ICT Introduction to Networks ??. ????????? ???????? E-mail:[e-mail] [e-mail] URL:http://www.spu.ac.th/~surasak.mu

1
ICT
Introduction to Networks ??.
????????? ???????? E-mail surasak.mu_at_spu.ac.t
h mungsing_at_gmail.com URL http//
www.spu.ac.th/surasak.mu
2
ICT Agenda
3
Switching and Routing
4
Switching Networks

• ??????????????????????????????????????????????????
  ? (switched nodes)
• ???? (Nodes) ????????????????????????????
• ????????????
• Computer, terminal, phone, etc.
• ??????????????????????????????????????????????
  (communications network)
• ???????????????????????????????? ???? ??????
  ?????????????????????????????

5
Simple Switched Network
6
Circuit Switching

• ???????????????????????????? 2 ????????????
• 3 ????????????
• ?????????????????? (Establish)
• ???????????? (Transfer)
• ?????????????????? (Disconnect)
• ??????????????????????????????????????????
  (switching capacity and channel capacity)
  ???????????????????????
• ?????????????????????????????????????

7
Circuit Switching - Applications

• ???????????????? (Inefficient)
• ??????????????????????????????????????????????????
  ????????????????????
• ?????????????? ???????????????????????????????????
  ??
• ?????????????????????????????????????????????
• ??????????????????????????? ??????????????????????
  ???????????????????????????????
• ????????????????????????????????????????(????????)
  

8
Public Circuit Switched Network
9
Telecomms Components

• ????????????? (Subscriber)
• ??????????????????????????????????????
• ?????????????????????? (Subscriber line)
• ??????????????????????????????????????????????????
  ?? (Local Loop ???? Subscriber loop)
• ???????????????????????????? (Connection to
  network)
• ?????????????? 10 ????????
• ?????? (Exchange)
• Switching centers
• End office - supports subscribers
• ??????????????? (Trunks)
• Branches between exchanges
• Multiplexed

10
Circuit Establishment
11
Circuit Switch Elements
12
Circuit Switching Concepts

• ??????????????? (Digital Switch)
• ????????????????????????????????????????
• ?????????????????????? (Network Interface)
• ??????????? (Control Unit)
• ?????????????????? (Establish connections)
• ????????????????????????????????????????
• ???????????????????????????
• ????????????????????????????
• ????????????????????????
• ????????????????? (Maintain connection)
• ?????????????????? (Disconnect)

13
Blocking or Non-blocking

• ??????????????????????????????????????????????????
  (Blocking)
• ??????????????????????????????????????????????????
  ??????????????
• ??????????????????? blocking network
• ?????????????????????????
• ??????????????????????
• ???????????????????????????????????????
  (Non-blocking)
• ?????????????????????????????????
• ?????????????????????????

14
Space Division Switching

• ????????????????????????????????
• ???????????????????????????????
• Crossbar switch
• Number of crosspoints grows as square of number
  of stations
• Loss of crosspoint prevents connection
• Inefficient use of crosspoints
• All stations connected, only a few crosspoints in
  use
• Non-blocking

15
Multistage Switch

• ??????????crosspoints
• ???????????????????????????????
• ?????????????????????
• ?????????? blocking

Three Stage Space Division Switch
16
Time Division Switching

• ??????????????????????????????????????????????????
  ????????????????????????????????
• ??????????????????????????????????????????????????
  ?????????(virtual circuits)
• ??????????????????????????????????????????????????
  ??????????????????????????????????????????????????
  ????????

17
Circuit-Switching Stages

• ????????????? (Circuit establishment)
• ???????????? (Data transfer)
• point-to-point from endpoints to node
• internal switching/multiplexing among nodes
• ????????????? (Circuit disconnect)

18
Circuit Establishment

• Station ????????????????????? node
• Node ????????????????????????????????????
  ?????????????????? link ?????
• ????? node ???????????????????????????????????????
  ???
• ?????????? node ??????????????????????????????????
  ?????????? test message ????????????????????????
  ? ?????/?????? ????????????????

