Recording links
for CS70 Zoom meetings

September 3, 2020

September 10, 2020 - Google Drive, remote server, RFCs (request for comment), Wireshark slides, demo of Wireshark exercise

    General meeting to troubleshoot virtual machine issues Sunday, 9/13/20

September 17, 2020 - usage of scripts for setting up "wireshark" exercise, ethernet slides, Bob Metcalf inventor of ethernet, described upcoming "ethernet frames:" exercise, undersea cables

September 24, 2020 - IP protocol (slides entitled "Interfaces & Routes"), netmasks, discussed "netmask legality" homework

October 1, 2020 - significance of route tables, arp (address resolution protocol) lecture, reviewed significant conclusions from the wireshark capture assignment

October 8, 2020 - slides "IP packet delivery" and its 2 "golden rules," slides "IP Addresses" and bit masking, map of home network, nmap "network map" utility, demo of arp as prerequisite for ping (or any other exchange), network calculators, hub vs switch

    October 10, 2020 - office hours Zoom meeting

October 15, 2020 - error detection slides and homework, cursory treatment of internetworking slides, traceroute utility slides, commentary about ICANN and IANA and a real-world ISP subnet order

October 22, 2020 - discussed upcoming internetworking assignment in some detail, first half of "Networks: services" slides, "netcat" slides

October 29, 2020 - discussed the socket api, covering the slides and the "letter upgrader" client3.c and server3.c demo pair. You exercised those between two VMs within your host computer, and also between client3 on your computer and server3 on mine, over the internet. In order to do so, I had to set port forwarding in my ISP router so that your requests incoming to the router would be dished off (forwarded in) to the machine where server3 was actually running ( Discussed upcoming test content.

    October 31, 2020 - office hours Zoom meeting

November 5, 2020 - summarized take-away lessons from the "internetworking" homework
 - the internet is the same, just on a larger scale
 - no chain is stronger than its weakest link, everything has to be right in order for something to work
 - there are multiple paths between the same endpoints
 - our routers used static routing (fixed routing tables); dedicated internet backbone routers employ routing protocols among themselves to achieve dynamically self-modifying tables
physical layer - wired and wireless media/channels
ping and ICMP - demonstration and free description (did not use the slides)
nmap/netstat - demonstration and free description (did not use the slides)

November 12, 2020 - netstat and nmap slides, performed the exercise at course outline section 12 link entitled "xinetd" to give a non-network program trans-network behavior

November 19, 2020 - udp and tcp slides, demonstrated the "tcp interactive dataflow tracking" homework activity, demonstrated a file transfer of a data stream (text of the novel Moby Dick) and observed evolution of the values of sequence and acknowledgement numbers in the tcp headers. Revisited the udp rendition of the echo protocol from past homework sending "hi" then "bye" over and back, noting that ethernet padding to meet the 46-byte minimum requirement appears only in the bounceback not the outbound. Explained why.

    November 28, 2020 - office hours Zoom meeting

December 3, 2020 - dns protocol and BIND program, a nameserver that implements dns. Includes a demo of the homework exercise. Demo was not successful, a successful video demo of same can be found here. Also analyzed question 42 from the midterm test. (Linked video is not from our class meeting but a meeting covering the same main topic.)

December 10, 2020 - reviewed dns, mentioned my /etc/hosts solution to utilizing the "" domain name locally at home. Showed account for on website of name registrar Demonstrated the version of the letter upgrader client and server that defines and employs a (minor) protocol, in that it varies the server's behavior between upgrading or downgrading the letter presented by the client, at the client's direction. Demonstrated the solution to the "reconnect" problem ( Covered slides for "HTTP protocol" and "Apache (web server)" in course outline section 14. Demonstrated the "apache web server" in-class section 14.