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Networking test 2



Multiple choice cards
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Language
From
SSH(secure shell)
Prot 22
What does Wireshark analyze
Protocol
Along an IP route you can change
the L2 protocol based on reliablilty, bandwith, delay, and security
TFTP commands/resonses
client(RRQ, WRQ) server,( DATA, ACK, ERROR)
What is a Hub
a repeater( forwards out of all ports except receiving port
How many layers does a router go up to
3
Backward Error correction
Retransmit
ALOHA
MAC with random partitioning, like TDMA but any node can transmit within a time slot
Error detection
use a parity bit or CRC
Rx Adaptor
looks for errors, extracts datagram, passes to node
FDMA
MAC with channel partitioning, Frequency Division multiple access. Each node gets frequency channel, unused channels go idle
Hypertext Transfer Protocol over SSL/TLS
Secure HTTP using Secure Sockets Layer(SSL) / Transport Layer Security(TLS)
CSMA with collision detection
Like CSMA but, if a collision is detected, stops transmitting. No fragmenttation, the node gets a randomly assigned time out before it can try again
Port 67/68
Dynamic Host Configuration protocol
::
means everything between it is 0 and can only be used once in an IPv6 address
Advantaghe of TCP
Reliable in order delivery
What is the difference between a stop and wait protocol and a piplelined protocol
stop and wait waits for acknowlagement of a sent data packet before sending the next one. A piplined protocol fires off data packets quickly and may have sent multiple packets before it starts receiving the acknowalagemnts.
Random Access
Cnanel not divided, allows collisions, recover from collisisons
Network protocol is a service between two
hosts
How do applications interact with the network
through sockets
Port 1024-49151
Any protocol you want!
Server process
pro ess hat waits to be contacted
Are there timing or QoS built into internet transport services?
no
File Transfer Protocol
Port 20/21
For display filters, what is the syntax
frame.len>10 or ip.addr == 129.111.0.0/16[CIDR masking]
Which Socket Type only takes in segments that come over connection
TCP
A transport protocol is a service between two
processess
Tx Adaptoer
encapsulate datagram in a frame, adds error checking bits
CWND IS
lcoal to sender only but can be inferred by receiver
What is added by layer
application - payload, transport - segment, network - datagram, data link - frame
Does IPv6 have the network host arrangement
yes. /64 is half host half network
What are the main transport layer services of the internet
TCP or UDP
In TCP, retransmit means
qresend bytes on backet delay/loss
Why does UDP need checksum
Because not every L2 layer supports error checkng and because deice memory could be corrupted
What provides an API
Socket
DHCP
Dynnamic Host Configuration Protocol
Which transport layer protocol controls the ordering and control of the segments
TCP
NAT port
the NAT port is in the router and assigns a port number to outgoing data. Incoming data comes in through that port and is then routed to the appropriate place on the network. All of the inter-network IP/ports are different than the outward facing ones
HTTP 200
OK, request succeeded, requested object later in this msg
Timing considerations
Does an application require low delay or is it Delay - Tolerant
At the data link layer we call routers and hosts
nodes that send frames along links
In TCP, MSS means
Maximum Sergment size
File Transfer Protocol
FTP most commonly used on internet and within private networks
An ARP table knows
the MAC address of an IP address on the LAN
Disadvantgae of UDP
unreliable, unordered
Unicast
Globally unique network and host portion, typical web traffice, UDP or TCP
parity bit
did you count an even number of 1 bits?
NIC
network interface card
An ARP table is like a
street sign that direcets traffic based on MAC address
A socket can be thought of as an
API for the application to access the network.
In TCP, all process in the network are addressed by
Source IP, Source Port, Destination IP, Destination Port
Telnet
Port 23
Domain Name System
Port 53
FTP server response 425
Can't open data connection
rtt
round trip time
In TCP, RTT Timeout means
IF ack not received within a time value dependant on RTT
Why ARPtable
to know the MAC address of an IP address on the LAN
What are some characteristics of P2P Applications
No server, No predictable communication, Intermittenly connected and can change IP, Highly scalable, but difficult to manage. Thins bittorrent, host has to be active, no server. You can move a lot of data but need cooperation
Prot 22
SSH(secure shell)
IP network is ______, TCP connections are ____________
simple complex
Data Integrity
Does it need to be 100% reliable or is it loss-tolerant
Ethernet is
connectionless, unreliable, CSMA/CD
Forwarding
Moving packets from router input to output.
In P2P does a peer have a client or server process?
Both
CSMA
MAC with random partitioning, any node can transmit in an idle channel
what layer is between adapters
data link layer
EDC
Error detection and correction
What does TCP offer that UDP doesn't
connection-orientation, reliable transport, flow control, congestion control
native
if something is native to something, it is included with it. If you have to download a library, it's third party
What sens/recieves messgaes to/from a socket
A process
FTP server response 452
Error writing file
Taking turns
nodes take turns, but nodes with more to send can take longer turns
Can an application run multiple processes
Yes
What is the TCP/IP protocol Suite by layer
7. Varies, 4. TCP, 3. IP, 2. Varies, 1. varies
What is a switch
selectively forward frames(like a router for frames)
In TCP, ACK# is
number of bytes received/next byte # expected
Display Filter
More detailed filtering. Allows to compare values in packets, not real time
Network Time Protocol
Port 123
Port 69
Trivial File Transfer Protocol
Hybrid P2P and server/client
Server performs some centralized activity so that peers can establish communication. Peer has two client processes(server and peer) and a server process. Think online gaming.