19
Data Transfer

• ??????????????????? Point-to-point ??? station
  ??????????? node
• ????????????????????? Internal switching ???
  multiplexed ??? node ??? node
• ????????????????? Point-to-point ??? node ?????
  station ??????
• ?????????????????????????????? full-duplex
  ??????????????????

20
Circuit Disconnect

• ????????????????????????????? station
  ????????????????????????
• ?????????????????????????? nodes
  ??????????????????????????????????????????????????
  ???

21
?????????????????? Packet Switching

• ??????????????????????????????????
• ???????????????1000 octets
• ??????????? ???????????????????????????
• ??????????????????????????????????????????????????
  ??????????????
• ???????????? (Control info)
• ??????????????????? (????????????????)
• ??????????????????????????????????????
  ?????????????????????????
• ????????????????????? Store and forward

22
Use of Packets
23
Advantages

• ??????????????????????????????????????? (Line
  efficiency)
• ??????????????????????????????????????????????????
  ???????????????????????????????????????????????
• ??????????????????????????????????????????????????
  ??????????
• ????????????????????????????? (Data rate
  conversion)
• ??????????????????????????????????????????????????
  ??
• ??????????????????????????????????????????????????
  ???????????????????????????
• ??????????????????????????????????????????????????
  ???
• ??????????????
• ?????????????????????????

24
Packet Switching Technique

• ??????????????????????????????????
• ??????????????????????????????????????????????????
  
• ?????????????????????? 2 ??? ???
• ????????? (Datagram)
• ?????????? (Virtual circuit)

25
Datagram

• ?????????????????????????????????
• ?????????????????????????????????????????????????
  
• ??????????????????????????????????
• ?????????????????????????????????
• ??????????????????????????????????????????????????
  ???????????????????????????????????????

26
DatagramDiagram
27
Virtual Circuit

• ??????????????????????????????????????????????
• ???????????????????????????????????????????(handsh
  ake)
• ??????????????????????????????????????????????????
  ????????? (virtual circuit identifier)
• ??????????????????????????????????????????????????
  ?????????
• ????????????????????????????
• ??????????????????????????????? (Not a dedicated
  path)

28
VirtualCircuitDiagram
29
Virtual Circuits vs Datagram

• Virtual circuits
• ??????????????????????????????????????????????????
  ?
• ???????????????????????????????????
• ???????????????????????????????????????
• ?????????????????????
• ????????????? ???????????????????????????????????
  
• Datagram
• ????????????????????????????
• ??????????????????????????????????????
• ??????????????????
• ??????????????????????????????????????????????????
  ???????????????

30
Packet Size
31
Circuit vs Packet Switching

• Performance
• ??????????????????????????????????? (Propagation
  delay)
• ????????????????????????? (Transmission time)
• ???????????????????????? (Node delay)

32
Event Timing
33
Packet-Switched Congestion Control

• ??????????????????????????? 80
  ??????????????????????????????????
• ??????????????????????????????????????????????????
  ?????????????????
• ?????????????????????????????????????
• ??????????????????????????????????????????????????
  ?????????????????? (?????????? X.25)

34
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35
Routing Algorithms

36
Network Layer Design Issues

• ?????????????????????????????????????????????????
  (Store-and-Forward Packet Switching)
• ????????????????????????????????????? (Services
  Provided to the Transport Layer)
• ?????????????????????????????????????????????
  (Implementation of Connectionless Service)
• ??????????????????????????????????????????
  (Implementation of Connection-Oriented Service)
• ???????????????????????????????????????????
  (Comparison of Virtual-Circuit and Datagram
  Subnets)

37
Store-and-Forward Packet Switching

• ??????????????????????????????????????????????????
  ?????????????????????
• Router ???????????????????????????????????????????
  ???? router ????????

• The environment of the network layer protocols.

38
Services Provided to the Transport Layer

• ??????????????????????????????????????????????????
  
• ??????????????????????????????????????????????????
  ????????????????????????????????????????
• ??????????????????????????????????????????????????
  ??????????????????
• ??????????????????????????????????????????????????
  ??????????????????????????????????????????????????
  ?????????????????

