1. Chapter 2 Communicating Over the Network
Modified by Profs. Chen and Cappellino 1

2. Objectives This chapter prepares you to:
Describe the structure of a network, including the devices and media that are necessary for successful communications.
Explain the function of protocols in network communications.
Explain the advantages of using a layered model to describe network functionality.
Describe the role of each layer in two recognized network models: The TCP/IP model and the OSI model.
Describe the importance of addressing and naming schemes in network communications.

3. The three Elements of Communication
The first - message ___________, or sender.
The second -________________, or receiver
receives the message and interprets it.
A third - a __________________
the media that provides the pathway over which the message can travel from source to destination.

4. Communicating the Messages
In theory, a single communication, such as a an message, could be sent across a network from a source to a destination as one massive continuous stream of bits.
Why is this not a good idea?
The solution: divide data into _____________, more manageable pieces to send over the network.
This division of the data stream into smaller pieces is called ___________________.

5. Communicating the Messages
Segmenting messages has two primary benefits.
First, many ___________________________ _________ or mixed together on the network.
The process used to mix together the pieces of separate and distinct conversations on the network is called ______________.
Second, segmentation can _______________ ______________ of network communications.
Separate pieces need __________________________ across the network from source to destination.
If part of the message fails to make it to the destination, _______ __________________________________________________

6. Communicating the Messages
Disadvantage of segmentation and multiplexing
______________________________________
Each packet must be individually addressed and numbered
Then reassembled into the content of the original message.
Devices throughout the network and protocols ensure that the pieces of the message arrive reliably at their destination.

7. Components of the Network
_____________________ are the physical elements or _____________________ of the network.
Can you list some examples of devices?
Can you list some examples of media?
_______________________________________ that run on the networked devices.
Services include ______________________________ we use. What are some examples?
____________________________________ that directs and moves the messages through the network
The set of rules which help determine what goes where
______________________ consist of ___________ or _________________________ (more to come…)

8. End Devices and their Role on the Network
Example of end devices:
____________________________ (work stations, laptops, file servers, web servers)
Network _____________________
______________________________
Security cameras
__________________________________ (such as wireless barcode scanners, PDAs)
End devices are referred to as ______________.
A host can act as a client, a server, or both.
______ have software installed that enables them to provide information and services, like or web pages, to other hosts on the network.
Network computer that responds to client requests for network resources
_____________________________________ obtained from the server.

9. Intermediary Devices and their Role on the Network
Networks rely on ___________________________ _______________________ and ensure that data flows to destination
work behind the scenes
Examples of intermediary network devices are:
_________________________ Devices (____________ __________________, and wireless access points)
_______________________________ (____________)
Communication Servers and Modems
_______________________ (_________________)
In managing data, _________________ devices use the ___________________________, in conjunction with information about the network interconnections, in path determination

10. Intermediary Devices and their Role on the Network
Processes possibly running on some or all the intermediary network devices are:
________________________________
_____________________________ about what _________________________________
_____________________ other devices ____________ and communication failures
Direct data along __________________________ when there is a link failure
Classify and direct messages according to QoS priorities
__________________________________, based on security settings – ACL’s

11. Network Media
Communication across a network- from source to destination is carried on a _____________________.
These media are:
____________ within cables
Data sent via ___________ pulses
___________________ (fiber optic cable)
Data sent via ________________
______________ transmission
Data sent via electromagnetic _________________

12. Network Media
Different types of network media have different features and benefits.
The ___________________ the media can successfully carry a signal
_____________ can carry a signal the farthest
The __________ in which the media is to be installed
___________ best in “noisy” environments
The ________________________ at which it must be transmitted.
Cat 5 can go fairly high and is often very sufficient but fiber is best
The ________________ of the media and installation
________________ is most costly!

13. Network Infrastructures
Vary greatly in terms of:
The size of the area covered
The number of users connected
The number and types of services available
Different types include:
___________ (Local Area Networks)
___________ (Wide Area Networks)
___________ (Storage Area Networks)
ETC

14. Local Area Networks An individual ______________ network
__________________________ _____________________
providing services to people within a __________________________,
single business, campus or region.
Administered by a ___________ ______________________
The administrative control that governs the security and access control policies are enforced on the _______________________
Ie. – under control of that business itself

15. Wide Area Networks __________________________ ________________________
Typically _________________ capacity
slower than LAN’s
_____________ (businesses) that are at distant locations
businesses generally use a _________________________ ___________ (TSP) to interconnect the LANs at the different locations.
WANs use specifically designed network devices to make the interconnections between LANs.

