EECS 122 Introduction to Computer Networks Network Service and Applications Computer Science Division Department of Electrical Engineering and Computer Sciences University of California Berkeley Berkeley CA 94720 1776 Katz Stoica F04 1 Overview Taxonomy of Communication Networks Services and Applications Katz Stoica F04 2 Taxonomy of Communication Networks Communication networks can be classified based on the way in which the nodes exchange information Communication Network Switched Communication Network CircuitSwitched Communication Network Broadcast Communication Network PacketSwitched Communication Network Datagram Network Virtual Circuit Network Katz Stoica F04 3 Broadcast vs Switched Communication Networks Broadcast Communication Networks Information transmitted by any node is received by every other node in the network Examples usually in LANs Ethernet WiFi Problem coordinate the access of all nodes to the shared communication medium Multiple Access Problem Switched Communication Networks Information transmitted to a sub set of designated nodes Examples WANs Telephony Network Internet Problem how to forward information to intended node s Done by special nodes e g routers switches executing routing protocols Katz Stoica F04 4 Taxonomy of Communication Networks Communication networks can be classified based on the way in which the nodes exchange information Communication Network Switched Communication Network CircuitSwitched Communication Network Broadcast Communication Network PacketSwitched Communication Network Datagram Network Virtual Circuit Network Katz Stoica F04 5 Circuit Switching Three phases 1 circuit establishment 2 data transfer 3 circuit termination If circuit not available Busy signal Examples Telephone networks ISDN Integrated Services Digital Networks Katz Stoica F04 6 Telegraph Network Alexander Graham Bell 1876 Demonstrates the telephone at US Centenary Exhibition in Philadelphia Katz Stoica F04 7 Telephone Network Almon Brown Strowger 1839 1902 1889 Invents the girl less cuss less telephone system aka the mechanical switching system Katz Stoica F04 8 Timing in Circuit Switching Host 1 Node 1 Node 2 Host 2 processing delay at Node 1 propagation delay between Host 1 and Node 1 Circuit Establishment Data Transmission propagation delay between Host 2 and Node 1 DATA Circuit Termination Katz Stoica F04 9 Circuit Switching Node switch in a circuit switching network incoming links Node outgoing links Katz Stoica F04 10 Circuit Switching Multiplexing Demultiplexing Frames Slots 0 1 2 3 4 5 0 1 2 3 4 5 Time divided in frames and frames into slots Relative slot position inside a frame determines to which conversation data belongs E g slot 0 belongs to red conversation Requires synchronization between sender and receiver surprisingly difficult In case of non permanent conversations Needs to dynamically bind a slot to a conservation How to do this If a conversation does not use its circuit the capacity is lost Katz Stoica F04 11 Taxonomy of Communication Networks Communication networks can be classified based on the way in which the nodes exchange information Communication Network Switched Communication Network CircuitSwitched Communication Network Broadcast Communication Network PacketSwitched Communication Network Datagram Network Virtual Circuit Network Katz Stoica F04 12 Packet Switching Data sent as formatted bit sequences Packets Packets have following structure Header Data Trailer Header and Trailer carry control information e g destination address check sum Each packet traverses the network from node to node along some path Routing At each node the entire packet is received stored briefly and then forwarded to the next node Store and Forward Networks Typically no capacity is allocated for packets Katz Stoica F04 13 Packet Switching Node in a packet switching network incoming links Node outgoing links Memory Katz Stoica F04 14 Packet Switching Multiplexing Demultiplexing Data from any conversation can be transmitted at any given time Single conversation can use the entire link capacity if it is alone How to tell them apart Use meta data header to describe data Katz Stoica F04 15 Taxonomy of Communication Networks Communication networks can be classified based on the way in which the nodes exchange information Communication Network Switched Communication Network CircuitSwitched Communication Network Broadcast Communication Network PacketSwitched Communication Network Datagram Network Virtual Circuit Network Katz Stoica F04 16 Datagram Packet Switching Each packet is independently switched Each packet header contains destination address No resources are pre allocated reserved in advance Example IP networks Katz Stoica F04 17 Timing of Datagram Packet Switchi ng Host 1 transmission time of Packet 1 at Host 1 Node 1 Packet 1 Packet 2 Packet 3 Host 2 Node 2 propagation delay between Host 1 and Node 2 Packet 1 Packet 2 Packet 3 processing delay of Packet 1 at Node 2 Packet 1 Packet 2 Packet 3 Katz Stoica F04 18 Datagram Packet Switching Host C Host D Host A Node 1 Node 2 Node 3 Node 5 Host B Node 6 Node 7 Host E Node 4 Katz Stoica F04 19 Taxonomy of Communication Networks Communication networks can be classified based on the way in which the nodes exchange information Communication Network Switched Communication Network CircuitSwitched Communication Network Broadcast Communication Network PacketSwitched Communication Network Datagram Network Virtual Circuit Network Katz Stoica F04 20 Virtual Circuit Packet Switching Hybrid of circuit switching and packet switching Data is transmitted as packets All packets from one packet stream are sent along a pre established path virtual circuit Guarantees in sequence delivery of packets However packets from different virtual circuits may be interleaved Example ATM networks Katz Stoica F04 21 Virtual Circuit Packet Switching Communication with virtual circuits takes place in three phases 1 VC establishment 2 data transfer 3 VC disconnect Note packet headers don t need to contain the full destination address of the packet Katz Stoica F04 22 Timing of Virtual Circuit Packet Switching Host 1 Node 1 Host 2 Node 2 propagation delay between Host 1 and Node 1 VC establishment Packet 1 Packet 2 Data transfer Packet 3 Packet 1 Packet 2 Packet 3 Packet 1 Packet 2 Packet 3 VC termination Katz Stoica F04 23 Datagram Packet Switching Host C Host D Host A Node 1 Node 2 Node 3 Node 5 Host B Node 6 Node 7 Host E Node 4 Katz Stoica F04 24 Packet
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