39
Connectionless and Connection-oriented Services

• ????????????????????????????????????? 2 ???
• Connectionless Service
• ??????????????????????????????????????????????
• ???????????????????????? Datagram
• ????????????????????????? datagram subnet
• Connection-oriented Service
• ???????????????????? router ??????????? router
  ???????????????????????????
• ???????????????????????????????????? (virtual
  circuit)
• ????????????????????????? virtual circuit subnet

40
Implementation of Connectionless Service

• Routing within a diagram subnet.

41
Connection-Oriented Service

• Routing within a virtual-circuit subnet.

42
Comparison of Virtual-Circuit and Datagram Subnets
5-4
43
Routing Algorithms

• The Optimality Principle
• Shortest Path Routing
• Flooding
• Distance Vector Routing
• Link State Routing
• Hierarchical Routing
• Broadcast Routing
• Multicast Routing
• Routing for Mobile Hosts
• Routing in Ad Hoc Networks

44
Routing Algorithms (2)
???????????????????????? A ?? A ??? B ?? B
?????? C ?? C ???????????????????????????????????
???????? ?????????????????????????????????????????
???????? ????????????????? X ??? X
????????????????????????

• Conflict between fairness and optimality.

45
The Optimality Principle
??? router ????? (??? B) ????????????????????????
?????????????????? (??? A) ??????????????? (???
C) ???? ??????????????????????????????????????????
????? router ???? (??? B) ??????????????? (??? C)
????

• (a) A subnet. (b) A sink tree for router B.

46
Shortest Path Routing
Dijkstra (1959) ????????? algorithm
???????????????????????????????????????????? 2 ???

• The first 5 steps used in computing the shortest
  path from A to D. The arrows indicate the
  working node.

47
Flooding

• ?????????????????????????????????????????????????
• Router ???????????????????????????????????????????
  ??????????????? router ?????? router
  ???????????????????
• ??????????????????????????????????????????????????
  ????????????????????????????????????
• ??????????????????????????????????????????????????
  ??????????????
• ???????????????????? router ?????????????????????
• ??????????????????????????????????????????????????
  ????????????????????

48
Distance Vector Routing

• ???? algorithm ??????????????? dynamic
• Router ???????????????????????????????????????????
  ???????????????????????????????????? router ?????
• ??????????????????????????????????????????????????
  ?????????????? router ?????????????
• ??????????????????? ????? router ?????????
  ???????????????????? ?????????????????????????
  ???????

49
Distance Vector Routing
??? Router J ??????????????????????????????
Router G 1) ????????????? Router A??????? 8
??????????? 2) ??? A ????? G ??????? 18
???????????? ??????? 81828 ???????????
??????????????? ?????????? I, H, ??? K
???????????? (103141), (12618), ??? (63137)
???????? ??????????????????18 ??????? J
??????????18 ???? H

• (a) A subnet. (b) Input from A, I, H, K, and the
  new routing table for J.

50
Link State Routing

• ???? algorithm ??? dynamic ???????????????????????
  ??????????
• ????? Router ??????????????????????
• ??????????????? Router ???????????????????????????
  ?????????????? Router ?????????
• ?????????????????????? cost ?????????????? router
  ?????????
• ??????????????????????????????????????????????
• ??????????????? router ??????
• ??????????????????????????????????????????????????
  router

51
Hierarchical Routing

• ??????????????????????????????????? router
  ????????????????
• ???? algorithm ??????? router ????????????????????
  ??????????? region
• Router ?? region ?????????????????????????????????
  ?????? ??????????????????????? router ?? region
  ????

52
Hierarchical Routing
???????????????????????????????????? 2 ?????
?????????? 5 region ????????????? router 1A
??????????????? 17 ?????? ??????????? 2 ?????
router 1A ???????????????????? 7 ??????
????????????????? router ??????????????????
??????????????????????????????????????????????????
??????

• Hierarchical
• routing.