16. The Internet – A Network of Networks
Enables user to communicate with a resource on another network, outside of our local organization.
Internetwork (aka Network)
The most well-known and publicly-accessible internetwork is the Internet.
Internet Service Provider (ISP) networks _____________ _________________ to help form the Internet
Use generally accepted standards and protocols
Intranet
Refers to ____________________________________ ___________________________________________ _______________________, or others with authorization.
Accessed internally or remotely

17. Network Representations
Recall “Elements of a Network” from Chapter 1
We will be using visual representations often so please commit them to memory
Additional important terms:
______________________ - A NIC, or LAN adapter, provides the ________________ __________________ or other host device.
The media connection plugs directly into the NIC.
Physical Port - A _________ or outlet on a networking device ___________________ ___________________
Interface - Specialized ports on an internetworking device ________________ _________________________________
the ports on a router are referred to _____________________

18. Rules that Govern Communications
For successful communication, _____________________________ must be followed by both parties
These protocols are ________________ ______________________ that is loaded on each host and network device.
Easy way to think of protocols interacting with each other to help move data along, is to think of a stack or layered hierarchy.
Each __________________________ depends on the functionality defined by the ____________________________
Higher level protocols focus on message being sent and user interface
The ____________________ of the stack are concerned with __________________ __________________________

19. Network Protocol Suite:
____________________________________ ______________________________
used in a computer network
Example: ________________protocol suite
Must describe precise requirements and interactions such as:
The ______________ or structure of the message
The ____________ by which networking devices share information about pathways with other networks
How and when __________ and system messages are ______________________________
The ___________________ of data transfer sessions

20. Proprietary Network Protocols
Individual protocols in a protocol suite _____ _________________________________
_______________ or vendor ___________ the definition of the protocol and how it functions.
Not so with the TCP/IP protocol suite
________________________________

21. Industry Standards-
A process or protocol that ______________ _________________________ and ratified by a ________________________
Ex: the Institute of Electrical and Electronics Engineers (IEEE) or the Internet Engineering Task Force (IETF).
Use of standards ensures that products _____ ____________________________________ for efficient communications.
Can anyone think of an example of a product/process or protocol that is considered standard?

22. Example: interaction of protocols between a web server and a web browser.
___________________________:
Hypertext Transfer Protocol (HTTP) is a protocol that governs the way that a web server and a web client interact.
HTTP defines first- the content and formatting of the requests and second- the responses exchanged between client and server.
How are the messages transported?... ___________________________:
______________________________ ________________________________ ________________ - in this example- between web servers and web clients
TCP divides the HTTP messages into __________ _________________________, to be sent to the destination client.
TCP also controls the rate at which messages are exchanged.

23. Example: interaction of protocols CONT…
____________________________:
Internet Protocol (IP) is responsible for taking the segments (from upper transport layer), ___________________________, _______ ___________________________________
Then selecting the ________________________ to the destination host.
________________________________:
Network access protocols describe two primary functions, _____________________ and the ______________________ of data on the media.
Data-link management protocols take the packets from IP (the above layer) and format them to be transmitted over the media.
The standards and protocols for the physical media govern ______________________________________________ and how they are interpreted by the receiving clients.
Transceivers on the network interface cards (NICs) implement the appropriate standards for the media that is being used.

24. Technology Independent Protocols
Networking protocols describe the _______ __________ during network communications.
Protocols generally __________________ ________________ a particular function.
This is why many protocols are said to be ___________________________
This means that a computer - and other devices – can, for example, access a web page stored on any type of web server (IIS, Apache, etc) that uses any form of operating system (Windows, MAC, Linux) from anywhere on the Internet.

