ICS 451 Final (EVERYTHING YO!)

SSH: Between Symmetric and Assymmetric keys describe: 1) What it is? (number of keys, what is "clear", "key", and "code") 2) Which is the preferred two-way communication and one-way communication. 3) How do performances compare to each other?

1) Symmetric - One Key > Clear (Data) > Key (Encryption) > Code (Encrypted Data) Asymmetric - Two Keys (Public, Private) > Clear (NONE) > Key (Encryption - Public Key) > Code (Encrypted Data) - no one can decrypt unless they have a private key 2) >Symmetric - two way > Asymmetric - one way 3) > Symmetric - BETTER > Asymmetric - not as efficient b/c requires a lot of configuration/maintenance to keep security safe

DNS: 1) What is a "A" Record? 2) What is a "AAAA" Record?

1) "A" Record (most common - IPv4) - hostname to IP address mapping 2) "AAAA" Record (IPv6) - hostname to IP address mapping

HTTP: Name (5) response/status codes from at least 3 different ranges (ex. 100s, 200s, 300s, etc.) and state what they mean.

1) 200 - OK: request was successful - information returned from server 2) 301 (Permanent), 302 (Temporary) Redirect : the requested information is no longer (302 - for now) at the designated host and is located under a new hostname and/or IP 3) 304 - Not Modified: Server can tell that the client has a local up-to-date copy of the requested information and is instructing the client to use their local copy instead of asking for a GET of the info 4) 404 - Page Not Found: Server hasn't found anything matching the requested host 5) 500 - Server Error: Server encountered an unexpected condition which prevented it from fulfilling the request.

ICMP: What is Echo Reply?

Echo Reply - Wants to check if the destination (server) is alive [similar to ping command]

CSMA/CD: What does this protocol do when a collision is detected?

If collision is detected, stops senders from sending any more packets and has senders wait using binary exponential back-off then try again.

Network: What is IEEE? What do they do?

Institute of Electrical and Electronics Engineer - develops standards for computer/electrical industry (ex. IEEE 802 standards - local area networks)

Routing: 1) What is a routing table? 2) What layer(s) of the OSI model and TCP/IP model does this belong to?

1) A list of IPs in a table that handles a variety of routing protocols of where to send packets to get those packets to their destination. 2) Network - Network

Aloha Protocol: 1) What is the Aloha Protocol? 2) What OSI and TCP/IP layer(s) did it pertain to?

1) Aloha Protocol: A protocol that creates a shared channel where broadcasts are known by everyone and everyone shares a channel to share data. Had a 19% success rate. 2) Data Link Responsible for providing reliable transfer of data between communication parties, like avoid/detect collisions and the physical addressing

Signaling: 1) Name the two types. 2) What OSI and TCP/IP layer(s) do these reside in?

1) Analog, Digital 2) Data link & Physical - Network Interface

IP: 1) What does IP stand for? 2) What OSI layer and TCP/IP layer is IP apart of? Why? 3) What is IP used for?

1) IP - Internet Protocol 2) Network - Network - IP are the ids of hosts and are used in the addressing and routing of data packets. 3) IDs of hosts in a network

IP: 1) How many IPv4 addresses are there? 2) How many IPv6 addresses are there?

1) IPv4: ~4billion (ran out) 2) IPv6: ~340 gazillion

HTTP: 1) What is a sticky session? 2) How is this established and maintained?

1) Indicator to keep sessions alive by the server's load balancer by always being physically routed to the same physical web server for every request 2) If the load balancer of the server is configured where a client's request will always be routed to a single server, its possible to keep sessions alive

HTTP: 1) What is a non-sticky session? 2) How is this established and maintained?

1) Indicator to not keep session by the server's load balancer choosing any web server to serve the client's request 2) Load balancer is configured to route the client's request to any web-server that can answer the request.

ICMP: 1) What is ICMP? 2) What OSI and TCP/IP layer is NAT working in?

