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Application Protocols. SMTP: Simple Mail Transport Protocol HTTP: Hyper Text Transport Protocol HTTPS: Hyper Text Transport SSL (Secure) SNMP: Simple Network Management Protocol FTP: File Transfer Protocol Telnet: Interactive login SSH: Secure Shell telnet DNS: Domain Name Service.

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Application protocols l.jpg
Application Protocols

  • SMTP: Simple Mail Transport Protocol

  • HTTP: Hyper Text Transport Protocol

  • HTTPS: Hyper Text Transport SSL (Secure)

  • SNMP: Simple Network Management Protocol

  • FTP: File Transfer Protocol

  • Telnet: Interactive login

  • SSH: Secure Shell telnet

  • DNS: Domain Name Service


Ip header l.jpg
IP header

  • Source and Destination IP addresses

  • Type of Service

    • Selects delivery speeds vs. accuracy

  • Protocol (TCP,ICMP, UDP)

  • Time to Live (Router hops)

  • Identification and Fragment offset

    • Reassembly of a fragmented datagram


Slide3 l.jpg

IP Header

Version

Leng

Type of Svc

Total Length

Identification

Flags

Frag Offset

Time to Live

Protocol

Header Checksum

Source Address

Destination Address

TCP Header then your data...


Tcp fields l.jpg
TCP fields

  • Ports (service identifiers)

  • Sequence numbers

  • Acknowledgement numbers

  • Windowing

    • More retries (less acks) smaller packets

    • Less retries (more good data) larger packets


Slide5 l.jpg

TCP Header

Source Port

Destination Port

Sequence Number

Acknowledgement Number

Reserved

Data

Offset

Window

Flags

Checksum

Urgent Pointer

Your Data… next 500 octets


Services l.jpg
Services

  • RFC’s (Requests for Comments)

  • /etc/services or multinet:services.master_server

  • lists service name and port number

  • Common (well known) ports:

    • FTP 21

    • TELNET 23

    • SSH 22

    • SMTP 25

    • HTTP 80

    • NTP 123

    • Finger 79


Tcp data flow l.jpg
TCP Data Flow

Listens on port

23

129.123.7.33, 129.123.1.86

Port info:1234, 23

129.123.1.86

Computer

1234

Returning Port


Udp data flow l.jpg
UDP Data Flow

129.123.7.33, 129.123.1.86

Port info:1234, 123

129.123.1.86

Computer

Reply 1 Port 123

Reply 2 Port 123


Tcp udp icmp l.jpg
TCP, UDP, ICMP

  • TCP (Transmission Control Protocol)

    • Datagrams

    • Connection Oriented

    • End to End error checking

    • Source Port, Destination Port

      • Sockets, Well Known Ports

    • HTTP, SMTP, TELNET,FTP


Udp user datagram protocol l.jpg
UDP (user datagram protocol)

  • Connectionless

  • One Way

  • Fast, Simple

  • No guarantee of delivery

  • NFS, DNS, DHCP, NTP, TALK


Icmp internet control message protocol l.jpg
ICMP (Internet control message protocol)

  • Error Messages

  • Intended for the TCP/IP software itself

  • PING (host unreachable messages)

  • Simple Headers


Slide12 l.jpg
FTP

  • File Transfer Protocol (TCP)

    • User authentication

    • Anonymous

  • GET/PUT/DEL/CWD

  • Binary/Ascii


Ftp example l.jpg
FTP Example

  • requires 2 ports

  • telnet ftp.remotesite.com 21

    • 220 ftp.remotesite.com FTP server ready

    • user anonymous

    • 331 password required for anonymous

    • password user@cc.usu.edu

    • 230 user anonymous logged in

    • PORT 1200


Ftp example cont l.jpg
FTP Example cont.

  • PORT 129,123,7,55,4,76

  • 200 PORT command successful

  • pwd

  • 257 “/export/guest/bobw” is current directory

  • RETR ./.login

  • 150 ASCII data connection for ./.login(129.123.7.55,1100)(795 bytes)

  • QUIT


Http application l.jpg
HTTP Application

  • HTTP is a pull protocol, the user pulls information from a remote site.

  • Protocol consists of GET and POST commands to transfer data.

  • Persistent vs. Non-Persistent connections


Non persistent connections l.jpg
Non-Persistent Connections

  • TCP connections are opened and closed for each request.

  • Allows for parallel transfer of objects.


Persistent connections l.jpg
Persistent Connections

  • TCP connection left open until requested to disconnect or times out.

  • Takes advantage of pipelining to improve transfer rates.


