What does the application layer provide?
the interface between the applications we use to communicate and the underlying network over which our messages are transmitted
What are the three elements of communication?
Sender, Receiver, Chanel
What are the five aspects of the information network we will focus on in this course?
Devices that make up the network
Media that connect the devices
Messages that are carried across the network
Rules and processes that govern network communications
Tools and commands for constructing and maintaining networks
What is the definition of the term network for this course?
data or information networks capable of carrying many different types of communications, including traditional computer data, interactive voice, video, and entertainment products.
What would happen to the network if a message was sent as one massive continuous stream of bits?
no other device would be able to send or receive messages on the same network while this data transfer was in progress
Define segmentation of messages
division of the data stream into smaller pieces
What are the 2 advantages of segmentation?
many different conversations can be interleaved on the network
segmentation can increase the reliability of network communications
What is multiplexing?
process used to interleave the pieces of separate conversations together on the network
What is hardware on a network?
the visible components of the network platform
the visible components of the network platform
Computers (work stations, laptops, file servers, web servers)
Network printers
VoIP phones
Security cameras
Mobile handheld devices (such as wireless barcode scanners, PDAs)
What is the definition of a host?
either the source or destination of a message transmitted over the network
What is the definition of a server?
hosts that have software installed that enables them to provide information and services
What is the definition of a client?
hosts that have software installed that enables them to request and display the information obtained from the server
List examples of intermediary devices.
Network Access Devices (Hubs, switches, and wireless access points)
Internetworking Devices (routers)
Communication Servers and Modems
Security Devices (firewalls)
List examples of process that intermediary devices perform.Regenerate and retransmit data signals
Regenerate and retransmit data signals
Maintain information about what pathways exist through the network and internetwork
Notify other devices of errors and communication failures
Direct data along alternate pathways when there is a link failure
Classify
What are the 3 primary types of media used in modern networks?
Metallic wires within cables
Glass or plastic fibers (fiber optic cable)
Wireless transmission
What criteria should be used to select network media?
The distance the media can successfully carry a signal.
The environment in which the media is to be installed.
The amount of data and the speed at which it must be transmitted.
The cost of the media and installation
What are the ways in which network infrastructure can vary?
The size of the area covered
The number of users connected
The number and types of services available
What is the definition of a LAN?
individual network usually spans a single geographical area, providing services and applications to people within a common organizational structure
What is the definition of a WAN?
networks that connect LANs in geographically separated locations
What is an internetwork?
A global mesh of interconnected networks (internetworks) meets these human communication needs.
What is an intranetwork?
a private connection of LANs and WANs that belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization
Define a NIC
provides the physical connection to the network at the PC or other host device.
Define a physical port
A connector or outlet on a networking device where the media is connected to a host or other networking device.
Define an interface
Specialized ports on an internetworking device that connect to individual networks.
What are the 3 layers of protocols described?
Content Layer, Rules Layer, Physical Layer
What process do networking layer protocol suites describe?
The format or structure of the message
The process by which networking devices share information about pathways with other networks
How and when error and system messages are passed between devices
The setup and termination of data transfer sessions
What is proprietary?
one company or vendor controls the definition of the protocol and how it functions
What does the use of standards and protocols provide?
products from different manufacturers can work together for efficient communications
What is an application protocol?
defines the content and formatting of the requests and responses exchanged between the client and server
What is a Transport Protocol?
manages the individual conversations between web servers and web clients
What is the Internetwork Protocol
responsible for taking the formatted segments from TCP, encapsulating them into packets, assigning the appropriate addresses, and selecting the best path to the destination host.
What is the Network Access Protocol?
Network access protocols describe two primary functions, data link management and the physical transmission of data on the media.
What do networking protocols describe?
the functions that occur during network communications
What are the benefits of using a layered model to describe networking?
Assists in protocol design, because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below.
Fosters competition because products from different vendors can work together
What are the two basic types of networking models?
protocol models and reference models
What are the two primary models used when describing networking?
TCP/IP and OSI
What is done at the Application Layer?
Represents the data to the user plus encoding and dialog control
What is done at the Transport Layer?
Supports communication between diverse devices across diverse neworks
What is done at the Internet Layer?
Determines the best path through the network
What is done at the Network Access Layer?
Controls the hardware devices and media that make up the network
What are the seven steps in a complete communication process?
1. Creation of data at the application layer of the originating source end device
2. Segmentation and encapsulation of data as it passes down the protocol stack in the source end device
3. Generation of the data onto the media at the network access layer
What is the PDU for the application layer?
Data
What is the Transport Layer PDU?
Segment
What is the PDU for the Internet Layer?
Packet
What is the PDU for the Network Access Layer?
Frame
What PDU is used when physically transporting the information over the medium?
Bits
How is the protocol stack processed when sending information?
Top to bottom
What is the process use at the receiving end called?
Decapsulation
What are the seven layers of the OSI Model?
Application, Presentation, Session, Transport, Network, Data Link, Physical
Which Layers of the OSI Model parallel with the TCP/IP Model?
Application, Presentation, Session-Application
Transport-Transport
Internet-Network
Data Link, Physical-Network Access
What does the physical layer do?