1) Internet Control Message Protocol 2) Transport An upper layer protocol doesn't go into the IP routing and framing of packages, but is used in the transport of packets.

DNS: 1) What are two types of DNS queries? 2) Describe how each types performs DNS resolution?

1) Iterative & Recursive 2) > Iterative - DNS Client -> Local DNS Server DNS Client -> -> -> DNS Client <- ________ (if record is not found in cache of Local DNS Server, Local DNS Server sends client a referral to a root server that they can try instead) > Recursive - DNS Client -> Local DNS Server) (if record is not found in cache of Local DNS Server, the Local DNS Server will look for the record for the request) *** Better than iterative

Signaling: 1) What is modulation? 2) Describe (3) types of modulations?

1) Modulation - sending some type of data on a different type of signal 2) > Amplitude - the modulation of a wave by varying its amplitude, used chiefly as a means of radio broadcasting, in which an audio signal is combined with a carrier wave. > Frequency - the modulation of a radio or other wave by variation of its frequency, especially to carry an audio signal. > Phase - variation of the phase of a radio or other wave as a means of carrying information such as an audio signal.

HTTP: What status/response code does the client receive from the server after every successful GET method HTTP request?

206 - Partial Content (OK GET)

LINUX Commands: What does TELNET do?

Access/communicate remote systems [TCP/IP]

ABR: What is an adaptive bit rate?

Adaptive Bit Rate (ABR) - adjusted bit transfer rate of data from server to client based on how much sender can send and receiver can receive. Reason why quality switches between HD-low quality when accessing media.

Cache: What is the benefits of having a large TTL for cache in DNS?

Allow information to be more widespread among more servers for longer periods of time -> Faster DNS Queries b/c servers now can have access to direct routes to server with the requested for info

ICMP: Why is ICMP in the middle of the transport and network layer?

Transport An upper layer protocol doesn't go into the IP routing and framing of packages, but is used in the transport of packets. Network Its job is to help the routers figure out the shape of the internet and what direction to send packets with different protocols. Consequently, it's considered a network-layer protocol, since its job is to ensure that data is routed to the right place but doesn't actually route the data. Error Control to IP.

IP: How do you compute a subnet mask?

Turn all bits in the network part of the IPv4 address to 1.

DNS: How is a zone different from a domain?

Zones are sections that make up a domain (ex. ics.hawaii.edu is a zone of the domain hawaii.edu)

OSI Model: What are the seven layers of the OSI model (top to bottom)?

OSI Model: 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

Sockets: Describe step-by-step the server-side function sequence process for a TCP connection (start-middle-end).

SERVER ------------------ 1 Socket() - creates an unbound endpoint for communication with another socket 2 Bind() - assigns an address to the socket 3 Listen() - listen for connections on a socket based on socket's address assigned in bind() 4 Accept() - accept a connection on a socket (after client tries to connect to socket's port) 5/6 Recv(), Send() - recv and send data 7 Close() - closes the connection on the socket

DNS: What is a SOA record?

SOA (State of Authority) - one of the most essential DNS records b/c it sotead important info like when the domain was last updated and zone's admin info

TCP: Describe the TCP start, middle, and end process of just getting information from a server from a client and then immediately close the connection w/ flags, ack, and sequ no?

START: TCP 3-Way Handshake ----------- 1) C -> S [SYN] SEQ:0, ACK: 0 2) S -> C [SYN, ACK] SEQ: 0, ACK: 1 3) C->S [ACK] SEQ: 1, ACK: 1 MIDDLE: Data Request-Response 4) C->S [PSH, ACK] SEQ: 1, ACK: 1 5) S->C [ACK] SEQ: 1, ACK: 726 (how much was sent) 6) C->S [ACK] SEQ: 726, ACK: 927(next sequence of wanted bytes next) END: Close Connection 7) C-> S [FIN] SEQ: 726, ACK: 927 8) S->S [AC] SEQ: 927, ACK: 727 9) C->S [ACK] SEQ: 727, ACK: 928 10) S->C [FIN] SEQ: 928, ACK: 728 CLOSE CONNECTION

SSH: What OSI and TCP/IP layer is SSH at? Why?

