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Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 1
Figure 3.1 Network types
Range Bandwidth (Mbps) Latency (ms)
LAN 1–2 kms 10–1000 1–10
WAN worldwide 0.010–600 100–500
MAN 2–50 kms 1–150 10
Wireless LAN 0.15–1.5 km 2–11 5–20
Wireless WAN worldwide 0.010–2 100-500
Internet worldwide 0.010–2 100–500
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 2
Figure 3.2 Conceptual layering of protocol software
Layer n
Layer 2
Layer 1
Message sent Message received
Communicationmedium
Sender Recipient
•
•
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 3
Figure 3.3 Encapsulation as it is applied in layered protocols
Application-layer message
Presentation header
Session header
Transport header
Network header
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 4
Figure 3.4 Protocol layers in the ISO Open Systems Interconnection (OSI) protocol model
Application
Presentation
Session
Transport
Network
Data link
Physical
Message sent Message received
Sender Recipient
Layers
Communicationmedium
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 5
Figure 3.5 OSI protocol summary
Layer Description Examples
Application Protocols that are designed to meet the communication requirements of specific applications, often defining the interface to a service.
HTTP, FTP, SMTP, CORBA IIOP
Presentation Protocols at this level transmit data in a network representation that is independent of the representations used in individual computers, which may differ. Encryption is also performed in this layer, if required.
Secure Sockets (SSL),CORBA Data Rep.
Session At this level reliability and adaptation are performed, such as detection of failures and automatic recovery.
Transport This is the lowest level at which messages (rather than packets) are handled. Messages are addressed to communication ports attached to processes, Protocols in this layer may be connection-oriented or connectionless.
TCP, UDP
Network Transfers data packets between computers in a specific network. In a WAN or an internetwork this involves the generation of a route passing through routers. In a single LAN no routing is required.
IP, ATM virtual circuits
Data link Responsible for transmission of packets between nodes that are directly connected by a physical link. In a WAN transmission is between pairs of routers or between routers and hosts. In a LAN it is between any pair of hosts.
Ethernet MAC, ATM cell transfer, PPP
Physical The circuits and hardware that drive the network. It transmits sequences of binary data by analogue signalling, using amplitude or frequency modulation of electrical signals (on cable circuits), light signals (on fibre optic circuits) or other electromagnetic signals (on radio and microwave circuits).
Ethernet base-band signalling, ISDN
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 6
Figure 3.6 Internetwork layers
Underlying network
Application
Network interface
Transport
Internetwork
Internetwork packets
Network-specific packets
MessageLayers
Internetworkprotocols
Underlyingnetworkprotocols
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 7
Figure 3.7 Routing in a wide area network
Hosts Linksor local networks
A
D E
B
C
12
5
43
6Routers
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 8
Figure 3.8 Routing tables for the network in Figure 3.7
Routings from A Routings from B Routings from C
To Link Cost To Link Cost To Link Cost
ABCDE
local1131
01212
ABCDE
1local
214
10121
ABCDE
22
local55
21021
Routings from D Routings from E
To Link Cost To Link Cost
ABCDE
336
local6
12201
ABCDE
4456
local
21110
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 9
Figure 3.9 Pseudo-code for RIP routing algorithm
Send: Each t seconds or when Tl changes, send Tl on each non-faulty outgoing link.
Receive: Whenever a routing table Tr is received on link n:for all rows Rr in Tr {
if (Rr.link ≠ n) {Rr.cost = Rr.cost + 1;Rr.link = n;if (Rr.destination is not in Tl) add Rr to Tl; // add new destination to Tlelse for all rows Rl in Tl {
if (Rr.destination = Rl.destination and (Rr.cost < Rl.cost or Rl.link = n)) Rl = Rr;// Rr.cost < Rl.cost : remote node has better route// Rl.link = n : remote node is more authoritative
}}
}
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 10
Figure 3.10 Simplified view of the QMW Computer Science network
file
compute
dialup
hammer
henry
hotpoint
138.37.88.230
138.37.88.162
bruno138.37.88.249
router/sickle
138.37.95.241138.37.95.240/29
138.37.95.249
138.
37.9
4.24
7
copper138.37.88.248
firewall
web
138.37.95.248/29
server
desktop computers 138.37.88.xx
subnet
subnet
Eswitch
138.37.88
server
server
server
138.37.88.251
custard138.37.94.246
desktop computers 138.37.94.xx
Eswitch
138.37.94
hubhub
Student subnetStaff subnet
otherservers
router/firewall
138.37.94.251
138.
