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Practically pervasive convention for correspondence over system. Numerous other systems administration conventions ... TCP/IP synonymous with transport layer and system layer (consolidated) ...
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Organizing Overview Networking Overview 1

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TCP/IP TCP/IP == Transmission Control Protocol/Internet Protocol Almost universal convention for correspondence over system Many other systems administration conventions ATM, X.25, SS7, Sonet,… But TCP/IP has assumed control over the world Networking Overview 2

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TCP/IP Here, a brief review of TCP/IP For more data, see, for instance, Computer Networks , Tanenbaum Computer Networks and Internets , Comer Computer Networking: A Top Down Approach Featuring the Internet , Kurose and Ross TCP/IP Protocol Suite , Forouzan Networking Overview 3

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Why TCP/IP? Everywhere Author created payphone charging convention in 1992 Used X.25, later ported to SS7 Today would in all likelihood use TCP/IP TCP/IP makes the world "to a great degree hackable" Networking Overview 4

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OSI Reference Model In 1980, ISO created OSI Computer correspondence over system Protocol layering Breaks issue into little parts Layer gives administration to next higher Modular Makes it simple, for instance, to supplant Ethernet with remote Networking Overview 5

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OSI Reference Model Layer 7 - Application Layer Links application to the correspondence station Layer 6 - Presentation Layer How to speak to bits for transmission Layer 5 - Session Layer Coordinate (various) sessions Layer 4 - Transport Layer Logical station between frameworks Networking Overview 6

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OSI Reference Model Layer 3 - Network Layer Move information from host-to-host, crosswise over system center (interconnected lattice of switches) Layer 2 - Data Link Layer (or Link Layer) Move information crosswise over one "bounce" Layer 1 - Physical Layer Transmit bits over a physical connection (fiber optic, copper link, remote, and so forth.) Note: Layers 7,6,5 frequently regarded as one Networking Overview 7

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TCP/IP, Our Hero Layers from TCP/IP\'s point of view… Application Layer - Program attempting to impart utilizing TCP/IP E.g., email servers, SSH customer and server, and so forth Transport Layer - Includes TCP and UDP TCP gives dependable conveyance UDP is "stripped down" transport layer convention Networking Overview 8

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TCP/IP, Our Hero Network Layer - Based on IP Deliver bundles from end-to-end To be cool, you should say "layer 3" Data Link Layer - One jump "Layer 2" Physical Layer - The physical media Networking Overview 9

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TCP/IP Protocol Stack TCP/IP synonymous with transport layer and system layer (joined) For instance… Networking Overview 10

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Layering (Again) Each layer adds some information Usually added to starting, supposed a header Networking Overview 11

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Terminology Application layer  parcel Transport layer  TCP section (for instance) Network layer  IP datagram Data join/physical layer(s)  outline We may utilize "bundle" for these Networking Overview 12

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TCP/IP Protocols: TCP, UDP, IP, ICMP Defined in RFCs 791 through 793 Developed for scholastic research No considered security No privacy, uprightness, confirmation, … Networking Overview 13

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TCP/IP and Security Originally, no security in TCP/IP Any security gave by applications But TCP/IP retrofit for security IPSec - security at the "IP layer" "Implicit" security for applications IPSec is a bloated and complex convention Networking Overview 14

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TCP gives solid conveyance Most well known applications use TCP Web skimming (HTTP) Secure shell (SSH) File exchange (FTP) Email (SMTP, POP, IMAP) Etc., and so on., and so on. For most applications, TCP spares a considerable measure of work Networking Overview 15

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TCP Header Every TCP bundle incorporates header Networking Overview 16

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TCP Port Numbers Source port, goal port 16-bit numbers Tells which "entryway" to send information to Source == active "entryway", and so on. Server application "tunes in" on a port Listening ports are open Non-listening ports are shut Networking Overview 17

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TCP Port Numbers Examples of understood ports TCP port 21 - FTP TCP port 22 - SSH TCP port 23 - telnet TCP port 25 - SMTP TCP port 80 - HTTP TCP port 6000 - The X Window System (X11) Note these ports are utilized by tradition Could utilize 8080 for HTTP and not get captured But rather both customer and server must know this Networking Overview 18

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Ports Example Note that assailants need to know which ports ("entryways") are open Networking Overview 19

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Ports To see which ports are being used Locally, utilize netstat - na Networking Overview 20

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TCP Control Bits Control bits or banners For "3-way handshake", and other unique things Networking Overview 21

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TCP Control Bits Originally, 6 control bits URG - critical information, give it need (or not… ) ACK - recognize prior information PSH - push information through now RST - reset the association, because of blunder or an interference (unusual end) SYN - synchronize succession numbers FIN - no more information, so tear down association Networking Overview 22

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TCP Control Bits Two extra control bits CWR - blockage window diminished; because of system clog, decreased window size ECE - express blockage notice reverberation; association is encountering blockage For clog control issues Networking Overview 23

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TCP 3-Way Handshake Used to set up TCP association Note grouping numbers: ISN An and ISN B ACK and SYN banner bits utilized here Networking Overview 24

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TCP 3-Way Handshake Establishes "association" Sequence numbers empower TCP to Make beyond any doubt all bundles arrive Make beyond any doubt all parcels conveyed all together FIN bit utilized when session torn down RST used to end in "mistake" cases Networking Overview 25

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Other Fields in TCP Header Data counterbalance - where the information starts Reserved - held for future use (or for smart aggressors… ) Window - controls number of extraordinary bundles; keeps one side from sending too quick (stream control) Checksum - mistake discovery (utilizes CRC) Networking Overview 26

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Other Fields in TCP Header Urgent pointer - if URG banner set, tells where the earnest information is found Options - extra data (e.g., the maximum size of bundle); variable size Padding - used to make things line up on 32-bit limits Networking Overview 27

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UDP == User Datagram Protocol Minimal "nitty gritty" transport convention Does least conceivable "Connectionless" No stream control, no clog control, parcels can be out of request, not arrive, … UDP == Unreliable Damn Protocol Networking Overview 28

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UDP Why use UDP? Low overhead 8 byte header versus 20 bytes (or more) for TCP No blockage control/stream control How would this be able to be great? Organizing Overview 29

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Where is UDP Used? Spilling sound/video Some bundle misfortune is OK Example: Real Player, UDP port 7070 Apps where low overhead is helpful Trivial FTP (TFTP), UDP port 69 Simple Net

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