Session Facilitates the starting, handling, and ending of connections between two parties. Synchronizes related streams of data, like video/audio streams in a video session (ex. NetBIOS, SOCKS)

Port: Name the port numbers for: 1) HTTP 2) HTTPS 3) SMTP

1) HTTP: 80 2) HTTPS: 443 3) SMTP: 25

Signaling: 1) What are two factors in regards to signaling? 2) Between analog and digital, which is better?

1) How far the signal goes & how much data can be transmitted on the signal 2) Digital > Analog

Cookies: How does cookies work between clients and servers (3 steps)?

1 C->S [Request has Cookies header Enabled] 2 S->C [Response has Set-Cookies header with a cookie id; question if client wants to set cookie] 3 C->S - Accepts: Sets Cookie header with the id given by Server - Denies: Requests will not have cookies enabled (nothing specified in field)

DNS: What is the hierarchy of DNS (Bottom-Up)?

1 Local DNS Servers 2 Root Servers - contains info on every domain (ex. .edu, .org, .com) 3 Top-Level-Down (TLD) - maintains root zones, basically a bunch of root servers 4 Authoritative Servers - contains the hostname IP mappings

DNS: What is a zone?

A collection/unit of information belonging to and maintained by a system adminstrator that is a sub-domain.

Access Mechanism: 1) What is a Bus network topology? 2) What is it's access mechanism? 3) What are 2 advantages and 2 disadvantages?

1) Bus (network topology): each network device is connected to a common linear link called a bus (cable) that is used for communication in the network. 2) Access Mechanism: Token Passing (When a host wants to communicate with another host on a network, sender broadcasts token with recipient specified. If token matches a host, then recipient would accept the token and they two could communicate with one another.) 3) Advantages & Disadvantages > Advantage(2): - Easy to connect to the recipient in network through the bus - Works well for small networks > Disadvantage(2): - entire network shuts down if there is a break in the bus - large amount of packet collisions on the network

SSL: Describe the 7 steps of how SSL works.

1) C -----> S [C-PK, "Who Are You?"] Browser connects to a web server (website) secured with SSL (https). Browser requests that the server identify itself. 2) S -----> C [S-SSL Certificate + S-PK] Server sends a copy of its SSL Certificate, including the server's public key. 3) C ------> CA [S-SSL Certificate] Browser checks the certificate root against a list of trusted CAs and that the certificate is unexpired, unrevoked, and that its common name is valid for the website that it is connecting to. 4) CA ----> C [S-SSL-Certificate-Sign [OK]] If the certificate is ok, then the CA will sign it by encrypting it into a hash 5) S ((SK*(S-PK)) / S-PK) = SK C ------> S [SK * (S-PK)] If the browser trusts the certificate, it creates, encrypts, and sends back a symmetric session key (SK) using the server's public key. 6) S -----> C [ACK * (SK)] Server decrypts the symmetric session key using its private key and sends back an acknowledgement encrypted with the session key to start the encrypted session. 7) S <-----> C [..... * (SK)] Server and Browser now encrypt all transmitted data with the session key.

Cache: 1) What is the danger of cache? 2) How can it be avoided?

1) Cache can become outdated and if relied upon without updates, can lead to getting wrong information or no information 2) Purge cache using TTL property

CSMA/CD: 1) What is CSMA/CD? 2) What OSI and TCP/IP layer does this pertain to? Why? 3) How does it work?

