Local-Area-Network (LAN) Architecture Department of Computer Science Southern Illinois University Edwardsville Fall, 2013 Dr. Hiroshi Fujinoki Switch & Router/000 CS 447 Networks and Data Communication

Switch and Routers What are the difference between switches and routers? QUESTION Application Presentation Session Transport Network Data-Link Physical Repeater Bridge Router Network Connecting Devices Where is “switch”? Switch Switching Hub Layer-3 Switch Same Switch & Router/001 CS 447 Networks and Data Communication

Connecting Devices in LAN Bridge Router Repeater Low level High level Switch & Router/002 IP address Network-layer address Datalink-layer address MAC address Physical Ports Routers: the network devices that forward (or drop) packets by software Switches: the network devices that forward (or drop) packets by hardware Simple Definitions Information used for decision making CS 447 Networks and Data Communication

Repeater = signal re-former (+ amplifier) Input (segment 1) Output (segment 2) Repeater LAN Segment 2 LAN Segment 1 Repeater One LAN segment Signal with noise Clean signal Repeater Switch & Router/003 CS 447 Networks and Data Communication

Repeater Hub Repeater Hub = a multi-port repeater Ports Internal shared bus Repeater Broadcast messages go through a hub (or Repeater) Hub Switch & Router/004 (Repeater-HUB) CS 447 Networks and Data Communication

Bridge (switch) = a packet localizer (packet filter) LAN 1 LAN 2 ABC XYZ 1 2 Bridge HOST PORT A B C X Y Z Bridge (switch) Switch & Router/005 Switching Table CS 447 Networks and Data Communication

LAN 1 LAN 2 ABC XYZ 1 2 Bridge Bridge Example: if A sends data to B The bridge will NOT forward packet to LAN2 HOST PORT A B C X Y Z A tries to send data to Host B Switch & Router/006 CS 447 Networks and Data Communication

LAN 1 LAN 2 ABC XYZ 1 2 Bridge The bridge will forward the packet to LAN2 A tries to send data to Host Y HOST PORT A B C X Y Z Bridge Example: if A sends data to Y Switch & Router/007 CS 447 Networks and Data Communication

Bridge = a packet localizer (packet filter) LAN 1 LAN 2 ABC XYZ 1 2 Bridge HOST PORT A B C X Y Z 1 2 A C Data Origin Destination A C Data A Z A Z Origin Destination Switch & Router/008 CS 447 Networks and Data Communication

LAN 1 LAN 2 ABC XYZ 1 2 Bridge HOST PORT A B C X Y Z 1 2 Z X Data Z X Origin Destination 2 Bridge = a packet localizer (packet filter) Switch & Router/009 CS 447 Networks and Data Communication

Switching Hub Switching Hub = a multi-port bridge Ports Hub Switch & Router/010 (Switching-HUB) Multi-Port Bridge Switching Table A BCD E ADADBEBE CS 447 Networks and Data Communication

Router = intelligent packet forwarding device between two network domains The problem of repeaters and bridges (what repeaters and bridges can’t do?) Your destinations must be only one-hop away! You Repeater/Bridge Your Destination What if your destination is more than one-hop away? Switch & Router/011 Your Destination Internet Request Response Request (1) Response with tag (2) Request (3) Response (4) Internet Request Response You Internet Request Response Request (1) Response with tag (2) Request (3) Response (4) Internet Request Response Network 1 Network N Repeater/Bridge ? CS 447 Networks and Data Communication

Switch & Router/012 Receiver Sender Routers exchange routing tables Router Network D Network C Network (= LAN or WAN) A Network B Router = intelligent packet forwarding device between two network domains CS 447 Networks and Data Communication

Switch and Routers Now we know: Layer-3 Switch Switch Router Bridge Repeater Switching Hub Switch & Router/013 CS 447 Networks and Data Communication

Switch and Routers What is the definition of “switch”, then?  Network connecting device  Packet forwarding is performed by hardware  Cut-Through forwarding (not store-and-forward) forwarding  MAC-address is used as address Switch & Router/014 CS 447 Networks and Data Communication

MAC Frame Switch and Routers What is MAC address?  It’s a hardware address associated to each NIC (usually hardwired in a ROM chip on a NIC)  The address used in Data-Link layer  Address deeply related to hardware We can never change it! Source MAC Address Frame Preamble Payload 8 bytes6 bytes bytes Switch & Router/015 CS 447 Networks and Data Communication

Switch and Routers MAC Address (48 bits) 8 bits Vendor ID Model # Serial # 00 AA00 474E85 00 A0 24 – 3COM 00 AA Intel C0 -- SMC 47 – EtherExpress16 4E 85 = 20101th card Switch & Router/016 What is MAC address? How does it look like? CS 447 Networks and Data Communication

Router Router_Switch/017 Internal structure of typical router CPU Routing Algorithm Routing Table Routing Protocol Memory Output Buffer Input Lines Output Lines CS 447 Networks and Data Communication

