1 / 12

Computer Networks

Computer Networks. Marwan Al- Namari Week 5. The Network Layer. Application. Transport. Responsible for delivering packets between endpoints over multiple links. Network. Link. Physical. Design Issues. Store-and-forward packet switching » Connectionless service – datagrams »

gent
Download Presentation

Computer Networks

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. Computer Networks Marwan Al-Namari Week 5

  2. The Network Layer Application Transport Responsible for delivering packets between endpoints over multiple links Network Link Physical

  3. Design Issues • Store-and-forward packet switching » • Connectionless service – datagrams» • Connection-oriented service – virtual circuits » • Comparison of virtual-circuits and datagrams»

  4. Store-and-Forward Packet Switching ISP’s equipment Hosts send packets into the network; packets are forwarded by routers

  5. UDP: Connectionless Service – Datagrams UDP : User Datagram Protocol. Packet is forwarded using destination address inside it Different packets may take different paths ISP’s equipment A’s table (initially) A’s table (later) C’s Table E’s Table

  6. TCP: Connection-Oriented – Virtual Circuits TCP: Transmission Control Protocol. Packet is forwarded along a virtual circuit using tag inside it Virtual circuit (VC) is set up ahead of time ISP’s equipment A’s table C’s Table E’s Table

  7. Comparison of Virtual-Circuits & Datagrams

  8. TCP/IP Ports and Sockets Almost everything on the Internet involves two programmes talking to each one another. e.g. browsing a web site Connecting a programme on one computer to another programme on another computer is like making a telephone call. The server must know the phone number of the receiver and the receiver must be around to pick up the phone. In the TCP/IP world a phone number is called a SOCKETcomposed of three parts: IP address of the receiver, receiving programmes port number and protocol being used

  9. Sockets socket = protocol ip address : port number e.g. TCP 195.44.0.112 : 80 UDP 143.52.28.10 :53

  10. UDP operation UDP provides a connectionless datagram service that offers unreliable, best-effort delivery of data transmitted in messages. This means that neither the arrival of datagrams nor the correct sequencing of delivered packets is guaranteed. UDP does not recover from lost data through retransmission. UDP is used by applications that do not require an acknowledgement of receipt of data and that typically transmit small amounts of data at one time. NetBIOS name service, NetBIOS datagram service, and SNMP are services and applications that use UDP. UDP is defined in RFC 768. E.g. When Net Send * is used; messages go out on UDP port 138. The following table describes the key fields in the UDP header.

  11. Field Function Source Port UDP port of sending host. Destination Port UDP port of destination host. UDP Checksum Verifies the integrity of the UDP header and the UDP data. UDP header

  12. UDP Port Number Description 53 Domain Name System (DNS) Name Queries 69 Trivial File Transfer Protocol (TFTP) 137 NetBIOS name service 138 NetBIOS datagram service 161 SNMP Well known UDP ports

More Related