.

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Page last modified on July 31, 2014, at 01:48 AM