Upload
eden-estes
View
44
Download
2
Tags:
Embed Size (px)
DESCRIPTION
Packet-Switched Networks. Communication Networks. A generic communication network:. end system. Communication Network. node. Other names for “end system”: station, host, terminal Other names for “node”: switch, router , gateway. Taxonomy of Networks. - PowerPoint PPT Presentation
Citation preview
© Jörg Liebeherr ECE 1545
Packet-Switched Networks
ECE 1545
• A generic communication network:
Communication Networks
Other names for “end system”: station, host, terminalOther names for “node”: switch, router, gateway
CommunicationNetwork
end system
node
ECE 1545
• Communication networks can be classified based on the way in which the nodes exchange information:
Taxonomy of Networks
Communication Network
Circuit-SwitchedNetwork
Packet-SwitchedNetwork
Datagram Network
Virtual Circuit NetworkFrequency
DivisionMultiplexing
Time DivisionMultiplexing
Wavelength Division
Multiplexing
ECE 1545
Packet Switching
• Data are sent as formatted bit-sequences, so-called packets • Packets have the following structure:
• Header and Trailer carry control information
• Each packet is passed through the network from node to node along some path (Forwarding/Routing)
• At each node the entire packet is received, stored briefly, and then forwarded to the next node (Store-and-Forward Networks)
• Packet transmission is never interrupted (no preemption)• No capacity is allocated for packets
Header Data Trailer
ECE 1545
A Packet Switch
memory
outputqueues
inputqueues
switchfabric
ECE 1545
Packet 1
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
Timing of Datagram Packet Switching
Packet 1
Packet 2
Packet 3
1 2 3 4
Transmissiondelay
Host
HostNod
eNod
e
ECE 1545
4
5
7
C
B
A E
1 2D
6
3
A.3
A.2
C.2A.1
C.1
A.3
A.2
A.1
C.1
C.2
Datagram Packet Switching
A.3A.2A.1
C.1C.2
A.3
A.2
C.2A.1
C.1
A.3A.2A.1
C.1C.2
A.2
A.3
A.1
A.2A.2A.2
C.2
A.2
A.3
A.1
A.2A.3
A.2
A.1
ECE 1545
Pkt1
Pkt2
Pkt3
Pkt1
Pkt2
Pkt3
Timing of VC Packet Switching
Pkt1
Pkt2
Pkt3
1 2 3 4
VC Establishment
VC Termination
Host
Host
Node
Node
Transmissiondelay
ECE 1545
4
5
7
C
B
A E
1 2D
6
3
A.3
A.2
A.1
Virtual-Circuit Packet Switching
VC 2
VC 1
C.1
C.2
C.1
C.2
A.3A.2A.1
A.3A.2A.1
C.1
C.2
A.3A.2A.1
A.3A.2A.1
A.3A.2C.2
A.1C.1
A.3A.2C.2
A.1C.1
C.1
A.3
A.1
C.2 A.3
A.1
A.2A.3
A.2A.1
C.1
A.3
A.1
C.2 A.3
A.1
A.2A.3
A.2A.1
ECE 1545
Packet Switching Technologies
• Both packet switching technologies are used today:
• Datagram packet switching: – IP routers (Internet)– Ethernet Switches (Switched LANs)
• Virtual-circuit packet switching– Asynchronous Transfer Mode (ATM)– Multi-protocol label switching (MPLS)
ECE 1545
Packet Switch Architectures
ECE 1545
Packet Switches
• Different types of packet switches: – IP routers– ATM switches– MPLS switches– Ethernet (LAN) switches– Frame Relay
• All types of packet switches have very similar characteristics
ECE 1545
Switch Components
• Hardware components of a router:– Network interfaces– Interconnection network– Processor with a memory
and CPU
Interface Card
Interconnection Network
Interface Card Interface Card
Processor
CPUMemory
Basic Architectural ComponentsPer-packet processing
RoutingDecision
ForwardingDecision
ForwardingDecision
RoutingTable
RoutingTable
RoutingTable
Switch Fabric
OutputScheduling
ECE 1545
Functional Components
Control
Datapath:per-packet processing
routingtable
Routingfunctions
Forwarding
routing tablelookup
routing tableupdates
Incoming packets
outgoing packets
routing protocol
routing protocol
ECE 1545
Routing and Forwarding
Routing functions include:– route calculation– maintenance of the routing table– execution of routing protocols
Forwarding is per-packet processing• On high-end packet switches routers, forwarding is highly
parallelized, and most work is done on the interface cards
© Jörg Liebeherr, 2005 ECE 1545
IP Router
• Lookup packet destination address in forwarding table.– If known, forward to correct port.– If unknown, drop packet.
• Decrement TTL, update header checksum.• Forward packet to outgoing interface.• Transmit packet onto link.
© Jörg Liebeherr, 2005 ECE 1545
ATM Switch
• Look up VCI/VPI of cell in VC table.• Replace old VCI/VPI with new.• Forward cell to outgoing interface.• Transmit cell onto link.
© Jörg Liebeherr, 2005 ECE 1545
Ethernet Switch
• Lookup frame destination address in forwarding table.– If known, forward to correct port.– If unknown, broadcast to all ports.
• Learn source address of incoming frame.• Forward frame to outgoing interface.• Transmit frame onto link.