Chapters 1-4 Flashcards
(121 cards)
1
Q
The scripting language invented by Dutch programmer Guido van Rossum
A
Python
2
Q
Python has these instead of Arrays
A
Lists
3
Q
The way to access values at the end of a string
A
Negative indexes
4
Q
What is a host
A
An end system
5
Q
What is a packet switch
A
A device that forwards packets
6
Q
Communication Links
A
fiber, copper, radio satellite
7
Q
Network
A
A collection of devices, routers, and links managed by an organization
8
Q
This is called a “network of networks”
A
The Internet
9
Q
Protocols
A
Control sending, receiving of mesages
10
Q
RFC
A
Request for Comments
11
Q
IETF
A
Internet Engineering Task Force
12
Q
Network edge
A
clients and servers
13
Q
Network core
A
interconnected routers, network of networks
14
Q
Frequency Division Multiplexing(FDM)
A
Different channels transmitted in different frequency bands
15
Q
Wireless Local Area Networks(WLAN)
A
Provide connection within or around a building
16
Q
Wide-area Cellular Access Networks
A
Provide connection from mobile, cellular network operators, typically within 10’s of Kilometers
17
Q
Bit
A
Propagates between transmitter/receiver pairs
18
Q
Physical link
A
What lies between transmitter and receiver
19
Q
Guided media
A
signals propagate in solid media such as copper, fiber, coax
20
Q
Unguided media
A
Signals propagate freely, e.g. radio
21
Q
Twisted pair (TP)
A
Two insulated copper wires
22
Q
Packet-switching
A
Hosts break application-layer messages into packets
23
Q
Length (L)
A
Length of a packet in bits
24
Q
Transmission rate (R)
A
How fast bits are being transmitted in bits/sec
25
Transmission delay
Takes L/R seconds to transmit (push out ) L-bit packet into link at R bps
26
Store and forward
Entire packet must arrive at router before it can be transmitted on next link
27
End-end delay
2L/R, assuming zero propagation delay
28
What happens if arrival rate to link exceeds transmission rate of link for a period of time
Packet queuing and loss, packets will queue and wait to be transmitted on output link, some may be dropped if router fills up
29
Forwarding
Local action, move arriving packets from router's input to appropriate router output link
30
Routing
Global action, determine source-destination paths taken by packets
31
Time Division Multiplexing (TDM)
Time divided into slots, in which a user can utilize the entire bandwidth for a limited time
32
How do hosts connect to the internet
Internet Service Providers (ISPs)
33
"Tier-1" commercial ISPs
National and international coverage
34
Content Provider Networks (CPNs)
Private network that connects its data centers to Internet, often bypassing tier-1, regional ISPs
35
What happens when arrival rate to link exceeds output link capacity
Packet Loss
36
What are the four sources of packet delay?
Nodal Processing, Queueing, Transmission, and Propagation
37
Throughput
Rate at which bits are being sent from sender to receiver
38
Instantaneous throughput
Rate at given point in time
39
Average throughput
Rate over longer period of time
40
Bottleneck link
Link on end-end path that constrains end-end throughput
41
Virus
Self-replicating infection by receiving/executing object (e.g., e-mail attachment)
42
Worm
Self-replicating infection by passively receiving object that gets itself executed
43
Spyware
Can record keystrokes, websites visited, upload info to collection site
44
Denial of Service (DoS)
Attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic
45
Packet sniffing
Promiscuous network interface reads/records all packets, including passwords, passing by
46
IP spoofing
Send packet with false source address
47
Layer 5
Application layer, highest in IP stack model, contains supporting network applications such as IMAP, SMTP, HTTP
48
Layer 4
Transport layer, process-process data transfer, TCP, UDP
49
Layer 3
Network layer, routing of datagrams from source to destination, IP and routing protocols
50
Layer 2
Link layer, data transfer between neighboring network elements through things like Ethernet, WiFi, or PPP
51
Layer 1
Physical layer, bits "on the wire"
52
Arpanet
The proto version of the Internet developed by DARPA back in the 60's
53
ISO/OSI reference model
A model similar to the IP stack, but contains the two extra layers of presentation and session
54
Wireshark
A type of packet sniffer
55
Socket
analogous to a door, data is shoved through the socket from the application layer to the transport layer
56
Identifier
A part of a process which includes both the IP address and port number associated with process on host
57
Data integrity
Ensures that the data sent is received unchanged, some apps require 100%, other can tolerate some loss
58
TCP service
A reliable protocol which won't overwhelm the receiver and maintains integrity, but will go slower
59
UDP
An unreliable data transfer protocol which doesn't provide security congestion control or other features, but does go much faster than TCP
60
Transport Layer Security (TLS)
provides encrypted TCP connections, ensures data integrity
61
hypertext transfer protocol (HTTP)
Web's application layer protocol, a client sends a request and the server sends a response
62
HTTP uses this type of socket
TCP
63
Non-persistent HTTP
1. TCP connection opened
2. At most one object sent over TCP connection
3. TCP connection closed
Downloading multiple objects required multiple connections
64
Persistent HTTP
1. TCP connection opened to a server
2. Multiple objects can be sent over single TCP
connection between client, and that server
3. TCP connection closed
65
Round Trip Time (RTT)
Time for a small packet to travel from client to server and back
66
200
OK
67
301