Timing and synchronization of bits
What addresses does the data link layer use?
Destination and source physical address
What address does the network layer use?
Destination and source logical address
What does the transport layer use?
Destination and source process number (ports)
What do the upper layers use?
Encoded application data
What is the PDU for Layer 2 called
Frame
What is the layer 2 address called?
MAC address
What happens after the frame has reached its' destination?
the Layer 2 address information is removed as the data is decapsulated and moved up the protocol stack to Layer 3
What are layer 3 devices primarily designed for?
to move data from one local network to another local network within an internetwork
What address is used at Layer 3?
IP address
What is the PDU of the Layer 3 information?
Packet
Which device decapsulates the frame at the edge of a network?
Router
What does a router do?
use the network identifier portion of this address to determine which path to use to reach the destination host
What happens when the frame reaches the end device?
the frame and packet headers are removed and the data moved up to Layer 4
What does the information in the frame provide at Layer 4?
identifies the specific process or service running on the destination host device that will act on the data being delivered
How is each application or service represented at Layer 4?
Port number
What are application layer protocols used for?
to exchange data between programs running on the source and destination hosts
What are the three primary functions of the Presentation Layer?
Coding and conversion of Application layer data to ensure that data from the source device can be interpreted by the appropriate application on the destination device.
Compression of the data in a manner that can be decompressed by the destination device.
What is the main function of the session layer?
create and maintain dialogs between source and destination applications
What do the Application Layer protocols of the TCP/IP protocol specify?
the format and control information necessary for many of the common Internet communication functions
What are the two forms of software programs or process that provide network access in the Application Layer
applications and services
What do protocols provide?
the rules and formats that govern how data is treated
What is the difference between an application and a service?
Applications interact with the user and services prepare data for the network
What do application layer protocols do?
Protocols provide the rules and formats that govern how data is treated.
What 6 things do protocols define?
1. processes on either end of the communication
2. types of messages
3. syntax of messages
4. meaning of any informational fields
5. how messages are sent and the expected response
6. interaction with the nextlower layer
What is the difference between a client and a server?
the device requesting the information is called a client and the device responding to the request is called a server
In general networking sense what is a server?
any device that responds to requests from client applications is functioning as a server
Describe the 2 processes a daemon uses (listening and hears)?
listening" for a request from a client, because they are programmed to respond whenever the server receives a request for the service provided by the daemon
"hears" a request from a client, it exchanges appropriate messages with the client, as required b
What is a peer-to-peer network?
two or more computers are connected via a network and can share resources (such as printers and files) without having a dedicated server
Are peer-to-peer networks easy to secure?
No
What are peer-to-peer applications?
allows a device to act as both a client and a server within the same communication
What do port numbers identify?
applications and Application layer services that are the source and destination of data
What does the DNS protocol do?
defines an automated service that matches resource names with the required numeric network address.
What does the nslookup utility allow you to do?
allows the user to manually query the name servers to resolve a given host name
What does the command ipconfig /displaydns show?
Displays all of the cached DNS entries on a Windows XP or 2000 computer system
What happens if a DNS server does not have a name in its stored records?
It passes the request on to another DNS server
If the same request is made again where does the DNS server look?
In its cache
When is a server declared to be an authoritative server?
When the resource is directly held on that server
Define the three parts of a url as listed on the page?
http:- protocol
www.cisco.com- name of server
web-server.htm- name of file or page
What type of request is sent to the server when retrieving a web page?
GET
What does the POST command do?
Sends information to the web server
What does the PUT command do?
Sends resources or content to the web server
What protocol is used for secure transmission across the web?
HTTPS:
What 2 Application Layer protocols are used in sending and receiving email?
POP (Post Office Protocol) and SMTP (Simple Mail Transfer Protocol)
What is another name for an email application?
MUA Mail User Agent
What are the two processes that email servers perform?
MTA Mail Transfer Agent
MDA Mail Delivery Agent
What happens to emails in many companies once the email reaches the internal server?
Converted to a proprietary protocol for mail delivery
List and describe some of the commands used by the SMTP protocol.
HELO - identifies the SMTP client process to the SMTP server process
EHLO - Is a newer version of HELO, which includes services extensions
MAIL FROM - Identifies the sender
RCPT TO - Identifies the recipient
DATA - Identifies the body of the message
What is File Transfer Protocol (FTP)?
developed to allow for file transfers between a client and a server
What are the 2 ports used and their purpose in FTP?
21- Used for control
20- Used for actual file transfer
What does Dynamic Host Confirmation Protocol (DHCP) do for a network?
allows a host to obtain an IP address dynamically when it connects to the network
What are the 4 types of messages sent and received in DHCP?
DHCP Discover
DHCP Offer
DHCP Request
DHCP Acknowledge
What is SMB (Server Message Block)?
the structure of shared network resources, such as directories, files, printers, and serial ports
What are the 3 message types of SMB messages?
Start, authenticate, and terminate sessions
Control file and printer access
Allow an application to send or receive messages to or from another device
What does the Telenet application provide?
provides a standard method of emulating text-based terminal devices over the data network.
What protocol is recommended alternative to Telnet when security is a concern?
SSH Secure Shell protocol