25. The Benefits of Using Layered Model
________________________
protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below.
_________________ because products from different vendors can work together.
_____________ technology or capability _______________________________ _______________ above and below.
________________ to describe networking functions and capabilities.
Helps us visualize and __________ about networking and protocol interaction

26. Protocol and Reference Models
There are two basic types of networking models: protocol models and reference models.
A _______________ model: provides a model that ________ ________________________________________________.
The hierarchical set of related protocols in a suite typically represents all the functionality required to interface the human network with the data network.
The ____________________ (seen in previous example) is a protocol model because it describes the functions (and protocols) that occur at each layer of the TCP/IP suite.
________ Model

27. Protocol and Reference Models
A _______________ model: helps provide ____________ _______________________ involved in all types of network protocols and services.
Not intended to provide a sufficient level of detail to define precisely the services of the network architecture.
The _________________________ ___________ is the most widely known internetwork reference model.
Used in ___________, operation specifications, and troubleshooting.
________ Model

28. Please memorize the functions represented at leach layer
The TCP/IP Model
It defines ________ categories of functions (in layers) that must occur for communications to be successful.
An _____________________ ________________________
________________________ over definitions and standards of the model
Definitions and standards (including use of the protocols) defined in a publicly-available set of documents
_____________________________
Please memorize the functions represented at leach layer

29. Communication Process (through the TCP/IP model)
A complete communication process includes these steps:
1. _____________ at the application layer of the __________ device
2. __________________________________ of data as it passes down the protocol stack in the source end device
3. Generation of the data _______________________ at the network access layer of the stack
4. _____________________________________________, which consists of media and any intermediary devices
5. _________________ of the data at the network access layer of the _____________________ device
6. _____________________ of the data as it passes up the stack in the destination device
7. Passing this data to the destination application at the Application layer of the destination device

30. Protocol Data Units and Encapsulation
______________________
__________________________ _______________________
The encapsulation process:
As application data is passed down the protocol stack various ________________________ to it _______________________.
The form that a piece of data takes at any layer is called a _______________________
During encapsulation, each succeeding layer encapsulates the PDU that it _____________ __________________ in accordance with the protocol being used.

31. Protocol Data Units and Encapsulation
At each stage of the process, a PDU has a different name to reflect its new appearance.
______ - The general term for the PDU used at the _____________
________ - _____________ PDU
_________ - _______________ Layer PDU
____________ - _____________ ___________ PDU
______________ - A PDU used when __________________ data over the medium

32. The Sending and Receiving process (from Web Server to client)
In the web server example from earlier:
The Application layer: HTTP begins the process by delivering the HTML web page data to the Transport layer.
The Transport layer: The application data is broken into TCP segments.
Each TCP segment is given a label, _____________, containing information about which process running on the destination computer should receive the message.
The Transport layer: encapsulates the web page HTML data within the segment and sends it to the Internet layer,
The Internet layer: Here the entire TCP segment is encapsulated within an IP packet, which adds another label, called the IP header.
The IP header contains source and destination IP addresses.
The Network Access layer: Using the Ethernet protocol, the packet is encapsulated within a frame header and trailer.
Frame header contains source and destination physical address.
The trailer contains error checking information.
Finally the bits are encoded onto the Ethernet media by the server NIC.
This process is reversed at the receiving host.
Data travels up the layers of the model

33. The OSI Model
Designed by the ______________ ________________________________________ (ISO)
Provides an extensive list of functions and services that can occur at each layer.
It also describes the ____________ _________________________________________________________
NOTE:
Although the content of this course will be structured around the OSI Model
the focus of discussion will be the protocols identified in the TCP/IP protocol stack.

34. Supplementary OSI layer slides
ALL PEOPLE SEEM TO NEED DATA PROCESSING

35. 7. The Application Layer
_______________________________ ________________________
provides general network access
Directly supports user applications
The OSI layer ____________________
Applications it supports are outside the OSI layer model
Example of applications:
________________________________

36. 6. The Presentation Layer
Ensures that data sent by the application layer of one system is readable by the application layer of another system
________ the way data is _____________ __________________________

37. 5. The Session Layer
____________________________ _____________________ between applications on different computers

38. 4. The Transport Layer
Segments data from the sending host & reassembles data on the receiving host
____________________________________________________________________________________________.
Error detection-and-recovery
Information flow control
Involved in Quality Of Service, Reliability

