Networking Basics CCNA 1 Chapter 11

Name: Networking Basics CCNA 1 Chapter 11
Uploaded: 2017-10-10T04:07:24+00:00
Duration: PTM22S28
Channel: Kathleen Logan
Description: Networking Basics CCNA 1 Chapter 11

Networking Basics CCNA 1 Chapter 11

The TCP/IP Transport Layer
TCP/IP transport layer includes several protocols Transmission Control Protocol (TCP) User Datagram Protocol (UDP) TCP has more functions UDP has less overhead Main goal of the transport layer: Provide the service of taking data from one application process on one computer and delivering that data to the correct application process on another computer

Comparing transport and internet layers: Internet layer delivers packets from one computer to another, but is not concerned with which application sent the data or which application on the receiving computer needs the data If multiple instances of an application are running on the destination computer, the transport layer works to ensure the proper instance gets the data and not the others

Comparing TCP and UDP

Flow Control and Windowing When a host sends data using TCP, the receiving host can control how fast each TCP sender sends the data over time – this is called flow control Flow control is used for many reasons Receiver needs time to process the data Receiver has finite amount of memory, so if data keeps arriving, it could run out of memory

Flow Control Through Dynamic Sliding Windows Receiver tells sender how many bytes the sending host can send before it receives an acknowledgement – a value called a window When the sending host has sent an entire window’s worth of data, it must wait for an acknowledgement, slowing its rate of sending data The window size can be increased to allow a faster transfer rate

Dynamic Windowing

Flow Control Through Withholding Acknowledgements After a sending host has sent one window worth of bytes, it must wait to send more The receiver can wait to send acknowledgements, which prevents the sender from sending more data This process of withholding acknowledgements is sometimes known as start/stop flow control

Withholding Acknowledgements

Establishing and Terminating TCP Connections TCP is a connection-oriented protocol Allows it to set initial values to the window and to initialize sequence number values TCP uses a process called a three-way handshake to create a new TCP connection Uses three TCP segments that use two of the TCP flags in the TCP header The synchronize (SYN) flag The acknowledge (ACK) flag

Three-Way TCP Connection Establishment

TCP Error Recovery (Reliability) TCP is a reliable protocol (at least in a networking perspective) Performs error recovery All data eventually gets to the destination, even if some is initially lost in transport

TCP Acknowledgements with no Error Recovery Needed

TCP Error Recovery (Reliability) TCP uses two header fields to signal to other computer as to whether a segment was received Sequence number Keeps track of all the bytes sent over a TCP connection Acknowledgement number Lets the sending device know the number of the segment the receiving device expects next Practice of stating the next byte expected to be received is called a forward acknowledgement or expectational acknowledgement

TCP Error Recovery

TCP Error Recovery (Reliability) If a segment is lost or destroyed during transmission, the receiving PC requests that it be retransmitted If an acknowledgement is not received by the sending PC within a certain time (a timer has been set), the sending PC resends the segment

Segmentation, Reassembly, and In-Order Delivery TCP segmentation refers to the process of accepting a large chunk of data from the application protocol and breaking it into pieces that are small enough for transmission The size of the segment is limited Ethernet limits frames to 1500 data bytes in the data field of a frame IP and TCP headers are each 20 bytes long Maximum data portion is therefore 1460 bytes

Segmentation, Reassembly, and In-Order Delivery TCP on the receiving computer reassembles data into its original form The data is put in the correct order If segments of a file are assembled out-of-order, the file is useless TCP provides a guarantee of in-order delivery

Segmentation, Reassembly, and In-Order Delivery Due to IP routing, a TCP receiver can receive data out of order If multiple routes exist between a source and a destination, routers can load-balance over several routes Packets can arrive out of order

TCP Providing In-Order Delivery

TCP and UDP Header Reference TCP and UDP use a header to hold information for performing tasks TCP needs ACK and SYN flags First two fields in TCP and UDP are identical Both use port numbers to identify application processes TCP has a longer header (20 bytes vs. 8 bytes)

TCP and UDP Headers

TCP Header Fields

UDP Header Fields

Identifying Application Processes Using Port Numbers Both TCP and UDP identify the specific application process that sends the data and the application process that needs to receive the data To make this determination, TCP and UDP use port numbers Each application uses a different local port number