Layer 3 and 4 are controlled by
the OS
FTP
File transfer protocol
How many bits are dedicated to sequence number or acknowledgement number in TCP
32
Broadcast
all 1's in host portion, UDP only, typical for local networks that sharet he same network address prefix
Which 0s can be dropped in IPv6
leading 0's in each quartet
Data Link layer coordinates media to be shared among the network devices using
the broadcast media
Hypertext Transfer Protocol over SSL/TLS
Port 443
The NAT port changes the TCP header
This is ahack that works
Disadvantage of a TCP server application
Runs on a specific port, must completely serve the client before it can handle another client
Multicast
restricted to certain address spaces 224.0.0.0/4, hosts must subscribe to see multicast datagrams, all routers along the way must support, UDP only
In TCP, cwnd means
Congestion window - Amount of unACK'd data sender can send
Main difference between IP and TCP
IP is connectionless(stateless) and best-effort and unreliable, TCP is reliable and connection oriented(stateful)
nodejs is written in
javascript
Which transport layer service delivers segments that are dependant on each other
TCP
Two types of correction
Backward and Forward
NICs are
local modems which modulate the data into the medium
Congestion control
thorrle's the sender when the network is overloaded
Slotted aloha
MAC with random partitioning, if a node has a successful Tx, it can keep going
Every router and host has what running it
a network layer protocol
Flow control throttles
the sender
What does the Transport Layer provide
Logical communication across host processes
Secure Sockets hav a security sublayer in
The Kernel Space between the Security API and the socket
Network Time Protocol
NTP is used to sychronize devices on the internet
Different versions of TCP
Tahoe, reno, vegas, cubic, bbr
What do process need to be addressed by
a port number
you can capture UDP packets at certain ports by saying
udp dst/src port 53. You can capture source and destination by udp port 53"
Which transport layer service is connectionless
UDP
Port 80
Hypertext Transfer Protocol
How does a router know which output link to send a packet to
It reads the IP header, then the routing algorithm consults the forwarding table
Where is the link layer protocol implemented
in adaptor, NIC or ethernet card
routing
tunning an algorithm to determine route packet shold take between source and destination
Sockets are
a networking construct that interface with the application and the local operating system networking functions
HTTP 505
HTTP Version not supported
Which transport layer might lose or deliver segments out of order
UDP
What two things are routers engineered to do
Routing and forwarding
Ethernet functions
Switch, Hub
Can an OS run multiple applications
Yes
Can you monitor other people's traffic with wireshark?
Yes
A switch goes up to what layer?
2
do Ips or MACs move with the NIC
MACs
What is HTTP
Double check, but a transport level protocol
Forward error correction
auto- recover damaged bits
A MAC runs constantly at
every similar NIC
FTP server response 125
data connection already open; transfer start
Does a hub store and forward or read frame headers
no
Client Process
process that initiates communication
Inet addresses are
Hierarchical
Hypertext Transfer Protocol
Port 80
DNS
Domain Name System
Port 443
Hypertext Transfer Protocol over SSL/TLS
Wireshark understands
protocol sequences
To the network layer the IP network looks like
a single ethernet cable because of the subnet mask the network address is what it sees regardless of what all is on there
What makes up a frame
Payload, Transport header, network header, Data Link header
Different types of DNS servers
com, org, edu. Under these you have DNS serves like yahoo.com or KSU.edu or PBS.org
Which transport layer service is best effort
UDP
HTTP 404
NOT FOUND, requested document not found on this server
Telnet
Unsecure version of SSH
How to determine minimus size of message
anything that says variable is optional, if it doesn't say variable, it has to be there.
Which Transport layer service has the smallest minimum size segmenty
UDP has a minimum size of 64 bits where TCP has a minimum size of 160
At their core, sockets are
just some function calls made on behalf of the application developer
Sercurity considerations
Does data need to be encrypted, Authenticated?
ARP table is built by
each network device
Which TCP layer requires checksum
UDP and TCP
TDMA
MAC with channel partitioning, Time Division multiple access - each node gets assigned a time slot and a fixed duration, unused slots go idle
Port 53
Domain Name System
Sometimes layer 2 is controlled by the os but it it usually embedded
into the network interface card with L1.
What does a switch do
Store and forward, examines frame header. Transparent to hosts(no tracerout or ping). Maintains a switching table(like an ARP but no IP addresses). Act as filters
Above com, org, edu DNS server is
root DNS Servers
Any protocol you want!
