M6: Verifying Connectivity Flashcards
What are the functionalities built into protocols and devices that protect against issues?
Error detection and error recovery
What is the Ability for a protocol or program to determine that something went wrong
error detection
the ability for a protocol or program to attempt to fix something that went wrong
error recovery
What are used buy multiple layers to make sure that the correct data was received by the receiving end?
cyclical redundancy checks
What happens if a CRC value doesn’t match the data payload?
the data is discarded
What layer decides if data needs to be resent?
the transport layer
When network problems come up what is the most common issue I’ll run into?
inability to establish a connection
what protocol is used to communicate issues of network errors, a router not knowing how to route a destination, a certain point not being reachable, the time to live of an IP data gram expired and no further hops will be attempted, etc?
ICMP, internet control message protocol
what protocol is mainly used by a router or remote host to communicate why transmission has failed back to the origin of the transmission?
ICMP
describe the makeup of an ICMP packet
Header with a few fields, data section used by a host to figure out which of their transmissions generated the error.
Which field in an ICMP packet is the first field, 8 bits long, and specifies what type of message is being delivered?
Type field
what field of an ICMP packet would you find the destination unreachable or time exceeded information, as the type of message?
Type field
what is the second field in the ICMP Packet, * bits, which indicates a more specific reason for the message than just the type?
Code field
what are individual codes or examples of them for the destination unreachable type of ICMP packet/
destination network unreachable, destination port unreachable
What ICMP packet field, the third field, is a 16 bit field that a CRC is performed on later/
Check sum field
What is the fourth ICMP header field, a thirty two bit field optionally used by some of the specific types and codes to send more data?
Rest of header
In ICMP, what exists so that the recipient of the message knows which of their transmissions cause the error being reported? containing the entire IP header and the first 8 bytes of the data payload section of the offending packet.
Payload of the ICMP packet
Was ICMP designed for humans to interact with it?
no
What is the point of ICMP packets?
So that error messages can be delivered between network computers automatically
What tool for ICMP is useful to human operators?
Ping
What tool exists on every operating system and has for a long time?
Ping
What tool lets you send a special type of ICMP message called an Echo request?
PIng
What kind of message asks a destination if it is there?
ICMP echo request
In Pinging, what kind of message will be sent back if the destination is up and running and able to communicate on the network?
ICMP Echo Reply Message type
How can I invoke the ping command?
command line, type ping and a destination IP or fully qualified domain name.
When pinging, what displays the address sending the ICMP echo reply and how long it took for the round-trip communications?
Every line of output
What does every line of output have on top of the address sending the ICMP echo reply and how long it tooK?
the TTL remaining and how large the ICMP message is in bytes
What happens when the ping command ends? What is displayed?
statistics like Percentage of packets transmit then received, average round trip time.
where will the pink command run until it is interrupted by an end user sending an interrupt event?
Linux and MacOS
how does an end user send an interrupt event?
Press Ctrl+C
Where does pinging default to only sending four echo request?
windows OS
what does ping’s support that lets you change its behavior, like the number of echo request to send, how large they should be, and how quickly they should be sent?
command line flags