1) Carrier Sense Multiple Access With Collision Detection (CSMA/CD): The Standard Ethernet protocol that regulates when multiple network devices can transmit on a shared channel to best avoid a collision event from occurring (i.e. ALOHA + Collision Free+ N-Persistence) 2) Data Link Layer Responsible for providing reliable transfer of data between communication parties, like avoid/detect collisions and the physical addressing 3) Process 1) All network devices listen on the shared channel 2) When a network device wants to send a packet check if the channel is busy 2a) Channel idle -> Send Packet 2b) Channel busy -> wait until channel is free enough to transmit without collisions occurring using binary exponential back-off

CDMA: 1) What is CDMA? 2) What OSI and TCP/IP layer(s) does this reside in?

1) Code Division Multiple Access - a channel access method used by various radio communication technologies where several transmitters can send information simultaneously over a single communication channel. 2) Physical - b/c another frequency modulation type

LINUX Commands: 1) Explain what the curl command does. 2) What is the curl command used for?

1) Command line version of the world wide web (performs HTTP + DNS procedures of getting a website's content) 2) Used to view/modify HTTP response headers

TCP & UDP: What are 3 differences between the two? Explain each difference.

1) Connection Type - TCP: Connection Oriented - transmits data in order - UDP: Connectionless Oriented Protocol - can transmit data out of order, but is faster b/c doesn't need to do TCP 3-Way Handshake 2) Header Size - TCP: 20 bytes - UDP: 8 bytes 3) Speed & Performance - UDP: Faster (less reliable) - TCP: Slower (more reliable - flow control, congestion control)

CDN: 1) What does CDN stand for? 2) What OSI layer and TCP/IP layer(s) does SMTP belong to and why?

1) Content Delivery Network - companies that buy up a ton of servers all over the world to deliver server's services to a large geological user base (i.e. not just local area, but more closer to a nationwide or global) 2) Network - Network Used in caching and dynamic routing of data packets.

LINUX Commands: 1) Explain what the nslookup command does. 2) How does he nslookup command do that?

1) Displays what the DNS client is doing when communicating with the DNS server with less info than dig. 2) Carries out the DNS protocol from the terminal and prints to screen partially of the DNS return results

LINUX Commands: 1) Explain what the dig command does. 2) How does the dig command do that?

1) Displays what the DNS client is doing when communicating with the DNS server(s) (ex. dig www.walmart.com) 2) Carries out the DNS protocol from the terminal and prints to screen the DNS return results

DNS: 1) What does DNS stand for? 2) What layer(s) of the OSI and TCP/IP model is DNS apart of? 3) What is DNS used for?

1) Domain Name System 2) Application - Application 3) A database that contains all the IP hostname mappings on the internet (i.e. maps hostnames formatted in HTTP to IP addresses so that web browsing/communication can work)

Access Mechanism: 1) What is the advantage of the token passing access mechanism? 2) What is the disadvantage of the token passing access mechanism?

1) Fair Access, Cap on the worst case scenario (i.e. worst case being the last one in line to get the token) 2) Consistent reconfiguration every time there is a change in host order

HTTP: Name (4) HTTP methods and explain what they are used for.

1) GET - requesting information (usually client -> server) MOST POPULAR 2) POST - uploading information (usually client -> server) 2nd MOST POPULAR 3) PUT - update a record (usually client -> server) 4) HEAD - like GET, but doesn't get any information, but receives response from server. Used to check connection between client and server vice-versa (like a ping for HTTP)

HTTP: 1) What does HTTP stand for? 2) What OSI layer and TCP/IP layer is HTTP apart of? Why? 3) What is HTTP used for?

1) HTTP - Hypertext Transfer Protocol 2) Application - Application - HTTP is what runs in the web browser that the user directly interacts with on a application like a web browser, that sends input to the lower parts of the OSI model and displays the OSI model's output. 3) Format of data communication on the internet

IP: 1) What is NAT? 2) What OSI and TCP/IP layer does it belong to?