Moved Permanently
68
400
Bad Request
69
404
Not Found
70
505
HTTP Version Not Supported
71
Cookie
Used to maintain some state between transactions
72
Web cache
A copy of an object from another client which is being served to a client by a server
73
Simple Mail Transfer Protocol (SMTP)
A protocol used by mail servers to send, receive, and relay outgoing email between senders and receivers
74
Internet Mail Access Protocol (IMAP)
Provides retrieval, deletion, folders of stored messages on server
75
Domain Name System (DNS)
Distributed database implemented in hierarchy of many name servers. provides hostnames and aliases among other things. Is decentralizeed
76
Hierarchy of DNS
Root, highest
Top Level Domain, middle
Authoritative, lowest
77
Root name servers
Contact-of-last-resort by name servers that can not resolve name, incredibly important to internet function. 13 logical root name "servers" worldwide
78
ICANN (Internet Corporation for Assigned Names and Numbers)
Manages root DNS domain
79
Top-Level Domain (TLD) servers
Responsible for .com, .org, .net and others, along with top-level country domains such as .cn, .uk, .fr
80
Authoritative DNS servers
Organization's own DNS servers, providing authoritative hostname to IP mappings for organization's named hosts
81
Local DNS name servers
Does not strictly belong to hierarchy, each ISP has one, when host makes DNS query, query is sent to its local DNS server
82
Peer-to-peer (P2P) architecture
No always-on server, arbitrary end systems directly communicate as peers who request and send files to each other
83
Tracker
A server within P2P, while there is not supposed to be an always-on server, there has to be this to let peers find each other
84
CBR (constant bit rate)
Video encoding rate fixed
85
VBR (variable bit rate)
Video encoding rate changes as amount of spatial, temporal coding changes
86
Streaming
Video is being sent played and deleted as user is watching
87
Apache
A commonly used HTTP server
88
Multiplexing
Multiple datagrams are combined into one in order to send more efficiently through sockets
89
Demultiplexing
Splitting up multiplexed datagrams and distributing each datagram to the proper host system
90
Checksum
The sum of bits in a message which is appended to the end, meant to ensure integrity
91
ACK
Receiver explicitly tells sender that pkt received OK
92
NAK
Receiver explicitly tells sender that pkt had errors
93
Time-to-live (TTL)
In UDP connections is a limit to how many times a packet can hop inside a network before being discarded by a router
94
Timeout
The amount of time a round trip can take before being reported as lost and requesting a copy from the sender
95
Flow control
Mitigates one sender sending data too fast for one receiver
96
Handshake
A client and server introduce each other and identify themselves, establishing a connection that data can be sent through
97
Congestion control
Mitigates too many senders sending data too fast
98
QUIC (Quick UDP Internet Connections)
An encrypted transport layer protocol designed by google, meant to get the positives of UDP and TCP without the downsides of either
99
Data plane
Local, per-router function, determines how datagram arriving on input port is forwarded to output port
100
Control plane
Network-wide logic, determines how datagram is routed among routers along end-end path from source host to destination host
101
Software-Defined Networking (SDN)
Remote controller computes, installs forwarding tables in router on the control plane
102
Per-router control plane
Individual routing algorithm components in each and every router interact in the control plane
103
Routing table
A data table stored in a router that lists the routes to particular network destinations, can be user defined, or software defined
104
Longest prefix match
When looking for forwarding table entry for given destination address, use longest address prefix that matches destination address
105
Multistage switch
(n)x(n) switch from multiple stages of smaller switches
106
Head-of-the-line (HOL) blocking
Queued datagram at front of queue prevents others in queue from moving forward
107
Buffering
Required when datagrams arrive from fabric faster than link transmission rate
108
Drop policy
Defines which datagrams to drop if no free buffers
109
Scheduling discipline
Chooses among queued datagrams for transmission
110
Packet scheduling
Deciding which packet to send next on link
111
IPv4 address
32-bit identifier associated with each host or router interface
112
IPv6 address
128-bit identifier associated with each host or router interface
113
Interface
Connection between host/router and physical link
114
Subnet
Device interfaces that can physically reach each other without passing through an intervening router
115
CIDR (Classless InterDomain Routing)
Standard that tells how many digits of an IP address are fixed and which can be changed within a subnet
116
Subnet mask
A standard which tells how many characters in each byte of an IP address can be changed
117
DHCP (Dynamic Host Configuration Protocol)
Dynamically get IP address from server
118
NAT (Network Address Translation)
All devices in local network share just one IPv4 address as far as outside world is concerned, but NAT server routes them to the correct end system, meant to save on IPv4 addresses which have run out
119
Tunneling
IPv6 datagrams are given an IPv4 header in order to be cleanly sent over to the destination port
120
The internet's "thin waist"
IP, the only network layer protocol
121
Middleboxes
Network layer protocols which used to exist before IP was standardized as the one network layer protocol to be used