Using Port Numbers to Identify the Correct Application Process

Identifying Application Processes Using Port Numbers In previous slide, the application was assigned a dynamic port number by the host computer A host typically dynamically allocates port numbers of value 1024 (210) through 65,535 ( ) When a host starts a new application process, it allocates a dynamic port number that is not already in use by another process By each process having its own port number, a PC can have multiple conversations with other PCs (sometimes called multiplexing)

Identifying Application Processes Using Port Numbers Connection to Servers: Well-Known Ports Most TCP/IP applications use a client/server model for communications Servers cannot use dynamic port numbers because clients must know ahead of time what port numbers servers use Servers must wait and listen on certain port numbers for client requests

Identifying Application Processes Using Port Numbers Connection to Servers: Well-Known Ports (continued) For servers to work well, TCP/IP defines one or more well-known ports, each reserved for use by a specific application protocol For example, HTTP connects to a server listening on port 80 A server might be a single, high-powered computer; in this chapter it means “TCP/IP software application,” one that uses port numbers Multiple software server applications could be running on one physical server

Client Connecting to Well-Known Port of a Web Server (80)

Popular Applications and Their Well-Known Port Numbers

Identifying Application Processes Using Port Numbers Comparing Well-Known, Dynamic, and Registered Ports IANA assigns the values for well-known ports and for registered port numbers Registered ports are assigned to servers that the average end-user can start, such as instant-messaging applications Well-known ports are started by IT staff for applications such as web servers, , FTP servers

Uses of Port Numbers

Identifying Application Processes Using Port Numbers Comparing Well-Known, Dynamic, and Registered Ports (continued) Both TCP and UDP use port numbers To see the port numbers used on a computers running a Microsoft OS, use the netstat –an command

The TCP/IP Application Layer
The TCP/IP application layer performs the same functions as the top three layers of the OSI model Defines format of data being transferred Performs encryption Sets protocol rules for transferring data Sets up combinations of messages, called dialogs or sessions, that must be sent before a transaction can be considered complete Do not confuse the application layer with the applications themselves!

Distinction Between an Application and Application Layer Protocols

Application Protocols Used by End Users Domain Name System (DNS) – resolves names into IP addresses Hypertext Transfer Protocol (HTTP) – transfers files from web servers to web browsers Simple Mail Transfer Protocol (SMTP) and Post Office Protocol version 3 (POP3) –send and receive , respectively File Transfer Protocol (FTP) – stores and retrieves files

Application Protocols Used by End Users Name Resolution Using DNS Easier to remember names than IP addresses A name like is generically called a hostname The cisco.com part is the domain name The last part (.com) is a top-level domain

DNS Resolution After Inserting a URL into a Web Browser

Common High-Level DNS Domains

Application Protocols Used by End Users World Wide Web and HTTP Web server software stores information that the web server wants to make available to web browsers such as Internet Explorer and Firefox Web servers use HTTP to transfer the files that make up a web page

Application Protocols Used by End Users World Wide Web and HTTP (continued) HTTP transfer process: The browser asks the web server to send one file that contains instructions and displayable content The browser displays the file’s contents The browser looks for instructions inside the first file, which might tell it to get more files The browser asks the web server for additional files The browser displays the additional content, which might include instructions to download additional files The process continues until all files are downloaded and displayed HTTP uses a GET request to ask for a file

HTTP Transfers Three Files

Application Protocols Used by End Users World Wide Web and HTTP (continued) The term HTTP is from the first type of file supported by a web browser Hyper Text Markup Language (HTML) Web browsers needed to download files of this type, so HTTP was created as a protocol to handle HTML files Universal Resource Locators (URLs), commonly referred to as web addresses, identify web pages that need to be displayed, or a hyperlink can be clicked on

Application Protocols Used by End Users Protocols: SMTP and POP3 A PC sends mail to its SMTP server using its client software The SMTP server forwards the to the destination SMTP server The destination PC retrieves the with the POP3 protocol used by its client

Process of Sending an

Application Protocols Used by End Users Protocols: SMTP and POP3 (continued) In some cases, the physical server sending the is a different server than the one used for checking POP3 is the most common protocol for an incoming server, but IMAP4 is sometimes used Most SMTP servers are configured to only accept from inside the same internetwork, due to security reasons

