Flashcards
Network Part 2
Flashcards do conjunto (24)
- 1In classful addressing the network and host portions of the address are predefined based on the 5 classes, in classless addressing where are these portions defined ?By the CIDR Classless Interdomain Routing, the number after the forward slash.
- 2What if the packet arrival rate to a router is higher than the processing rate?The queue becomes larger and larger
- 3What is congestion?Too many packets are in transit over a particular section of a subnet.
- 4How can we avoid congestion?Traffic shaping:
Leaky bucket, token bucket
Open-loop congestion control ( prevention)
Closed loop congestion control (reacting/ removal of congestion) - 5What is Traffic Shaping?A mechanism to control the rate of traffic in the network
Used to improve congestion on a network, increasing QoS - 6What is Leaky Bucket?The amount of packets sent at a time can vary, but the rate of removal is kept constant. Hency Leaky bucket.
If full, discards the packet. - 7What is token bucketOne token added per tick, one token removed and discarded per byte transmitted
- 8What is fair queuingFair queing gives priority to certain types of data such as video servers
- 9What are the characterstics of Open-loop Congestion control- Retransmission : The packet is retransmitted if the sender feels the packet is lost
- Window - selective repeat or go back n
- Acknowledgement - the sender waits for acknowledgements from the receiver
- Discarding - discarding less sensitive packets when congestion is likely to happen
- Admission - QOS mechanisms used in VC networks. A router can deny establishing a connection due to congestion on the network - 10What is a NACK and when can it be used?A Nack is used to tell the sender that a specified packet has not been received, this will prompt the sender to continue the sending from that packet.
- 11What are the characteristics of some closed loop congestion controlsBackpressure - a congested router stops receiving datagrams from immediate nodes
Choke Packet - A choke packet sent to the source to notify of congestion
Implicity signalling - The source finds out about congestion using different nodes, eg lack of acknowledgement
Explicit Signalling - The congested node sends an explist congestion message straight to the source. Message is included in the payload of the packet unlike choke packet
Backward Signaling - Add a bit of warning of congestion, add to a packet moving in the opposite direction to the congestion
Forward signaling - Add a warning packet moving in the direction of the congestion - 12What is load shedding?When a route becomes inundated with packets, it just discards the packets
- 13In routing what is the difference between direct and indirect deliveryDirect Delivery - Transmission of packet from one host to other. both hosts directly connected via a physical network.
Indirect Delivery - The opposite, the destination is not attached directly to the same underlying network, employs the use of a router - 14What constitutes the shortest path?- number of hops
- geographic distance
- transmission delay
-bandwidth - 15What is flooding?Flooding is a simple computer network routing algorithm in which every incoming packet is sent through every outgoing link except the one it arrived on.
- 16What is counting to infinity?When A informs B that it has a valid path, B has no way of checking to see if itself is actually on that path.
GOOD NEWS TRAVELS FAST, BAD NEWS TRAVELS SLOWLY - 17What is Link-State Routing?Each node periodically sends info on the state of links to neighbours by flooding the network with LSP(link state packets)
- Nodes receive the LSPs and use Dijkstras algorithm to build and maintain a routing table. - 18How does each router determine when to build LSPs?When a significant change on the line occurs or a periodic build
- 19What is an Interior gateway protocolA routing algorithm that routes within a single AS is known as an interior gateway protocol (intradomain routing)
- 20What is an exterior gateway protocol?A protocol routing between many autonomous systems is an exterior gateway protocol (interdomain routing)
- 21What is the Path Vector?Path vector routing similar to distance vector routing, considering the routes a packet takes based upon where the source wants it to avoid, best route is determined by the source and its policy. Used to route packets between ISPs between separate autonomous systems. Makes use of spanning trees
- 22What is RIPRouting information protocol, an interior gateway routing protocol. used for routing computation in the early days of ARPANET. Implementation of distance vector routing useing UDP.
Computes cost of reaching another network
Prevents looping problems by limiting hops
Implements other mechanisms to avoid problems with distance vector routing - 23What is OSPFOpen shortest path first.
Based on the link-state routing algorithm. - 24What is BGPBorder gateway protocol. An exterior gateway protocol. Might need to send packets from one network to another. Based on the path-vector algorithm. Each node holds a cost to each destination, and previous routes that have been used
Paths are being periodically updated
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- FlashCards sobre Network Part 2 , criado por Luke Garrigan em 06-05-2016.
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- Luke Garrigan
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