Report Blog Entry
- "be an asker"
- "My mom was the one who taught me how to be insistent. When I was a kid and she was trying to change a flight reservation or persuade someone to do something she would spend literal hours on the phone—she’d just keep calling back until she found someone who would do it. At the time I found that super embarrassing, as kids do. But looking back, I see that I internalized something important: how to ask for what you want [...]"
- "no worries if not" (ask v. guess culture)
- "My sister is a dyed-in-the-wool non-confrontationist, but she also has high expectations. This makes her a model subject of the “no worries if not” meme—a running joke on Twitter that pokes fun at people who use the verbal tick in inappropriate situations and a phenomenon I’ve been thinking about a lot lately. As in: “Any chance you could treat me with decency and respect? No worries if not!”"
- "Are you a baby? A litmus test"
- "Unfortunately I’ve spent a lot of my life trying to navigate social situations using a tawdry, homespun radar for what everyone’s thinking and feeling at a given time, and instead of transforming me into an intuitive genius, it’s made me (at times) a neurotic little freak. To be fair, I love the neurotic freaks in my life, but together we can make life more complicated than it needs to be. Learning to anticipate, gauge, and state your needs isn’t just irritating therapy-speak, it’s a relief for everyone involved."
- "Everything Happened | vol. 213"
- "Nick wakes me up at 9:30 on Sunday to tell me that he and Desi are leaving. Nick’s dad, hundreds of miles away in Ohio, is in that last room of life: sick with an illness that can’t be cured and for which treatment has stopped. Our deal is that he can visit Ohio as frequently as he needs as long as he takes at least one child with him. Nick let me sleep in as they loaded up the van but now they needed to start the journey. “Shit,” is what I say to this info."
- "Jane, my three-year-old, is outraged that they are leaving her behind. She sits on the threshold, holding the glass storm door open with her knees, wailing. I envision the outdoor air whooshing in through the opening and choking out all the expensive, chilled air inside. I tell her she can sit inside or outside but she needs to close the a door. She snaps her head to look at me, a vengeful ghost, and stares like I’ve pissed on the graves of her ancestors. Her legendary frown gives way to an unintelligible scream rant. I ask her if she would like some blueberries. The killswitch. All darkness is instantly snuffed out and she floats behind me to the kitchen where she swoons. “I love blueberries, mama. Thank you so much!”"
- designing data intensive applications chapter 3: stuff about indices, db data store structures
- log structured merge trees
- sstables v append only in memory indices
- lucene
- b trees / write ahead logs / copy on write
- b trees faster for reads, lsm trees faster for writes
Things I'm watching:
- 【Lecture 01】 CS144, Introduction to Computer Networking:
- (reliable) bi-directional byte stream, either end (server/client/requester/responder) can close the connection
- many different kinds of applications:
- example: World Wide Web uses HTTP
- document-centric protocol that sends data that is human readable / ascii
- client / server requesting / responding to connections
- example: bit torrent
- swarms of peers
- tracker: node that keeps track of clients and what pieces of the file they have
- new clients connect to tracker first, then other peers
- dense graph of connections
- skype video / audio calls
- two personal computers instead of client/server machines
- NAT gets in the way: network address translator; red/green gradient (blocks incoming connections but permits outgoing connections)
- rendezvous server / reverse connection: client b connects to skype; client a tries to connect to client b, skype sends message to client b; client b accepts request and initiates a connection to client a (not behind a NAT)
- when both client a & b are behind NATs, a relay server is used: which just forwards messages between both clients
- 【Lecture 02】 CS144, Introduction to Computer Networking: the four-layer internet model
- link layer
- internet is made up of end-hosts, links, and routers
- data is delivered hop by hop over each link
- in packets: self-contained data bundle we want to be delivered, along with header with delivery address, origin, etc.
