4 - Packet Delivery Flashcards
What device ampifies and regenerates the signal on its remaining ports?
Hub
What is a repeater?
Hub with only two ports
How does a switch know that the entire frame arrived safely?
FCS or Frame Check Sequence
How does a router check the integrity of an IP Header?
Checksum
How does a router check the integrity of the data in a packet?
CRC or cyclic redundancy check
What is the default MTU size?
1500 bytes without the header
1518 bytes with the header and crc trailer
What is runt?
Frame that is less than 64 bytes and has a bad FCS
What is a jumbo frame?
Frame that ranges in size up to 9216 bytes
What is the command to change the MTU size?
system mtu xxxx for ethernet and fast ethernet
system mtu jumbo xxxx for gigabit ethernet
Whose responsibility is it reassemble fragmented packets?
receiving host
What happens to a frame as it passes through a router?
the router strips out the source mac address and replaces it with the outgoing interfaces mac address and the destination mac address will be replaced with the next hops mac address
What happens to a packet as it passes through a router?
The router can change the TTL, but most of the IP header is unchanged
What is a packet referred to when its a the transport layer or higher?
Flow
What is a default gateway?
gateway that is used to communicate with hosts on another network
Where does a host operate on the network models?
application layer of the tcp/ip model
session layer and above on the osi model
Which device is ultimately the source and destination of packets that traverse the network?
host
What is intra-layer communication?
transfer of information between identical tcp/ip layers on different devices
What is inter-layer communication?
transfer of information between adjacent tcp/ip layers on the same device
What is a PDU that is passed to the next lower layer referred to?
an SDU or service data unit
Which layer is referred to as the Host-to-host layer?
Transport layer
At what layer of the osi model is a port bound to an application process?
transport layer
Describe the TCP three way handshake.
- Sending host sends a pdu with SYN and sequence number
- receiving host sends a pdu with SYN and its own sequence number and an ACK with a sequence number one higher of the sending hosts sequence number
- Sending host sends a pdu with ACK and sequence number one higher of the receiving hosts sequence number
What is the port number used for at the transport layer?
used to determine the appropriate application layer process associated with that pdu
What does windowing do?
- improves the speed of tcp communications
2. can improve the reliability by mitigating traffic congestion
What does sliding windowing do?
enables tcp to negotiate the window size of a tcp session
What happens when a window size is reduced to 0?
the tcp session is dropped
Path selection is provided by which layer of the tcp/ip and osi models?
internet layer
network layer
What is ARP?
Used to determine the mac address of a particular ip address
ARP sends a request to all hosts, what is all hosts at the data link layer?
FF:FF:FF:FF:FF:FF
What was reverse arp replaced with?
DHCP because its more robust
How do you check arp on windows?
arp -a
How do you check arp on a cisco device?
sh ip arp