1) Network Address Translation - a method of remapping one IP address space into another by modifying network address information in Internet Protocol (IP) datagram packet headers while they are in transit across a traffic routing device (i.e. the source ip address). Used to save IP addresses by sharing one IP address of a NAT gateway for an entire private network. 2) Network In order to function, the router facing the Internet has to have a publicly routable address on the Internet interface. With NAT, none of the computers behind it needs a real address, so address space is conserved. As packets cross the router/firewall, it: a) replaces the private addresses/ports in each packet with its own public address and a selected source port b) keeps track of which addresses/ports it is NAT-ting to what c) undoes the translation as replies come back from the Internet. Neither your computer nor the computer on the other end ever sees that NAT is being done, so it is transparent. Since all of this is in the IP realm, it is all layer 3

Response Time: What are (3) ways to measure response time? Explain.

1) Reduce distance between the client(s) and the web server(s) - put web server content on "caching" servers => servers are closer to client(s) and can server web server content faster b/c they are closer to a client(s) and uses caching 2) Increase speed - Improve latency by using a lot of TCP performance techniques (get rid of slow start, larger starting window sizes) 3) Reduce the amount of data - Compression of data in request HTTP headers (Accept-Encoding: gzip) so that response compresses response w/ data

Access Mechanism: 1) What is a Ring network topology? 2) What is it's access mechanism? 3) What are 2 advantages and 2 disadvantages?

1) Ring (network topology): each network device is linked to exactly two other nodes to form a single continuous pathway like a ring. 2) Access Mechanism: Token Passing (Each host can only communicate one at a time based on if they have a singular token that allows a host to communicate (i.e. they have to take turns communicating) 3) Advantages and Disadvantages > Advantage (2): - Easy to add & remove network devices (b/c of simplicity of links) - Orderly network traffic as every host has to take turns to transmit traffic > Disadvantage (2): - a single Link failure could cripple the entire network - communication delay b/c of single token passing

LINUX Commands: 1) Explain what the traceroute command does. 2) How does the traceroute command do that?

1) Shows the route of message transmission from the client to the server. 2) Sends ICMP packets with incrementing TTL from the client to the server that will send a trace signal at every expired TTL (i.e. at least one ICMP packet will expire at every stop) so the terminal can trace the route of the message transmission

SMTP: 1) What does SMTP stand for? 2) What OSI layer and TCP/IP layer(s) does SMTP belong to and why?

1) Simple Mail Transfer Protocol - Used for emails 2) Application - Application b/c user interacts directly with this protocol for input on mail applications like Outlook

Access Mechanism: 1) What is a Star network topology? 2) What is it's access mechanism? 3) What are 2 advantages and 2 disadvantages?

1) Star (network topology): a central host (router, hub, switch) regulates traffic between multiple hosts on a network. 2) Access Mechanism: Central Host (routing tables) 3) Advantages & Disadvantages > Advantage: - network is able to adapt to if a host or connection fails - devices can be added/removed easily - good for large networks > Disadvantage: - expensive network layout b/c of amount of cable required for complexity - if central host fails, network traffic stops

Response Time: What are (2) ways to measure response time?

1) Streaming - How long it takes for the First Byte to be Served, Rebuffering (frequency of rebuffs and how much bytes are recv per response) 2) Website - Total page loading time

TCP & UDP: 1) Name 2 real-world applications that use TCP. 2) Name 2 real-world applications that use UDP.

1) TCP - SSH, SMTP 2) UDP - Media Streaming, Tunneling/VPN

Sockets: 1) What are ports? 2) What OSI and TCP/IP layer(s) does this pertain to? Why?

1) The "doors" for a client to gain access a host (NOTE: There are typically 2^16 ports on a system) 2) Session - Application - Ports are used to establish and control the connection between communicating parties

HTTP & DNS: Describe, step-by-step, how a web client initializes and connects to a web server (irregardless of UDP or TCP standards, just with HTTP to DNS resolution process) [About 7 Steps].

