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Our Last Class!!

Explore the journey of data packets traveling through layers of the Internet, predicting future trends and technologies. Learn about protocols, networking layers, security, and more in this insightful overview.

janethayes
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Our Last Class!!

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  1. Our Last Class!! • summary • what does the future look like?

  2. Summary: let's follow a packet

  3. Summary: let's follow a packet Application • user enters URL into WWW browser • URL may be text, audio, video with different requirements • browser determines host names, uses DNS to get server's IP address API • browser (client) creates stream socket, socket() • client calls connect(), server port 80 • upon return from connect(), will call rcvfrom() to read returned data

  4. Summary (cont.) Transport Layer • connect() call causes TCP connection to be established. • choose initial sequence number • generate SYN packet, server IP address, port 80 • TCP forms packet, computes checksum • TCP calls IP (no congestion control on SYN), passing SYN packet and IP address info

  5. Summary (cont.) Network Layer • adds IP source, destination address in IP packet • IP forwarding consults routing table • routing table computed by RIP, or OSPF intradomain protocol • routing table gives IP address of, and local interface to get to, next router (i.e., on its LAN), R, on route to destination • runs ARP to get 802.3 physical address corresponding to R1's IP address • ARP will generate Ethernet broadcast packet on LAN, requesting R1 to reply with its phys address • R1 replies with physical address

  6. Summary (cont.) Data Link Layer • TCP SYN packet (inside IP packet), as payload in Ethernet packet sent onto LAN using Ethernet protocol • transparent bridge may be involved (not shown) Physical Layer • Ethernet packet transmitted at 10, or 100 Mbps

  7. Summary (cont.) At router R1 • physical layer receives Ethernet packet, passes it up • data link layer computes OK checksum, removes IP packet, passes up • network layer consults routing table • routing table was computed using BGP interdomain routing • passes IP packet down to data link layer …

  8. Summary (cont.) At Router R2 • DLC packet arrives from "net", passed up to network layer • network layer determines outgoing interface to get to host B • RIP or OSPF intradomain routing protocol computed tables • DLC Ethernet packet sent (R2 knew/learned B's physical layer address)

  9. Summary (cont.) At Host B • Ethernet packet arrives, checksum OK, pass up to IP • IP layer extracts TCP packet, demultiplexes up to TCP (note: not UDP packet) • TCP sees SYN packet • server must have previously opened socket and made accept(), else SYN dropped • TCP determines flow control window, chooses initial sequence # • sends SYNACK back

  10. Summary (cont). At Host A • SYNACK eventually received • send transport-level ACK to B • move to established state • return from connect() system call Epilogue • host A can now perform sendto() • host B (after receiving ACK) will perform rcvfrom() and will eventually receive http command and send response • will use TCP • congestion and flow control • R1, R2 and A, B (network layer and below) act exactly same with data as with SYN packet

  11. Gazing into the Crystal Ball General trends • ubiquity of communications • network-capable appliances (e.g., IP thermostat) • issues of scale important: billions of network-connected devices • mobility important : people move and need to communicate • multimedia important: it is how people communicate • increasing link rates, but bandwidth not free in near future • increased # "users" • increased access bandwidths • increased bandwidth requirements of enabled applications

  12. security critical concern • ubiquitous high bandwidth to home (ADSL, cable modems) a major driver for future • games, VR, education, information, entertainment • merger of networking and telephony • broadcast entertainment (TV), WWW, and ?? • agents, other technologies for dealing with large amounts of distributed, changing data

  13. The Very Last Note Page! • networking: will play a central role in all future computing systems • this course: • specific architectures, protocols, API's • fundamental issues: reliable data transfer, flow/congestion control, routing, multiple access, security • remember: you learned it HERE!

  14. Final Exam • similar to midterm • 5 problems • potpourri (all of course) • FSM for protocol • network layer • data link layer • security

  15. Network Layer • virtual circuit vs. datagram • two approaches to calculating routes • link state (OSPF) • distance vector (RIP, BGP) • intradomain, interdomain, hierarchical routing • broadcast/multicast routing • reverse path forwarding • core based trees • salient features of IP (v4, v6), ATM

  16. Data Link • functionality (framing, reliable communications, multiple access) • multiple access algorithms (Ethernet, ALOHA, slotted ALOHA, reservation, TDMA, token ring/bus,…) • advantages/disadvantages (low loads, high loads) • ARP • interconnected LANS, bridges

  17. security: • private/public key systems (DES, RSA) • authentication • digital signatures • key distribution • network management • functionality • SNMP, MIBs, … • QoS • issues • components

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