39. 3. The Network Layer
_________________________________ ______________ between two end systems
based on network conditions, priority of service etc
__________________ occurs at this layer

40. 2. The Data Link Layer
Provides reliable __________________ ______________________ (media)
______________ (vs. logical)addressing
Cyclical redundancy check (_______) allows for __________________________

41. 1. The Physical Layer
Defines the _______________________ __________________________ specifications for the ______________
Wires, connectors, voltages, data rates
Transmits ______________________ over the physical medium

42. Comparing the OSI and TCP/IP Model
The key parallels between the two models occur at the OSI model _______________________
L3 of OSI deals with addressing and routing of messages
The ___________________ is the TCP/IP suite protocol that includes the functionality described at ___________
Functions at L4 of OSI include acknowledgement, error recovery, and sequencing.
______________________________ includes the functionality described at ________________
Application layer and the Network Access layer of the TCP/IP model are further detailed in the OSI model
At the TCP/IP Network Access Layer,
the TCP/IP protocol suite does not specify which protocols to use when transmitting over a physical medium; it only describes the handoff from the Internet Layer to the physical network protocols.
The TCP/IP Application layer
OSI model Layers 5, 6 and 7 are used as references for application software developers and vendors to produce products that need to access networks for communications.

43. Addressing in the Network
The OSI model describes the processes of encoding, formatting, segmenting, and encapsulating data for transmission over the network.
Using the OSI model as a guide, we can see the different addresses and identifiers that are necessary at each layer.
Address identifiers are added to the data (using encapsulation) as it travels down the protocol stack on the source host.

44. Getting the Data to the End Device Focusing on Layer 2 PDU – Frame…
Host physical address, is contained in the header of the frame.
The physical address is also called the ______________________________
Layer 2 is concerned with the delivery of messages on a _____________ _______________________
The MAC address is unique on the local network and _______________________ _______________________________
Once a frame is successfully received by the destination host, the Layer 2 address information is removed as the data is decapsulated and moved up the protocol stack to Layer 3…

45. Getting the Data Through the Internetwork Focusing on Layer 3 PDU – Packet…
Layer 3 protocols are designed to ____ _____________________________________________ within an internetwork.
Layer 3 addresses must include _________ that enable intermediary network devices to _______________________________
Every _________________________ __________________________________________________________
___________ use the __________ identifier portion of this address to determine which path to use to reach the destination host.
Once the path is determined, the router encapsulates the packet in a new frame and sends it on its way toward the destination end device.
When the frame reaches its final destination, the frame and packet headers are removed and the data moved up to Layer 4.

46. Getting the Data To the Right Application
At Layer 4, information contained in the PDU header (segment) identifies the _____________________ _____________________________________________________________________________
Hosts can run ______________________________.
Example: client running at the same time as a web browser, an instant messaging program etc
All these separately running programs are examples of individual processes.
Each application or service is _______________ at Layer 4 by a ________________________
A unique dialogue between devices is identified with a pair of Layer 4 source and destination port numbers that are representative of the two communicating applications.
When the data is received at the host, the ____________ _____________________________________________________________________________________

47. Putting it all together
OSI Layer #
ISO Layer Name
TCP/IP #
TCP/IP layer Name
Encapsulation Units
Devices or Components
TCP/IP Protocols
Keywords/Description 7
Application (All) 4
Application
data PC
FTP, HTTP, POP3, IMAP, telnet, SMTP, DNS, TFTP
Network services for application processes, such as file, print, messaging, database services 6
Presentation (People)
Standard interface to data for the application layer. MIME encoding, data encryption, conversion, formatting, compression 5
Session (Seem)
Interhost communication. Establishes, manages and terminates connection between applications
Transport (To) 3
Transport
segments
TCP, UDP
End-to-end connections and reliability. Segmentation/desegmentation of data in proper sequence. Flow control
Network (Need) 2
Internet
packets
router IP
Logical addressing and path determination. Routing. Reporting delivery errors
Data Link (Data) 1
Network Access
frames
bridge, switch, NIC
Physical addressing and access to media. Two sublayers: Logical Link Control (LLC) and Media Access Control (MAC)
Physical (Processing)
bits
repeater, hub, tranciever
Binary transmission signals and encoding. Layout of pins, voltages, cable specifications, modulation