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Internet Protocol - Masters in computer networking
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CSC 573 Internet Protocols 2026 1
n millions of connected computing devices: wired links wireless links router mobile network global ISP regional ISP home network institutional network smartphone PC server wireless laptop khaled harfoush 2
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Application Presentation Session FTP TELNET (^) DNS NFS Application Layer Transport TCP UDP Network (^) IP ICMP IGMP ARP RARP Data Link Physical Protocols defined by the underlying networks User Kernel (^) Port address IP address Physical address 3
devices. How? n Covered in 570 – Layers 1 and 2
devices. How? n The general case n Will be covered in this class – Layers 3, 4 and 5 khaled harfoush 4
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§ Modulation is the process of converting
levels) -- Before this step, the information is in the form of a bit stream 8
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communication lines among many signals
§ In a way, it is similar to people having many conversations in the same room. 9
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multiple flows to compete over the same communication channel. § Compare MAC to multiplexing! § MAC Examples:
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avoid overwhelming the next hop
higher layers of the TCP/IP stack 14
§ is CSMA/CD § Time is divided into discrete slots whose length is equal to 2 t (51.2μsec) § Random delay (backoff) after collision is computed with BEB (Binary Exponential Backoff) § After a collision, § After 1st^ collision, a STA waits for 0 or 1 slot times before trying again § After 2nd^ collision, a STA waits for 0, 1, 2, or 3 slot times before trying again § After 10th^ collision, a STA waits for x slots, where x is chosen at random between 0 and 2^10 - 1 § Further collisions leads to freezing the randomizationkhaled harfoush 19
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hardware listens to the channel.
the one transmitted, then a collision exists
0’s are colliding with other 0’s. 21
detect n t is the time it takes to propagate over the Ethernet n Leads to minimum packet size for reliable detection (why?) khaled harfoush 22
§ Hubs are PHY layer devices. They only relay bits. Nothing more. § Wires all lines into a single collision domain § Ethernet STAs can be connected through hub instead of using a long cable – same performance khaled harfoush 25
§ Uses a switch to connect user cables (instead of long cable or hub) § Makes it easier to manage cables/identify problems § Switches and hubs look similar but are very different Switch Twisted pair/fiber ports Hub khaled harfoush 26
n Hubs (layer 1 devices) wire all lines into a single collision domain ( CSMA/CD still needed) n Switches (layer 2 devices) isolate each port to a separate collision domain ( CSMA/CD not needed with full-duplex lines) khaled harfoush 27
transmits the frame using the port corresponding to the frame’s destination MAC address. So, need to be able to
address in Layer 2 header
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negotiation step
so cable lengths and frame size relation still needs to be maintained in order to detect collisions in this case khaled harfoush 31
