1 / 19

Chabot College

Chabot College. ELEC 99.08 Ports (Layer 4). TCP/IP Protocol Suite (simplified). Layer 3 - Network Layer. In Chapters 10 & 11, we covered Layer 3 protocols: Internet Protocol (IP) Used for addressing Address Resolution Protocol (ARP) Used to relate IP and MAC addresses

alfonso-mccarthy
Download Presentation

Chabot College

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chabot College ELEC 99.08 Ports (Layer 4)

  2. TCP/IP Protocol Suite (simplified)

  3. Layer 3 - Network Layer • In Chapters 10 & 11, we covered Layer 3 protocols: • Internet Protocol (IP) • Used for addressing • Address Resolution Protocol (ARP) • Used to relate IP and MAC addresses • Internet Control Message Protocol (ICMP) • Used for ping and traceroute commands

  4. Layer 3 - IP, ARP, ICMP

  5. A Key Limitation of Layer 3 • No way to keep track of multiple conversations between between pairs of hosts running multiple applications. (e.g. mail & web)

  6. 4 Layer 4 - Transport Layer • Layer 4 uses port numbers to address this limitation.

  7. Port Numbers • Layer 4 uses port numbers to direct data to/from correct upper layer application.

  8. Port Numbers • Used to identify the application that Layer 4 should “hand off to.” • Like a “hole in the ceiling” that Layer 4 “throws” the data up into… • Applications “listen” on a particular port number. • IP address + port number = socketEach socket must be unique, and is another type of address.

  9. TCP & UDP port numbers • TCP/UDP use 16 bits to represent a port number (65,536 possibilities). 1 - 255 Used for standard public applications Used by companies for specific apps 256 - 1023 1024 & up Unregulated, but many have been “registered” by companies for specific uses.Also, this range is used as dynamically assigned “source port” numbers by TCP.

  10. Well-Known Port Numbers • Well-known port numbers are defined in RFC 1700. Port 80 is web/ www (TCP).

  11. Non-Standard Port Numbers • A host can run its services on any port, not just on the well-known ones. • To direct traffic to a non-standard port, specify the port number after the IP address: http://banner-web.clpccd.cc.ca.us:7000

  12. port Service (listening) 80 Web server 21 File server (FTP) 25 E-mail (SMTP) Port Numbers in Action Client LAYER 4 I want 207.35.52.4, but which service do I want? LAYER 3 207.35.52.4 LAYER 2 00-0c-4f-32-ab-41

  13. Port Numbers in Action Client TCP port 80 207.35.52.4 00-0c-4f-32-ab-41 The client addresses the message with the port # of the service it wants.

  14. Destination Port 80 - HTTP

  15. TCP port 80 TCP port 21 207.35.52.4 207.35.52.4 00-0c-4f-32-ab-41 00-0c-4f-32-ab-41 TCP port 25 207.35.52.4 00-0c-4f-32-ab-41 Port Numbers in Action Client The client can maintain multiple conversations with the same host, but using different applications.

  16. TCP port 1250 TCP port 80 24.1.103.109 207.35.52.4 00-4b-08-57-c6-9f 00-0c-4f-32-ab-41 Port Numbers in Action Web Server Client DESTINATION SOURCE Note that client applications, like web browsers, dynamically “grab” a source port number above 1023 when needed.

  17. TCP port 80 TCP port 1250 207.35.52.4 24.1.103.109 00-0c-4f-32-ab-41 00-4b-08-57-c6-9f Port Numbers in Action Web Server Client DESTINATION SOURCE

  18. An Example TCP Header : Sync Request TCP - Transport Control Protocol Source Port: 2352 Destination Port: 80 World Wide Web HTTP Sequence Number:102274726 Ack Number: 0 Offset: 7 Reserved: %000000 Code: %000010 Sync Sequence Window: 8192 Checksum: 0x6711 Urgent Pointer: 0 TCP Options:

  19. An Example TCP Header: Acknowlegement TCP - Transport Control Protocol Source Port: 80 World Wide Web HTTP Destination Port: 2352 Sequence Number:2913145779 Ack Number:102274727 Offset: 6 Reserved: %000000 Code: %010010 Ack is valid Sync Sequence Window: 17520 Checksum: 0x9640 Urgent Pointer: 0 TCP Options:

More Related