What messages are broadcasted in DHCP and why?
discover
src 0.0.0.0; dst 255.255.255.255
offer
src: DHCP, dst: Broadcast
Request
src: 0.0.0.0, dst: Broadcast
-> use server id to let servers know which one was chosen…
ack
src DHCP; dst Broadcast
Timers DCHPv6
preferred lifetime
IP can be used without restriction
-> if is 0, can still be used but should not for new connections…
valid lifetime
greater equal preferred
-> after this, not valid anymore… (must not be used)
and t1, t2,…
DHCPv6 prefix delegation vs address assignment?
IA_PD
IA_NA
Whas is an IA?
identity association
construct allowing management and grouping iPv6 addresses or delegated prefixes
-> identified with IA_ID
-> must be unique AT CLIENT and chosen by client
How is the strcuture of IAs at the client side?-
assign at least one IA wiht each interface the client wants an address / prefixes for…
contrary, …IA_PD can be assigned to client itself, one interface or mutliple interfaces…
-> each with unique (on client side) IA_ID identified..
NAT ICMP in active connection?
wont go through
have to be filtered and relayed by nat router
Ports and IP in PASV in ftp?
client indicates it want to connect to server
-> server responds wiht IP and Port it is listening to….
What is the difference between signatures and MACs?
signature:
uses pub key
MAC
private (symmetric) key -> increase in MAC…
What are tokens used for?
address validatoin
Why use address validatoin?
to prevent being misused for amplification attacks
-> verify that endpoint is able to receive messages at endpoint it specifies
-> used either during connection establishing or connection migration
How are amplificatoin attacks limited in quic?
server must not send more than three times the amount of data it received prior to client address validatoin
QUIC what is the difference between path and address validatoin?
address validation -> ensure endpoint is able to receive data at specified address
path validation -> ensures reachability, only done at connection migration
How is address vaildation done?
implicitly during connection establishment
prior to handshake with token in retry packet
must be included in subsequent client packets
server can provide address validatoin token to client for future connections
-> Client must use token in future connections unless provided new one with retry packet
Why and when is path validaiton used?
used FOR conneciton migration
can be used anytime by either endpoint
-> started by one endpoint transmitting a path challenge over the new path…
-> path response echoes the received data
Last changed2 years ago