1) The Client checks its host file for the hostname-IP mapping of server. If it doesn't find the mapping, goes into DNS process; otherwise is able to connect straight to server. DOESN'T FIND HOSTNAME-IP => DNS RESOLUTION PROCESS BEGINS 2) The DNS Client of the web client sends a request to the Local DNS Server for the hostname-IP mapping of the server. The Local DNS Server will check if it has the hostname-IP mapping of the server and if it does it returns it to the DNS Client; otherwise it contacts the root server for the hostname-ip mapping. 3) Root server checks if it has the hostname-ip mapping and if it does, returns that info to the the local dns server; otherwise will send a referral to either another root server or the TLD server for the local dns server to send the request to instead 4) Local DNS Server -> TLD Server [Request] If the TLD Server has the hostname-ip mapping will send info back to local dns server; otherwise will send back a referral to another TLD server or Authoritative server that may have the info. 5) Local DNS Server -> Authoritative Server Authoritative server checks for record and if it doesn't have the authoritative server will check other authoritative server for the record and then, return the A or AAAA record that has the hostname-ip mapping needed. 6) Local DNS Serer -> DNS Client the A or AAAA record. 7) DNS Client resolves the hostname's ip address in the web client and connects successfully to the server's ip address

HTTP: Name (6) HTTP headers used in CLIENT requests and state what each header is used for.

> Accept: specify the certain media types which the client can accept from the server's response (Accept: text/plain; q=0.5, text/html, text/x-dvi; q=0.8, text/x-c) > Accept-Language: similar to Accept, but restricts the set of natural languages that are preferred as a response to the request (Accept-Language: da, en-gb;q=0.8, en;q=0.7) > Cookie: contains a name/value pair of information stored for that url. Can be used to maintain session(s) on website(s). (Cookie: name=value) > Host: specify the Internet host and port number of the resource being requested (Host: www.w3.org) > If-Modified Since: a timestamp that is sent to the server to ask if the requested URL has not been modified since the time specified in this field, an entity will not be returned from the server; instead, a 304 (not modified) response will be returned without any message-body. (If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT) > User-Agent: contains information about the web client sending the request (ex. User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)

HTTP: Name (5) HTTP headers in Server responses and state what each header is used for.

> Age: contains the sender's estimate of the amount of time since the response (or its revalidation) was generated at the origin server. > Etag: provides the current value of the entity tag for the requested variant. Used to id data > Location: used to redirect the recipient to a location other than the Request-URI for completion. > Rety-After: can be used with a 503 (Service Unavailable) response to indicate how long the service is expected to be unavailable to the requesting client. > Set-Cookie: contains a name/value pair of information to retain for this URL

HTTP: What are (2) enhanced features of HTTP/2?

> Allows the server initiate communication with client (ex. request/push data from client before client talks to server) > Converts HTTP requests from default ASCII format to binary (compresses requests - decreases the size of the HTTP Request)

Signaling: What are (3) types of signal loss/errors?

> Attenuation - farther signal goes out, the weaker it gets > Interference - signals weaken/modify with collisions with other signals or objects > Propagation Delay - amount of time it takes for the head of the signal to travel from the sender to the receiver

Collisions: What are 3 types of collisions?

> Detection > Free > Avoidance

SSL: What are 3 important fields in a SSL Certificate?

> Hostname/Common Name (CN)/ Subject Alternate Name (SAN) > Expiration Date > Cipher Suite (combination of authentication, encryption, message authentication code (MAC) and key exchanged algorithms used in SSL)

OSI & TCP Model: Which model is better for theory and which model is better for programming?

> OSI Model => Theory > TCP Model => Programming

SSL: What Types of SSL certificates rely heavily on Hostname Field?

> Single Hostname - one hostname per SSL Cert. > Wildcard - *.hostname (used mainly for organizations with a ton of sub-domains) on the SSL Cert. > Subject Alternate Name (SAN) - has multiple hostnames from different domains

UDP: Name all the fields of the UDP header (4) and how many bytes is the UDP header.

> Source Port > Destination Port > Length > Checksum

HTTP: What is a conditional GET?

