576 quiz cheatsheet

1. What is a network?
A system of “links” that interconnect “nodes” in order to move “information” between nodes

2. types of networks
Internet/telephone/transport/cellular/supervisory control and data aquisition/optical/sensor

3. Channels concept
*Peer entities communicate over channels
*Peer entities provide higher-layer peers with higher-layer channels
A channel is that into which an entity puts symbols and which causes those symbols (or a reasonable approximation) to appear somewhere else at a later point in time.

4. Channel characteristics:
Symbol type, capacity, delay, fidelity, cost, reliability, order-preserving, connectivity

5. Physical channels:
Twister Pair (TP)
Coaxial cable
Fiber optic cable
Radio

6. Properties of links
Bandwidth (bits/sec)
Latency (propagation time, sec)
Bandwidth-delay product (BPD): latency * bits/second

7. Circuit switching
Nodes request a reservation of a circuit, circuit is built, node sends data, node sends circuit teardown request
Pros: guaranteed performance, fast transfers once circuit is established
cons: wastes bandwidth, has setup time overhead, slow recovery from failure

8. Time division mux/demux
x=time, y=freq. regions of a frame in x correspond to different channels. message: [c1,c2,c3],[c1,c2,c3],...

9. packet switching
data's send in packets of header and payload
header: address, age, checksum
switchers forward the packets per the header
no circuits, each packet travels independently
leverages statistical multiplexing

10. OSI
Application->presentation->session->transport->network->link->physical
(presentation = interpreting the data, e.g. type, compression, encryption, etc., session=syncing,checkpointing,data recovery)

11. What is a protocol?
protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt

12. Purpose of IP
A logical network address that identifies a host

13. IPv4 vs IPv6
ipv4: 32bits/4octets, dotted decimal notation, over 4 billion possible combinations
ipv6: 128 bits, 3*10^38 addresses.

14. Parts of an IP address
Network and host. Subnet mask determines the bits that belong to the network part.

15. Types:
Class A: 1-127. N.H.H.H. 255.0.0.0.
Class B: 128-191. N.N.H.H. 255.255.0.0
Class C: 192-223. N.N.N.H. 255.255.255.0
Class D: 224-239.
Class E: 240-255.

16. Private IP
Solves finite IP issue, allows local host communication

17. Configuring DHCP
Client sends a DHCP discover message to 255.255.255.255. All hosts in the network receive this message, but only the DHCP server replies.