53
Broadcast Routing

• ?????????? Host ????????????????????????????????
  Host ???????????????????????????????
• ???????????????
• ?????????????????????????????? node
  ??????????????????
• ??????????????????????????????? node
• ????????????? Flooding - ????????????????????????
  ?????????????????????????????????
• ?????? Multi-destination routing
• ??????????????????????????????????????????????????
  ??????????????
• router ???????????????????????????????????????????
  ??????????????????????????????????????????????????
  ??????????????????????????????????????????????????
  ??????????????????????????
• ????????????????????? ????????????????????????????
  ??????????????????????????????? node ?????
• ???????????? sink tree ??? spanning tree ?????

54
Broadcast Routing
Reverse path forwarding. (a) A subnet. (b) a
Sink tree. (c) The tree built by reverse path
forwarding.
55
Multicast Routing

• ???????????? ????? ????? ??????????????????
  ????????????? ?????????????????????????????????
• Router ????????????? spanning tree ????????
• ????? process ??????????????? packet
  ????????????????????????? router
  ?????????????????????????????????????? spanning
  tree ???????????? ???????????????????????????
  host ?????????????????????? ??????????????

56
Multicast Routing
(a) A network. (b) A spanning tree for the
leftmost router. (c) A multicast tree for
group 1. (d) A multicast tree for group 2.
57
Congestion Control

58
Congestion Control Algorithms

• General Principles of Congestion Control
• Congestion Prevention Policies
• Congestion Control in Virtual-Circuit Subnets
• Congestion Control in Datagram Subnets
• Load Shedding
• Jitter Control

59
Congestion

• When too much traffic is offered, congestion
  sets in and performance degrades sharply.

60
General Principles of Congestion Control

• ?????????????? ???????????????????????????????????
  ???????????
• ?????????????????????????????????????????????
• ???????????????????????????????????????????

61
Policies that affect congestion
5-26
62
Congestion Control in Virtual-Circuit Subnets

• (a) A congested subnet. (b) A redrawn subnet,
  eliminates congestion and a virtual circuit from
  A to B.

63
Hop-by-Hop Choke Packets

• (a) A choke packet that affects only the source.
• (b) A choke packet that affects each hop it
  passes through.

64
Jitter Control
Jitter delay of packet delivery

• (a) High jitter. (b) Low jitter.

65
Quality of Service

66
Quality of Service

• ??????????? (Requirements)
• ??????????????????????????????????????
  (Techniques for Achieving Good Quality of
  Service)
• ????????????????????? (Integrated Services)
• ???????????????????? (Differentiated Services)
• Label Switching and MPLS

67
Requirements
5-30

• How stringent the quality-of-service requirements
  are.

68
Buffering

• ???????????????????????????????????????? Buffer

69
The Leaky Bucket Algorithm
????????????????????

• (a) A leaky bucket with water. (b) a leaky
  bucket with packets.

70
The Token Bucket Algorithm
5-34

• (a) Before. (b) After.

71
Admission Control
5-34

• An example of flow specification.

72
Packet Scheduling

• (a) A router with five packets queued for line O.
• (b) Finishing times for the five packets.

73
Integrated Services

• ???????????????????????????????????????
• Flow-based algorithm
• ??????????????????????????? unicast ??? Multicast
• Resource reServation Protocol (RSVP)
• ???????? Zhang et al., 1993
• ??????????????????????????????????????????????????
  ???
• ??????????????????????????????????????????????????
  ??????????????????
• ??????????????????????????????????????????????????
  ?????????????????????????????????????????

74
RSVP-The ReSerVation Protocol
(a) A network, (b) The multicast spanning tree
for host 1. (c) The multicast spanning tree
for host 2.
75
RSVP-The ReSerVation Protocol (2)
(a) Host 3 requests a channel to host 1. (b)
Host 3 then requests a second channel, to host 2.
(c) Host 5 requests a channel to host 1.
76
Expedited Forwarding
??????????????????????? (??????? RFC 3246)
???????? IETF

• Expedited packets experience a traffic-free
  network.

77
Assured Forwarding

• A possible implementation of the data flow for
  assured forwarding.

78
Label Switching and MPLS
??????????????????? router ????????????????????
label ????????????????????????????????????????????
???????????????????????????????? label
???????????????????????????????????
??????????????????????????????????????????????????
??????????????????????????????????????????????????
???????????

• Transmitting a TCP segment using IP, MPLS, and
  PPP.

79
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