Contents
• Link multiplexing
– Circuit switching
• Synchronous Time-domain Multiplexing
– Packet Switching
• Statistical Time-domain Multiplexing
• Connection oriented vs. Connectionless
– Datagrams & Routing
– Virtual Circuits & Forwarding
• Internal vs. External policies
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Connection oriented
vs. Connectionless
• Circuit Switching
– Intrinsically connection oriented
• Packet Switching
– Connectionless
• Each packet carries the destination address
• Routing decisions to be made for each packet
• Typical example : Internet Protocol
– Connection oriented : Virtual Circuits
• Each packet carries a local identifier (VCN) of the data
flow it belongs to
• Routing decisions at virtual circuit set-up.
• Typical examples : X25, Frame Relay, ATM
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Contents
• Link multiplexing
– Circuit switching
• Synchronous Time-domain Multiplexing
– Packet Switching
• Statistical Time-domain Multiplexing
• Connection oriented vs. Connectionless
– Datagrams & Routing
– Virtual Circuits & Forwarding
• Internal vs. External policies
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Datagram Routing
Based upon routing tables
3
a
1
2
b
3
c
3
2
1
4
a:1
b:2
c:3
d:3
1
3
4
2
a:3
b:3
c:2
d:2
Postacademic Interuniversity Course in Information Technology – Module C1
a:3
b:3
c:1
d:1
a:3
b:3
c:1
d:2
1
2
d
p4
Routing Tables
in Connectionless networks
• For ALL POSSIBLE destination addresses, they give the
“best” outgoing link, but
– the best can be different for different applications
– the best can get congested
• For EACH packet routing table needs to be consulted
• Routing tables need to be updated regularly
– Set of possible destinations can change
– Set of available links can change
– Destinations can be mobile
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Best route consequences
1
a
1
1
b
1
Idle
c
1
Risk of
congestion
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d
p6
Contents
• Link multiplexing
– Circuit switching
• Synchronous Time-domain Multiplexing
– Packet Switching
• Statistical Time-domain Multiplexing
• Connection oriented vs. Connectionless
– Datagrams & Routing
– Virtual Circuits & Forwarding
• Internal vs. External policies
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Virtual Circuit Number
a
b
a>b 10
a>c 11
a>d 12
b>c 11
b>d 12
a>b 21
b>c 20
a>c 21
d>c 22
a>c
a>d
b>c
b>d
10
11
12
13
d>c 11
a>d 20
b>d 21
c
d
Each virtual circuit is identified by a specific
number on each physical link
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Forwarding Tables
11
a
1
3
2
1.11>3.10
21
10
b
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1.10>3.21
c
3
2
d
p9
Permanent Virtual Circuit
Forwarding tables set-up and cleared
by network manager through “separate”
network
a>c 21
a a>c 11
c
1
3
2
1.11>3.10
1
1.10>3.21
“Separate”
signaling network
b
3
2
d
Signaling and data packets travel through
different (virtual) circuits
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Forwarding Tables
in Connection Oriented networks
• For Each V. C. in use, they give the outgoing link
– Different v.c. can connect the same end-points.
– Resources can be reserved for a v.c.
– They can be changed dynamically to follow mobiles
• Routing tables are only needed to establish a new V.C.
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Contents
• Link multiplexing
– Circuit switching
• Synchronous Time-domain Multiplexing
– Packet Switching
• Statistical Time-domain Multiplexing
• Connection oriented vs. Connectionless
– Datagrams & Routing
– Virtual Circuits & Forwarding
• Internal vs. External policies
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Internal vs. External Policies
Network services (NUI)
Connection oriented
Connectionless
Postacademic Interuniversity Course in Information Technology – Module C1
Network operation (NNI)
Connection oriented
Connectionless
p13
Introduced concepts
•
•
•
•
•
•
•
•
•
Multiplexing
Circuit Switching
Synchronous time multiplexing
Packet Switching
Statistical time multiplexing
Datagrams and routing
Virtual Circuits & packet forwarding
Resource reservation for a Virtual Circuit
Internal vs. External policies
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