Networking Devices

1. Networking Devices Bridging the gap, switching the way we communicate, routing us to new places, repeating what needs to be stronger – our hub for communication!

2. So what devices are there? The main players: • Repeaters • Hubs • Bridges • Switches • Routers • Gateways

3. 7 -Application 6 - Presentation 5 - Session 4 - Transport 3 - Network 2 – Data Link 1 - Physical Repeaters • Simplest networking device • Operates at Layer 1 of the OSI model • Receives a signal, cleans it up, regenerates it and passes it on • Extends the coverage of a network • Can only be used with similar networks • i.e. - 2 Ethernet OR 2 token ring NOT Ethernet to token ring • Can increase network traffic, so must consider placement and use

4. Repeater example: 1. Signal sent Repeater 2. Signal repeated to other section of network

5. 7 - Application 6 - Presentation 5 - Session 4 - Transport 3 - Network 2 – Data Link 1 - Physical Hubs • A central point of connection for many nodes/network devices • Essentially a repeater with many ports • Message comes in on 1 port and is then sent out on all ports to all attached devices • Pass along all data that they receive no matter where it is addressed to

6. Hub example: Hub receives message and send it to all attached devices Hub

7. 7 - Application 6 - Presentation 5 - Session 4 - Transport 3 - Network 2 – Data Link 1 - Physical Bridges • Can be used to split up a large network and reduce traffic (2 or more segments) • Operates at Layer 2 of the OSI model • Use MAC addresses for sending packets • Creates a bridging table to track locations of nodes on the network – learn as they go • Performs filtering and (selective) forwarding • Uses the Spanning Tree Protocol (STP) • Types: • Transparent • Translating

8. Filtering and Forwarding • Filtering • Examines each frame to decide whether it is on the correct network – this reduces excessive and unnecessary traffic often created by repeaters • Forwarding • Sends frames to the segment designated – (expressed in frames/second) Higher filtering and forwarding rates are what indicate the quality and performance of a bridge!

9. Spanning Tree Protocol (STP) • Used to decide whether to forward a packet to another segment • Two purposes: • Determines the “root” bridge responsible for decisions and problems • Prevents bridging loops • If a bridge repeats to one segment and that bridge were to repeat back to the original segment a “loop” would be created that would waste valuable resources and create unnecessary traffic

10. Spanning Tree Example: • Selects Root bridge • Designates root ports for forwarding • Other ports block traffic to prevent redundancy Loop free!!! Bridge A - ROOT Bridge C Forwarding ports Bridge B X Blocking port http://www.kulnet.kuleuven.ac.be/doc/kulnetdoc/kulnetdoc-2001-5.pdf

11. Types of bridges • Transparent • Connect LANs using the same protocol • Ethernet/Ethernet OR Token ring/Token ring • Translating • Connect LANs that use different protocols • Ethernet/Token ring • Translates between the different protocols

12. #1 #2 #3 A E I B F J C G K D H L Bridge example: E F G H #2 2. Bridge knows G is on #2 so only sends to #2 Bridge A B I J 1. Packet sent from B to G #1 #3 K L C D

13. Source: Internetworking Design Strategies: Segmentation, Goldman, Wiley Pareto principle of networks

14. 7 - Application 6 - Presentation 5 - Session 4 - Transport 3- Network 2 – Data Link 1 - Physical Switches • Allow different nodes to communicate directly • Connect directly by keeping track of the MAC addresses of each attached device • Connects 2 nodes long enough to transfer the current packet • Reduce traffic by creating separate collision domains • Each port on a switch is its own collision domain • Types: • Cut-through • Store-and-forward Most switches operates on Level 2 of the OSI model!

15. Types of switching • Cut-through • Read the MAC address • Store the first 6 bytes (address info.) • Sends packet to destination • Store-and-forward • Reads the entire packet and stores it in the buffer • Performs error checking • Removes bad packets • Sends the packet to destination Cut-through is faster than store-and-forward!!!

16. Switch example: 3. Switch looks up MAC address and sends to destination node 1. Switch receives message Switch 2. Switch reads all or part of message

17. 7 - Application 6 - Presentation 5 - Session 4 - Transport 3- Network 2 – Data Link 1 - Physical Routers • Forward data – but are more advanced than bridges • Operates at Layer 3 of the OSI model • Use IP addresses (not MAC) to send data • Used to interconnect different types of networks • Connect LAN segments within a building or even across the country • Create routing tables (using IP info.) in order to select the best route to send data • Static or dynamic routing • Various protocols can be used (RIP, IRGP, OSPF, etc.)