A Get request sent with a if modified since header which the client sends to the server if client already has the requested data from a previous result of an HTTP request, but client wants to make sure that the data is still valid (not modified since)

DNS: What is a domain?

A collection of information for an entire name space for a hostname.

HTTP: How is http://www.yahoo.com/?page=5 unsecure?

Anyone can see the query content in the HTTP URL and thus, makes it possible to do an SQL injection with a false HTTP URL with the queries modified and requested to the server.

SSL: What type of encryption does SSL use?

Both Asymmetric (Two hosts use their own public/private key) & Symmetric (Ultimately, SSL creates a unique browser/server key that is used in communication)

HTTP: What HTTP header is used in the sent GET request from the client to specify what section of the server's file that the client wants next?

Byte-Range Header.

IP: What are CIDR Blocks?

CIDR Blocks - Instead of specifying the network and host number by the number of bytes, can specify with any number of bits (ex. subnets)

DNS: What is a "CNAME" Record?

CNAME (Canonical) Record - indicates whether or not the hostname is an alias for another hostname and if it is an alias, provides the host name if it is an alias NOTE: After obtaining the "CNAME" record, the DNS protocol will obtain the A or AAAA record of the hostname obtained from the CNAME record

Aloha/CSMA/CD: What is better, Aloha or CSMA/CD? Why?

CSMA/CD - Better at collisions detection and prevention.

Cache: What is cache?

Cache - a temporary copy of information stored for better performance (ex. Local DNS Server stores referral route to the authoritative server with the hostname-ip mapping so the DNS Client can get the information faster)

Signaling: What is a carrier signal?

Carrier Signal - signal that carries the data

Sockets: Describe step-by-step the client-side function sequence process for a connection (start-middle-end)

Client ---------------- 1 Socket() - creates an unbound endpoint for communication with another socket 2 Connect() - connect the socket to the address of the server 3 Send(), Recv() - send and recv data to/from server 4 Close() - closes the connection on the socket with the server

HTTP: Explain how video/audio streaming works in terms using HTTP.

Client uses multiple GET method HTTP requests to get pieces of the overall file (ex. 5000 bytes per GET call) and stores them in a buffer to be played. NOTE: Lag is when there is not enough info in the buffer and the client is in the middle of getting more info from the server .

Communication: 1) What is a "communication protocol"?

Communication Protocol - The rules of communication between two parties (ex. the format a message has to be in order for a client and server to communicate)

DNS: What is a DNS resolution?

DNS Resolution - the process of translating a hostname into its mapped DNS IP address

Access Mechanism: What OSI and TCP/IP layer are access mechanisms at? Why?

Data Link - Network Interface Responsible for providing reliable transfer of data between communication parties, like avoid/detect collisions and the physical addressing

Signaling: What does goe-synchronous mean?

Geo-synchronous - (satellites that) move at the same speed of the Earth

HTTP: What are persistent connections?

HTTP Persistent Connection - using a single TCP connection to send and receive multiple HTTP requests/responses, as opposed to opening a new connection for every single request/response pair. This is indicated in the HTTP header "connection" with the value keep-alive.

CSMA/CD: What is IEEE 802.3 CSMA/CD Protocol?

IEEE 802.3: A working group and collection of IEEE standards that define the physical layer and data link layer's MAC (media access control) of wired Ethernet networks.

Routing: What is dynamic routing?

If a local server goes down, the routing will automatically reroute routes to establish functional routing again.

DNS: What is an MS Record?

MS (Mail Server) Record - provides the mapping to a mail server used in the requested for domain

DNS: What is an NS Record?

NS (Name Server) Record - Indicates which Name server is authoritative for the domain (i.e. indicates the authoritative server for the requested for domain)

IP: What are two parts of an IPv4 address?

Network, Host

LINUX Commands: What does PING do?

PING - checks whether or not a another host is alive by seeing if the current host system can connect to the other host, and then measures how long it takes in a round-trip communication between the request and the reply

Network Topology: What OSI and TCP/IP layer are network topology hardware setups at?

