Recording links
for CS70 Zoom meetings

February 20, 2021 - demonstrated VirtualBox and distributed fedora31 virtual machine, demonstrated Wireshark, slides at links in course outline titled "Network stack" and "Suites & layers"

February 27, 2021 - social protocols and computer network protocols; the rfc (request for comments) process for creating computer network protocols; Microsoft's Netmon and others in the same network sniffer product category as Wireshark; showed the slides at the link entitled "wireshark" in the Slides column of course outline's section 2; demonstrated use of scripts, documented in the links in the class web page's section titled "A virtual machine (VM) for you," for creating virtual machines and preparing to do the assigned exercise found in the Topic column of course outline's section 3.

   February 28, 2021 - office hours, VirtualBox installation and virtual machine importation

March 6, 2021 - physical layer, slides at course outline link "Transmission media," showed sample wires and equipment; undersea cabling; ethernet, slides at course outline link "Ethernet: a protocol example"

March 13, 2021 - physical layer, some of the slides at course outline link "Signals", composite waves, data transmission speed affected by number of digital signal levels. Reviewed significant conclusions from the wireshark capture assignment. Began discussing internet protocol, slides at link entitled "Interfaces & Routes". Discussed/demonstrated "network legality" homework.

   March 17, 2021 - office hours. Answered 2 main student queries: mechanical steps for transferring files, and getting VMs running using the vmconfigure scripts

March 20, 2021 - focus on route tables and the route command with my home network as live example, spent time giving technical commentary on the topics in several recent posts dated 3/13 and 3/15, discussed "netmask legality" homework, arp (address resolution protocol) formal lecture/slides

March 27, 2021 - demonstrations of routing table operation and effect, "IP packet delivery" slides featuring Sally and Harry, description of two assigned homework problems

   March 31, 2021 - office hours, focus on Harry and Sally (IP transmission/delivery rules) homework, and MAC vs IP homework

April 3, 2021 - IANA and centralized IP address distribution and administration. A sample real-world ISP network order for a small company. Demo highlighting extent and limit of netmasks' effect in determining addresses to which communication is enabled. Shoed slides and explained homework about error detection.

April 10, 2021 - supply chain example representing "macip" concept, that IP addresses stay constant as a packet traverses an internetwork while ethernet addresses vary. Discussed and demonstrated aspects of the internetworking homework assignment. Covered slides for IP Addresses and traceroute.

April 17, 2021 - spring break

    April 21, 2021 - office hours, internetworking homework help and discussion

April 24, 2021 - 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
"nmap" slides, first half of "Networks: services" slides
demonstrated netstat and nmap

May 1, 2021 - discussed the initial 1969-70 4-node internet, the concept behind it, and its similarities to it modern, descendent Internet; covered "Networks: sockets" slides about the socket API which is how a program can hook in to the network stack and avail itself of networking that way; demonstrated the world's most minimalistic server and its matching client, the letter-upgrader. It is structurally equivalent to the "big boys" among real-world production servers.

May 8, 2021 - equivalency of my primitive letter-upgrader server and its client with sophisticated production servers and theirs, in terms of their structure and use of the socket API. A version of letter-upgrader with addition of a protocol (ability of client to specify, and get, either incrementation or decrementation; asking the server for one of those is a request, protocols are about requests and replies). Reading from the Kurose/Ross networking textbook of analogy for transport and network layer by homes on both coasts inhabited by cousins. 2nd half of the "Networks: services" slides concerning xinetd. Performed xinetd homework. Covered udp slides.

May 15, 2021 - showed udp version of the letter-upgrader client/server pair. Examined coding differences, and wireshark trace of operation. Covered slides about tcp, emphasizing its mentality of orientation to datastreams (like the text of Moby Dick). Discussed homework and its focus on tcp's sequence numbers and acknowledgement numbers. Covered most of the netcat slides.

May 22, 2021 - concluded coverage and discussion of netcat slides (from "poor man's ftp") slide. Discussed dns, in two dimensions: the dns protocol, and the BIND (Berkeley Internet Name Daemon) implementation of it as a server. Discussed the upcoming "reconnect classroom to internet" homework.

May 29, 2021 - discussed issues raised by students on their "reconnect classroom to the internet" homework. Discussed the dns homework,and showed the example set up on my computer, to dish out made-up name-address mappings. Showed Windows Server, and how it offers services for administration, similarities and differences to how linux does so. Talked about dhcp. Covered slides about the http protocol. Next week, the apache implementation of the http protocol as a server, and more about dhcp. Showed the webmin graphical tool for remote admin of a linux machine (or, even, local).

June 5, 2021 - covered slides at "Apache (web server)" link.. Demonstrated virtual servers (two web sites served from a single copy of apache, depending on the domain name used in the URL that calls them). Covered slides at "dhcp" link.