Refer to the exhibit. Which path will traffic from the network take to get to the network?

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¡Escribe tu texto aData rate =

Shannon: Max bitrate depends on signal/noise ratio   

Nyquist: Max bitrate depends on n. Sampling levels


·Is a MAC protocol

·Exponential back-off strategy -> adapts to Load on ethernet

·RTT bounds determines a bound on throughput

IP tunnels

·Packets traveling in a tunnel carry IP as load

·Allows for any IP to be sent to any destination (regardless of the IP carried as load)

·Never carries Ethernet as load

·Always carry IP packets as load

·The service offered by the IP protocol is Unreliable.

Probability of error scenarios

·An error can occur if prob>0

·An error won’t always occur if prob<1


·Sender must always send a recessive symbol

·Sender is allowed to send a recessive

·Receiver is allowed to send a dominant symbol

·Receiver is allowed to send a recessive symbol

Switched Ethernet

·Switches carry out Ethernet frames forwardly

·The max. Aggregate throughput of a switch equals The sum of the max. Throughput of all input ports.

·Switches have no knowledge about IP addresses

·In case a switch is based on the concept of Input-buffering, it can suffer from head-of-line blocking problems.

TTE (Time Triggered Ethernet)

·Multiple senders can send at the same time over The same network

·A rate-constrained frame can delay other frames In a switch.

·A best-effort frame can delay other frames in a Switch.

·A time-triggered frame is never delayed by other Frames in a switch. (If switches don’t shuffle.)

·A link is used half duplex.

MACA Ethernet

·MACA is a MAC protocol.

·The header of the RequestToSend frame carries Information about the size of the data frame to send.

·If a host receives a ClearToSend frame, it will Remain quiet until the corresponding data frame has been received by the Destination host.

·In the MACA protocol, collisions can happen.

CAN, Flexray and Internet

·NOT possible to resolve contention on the Internet with CSMA/CR technique as used in CAN.

·The CSMA/CR protocol of CAN CAN’T also be Used on a wireless network.

·NOT possible to resolve contention on the Internet with a static or dynamic segment as is used in Flexray.

·Answer is:  None of the statements is true.


·Identifier (priority) is required to compute the Minimum bandwidth allocated to the sender of frames with that priority.


·Latency  of frame with higher priority.

·Bandwidth  of frame with higher priority.

·If bandwidth = 1, best case scenario, 100%


·Uses bit stuffing.

·Uses CSMA/CR.

·When frame is allocated an arbitration window, Priority is needed to calculate max. Latency.

·When frame is allocated 1 or more arbitration Windows, n⁰ Windows is needed to calc. Max. Lat.

FlexRay (for single and active star topology)


oMin. Bandwidth computed with n⁰ Slots.

oMin. Bandwidth of sender is independent of other Senders.

oAll nodes have same slot.


oMin. Bandwidth computed with minislot number.

oAll nodes have same minislot.Quí!

PAR (Positive Acknowledgement with Retransmission)

·Efficiency =  for

·Throughput(b/s) =  

·Time out < RTT:  Service is unreliable.

·Time out > RTT:  Service is reliable.

·Wire like network: Reliable

Wireless communication in vehicles

·The Time Slotted Channel Hopping (TSCH) Mechanism provides better robustness against interference from WIFI.

·The quality of low-power wireless links is in General unreliable and time-varying.

·The beacon-enabled mode of IEEE 802.15.4 Standard provides both contention-free and contention-based medium access.

·Wireless signals with high frequency suffer from Attenuation.

Worst case latency

·Sender does have priority: A is better than E.

·Sender does NOT have priority: E is better than A.

Polynomial F(x) CRC method

oEvery burst error of length n Or less will be detected.

oError  won’t be detected.

oThe error  is left undetected.

oThe transmitted code is of form  where  is the remainder when dividing  by  modulo 2.

oEvery error of form  for  will be left undetected because  and this is divisible by

oThe transmitted code is of form

oAll errors with degree n-1 or less Will be detected.

oBurst error of length n won’t Be detected.

o is a bad choice,  would be better.

oOnly errors that occur in the redundant bit will Be detected.

oErrors that occur in the original bitstream won’t Be detected.

Spanning tree

·Purpose is to eliminate forwarding cycles (loops.)

·Dynamically changes with the physical topology.

·Disadvantage: may introduce unnecessary Performance bottlenecks.

·Calculate paths with lower bridge number.

Aethereal TDM (answers to exam (always same exercise))

·In the same time slot circuits 1 and 2 can exit Router R2.

·In the same time slot circuits 2 and 4 can exit Routers R2 and R1 respectively.

·In the same time slot circuits 1 and 3 can exit Routers R1 and R2 respectively.

·It is possible for circuit 1 to have a higher Bandwidth than circuit 2.

·It is possible for circuit 1 to have a higher Bandwidth than circuit 4.

Aethereal Network (components that have to be configured)

·Master bus (demultiplexor).

·Network interface and router.

Jacobson/Karels protocol

·Purpose is to determine dynamically the time-out Time of the TCP.

·Computes estimations of expected values and Standard deviations of segment RTT.

· and  are used to tune the speed with which the Algorithm will adapt to varying RTT.

Dijkstra algorithm (in this case for router F)

·Just calculate every path asked.

·For each X (not equal to F), the shortest path Between F and X is unique.

Bit Stuffing

·4B/5B encoding does not allow more than three Consecutive 0's, and provides higher channel efficiency than the Manchester Coding scheme.

TTCAN uses bit stuffing.

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