CSCI 1001 Lecture Notes - Lecture 17: Bluetooth, Ethernet
Communication
Friday, April 27, 2018
11:19 AM
Clients and Servers
• All the work is happening on the server side
• Client benefits from use
Layers of Communication - OSI (Open Systems Communication)
• Lots of different abbreviations
• Levels
1. Physical level
i. E.g., DSL, wifi, bluetooth, 4G
ii. Might actually be a wire, doesn't have to be
1. DSL is a wire
2. All others can be radio or physical
iii. Basically 0s and 1s going by
1. Arguably nonsense
2. Data Link level
i. E.g., ethernet
3. Network level
i. E.g., IP (Internet Protocol)
4. Transport level
i. E.g., TCP (Token Control Protocol)
ii. Not heard of as much as the others
iii. Transport and network levels represent conversations
5, 6, and 7 Application level
i. http/https (encryption)
• No such thing as one level of communication, just like there is no one level of
software
o Everything is layered
o Bottom line is all bits
• Care a lot about upper level communication, not so much about lower level
o Has to do with security and safety
o Don't want to encrypt lower level, as that will mess with destination,
message, etc.
• At each different level, there is more structure to the communication
• Pieces of information are sent out at different levels, in different orders, but
are eventually assembled based on the sequence number
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Clients and servers: all the work is happening on the server side, client benefits from use. Layers of communication - osi (open systems communication: lots of different abbreviations, levels, physical level. E. g. , dsl, wifi, bluetooth, 4g: might actually be a wire, doesn"t have to be, dsl is a wire, all others can be radio or physical, basically 0s and 1s going by, arguably nonsense, data link level. E. g. , tcp (token control protocol: not heard of as much as the others. Header information trailer: where to, who from, how long, security, sequence number, matches header. Dns - domain name system: mapping from a domain name, like (www. google. com) to an ip address, which is a series of digits, resolution, check local cache, previously referenced urls (universal resource locator, e. g. , www. google. com. If not there, check all local host file entries (system software: check dns server (found at isp - internet service provider, or at employer, or the u of m, if not isp.