Port 1024-49151
Hypertext Transfer Protocol
HTTP is the main protocol that is used by web browsers
SSH(secure shell)
Primary methodused to manage netwrok devices securely at the command level
Domain Name System
Translate domain names into IP address
Capture Filter
Filtered while capturing. Like TCPDump. You can set capture filter too "dudp" or "tcp"
Throughput considerations
Quality of Service or elastic
FTP server response 331
Username OK, password required
What is the goal of every MAC protocol
Don't collide
HTTP 301
Moved Permanently, requestd object moved, new location specified later in this msg
Does the server or client require a static IP
server
What might an application require in choosing a Transport layer service
Data integrity, Timing, Throughput, Security
IPv6 can't have
the letters o or l
What is the interface between Application and Transpor layers
Sockets
When do you program sockets
when you are writing networking applications
What are the five layers
Physical, Data Link, Network, Transport, Application
What does every router examine
every ip header passing through it
Channel Partitioning
divides channel into smaller pieces(time slots, frequency, code), allocate piece to node fro exclusive use
Why fragmentation of IP
Because the layer 2 portocol may have limited space in it's frame. Reassembbly only happens at final destination
Closing a TCP Connection
FIN ->, ACK <-, FIN <-, ACK ->
You can also capture packets destined to a certain url
"dst host www.website.edu"
What is the 3 way handshake
TCP connection setup: SYNC, SYNACK, ACK
How many bits are dedicated to source port number in TCP
16
broadcast lan address
FF-FF-FF-FF-FF-FF
Data Link Layer is
concerned about a single-link betweeen one network device to another
TCP Reno
as the cwnd became larger, when a retansmit event occurred, it would rest cwnd to half it's last highest value
In a TCP connection, does the server or client know a connection is established first
Client
Transport Layer
concerned with a connection between tweo processes running at two end systems
What types of fileters can we use on Wireshark
Capture Filter and Display Filter
Port 23
Telnet
In java, using TCP, what needs to be included to read a bytestrem form the socket
A socket library
Flow control
keeps sender from overwhelming reciever
What is the only part of a header examined by the internet core
The network header
Which Socket type takes in all segments
UDP
Dynamic Host Configuration protocol
Port 67/68
Dynamic Host Configuration protocol
DHCP is used on networks that do not use static IP address assignment
CRC
Integreate Cyclic Redundancy Check"Did you compute all 0's when dividing with CRC appended to the data?"
Do you need superuser to access wireshark
yes
Three broad classes of MAC addresses
Channel partitioning, random access,taking turns
Transmission round
time over rtt
What is the world's most popular protocol analyzer?
Wireshark
Token passing
MAC, turn taking, token holder transmits until it can't, then passes the token
Filter operators
you can use &&, || or !(not)
NAT is helpful because
It limits the number of IPv4 addresses and it provides protection as individual hosts are not directly reachable from the internet
FTP Client Commands/responses
USER, PASS, LIST, RETR, STOR
Port 20/21
File Transfer Protocol
In UDP each packet has a source port and a return port.
As the packet bounces from server to server, the source port stays the same until the final destination is reached. The destination port changes to match each server along the way. On the way back the destination port remains the same and is the same as the original source port
In TCP, SEQ# is
number of bytes sent
Network layer is concerned with
route from one host to another host
Trivial File Transfer Protocol
TFTP offers a method of file transfer without the session establishment requirements that FTP uses
Which Transpor tlayer service provides relaibale data transfer
TCP
In TCP, rwnd means
Reciever Window Size, how much free space at receiver
what layer is between hosts and networks
Network layer
MAC
media access control
Port 123
Network Time Protocol
Two types of lInk layer channels
Broadcast and Point to point
Trivial File Transfer Protocol
Port 69
What is meant by connectionless
No prio communication with server is required. Each UDP segment is independent of each other.
IPv6 world wide routing is based on
the first 64 bits. The lasdty 64 bits can be used as a local private subnet address but are carried over the internet
TCP Tahoe
No matter how large the cwnd became, when a a retransmit event occurred, it would always get reset to 1MSS
Possible link layer services
Framing, access, reliability, flow control, error detection, error correction, half/full duplex
Receive window
This is the number of bytes rcvr is willing ot accept
Half/full duplex
Tx/Rx simultaneously or one at a time
What does Wireshark decode
packet bits and bytes as well as the relations btween packets and protocols
What medium does wireshark examin packets on
ethernet/wireless
How does a host learn a MAC address
Uses the MAC broadcast address(48 1's) until it knows the IP address. Then ARP reqeust to discover the MAC address associated with the IP address
IPv6 is made up of
128 bits, 8 x 16 bit groups
A Frame consists of
preamble, Dest Add, srce Address, Next protocol type, data, CRC
Is the client or server or both always on
server
Why is error correction important for layer 2?
Because errors can happen within the media(bit flips) old hardware
In a UDP, all process in the network are addressed by an
IP address and a port number
Polling
MAC with turn taking, a parent node tells the child nodes when to transmit. More overhead, latency, and if the parent goes down, it all goes down
Subnetting
take some bits from the host side. The subnets are labeled in between the network and host. Each subnet has it's own broadcast
HTTP 400
Bad Request, request msg not understood by server
In TCP, if there are different sorce ports then
the server has two different porcesses to receive them
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