- ethernet & wifi are two examples of different link layers
- network layer
- deliver packets end to end across internet from source
- network layer packets are called datagram
- often drawn as : [. data. . ][from][to]
- network hands datagram to link layer below
- link layer provides *service* to network layer: will transmit over one link for network layer
- router at end of link accepts datagram from link, and hands up to network layer in router
- network layer routes datagram one hop at a time to eventual destination by examining destination address and forwarding to each link
- network layer is not concerned about *how* link layer works; separation of concerns between each layers allows each to focus on own job
- means network layer has common way to talk to different link layers
- network layer in internet is special: must use the Internet Protocol (IP)
- makes best-effort attempt to deliver packets, but no guarantees
- failures are handled by the next layer... the transport layer
- transport layer
- most common transport layer is Transmission Control Protocol (TCP)
- ensures delivery and correct sequence
- will re-transmit packets if the network layer drops them
- will re-order data in correct order if network layer delivers out of order (e.g. due to different paths)
- other examples:
- user datagram protocol (UDP) -- useful if guaranteed delivery is unnecessary, e.g. transmitting video packets; UDP just bundles up data and hands to network layer without delivery guarantees
- there are others, but TCP & UDP are most commonly used
- application layer, e.g. bittorrent, skype, or world wide web (uses http)
- "IP is the 'thin waist' of the Internet"
- to use the Internet, we must use the Internet Protocol
- but have many layers for link layers (ethernet, wifi, dsl, 3g cellular)
- have many options for transport layers: TCP/UDP, RTP (real-time protocol), etc.
- and tens of thousands of applications
- in the 80s the International Standards Organization (ISO) created a 7-layer Open Systems Interconnection (OSI) model, which has been replaced with the 4-layer internet model
- (1) physical layer + (2) link layer -> today's link layer
- (3) network layer -> today's network layer
- (4) transport and (5) session -> today's transport layer
- (6) presentation and (7) application -> today's application layer
- real legacy of the OSI model is the numbering system which is still referenced today (network layer is "Layer 3")
- 【Lecture 03】 CS144, Introduction to Computer Networking (07.05.22)
- IP layer
- core feature: datagram, unreliable, best-effort, "connectionless"
- designed to be simple, dumb, minimal: faster, streamlined, low-cost to build/mantain
- end-to-end principle: "where possible, implement features in end hosts"
- different from telephone system: complicated network switches and simple handset receivers
- allows more kinds of systems to be built on top
- guaranteed delivery would not be appropriate for certain applications, like video calls. IP lets application layer choose reliability service it needs
- IP works over any link layer (wired or wireless, etc.)
- Internet was created to interconnect existing networks, so it made sense for it to work with any link layer
- services:
- prevents packets from looping forever (forward table in a router could be wrong and cause packets to be looping forever)
- will catch and delete packets that are apparently stuck in a loop, by using a hop-count field in the header: the time to live (TTL) field
- starts at # e.g. 128 and is decremented by every router it packet passes through
- if it reaches 0, IP router drops the packet
- IP will fragment packets if they are too long for certain link layers
- uses header checksum to reduce chances of delivering datagram to wrong destination
- allows for new versions of IP (e.g. IPv4 and IPv6)
- allows new fields to be added to header (for flexibility??)
- very few options are used / processed by routers
- fields in IPv4 header: destination IP address, source IP address, Protocol ID (e.g. "6" = TCP), version (e.g. v4, v6), total packet length including header + data, Time To Live field, flags and fragment, type of service field, header length for header, checksum for whole header, so if header is corrupted, we won't deliver data to wrong place
In other news, one of my front tooth crowns cracked and came off while I was munching a chicken wing (bone), and I had to get a temporary crown yesterday! This also fell off today while I ate crusty bread, forgetting my doctor's warnings to be careful. My mom's three crowns on one side of her mouth that we just got in Turkey less than a month ago also fell off on the same day my crown cracked. She had been complaining about hot/cold sensitivity with her implants. Now I have something in common with the guy who stared at me at the bus stop in Excelsior last weekend, mad that I couldn't understand what he was asking for - a missing tooth.
Comments
Displaying 0 of 0 comments ( View all | Add Comment )