IST 201 Chapter 11 Lecture 2

Ports Used by TCP & UDP Keep track of different types of transmissions crossing the network simultaneously. Combination of IP address & port number is referred to as a socket. Pass info to upper layer protocols Transmissions that originate w/o a known appl. port # get a dynamically assigned port number greater than 1023.

TCP – Transmission Control Protocol transport layer Part of the TCP/IP protocol suite Connection – oriented Breaks messages (data) into segments Passes to next layer Reassembles segments into messages

TCP Protocols FTPPort #21, #20 File Transport Protocol HTTPPort #80 Hypertext Transfer Protocol SMTPPort #25 Simple Mail Transfer Protocol DNSPort #53 Domain Name Service, System, Server TelnetPort #23 Terminal network

Sequence Number (32) TCP Segment Format Bit 0 Bit 15 Bit 16Bit 31 Source Port (16)Destination Port (16) Acknowledgment Number (32) Header Length (4) Reserved (6) Code Bits (6) Window (16) Checksum (16)Urgent (16) Options (0 or 32 if Any) Data (Varies) 20 Bytes

UDP – User Datagram Protocol transport layer Part of the TCP/IP protocol suite Connectionless No acknowledgements; no receipts Error handling & retransmission must be handled by upper layer protocols.

UDP Segment Format Bit 0 Bit 15 Bit 16Bit 31 Source Port (16)Designated Router (16) Data (If Any) Length (16) Checksum (16) No Sequence or Acknowledgement Fields 8 Bytes

UDP Protocols TFTP – Port 69 Trivial File Transport Protocol SNMP – Port 161 Simple Network Management Protocol DHCP – Port 67, Port 68 Dynamic Host Configuration Protocol DNS – Port 53 Domain Name Server, System, Service

Application Layer Closest layer to end user Intermediary between user’s software applications Provides services to application software Spreadsheets Word processing Banking Direct interface to web browsers,

Application Layer Responsibilities Identify and establish availability of intended communication partners Synchronize co-operating applications Establish agreement on procedures for error recovery Control data integrity

Direct Network Applications Application that operate on client/server network Examples FTP Web browsers request response Client Server

Indirect Network Client Server Redirector Using a host application – word processing, spreadsheet, etc. and opening, printing or saving to a network server.

Make/Break a Connection Alternative to connection-oriented and connectionless Examples Accessing a web page Printing to a network server

DNS – Domain Name Service System used on the Internet to translate domain names to IP addresses Each LAN usually has a least one DNS server.us.edu.com.gov.mil.org.net

FTP Download/upload files Client/server application Server must have the FTP software running for clients to be able to access it. Requires authentication Establishes a connection – uses TCP Commands are sent and executed on the server Create folders, copy, move, erase, rename files

TFTP Connectionless – uses UDP Small, easy to implement File downloads/uploads Read/write files only Fast

HTTP Works with the WWW Browser is client/server application Make/break a connection

SMTP servers communicate with one another to send/receive mail Supplies little security No authentication required POP3 (Port 110) or IMAP4 Clients use to download mail Both use TCP Clients use SMTP to send mail Clients use POP3 or IMAP4 to receive

SNMP Allows the exchange of management information between network devices Manage network performance Find/resolve network problems Plan for growth

SNMP Components Managed device Network node w/SNMP agent installed to collect and store local information Routers, servers, switches, hubs, hosts, printers Agent Software module that reside on a managed device Network Management System Executes applications that monitor and control devices Usually resides on a server; processing and memory resources there primarily used

Telnet Terminal emulation software that allows the capability to remotely access another device Commonly used to manage network devices Client – local host Server – remote host Special software called a daemon