Why TOC Switching Forwarding Why Switching Techniques Switch Characteristics Switch Examples Switch Architectures Summary Direct vs Switched Networks n links Single link Switches Direct Network Limitations Distance coordination delay propagation limitation Number of hosts collisions shared bandwidth address tables Single link technology cannot mix optical wireless Internetworking Externality gain at low cost TOC Switching TOC Switching Why Techniques Circuit Switching Circuit Switching e g Telephone net Packet Switching Mechanism Datagram e g IP Ethernet Virtual Circuits e g MPLS ATM Source Routing Comparison Features TOC Switching Techniques PS Datagram General idea no connection establishment but each packet contains enough info to specify destination Switches contain forwarding tables but no perconnection state Forwarding tables contain info on which outgoing port to use for each destination Two types of addressing Features Mechanism Layer 2 or Layer 3 TOC Switching Techniques Packet TOC Switching Techniques Circuit Packet Switching TOC Switching Techniques Packet Datagram Layer 2 e g Ethernet Layer 3 e g IP Topological structure match prefix Either fixed prefix length or longest match 13 23 0 2 1 L3 network e g IP Flat address space no structure Forwarding table Exact match of destination L2 address 3 TOC Switching Techniques Packet Datagram L2 TOC Switching Techniques Packet Datagram L3 Layer 3 e g IP 1 13 2 13 4 5 1 4 23 0 2 6 4 2 1 1 13 Layer 3 e g IP 13 23 0 2 1 3 3 TOC Switching Techniques Packet Datagram L3 TOC Switching Techniques Packet Datagram L3 Layer 3 e g IP PS Virtual Circuit 13 23 2 4 13 23 0 2 1 TOC Switching Techniques Packet Datagram L3 A virtual circuit ID VCI identifies path Uses packet switching with packets containing VCI VCIs are often indices into per switch connection tables change at each hop 7 7 7 7 7 7 8 7 0 3 Connection setup establishes a path through switches 7 7 TOC Switching Techniques Packet VC 7 7 9 Source Routing Comparison source 4 3 4 1 2 3 4 1 2 3 4 1 2 3 4 4 3 4 1 2 3 4 1 2 3 4 1 2 3 4 4 3 4 Datagram Virtual circuit switching Circuit switching Forwarding cost high low none Bandwidth utilization Resource reservations Robustness high flexible low none flexible yes high low low 7 TOC Switching Techniques Source Routing TOC Switching Techniques Comparison Characteristics Examples Ports Fast Ethernet OC 3 ATM Protocols ST Link Agg VLAN OSPF RIP BGP VPN Load Balancing WRED WFQ Performance Throughput Reliability Power TOC Switching Characteristics Juniper M160 Cisco GSR Cisco 7600 Cisco catalyst 6500 Extreme Summit Foundry ServerIron TOC Switching Examples Cisco GSR 12416 Juniper M160 WAN Router Large throughput SONET links Up to 16 line cards at 10 Gbps each 19 Crossbar Fabric Line Cards 1 port OC 192c 4 port OC48c Many others ATM Ethernet 6ft WAN Router Large throughput SONET links Crossbar Fabric Line Cards 1 port OC 192c 19 4 port OC48c Many others Capacity ATM Ethernet 80Gb s Power 2 6kW 3ft 2ft 2 5ft TOC Switching Examples GSR 9 TOC Switching Examples M160 Cisco 7600 MAN WAN Router Up to 128 Gbps with Crossbar Fabric 10Mbps 10Gbps LAN Interfaces OC 3 to OC 48 SONET Interfaces MPLS WFQ LLQ WRED Traffic Shaping TOC Switching Examples 7600 Extreme Summit 48 10 100 ports 2 GE SX LX or LX 70 17 5Gbps non blocking 10 1 Mpps Wire speed L2 Wire speed L3 static or RIP OSPF DVRMP PIM TOC Switching Examples Summit Architectures Generic Architecture First Generation Second Generation Third Generation Input Functions Output Functions Interconnection Designs OUT IN VOB Combined IN OUT TOC Switching Architectures Cisco cat 6500 From LAN to Access 48 to 576 10 100 Ethernet Interfaces 10 GE OC 3 OC 12 OC 48 ATM QoS ACL Load Balancing VPN Up to 128Gbps with crossbar L4 7 Switching VLAN IP Telephony E1 T1 inline power Ethernet SNMP RMON TOC Switching Examples Cat6k Foundry ServerIron Server Load Balancing Transparent Cache Switching Firewall Load Balancing Global Server Load Balancing Extended Layer 4 7 functionality including URL Cookie and SSL Session ID based switching Secure Network Address Translation NAT and Port address translation PAT TOC Switching Examples ServerIron Generic Input and output interfaces are connected through an interconnect A interconnect can be implemented by Shared memory low capacity routers e g PC based routers Shared bus Medium capacity routers Point to point switched bus High capacity routers TOC Switching Architectures Generic input interface output interface Interconnect First Generation Second Generation Shared Backplane CPU CP I Line U nte r fa ce M em or y CPU Buffer Memory Route Table Line Interface Line Interface Line Interface MAC MAC MAC Typically 5Gb s aggregate capacity Limited by shared bus Buffer Memory Route Table Line Card Line Card Line Card Buffer Memory Buffer Memory Buffer Memory Fwding Cache Fwding Cache Fwding Cache MAC MAC MAC Typically 0 5Gbps aggregate capacity Limited by rate of shared memory Slide by Nick McKeown Slide by Nick McKeown TOC Switching Architectures First TOC Switching Architectures Second Input Functions Third Generation Switched Backplane Li CPIn ne Uter fa ce M em or y Line Card CPU Card Line Card Local Buffer Memory Routing Table Local Buffer Memory Fwding Table Fwding Table MAC MAC Typically 50Gbps aggregate capacity Packet forwarding decide to which output interface to forward each packet based on the information in packet header examine packet header lookup in forwarding table update packet header Slide by Nick McKeown TOC Switching Architectures Third TOC Switching Architectures Input Functions Output Functions ct Output Functions Buffer management decide when and which packet to drop Scheduler decide when and which packet to transmit Buffer Scheduler Packet classification map each packet to a predefined flow connection for datagram forwarding use to implement more sophisticated services e g QoS Flow a subset of packets between any two endpoints in the network flow 1 1 2 1 2 Classifier flow 2 flow n Buffer management TOC Switching Architectures Output Functions TOC Switching Architectures Output Functions Scheduler Output Queued Input Queues Only output interfaces store packets Advantage Only input interfaces store packets Advantages Easy to design algorithms only one congestion point input interface output interface Disadvantage Requires an output speedup Ro C N where N is the number of interfaces not feasible for large N Easy to build Simple algorithms output interface
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