Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod11 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 1 Cisco Systems CCNA Version.

Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod11 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 1

Cisco Systems CCNA Version 3 Semester 1

Module 11


Students completing this module should be able to:

• Describe the functions of the TCP/IP transport layer. • Describe flow control. • Describe the processes of establishing a connection

between peer systems. • Describe windowing. • Describe acknowledgment. • Identify and describe transport layer protocols. • Describe TCP and UDP header formats. • Describe TCP and UDP port numbers. • List the major protocols of the TCP/IP application layer. • Provide a brief description of the features and operation of

well-known TCP/IP applications.


The Department of Defense (DoD) developed the TCP/IP reference model to provide a communication network that could continue to function in wartime.

Transport Layer


OVERVIEW11.1 TCP/IP Transport Layer

11.1.1 Introduction to transport layer

11.1.2 Flow control

11.1.3 Session establishment, maintenance, and termination overview

11.1.4 Three-way handshake

11.1.5 Windowing

11.1.6 Acknowledgment

11.1.7 Transmission Control Protocol (TCP)

11.1.8 User Datagram Protocol (UDP)

11.1.9 TCP and UDP port numbers

11.2 The Application Layer11.2.1 Introduction to the TCP/IP application layer

11.2.2 DNS

11.2.3 FTP

11.2.4 HTTP

11.2.5 SMTP

11.2.6 SNMP

11.2.7 Telnet



•Segmentation of upper-layer application data •Establishment of end-to-end operations •Transport of segments from one end host to another end host •Flow control provided by sliding windows •Reliability provided by sequence numbers and acknowledgments

MACd MACs IPs IPd Ps Pd

Ps Pd


MACd MACs

IPs IPd

Ps Pd

• Reliable• connection-

oriented




• Peer to Peer Communication is really communication between the headers at each layer.

• Layers 2 and 3 are best effort or connectionless.• Layer 4 Transport is connection oriented. The ‘connection’ is in the

header.

http://www.slctech.org/people/faculty/index.html




11.1.2 Flow control



• There may be more than one application using the TCP/IP stack at the same time.

• Port Numbers are used to keep them separate.

HTTP 80 HTTP 80

TELNET 23 TELNET 23

SMTP 25 SMTP 25

DNS 53 DNS 53



HTTPTELNETDNS53 23 80

TELNET

23

FTP

21

Congestion can be caused by:• Faster computers generate traffic volume greater than the network is able to transfer. • Large numbers of computers send data to the same location at the same time.








In TCP the three-way handshaking process begins when the sending host sends a SYN

segment.


11.1.5 Windowing




6603 – 6267 = 336 bytes or octets


11.1.5 Windowing


I can accept a window this

big.

Source Port = 80. my Host.

Destination Port = 3551. Marc’s server.

Window size is the size in Octets or Bytes that the device with the Source Port Transport Layer buffer is ready to accept.

This is Flow Control.



The source must receive an "ACK 4" acknowledgement

before sending more data.




567 bytes or octets of data.


567 bytes or octets of data.


In TCP the three-way handshaking process

begins when the sending host sends a SYN segment.

Source = 3550Destination = 80

1


The Destination ACK…

Source = 80Destination =

3550

… and requests a SYN of its

own.

2


The Source acknowledges.

Source = 3550Destination = 80

3


• Source port – Number of the calling port

• Destination port – Number of the called port

• Sequence number – Number used to ensure correct sequencing of the arriving data

• Acknowledgment number – Next expected TCP octet

• HLEN – Number of 32-bit words in the header

• Reserved – Set to zero

• Code bits – Control functions, such as setup and termination of a session

• Window – Number of octets that the sender is willing to accept

• Checksum – Calculated checksum of the header and data fields

• Urgent pointer – Indicates the end of the urgent data

• Option – One option currently defined, maximum TCP segment size

• Data – Upper-layer protocol data



• no guaranteed delivery of datagrams • reliability provided by the application layer • connectionless

• Source port – Number of the calling port • Destination port – Number of the called port • Length – Number of bytes including header and data • Checksum – Calculated checksum of the header and data

fields • Data – Upper-layer protocol data



You should at least remember these port numbers.







• Numbers below 1024 are considered well-known port numbers.

• Numbers above 1024 are dynamically assigned port numbers.

• Registered port numbers are those registered for vendor-specific applications.

• Most of these are above 1024.

1024 is 10 bits. There are 16 bits (65,536) available for port numbers.00000011 11111111

All zeros in the first six positions means it is a “well-known” port

number.






11.1.2 Flow control



11.1.5 Windowing






11.2.2 DNS

11.2.3 FTP

11.2.4 HTTP

11.2.5 SMTP

11.2.6 SNMP

11.2.7 Telnet


Application Layer

eg. Dialog Control is • Session Layer in OSI• Application Layer in

TCP/IP


11.2.1 Introduction to the TCP/IP application layer

• Domain Name System (DNS)

• File Transfer Protocol (FTP)

• Hypertext Transfer Protocol (HTTP)

• Simple Mail Transfer Protocol (SMTP)

• Simple Network Management Protocol (SNMP)

• Telnet


11.2.2 DNS

eg. http://www.harvard.edu/


11.2.2 DNS

eg. Non-Profit organizations


11.2.2 DNS

.us USA

.ca Canada

.au Australia

.cl Chile

.de Germany

.hk Hong Kong


11.2.3 FTP and TFTP

• Both TFTP and FTP are used to transfer files between systems.

• TFTP is limited to Read, Write and Mail.

In Semester 2 we will use TFTP to load and retrieve ISO images from a router.

FTP uses TCP thence is

connection oriented.

TFTP uses UDP thence is NOT

connection oriented.


11.2.4 HTTP

Eg. http://uno.slctech.org/~clark/ …the TCP protocol is http, the domain name is slctech.org, the machine is uno, and the folder is ~clark.

DNS is used to translate a web address into an IP address.

HTTP (not shown port 80) uses TCP thence is connection oriented.

DNS can use either TCP or

UDP.


SMTP• offers very little

security • no authentication

11.2.5 SMTP

Email servers communicate with each

other using SMTP.

Clients collect their mail using POP3 or IMAP4.

SMTP uses TCP


11.2.6 SNMP

•Network Management System is the central point for SNMP.•It uses the majority of memory resources.

Managed devices:Eg. Routers,

switches, hosts etc.Agents report back to the NMS the status of the items in their MIBs


• Network management system (NMS)

• NMS executes applications that monitor and control managed devices. The bulk of the processing and memory resources required for network management are provided by NMS. One or more NMSs must exist on any managed network.

• Managed devices

• Managed devices are network nodes that contain an SNMP agent and that reside on a managed network. Managed devices collect and store management information and make this information available to NMSs using SNMP. Managed devices, sometimes called network elements, can be routers, access servers, switches, and bridges, hubs, computer hosts, or printers.

• Agents

• Agents are network-management software modules that reside in managed devices. An agent has local knowledge of management information and translates that information into a form compatible with SNMP.


11.2.7 Telnet

Telnet uses TCP thence is connection

oriented.





11.1.2 Flow control



11.1.5 Windowing






11.2.2 DNS

11.2.3 FTP

11.2.4 HTTP

11.2.5 SMTP

11.2.6 SNMP

11.2.7 Telnet


FIN

Nov-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod11 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 1 Cisco Systems CCNA Version.

Documents

canada clark slide

transport layer slide

telnet slide

windowing slide

acknowledgment slide

cisco systems ccna version

cisco systems ccna semester

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