37.8
8.24
7
☎
1000 Mbps EthernetEswitch: Ethernet switch
100 Mbps Ethernet
file server/gateway
printers
138.
37.9
5.23
2/29
subn
et
Campusrouter
Campusrouter
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 11
Figure 3.11 Tunnelling for IPv6 migration
A BIPv6 IPv6
IPv6 encapsulated in IPv4 packets
Encapsulators
IPv4 network
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 12
Figure 3.12 TCP/IP layers
Messages (UDP) or Streams (TCP)
Application
Transport
Internet
UDP or TCP packets
IP datagrams
Network-specific frames
MessageLayers
Underlying network
Network interface
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 13
Figure 3.13 Encapsulation as it occurs when a message is transmitted via TCP over an Ethernet
Application message
TCP header
IP header
Ethernet header
Ethernet frame
port
TCP
IP
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 14
Figure 3.14 The programmer's conceptual view of a TCP/IP Internet
IP
Application Application
TCP UDP
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 15
Figure 3.15 Internet address structure, showing field sizes in bits
7 24
Class A: 0 Network ID Host ID
14 16
Class B: 1 0 Network ID Host ID
21 8
Class C: 1 1 0 Network ID Host ID
28
Class D (multicast): 1 1 1 0 Multicast address
27
Class E (reserved): 1 1 1 1 unused0
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 16
Figure 3.16 Decimal representation of Internet addresses
octet 1 octet 2 octet 3
Class A: 1 to 127
0 to 255 0 to 255 1 to 254
Class B: 128 to 191
Class C: 192 to 223
224 to 239 Class D (multicast):
Network ID
Network ID
Network ID
Host ID
Host ID
Host ID
Multicast address
0 to 255 0 to 255 1 to 254
0 to 255 0 to 255 0 to 255
0 to 255 0 to 255 0 to 255
Multicast address
0 to 255 0 to 255 1 to 254240 to 255 Class E (reserved):
1.0.0.0 to 127.255.255.255
128.0.0.0 to 191.255.255.255
192.0.0.0 to 223.255.255.255
224.0.0.0 to 239.255.255.255
240.0.0.0 to 255.255.255.255
Range of addresses
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 17
Figure 3.17 IP packet layout
dataIP address of destinationIP address of source
header
up to 64 kilobytes
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 18
Figure 3.18 IPv6 header layout
Source address(128 bits)
Destination address(128 bits)
Version (4 bits) Priority (4 bits) Flow label (24 bits)Payload length (16 bits) Hop limit (8 bits)Next header (8 bits)
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 19
Sender
Home
Figure 3.19 The MobileIP routing mechanism
Mobile host MH
Foreign agent FAInternet
agent
First IP packet addressed to MH
Address of FAreturned to sender
First IP packettunnelled to FA
Subsequent IP packetstunnelled to FA
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 20
Figure 3.20 Firewall configurations
Internet
Router/Protected intraneta) Filtering router
Internet
b) Filtering router and bastion
filter
Internet
R/filterc) Screened subnet for bastion R/filter Bastion
R/filter Bastion
web/ftpserver
web/ftpserver
web/ftpserver
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 21
Figure 3.21 IEEE 802 network standards
IEEE No. Title Reference
802.3 CSMA/CD Networks (Ethernet) [IEEE 1985a]802.4 Token Bus Networks [IEEE 1985b]802.5 Token Ring Networks [IEEE 1985c]802.6 Metropolitan Area Networks [IEEE 1994]802.11 Wireless Local Area Networks [IEEE 1999]
Instructor’s Guide for
Coulouris, Dollimore and Kindberg
Distributed Systems: Concepts and Design
Edn. 3 © Pearson Education 2001 22
Figure 3.22 Wireless LAN configuration
LAN
Server
WirelessLAN
Laptops
Base station/access point
Palmtop
radio obstruction
A B C
D E
Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3 © Pearson Education 2001 23
Figure 3.23 ATM protocol layers
Physical
Application
ATM layer
Higher-layer protocols
ATM cells
ATM virtual channels
MessageLayers
ATM adaption layer
Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3 © Pearson Education 2001 24
Flags
Figure 3.24 ATM cell layout
DataVirtual channel idVirtual path id
53 bytes
Header: 5 bytes
Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3 © Pearson Education 2001 25
Figure 3.25 Switching virtual paths in an ATM network
VPI in VPI out
23
45
VPI = 3
VPI = 5
VPI = 4
Virtual path Virtual channels
VPI = 2
VPI : virtual path identifier
VP switch VP/VCswitch
VP switch
Host
Host