Physical - Network Interface The physical hardware that makes up the network and defines physical specifications, protocols, transmissions modes, and network topology

Access Mechanisms: What are the 3 IEEE standard network topologies?

Ring, Bus, Star

Aloha Protocol: What is the difference between slotted Aloha and the Aloha Protocol?

Slotted Aloha: > 38% success rate > added time restrictions -> Less collisions -> Higher success rate Aloha: > 19% success rate > no time restrictions -> everyone could send on the shared channel anytime -> collisions could occur from the get go -> Lower success rate

TCP: What is congestion control? What (4) mechanisms are used in the TCP congestion control?

TCP Congestion Control: Used on the sender side to perform congestion avoidance on a network. The congestion window indicates the maximum amount of data that can be sent out on a connection without being acknowledged. TCP detects congestion when it fails to receive an acknowledgment for a packet within the estimated timeout and thus maintains an adaptive timer to adjust how much data the sender sends out. 1) Adaptive timer - adjusts the rate of waiting for an ack to be received and when to resend data (adjusted with binary exponentail backoff) 2) Slow Start - sender starts by sending only one segment and when the ack is received, increases the window size by one segment. Continues this process over and over until a collision is detected and then 3) Fast Retransmit - resend data before the adaptive timer expires 4) Fast Recovery - continues with transmitting packets without using resetting to slow start

TCP: What is flow control?

TCP Flow Control: Controlled by the receiver. Ensures the sender only sends what the receiver can handle by adjusting the window to indicate how much the receiver can receive from the sender.

TCP: Name all the fields of the TCP header (11) and how many bytes is the TCP header.

TCP Header - 20 bytes > Source Port > Destination Port > Sequence Number > Ack Number > Data Offset > Reserved > Control Bits (Flags) > Window > Checksum > Urgent Pointer > Options

TCP: What is sent during the TCP Handshake?

TCP Headers

OSI Model & TCP/IP Model: Where does each layer of the OSI model go into the TCP/IP Model?

TCP IP/Model - OSI Model: 4 Application - Application, Presentation, Setsion 3 Transport - Transport 2 Network - Network 1 Network Interface - Data Link, Physical

OSI Model: Explain what these layers do and what TCP/IP layer all these layers fit into: 1) Application Layer 2) Presentation Layer 3) Session Layer

TCP/IP Layer: Application 1) Application Layer: Layer that the user is actually interacting with I/O (ex. HTTP, DNS) 2) Presentation Layer: Works in the OS to translate text/ASCII and vice versa so that the application can send out and receive interpretative data (ex. MIME) 3) Session Layer: Facilitates the starting, handling, and ending of connections between two parties. Synchronizes related streams of data, like video/audio streams in a video session (ex. NetBIOS, SOCKS)

OSI Model: Explain what these layers do and what TCP/IP layer these layers fit into: 1) Data Link Layer 2) Physical Layer

TCP/IP Layer: Network Interface 1) Data Link Layer: Responsible for providing reliable transfer of data between communication parties, like avoid/detect collisions and the physical addressing (MAC - Ethernet). (ex. IEEE (CSMA/CD, Access Mechanisms)) Switches operate here. 2) Physical Layer: The physical hardware that makes up the network and defines physical specifications, protocols, transmissions modes, and network topology (ex. Digital/Analog, HUB, IEEE 802.11 (Wifi), Bluetooth, USB)

OSI Model: Explain what these layers do and what TCP/IP layer these layers fit into: 1) Transport Layer 2) Network Layer

TCP/IP Layer: Transport 1) Transport Layer: Provides how reliability, flow control, fragmentation, and port numbers are chosen/maintained in communication between two parties (ex. UDP, TCP). I.E. How style (ex. connection-based, connection-less) of how data is transported TCP/IP Layer: Network 2) Network Layer: Provides addressing and routing when transporting data between two parties in a network (ex. IP, ICMP) Where routers operate.