Internal structure of typical router Definition of the procedure for how to calculate the best path Define what is “the best path” Routing Algorithm Routing Table Routing Protocol Information the CPU uses to calculate the best path It’s implemented as software It’s data-structure (usually as “table” format) It’s software that constructs and maintains the routing table Routing protocol talks to other routers to collect the latest routing information in a network Entries in the routing table is network-layer addresses (e.g., IP addresses) Router_Switch/018 CS 447 Networks and Data Communication

Router Internal structure of typical router CPU Memory Input Lines Output Lines Routing Algorithm Routing Table Routing Protocol Router_Switch/019 IP address Data Procedure CS 447 Networks and Data Communication

Layer-2 Switch (Bridge) Internal structure of typical switch Switching Fabric Output Buffer Output Lines Crossbar switch, TDM switch, Bus switch, etc. Switch Control Unit Input Lines Switching Table Short-Term-Buffer (STB) Router_Switch/020 CS 447 Networks and Data Communication

The component where frames are switched Usually implemented by hardware (e.g., crossbar switch and bus switch) Checks the packet header Control switching fabric using the information in the switching table and the packet header Tells the switch control unit the correct output port (Destination MAC Address) + (Output Port #) STB Switching Fabric Switch Control Unit Switching Table Temporary buffer Internal structure of typical switch Router_Switch/021 CS 447 Networks and Data Communication

Layer-2 Switch (Bridge) Input Lines Output Lines Switch Control Unit Switching Table Router_Switch/022 Internal structure of typical switch CS 447 Networks and Data Communication

Switch Control Unit Switching Table Router_Switch/023 Port #1 Port #2 Port #3 Dest. MACPort# Sent to Host X Copy destination MAC Address Host X MAC=4A3D 4A3D 1 Switching Fabric STB Internal structure of typical switch CS 447 Networks and Data Communication

Layer-3 switches Router_Switch/024 Layer-3 switches = Switches that use layer-3 information (IP address) for forwarding The network devices that perform forwarding are traditionally routers Why not router any more? - LAN speed keeps increasing (10Mbps  100Mbps  1,000Mbps) - Intra-LAN repeaters and switches have been doing a good job in keeping up to the speed (because they are hardware devices) - Routers become throughput bottleneck Let switches take care of (replace) routers CS 447 Networks and Data Communication

Layer-3 switches Router_Switch/025 LAN Backbone Leaf-level Ethernet becomes faster Routers become performance bottleneck CS 447 Networks and Data Communication

Layer-3 switches Router_Switch/026 LAN Backbone Internet/WAN We still need a router here. (why?) CS 447 Networks and Data Communication

Two different types of Layer-3 switches - As core switches for virtual-circuit networks (ATM, FrameRelay)  Switching Router  Routing Switch It is a router that has built-in switch Route first and switch all the rest Typical applications: It is a switch that has built-in router It implements routing protocol (can communicate with other routers) Switches that know other networks (or sub-networks) more than one-hop away (this is the difference between L2 and L3 switches) It does not implement routing protocol (Routing table must be set up manually) Router_Switch/027 CS 447 Networks and Data Communication

Internal Structure of Switching Router CPU Routing Algorithm Routing Table Routing Protocol Memory Session Mngmnt Switching Fabric SW Ctrl Unit Switching Table Router_Switch/028 Switch Router CS 447 Networks and Data Communication

(For Virtual Circuit Packet Switching) CPU Routing Algorithm Routing Table Routing Protocol Switching Fabric Memory SW Ctrl Unit Session Mngmnt Switching Table Router_Switch/029 Internal Structure of Switching Router CS 447 Networks and Data Communication

Virtual Circuit SenderS1S2SnSnReceiver Time      Signaling Message A transmitting station needs to set up a path first Path set-up at switch S1 Router_Switch/030 CS 447 Networks and Data Communication

CPU Routing Algorithm Routing Table Routing Protocol Switching Fabric Memory SW Ctrl Unit Session Mngmnt Signaling message arrived STEP 1 Switching Table Router_Switch/031 CS 447 Networks and Data Communication

CPU Routing Algorithm Routing Table Routing Protocol Switching Fabric Memory SW Ctrl Unit Session Mngmnt STEP 2 Signaling message stored at STB Switching Table Router_Switch/032 No switching entry For this packet CS 447 Networks and Data Communication

CPU Routing Algorithm Routing Table Routing Protocol Switching Fabric Memory SW Ctrl Unit Session Mngmnt STEP 3 Signaling message sent to memory Routing will be performed for this packet Router_Switch/033 CS 447 Networks and Data Communication

CPU Routing Algorithm Routing Table Routing Protocol Switching Fabric Memory SW Ctrl Unit Session Mngmnt STEP 4 Router_Switch/034 CS 447 Networks and Data Communication

CPU Routing Algorithm Routing Table Routing Protocol Switching Fabric Memory SW Ctrl Unit Session Mngmnt STEP 5 Destination Host Address Output Port # Sender Host Address Output Port # Router_Switch/035 CS 447 Networks and Data Communication

SenderS1S2SnSnReceiver Path set-up at this switch Path set-up at this switch Path set-up at this switch Sender Host Address Output Port # Destination Host Address Output Port # Router_Switch/036 CS 447 Networks and Data Communication