Proxy servers l.jpg
Proxy Servers

  • HTTP uses cached files to speed up transfers

  • Proxy Server is a LAN accessible cache

  • Proxy allows for reduced load on the internet connection

  • Proxy Servers allow NAT (Network Address Translation) systems to protect internal networks.


Mime types encoding l.jpg
MIME Types/Encoding

  • Multipurpose Internet Mail Extensions

  • Handles Non-ASCII data in an ASCII transfer medium.

  • Imbeds the data stream into the email message


Simple mail transfer protocol l.jpg
Simple Mail Transfer Protocol

  • The protocol is very simple

  • SMTP is a push protocol, information is pushed to a remote sitre

  • Uses port 25

  • All files are ascii text

  • Syntax: user@host.domain

  • Mail relay: user%host1@host2.domain

  • Mail Exchange (MX)

    • Allows mail server redirection


Smtp example l.jpg
SMTP Example

1> telnet red.rutgers.edu 25

2> 220 RED.RUTGERS.EDU SMTP Service at 15 Apr 98 10:11:18 EDT

1> HELO pc15.logan.com

2> 250 RED.RUTGERS.EDU - Hello, PC15.LOGAN.COM

1> MAIL From:<student11@pc15.logan.com>

2> 250 MAIL accepted

1> RCPT To:<mailman@red.rutgers.edu>

2> 250 Recipient accepted

1> DATA

2> 354 Start Mail input; end with <CRLF>.<CRLF>

1> Date: Sat, 22 Mar 1998 13:26:31 MST

1> From: student11@pc15.logan.com

1>Subject: Meeting tomorrow


Smtp example cont l.jpg
SMTP Example cont.

1> The meeting is TOMORROW at 3:00 PM!

1>

1> .

2> 250 OK

1> QUIT

2> 221 RED.RUTGERS.EDU Service closing transmission channel


Slide23 l.jpg
POP3

  • Post office protocol

  • Mail access client

  • Uses port 110

  • Messages are downloaded to client but can be stored on server.

  • Does not easily allow multiple clients


Pop3 example l.jpg
POP3 Example

  • telnet cc.usu.edu 110

  • +OK POP3D(*) Server PMDFV6.1.2 at Wed, 8 Sep 2004 10:49:30 MdT 01LEMEHLU2FMBOTAK2@grumpy.usu.edu

  • user bobw

  • +OK password please

  • pass areukidding

  • +OK Mailbox open, 335 messages

  • list

  • (List of messages)

  • 1 4355

  • 2 106

  • 3 445567

  • retr 2

  • (dumps message, ends with a .)

  • quit

  • +OK bye


Slide25 l.jpg
IMAP

  • Internet Mail Access Protocol

  • Improved POP3

  • Automatically assigns folders

  • Leaves mail on server

  • Only transfers as much as needed per message (headers, subject only on list)


Slide26 l.jpg
DNS

  • Domain Name Services

  • What’s in a name?

  • Distributed hierarchical architecture

  • Caches and times DNS entries for speed

  • www.internic.net (root server)

  • Top Level Domain Servers

  • Authoritative Local Nameservers

    • thingy, watzit, doober


Dns configuration file l.jpg
DNS Configuration File

;

; Hosts file for domain flibble.orac.net.au.

;

;name ttl class type data

;

; Source of authority

@ IN SOA solaris.flibble.orac.net.au. root.solaris.flibble.orac.net.au. (

2000050201 ; Serial

10800 ; Refresh - 3 hours

3600 ; Retry - 1 hour

432000 ; Expire - 1 week

86400) ; Minimum - 1 day

IN NS solaris.flibble.orac.net.au.


More config l.jpg
More Config

;

; Machines for the flibble.orac.net.au domain

;

;name ttl class type data

localhost IN A 127.0.0.1

solaris IN A 10.5.3.1

win95 IN A 10.5.3.21

linux IN A 10.5.3.22

;

; Aliases

;

mail IN CNAME solaris

www IN CNAME solaris


More config29 l.jpg
More config

;

; Domain mailing addresses

;

flibble.orac.net.au. IN MX 10 solaris.flibble.orac.net.au.

flibble.orac.net.au. IN A 10.5.3.1


Dns resolution l.jpg
DNS Resolution

Want cc.usu.edu

homeuser.aol.com

Top Level Domain

Server (resolve .edu)

thingy.usu.edu

resolve usu.edu

resolve cc.usu.edu


Usu dns l.jpg
USU DNS

  • Handled by Network and Computing Services

  • thingy.usu.edu webpage for registrations and lookups