-
Notifications
You must be signed in to change notification settings - Fork 1
/
ece358.txt
102 lines (58 loc) · 2.74 KB
/
ece358.txt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
# Chapter 1
* What are the two network core functions?
Routing and forwarding
* What is routing?
Determining source-destination route taken by packets.
* What is forwarding?
Moving packets from router's input to appropriate router output.
* What is packet switching?
Hosts break application-layer messages into packets.
* What is store and forward?
The entire packet must arrive at a router before it can be transmitted on the
next link.
* When does queuing occur w.r.t packets?
When packets arrive at the link faster than they can be transmitted.
* What happens when the packet queue fills up?
Packets may be dropped.
* What is circuit switching?
End-to-end resources are allocated for transmission between a specific source
and destination. These resources are dedicated and not shared.
* What are the advantages of packet switching over circuit switching?
1. More users can use the network, because the chance that they are using it at
the same time is low.
2. It is simpler, since it does not require much setup.
* What is a disadvantage of packet switching?
Excessive congestion is possible.
* What are the four sources of packet delay?
Processing, queuing, transmission, propagation.
* What is processing delay?
The delay for checking the packet and determining the output link.
* What is queuing delay?
The time that a packet is waiting at a link for transmission.
In a store-and-forward setup, this starts counting when the incoming packet is
fully received.
* What is transmission delay?
The time it takes for the packet to be fully transmitted onto the link.
Packet length / link bandwidth.
* What is propagation delay?
The time it takes for a bit to arrive between the two nodes.
Length of physical link / propagation speed (200,000,000 m/s)
* What are the 3 situations for queueing delay, with respect to link bandwidth, packet length, and average packet arrival rate?
If La / R is small, then the average queuing delay is small.
If La / R is close to 1, then the average queuing delay is large.
If La / R is greater than 1, then the average queuing delay is infinite.
* How does packet loss occur?
Because the queue in a link has finite capacity, some packets arriving may be
dropped.
* What is throughput?
The rate (in bits/time) at which bits are transferred between the sender
and receiver.
* What are the two kinds of throughput?
Instantaneous: Rate at a given point in time.
Average: Rate over a long period of time.
* What is a bottleneck link?
The link in the end-to-end path that constrains the end-to-end throughput.
* How do bottleneck links affect throughput?
The end-to-end throughput can only be as high as the bottleneck link.
* What are the 5 layers in the internet protocol stack?
Application, transport, network, link, physical.