Basics Flashcards
What does LAN stand for?
Local Area Network
What is the characteristic of best effort delivery?
No notification about packet receipt
Name two characteristcs of ethernet broadcast
- All transeivers receive every transmission
- Host interface filters among packets those intended for them.
What are the 4 layers of TCP/IP?
- Link
- Internet
- Transport
- Application
What does TCP stand for?
Transmission Control Protocol
What does CSMA stand for?
Carrier Sense Multiple Access
Explain CSMA
– multiple machines can access the Ethernet simultaneously
– each machine determines whether the “ether” is free by
sensing carrier wave propagation
– each transmission is limited in duration and needs a
minimum time between transmissions to prevent
monopolization of the network
What is CD and explain its purpuse in data networks.
Collision Detection
each transceiver monitors the cable while transmitting to search for foreign signal interferences
Explain Non-persistent CSMA
– Sensing is not continuously but repeated after random time.
– If no collisions are sensed, the station sends a packet.
Explain p-Persistent CSMA
Continuously sensing, but sending of packet probabilistically:
send in current time slot with probability p and in another
time slot with probability 1-p
What type of scheme does ethernet have?
1-persistent CSMA/CD scheme
What does the IP specify?
Internet Protocol:
– specification of basic unit of transfer (packet)
– IP software handles the routing functionality
– IP includes the rules for unreliable,
connectionless, best-effort delivery
How long is the IP adress of IPv4?
32 bits / 4 bytes
How large is the IPv4 header?
6x 32 bits
How is the fragmentation counter updated per IPv4 packet?
It contains the offset of the data in octets.
Ex. 320 bits in the first packet means 80 octets, so the offset for the second packet is 80
Why does IPv6 extended its adress size?
More digital devices calls for more adresses.
Why does IPv6 no longer provide checksum?
Speed up: data integrity is checked in other layers already
Explain why Header options are ommited in IPv6?
Because headers can now be appended using the “Next Header” option, which defines that there will be more header information before the packet data.
What makes IPv6 easier to manage than IPv4?
Auto configuration of Adresses, as well as more clearer structuring of subnets (using predefined adresses).
How can shorten IPv6 adresses?
You skip leading 0’s and replace large range of 0’s with ::
Ex. 2010:00A1:0000:0004= 2010:A1::4
this example is shorter than standard size
How is the global unicast adress composed ususually (for IPv6) ?
– First 64 bits: Global Routing Prefix (n bits) + Subnet-ID
(64 - n bits)
– Last 64 bits: Interface-ID
– Interface-ID often generated using the interface’s MAC
address
Explain what neighbor discovery is and how it works.
Every IPv6 interface has a link-local address that identifies it and
is used for link-local communication (e.g., for Neighbor
Discovery)
* Neighbor Discovery: IPv6 nodes can find systems they are
physically connected to (other nodes and routers)
– Routers send periodic Router Advertisements (RAs)
– Hosts can also solicit RAs by broadcasting a Router Solicitation
– RAs contain Global Routing Prefix and Subnet-IDs that hosts need for
generating global unicast IP addresses
* Duplicate Address Detection automatically resolves
address conflicts
Dia Dump
Give two examples of Distanc Vector protocols
RIP + Bellman-Ford
Give two examples of Link-state protocols
OSPF or Dijkstra
In Link-State Protocols, who constructs the forward table?
The local routing algorithm.
In Distance Vector Protocols, who constructs the forward table?
The protocol itself.
What kind of routing information does a Distance-vector protocol maintain?
maintain list of shortest distances
What kind of routing information does a Link-state protocol maintain?
maintain entire map of network
What kind of information does the Distance-vector protocol exchange with its peers?
a list of distances with neighbors
What kind of information does the link-state protocol exchange with its peers?
flood topology information
Which is more complex Link-state or distance-vector protocols?
Link state