Application Protocols Used by End Users Protocols: File Transfer Protocol File Transfer Protocol (FTP) supports file transfers FTP clients store files on FTP servers and can retrieve files from them

Application Protocols Used by End Users Protocols: File Transfer Protocol (continued) FTP uses two separate TCP connections Control connection uses well-known port 21 on the FTP server and sends control information such as data transfer mode Connection on well-known port 20 is used for actual data transfer

Application Protocols Often Used for Network Management Three primary network management protocols: Trivial File Transfer Protocol (TFTP): works similar to FTP, but with some benefits when used on networking devices Simple Network Management Protocol (SNMP): Allows management software (the client) to query networking devices (the server) to manage and control the networking devices Telnet: allows a client to emulate a terminal; allows a user to sit at one computer (the Telnet client) and to use a remote computer (the Telnet server) through a text-based interface

Three primary network management protocols (continued): TFTP Performs some of the same functions as FTP TFTP has some advantages: server software is small, allows routers and switches to transfer files without consuming too much permanent storage space Most network engineers use a TFTP client package and a TFTP server package on their PCs

Three primary network management protocols (continued): SNMP Allows a network engineer to monitor an internetwork’s status The Network Management System (NMS) software can perform this function Uses SNMP GET requests The managed device (router, switch) must run an SNMP agent to be able to reply to the GET requests

NMS Using SNMP GETs to Retrieve Information from SNMP Agents

Three primary network management protocols (continued): Telnet Allows a user to sit at one computer and access another IP host by using Telnet client software (the other host must run Telnet server software) After connecting, the user at the Telnet client (called the local host) can issue commands that are executed on the other IP host (called the remote host) Telnet is the primary tool for remotely accessing routers and switches Cisco routers and switches come with built-in Telnet servers

Telnet Client Accessing a Router

Application Protocol Summary Many other application protocols exist, but the ones mentioned in this chapter are the mainstream The protocols all share a common feature: They use a TCP transport layer protocol (either TCP or UDP TCP: HTTP, SMTP, POP3, FTP, and Telnet UDP: DNS, TFTP, SNMP UDP does not do error recovery; implements error recovery at the application layer DNS and SNMP use a timeout mechanism that allows them to resend a request or allows the user to repeat the action

Summary Primary duty of the transport layer (OSI Layer 4), is to take data from the application process on one computer and deliver the data to the correct application process on another computer Both TCP and UDP identify data from upper-layer applications based on port number UDP provides only basic delivery of data and identification of applications by port number TCP provides additional functions, including error recovery (reliability), flow control, segmentation and re-assembly, and in-order data delivery TCP uses connection-oriented logic, connecting dynamically with a three-way handshake

Summary TCP numbers the first byte of each segment with a sequence number TCP acknowledges the receipt of data by using an acknowledgement number This process allows a receiving host to tell the sender to resend data The sequence numbers allow the receiving host to put data in the correct order before giving it to the application

Summary Flow control ensures a transmitting node does not overwhelm a receiving node The simplest method of flow control is when a receiving host sends a “not ready” signal by withholding acknowledgements TCP also uses dynamic windowing, which is a more efficient process Dynamic windowing allows the receiving host to vary the amount of data a sender can send before it has to receive an acknowledgement

Summary Positive acknowledgement with retransmission refers to the process of explicitly acknowledging received data, with the sender resending any unacknowledged segments Connection-oriented TCP provides a wide range of functions, but UDP has some advantages UDP has less overhead (an 8-byte header versus a 20-byte header for TCP) UDP does not slow down because of flow control

Summary Popular application layer protocols:
DNS: Used in IP networks to translate names of network nodes into IP addresses FTP: Transfers files between networks HTTP: Delivers HTML documents to a client application, such as a web browser SMTP: Provides services SNMP: Monitors and controls network devices and manages configurations, statistics collection, performance and security Telnet: Used to log in to a remote host that runs a Telnet server application and then to execute commands from the command line

Networking Basics CCNA 1 Chapter 11

Similar presentations

Presentation on theme: "Networking Basics CCNA 1 Chapter 11"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Networking Basics CCNA 1 Chapter 11

Similar presentations

Presentation on theme: "Networking Basics CCNA 1 Chapter 11"— Presentation transcript:

Similar presentations

About project

Feedback