Recording links
for CS70 Zoom meetings

September 2, 2021 -  - demonstrated VirtualBox and the distributed fedora31 virtual machine, demonstrated Wireshark, slides at links in course outline titled "Network stack" and "Suites & layers." Commented about RFCs ("requests for comment") as the blueprints for protocols.

September 9, 2021 - talked about 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 the "vmconfigure" 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.

September 16, 2021 - reviewed significant conclusions from the wireshark capture assignment. Talked about ethernet, slides at course outline link "Ethernet: a protocol example"

    September 17, 2021 - "office hours" help for getting virtual machine environment up and running

September 23, 2021 - background to ethernet protocol with players Norm Abramson and Bob Metcalfe. Reason behind choice of the term "data link." Connecting computers equals "networks." Then, connection networks equals "internetwork." Connecting computers is the data link layer's defining job. Connecting networks is the network layer's defining job. Discussion of internet protocol, slides at link entitled "Interfaces & Routes". Discussed/demonstrated "network legality" homework. Route tables: local interfaces through which to send an outgoing frame, determined as a function of the IP address displayed in the "Destination address" field of the IP header in the IP packet inside the frame. IP netmasks as expressions of networks' sizes. IP networks as 32-bit numbers of a particular pattern: bunch 'o pure 1's followed up by a bunch 'o pure 0's. "Networks," numerically, as a range of addresses expressed as the first one plus the number of them (embodied in a particular netmask).

September 30, 2021 - "network" - logical/numerical (consecutive address range) vs physical (computers with connecting wires). Paper and pencil demo of splitting a network (range) into subordinate, constituent subnets (subranges). Response to student question: how NAT (network address translation) allows a single IP address on a router to "front" for a houseful of separate computers. (NAT will be covered more later). ARP protocol slides/lecture. Role of "ethernet type" field in ethernet header, to control distribution of payload by ethernet at receiver to the right network layer software according to what network layer software at sender originally produced the payload.

October 7, 2021 - Facebook outage Monday, demo of arp preceding a ping (showing arp in operation), "longest prefix match" for resolving more than one address-to-routing-table matches. "IP Addresses" slides, "IP packet delivery" slides (about Sally and Harry), description of related "IP packet delivery" homework.

October 14, 2021- IANA and the administration of IP address allocation. MAC vs IP homework elaboration and explanation. Error detection slides. Explained error detection homework. Explained upcoming internetworking exercise, demonstrated it up and running on my machine. IPv6 motivation and IPv4 solutions blunting adoption of IPv6.

October 21, 2021 - demonstrated handling of MAC addresses, as in the MAC vs IP addresses assignment, on live VMs. Also on those VMs, demonstrated handling of IP addresses when using NAT (Network Address Translation). Covered first part of slides at link entitled "Network: services" in course outline section 10 Slides column. It presents "clients" and "servers" as processes (as opposed to machines), and their identifiers in the transport layer which are named "ports" or "port numbers." Covered most of slides at link entitled "Networks: sockets" in course outline section 10 Slides column. Parallelism between the coding of access to files, versus access to the nework (via the "socket API").

October 28, 2021 - talked about adding a protocol to the 1-dimensional "letter upgrader" client/server pair. Enabled it to either "up-" or "down-"grade. Also showed a version that uses udp instead of tcp. Collectively performed the xinetd exercise, featuring the byteme script under the name "chomper". Discussed the internetworking assignment, student questions. Talked a little about the upcoming test, probably to be held the weekend after next.

November 4, 2021 - primary topic was netstat. Discussed the first 4 nodes of the internet and the technique for overcoming communications incompatibility among platforms by different manufacturers. Supply chain analogy to the relationship between ethernet versus IP addresses, as products pass through the supply chain or the packets through the router chain. Discussed protocol developement, and plans for upcoming CS75 Winter class. Discussed upcoming exam questions.

November 11, 2021 Veterans' Day

November 18, 2021 - David Huberman from ICANN spoke to us about DNS security.

November 25, 2021 Thanksgiving

December 2, 2021 - topics were udp and tcp. The tcp slides presentation was interrupted at break time and, following the break, recording was not resumed.
 - the recording up to the break is here
 - a supplement from previous semester resuming the tcp slides from their point of interruption is here.

December 9, 2021 - discussed web service, covering slide about its http protocol and that protocol's implementation in the Apache web server product (links entitled "HTTP protocol" and "Apache (web server)" in course outline section 14). I demonstrated the exercise at the link entitled "apache web server," formerly done by students in the classroom but presented as an instructor demonstration instead. Showed a Windows Server 2016 computer and pointed out some of its networking features that parallel those we have studied in linux. Briefly discussed the upcoming test and the kinds of questions on it.