18. Router example: A Routing table #1 Dest. Path N 2 N 3,2 Routing table #3 #3 #1 Dest. Path A 1 A 2,1 1. Router receives message from A for N and consults routing table N #2 2. Router sends message through alternate path due to traffic (dynamic routing) Routing table #3 Dest. Path A 1 A 3,1

19. 7- Application 6 - Presentation 5 - Session 4 - Transport 3- Network 2 – Data Link 1 - Physical Gateways • Network point (node) that acts as an entrance/exit to other networks • Gateway features: • Protocol translator • Signal translator • Rate converter • Fault isolator

20. 7- Application 6 - Presentation 5 - Session 4 - Transport 3- Network 2 – Data Link 1 - Physical Gateways • Equipped for interfacing with another network that uses different protocols or communication methods • Example: Countries or continents can use different methods for digital transmission as long as gateways are used to connect them • Uses Media Gateway Control Protocol (MGCP) (a.k.a. H.248 and MEGACO) • Handling the signaling during a multimedia session • Operates at Layer 7 of the OSI model

21. Gateway example: WLAN#1 Makes connection possible due to protocol translator! 2. Gateway receives message and translates the protocol due to different protocols on LAN#1 and WLAN#1 K 3. Gateway consults gateway routing table and sends the message to K Gateway /Hot spot LAN#2 Internet Internet LAN#1 Gateway A Gateway 1. Gateway receives message from A for K and consults gateway routing table

22. All of these devices come together in order to make up the networks that we know today. Without these devices the Internet would not be possible!

23. Now, let us examine how the Internet actually works

24. ‘Dem bones, ‘dem bones… • 1969: Kai was born/ARPANET commissioned by DoD • 1973: ARPANET goes international (satellite link) • 1980: ARPA began converting machines to TCP/IP protocol • 1983: Transition to TCP/IP completed • 1985: NSF got involved in Internet • 1986: Backbone called NSFNET was built, and several regional nets connected to it (speeds of 56Kbps) • 1988: NSFNET backbone upgraded to T1 (~1.5Mbps) • 1991: NSFNET backbone upgraded to T3 (~45Mbps) • 1995: NSFNET reverts back to research network. Traffic now routed through interconnected network providers • 1996: MCI upgrades backbone to 622Mbps • 1999: Internet 2 launched. • 1999: MCI starts upgrading backbone to 2.5Gbps • Currently, private carriers such as MCI, Sprint, Qwest, and Level(3) have emerged for carrying Internet traffic. They exchange traffic between their respective backbones at peering points located in various major cities around the country. Source: http://www.zakon.org/robert/internet/timeline/

25. Internet Backbones

26. Internet growth

27. IP Addressing Schemes CIDR - Classless Internet Domain Routing does away with this kind of class system in order to allow better use of address space. Example: 206.13.01.48/25

28. Domain name addressing (DNS) • john@rastro.colorado.edu • Highest level domain: edu, gov, mil, org, etc. • Colorado is a sub-domain within edu • Rastro is a sub-sub-domain within colorado • John is a user in this host machine. DNS is like a directory enquiry service on the Internet.

29. IP: Connectionless Delivery System • Basic transfer unit is called a IP Packet Packet header Data Area • Service is connectionless because each packet is • treated independently of others • Service is unreliable because delivery not • guaranteed. • Uses best-effort deliverybecause the software • makes an earnest attempt to deliver packets.

30. IP Header Packet format

31. Routing IP Packets • Direct delivery between machines in the same Area or Autonomous System using OSPF. • Indirect delivery between machines in different Autonomous Systems using BGP. • Hosts and routers maintain routing tables containing: (network, router) pairs where network: destination network number router: address of next router • Default routes used when no entry in the routing table.

32. TCP: Transmission Control Protocol TCP header Data TCP is a software protocol which specifies : • Format of the data and acknowledgements that computers exchange for reliable and sequenced delivery. • How to distinguish multiple destinations on a given machine. • How machines recover from errors like lost or duplicated packets. • How two computers initiate a TCP stream transfer and how they agree it is complete.

33. Next Generation IP - (Ipv6) Objectives • Support billions of hosts. • Reduce size of routing tables. • Simplify the protocol for faster routing. • Provide better security. • Pay more attention to type of service, especially real-time data. • Make it possible for host to roam without changing address. • Allow the protocol to evolve in future. • Permit the old and new protocols to coexist for years. • Provide better security than current IP. • Will maintain compatibility with existing IP protocol. Source: Tanenbaum, Computer Networks, Prentice-Hall.

34. IPv6 Fixed header Version Priority Flow Label Payload Length Next header Hop Limit Source Address (128 bits) Destination Address (128 bits) • This is a required header. • There can also be optional, extension headers.

35. Summary • Bridges and Routers are the mainstays of internetworking. • Newer devices such as switches emerged in response to need for higher throughput. • Several internetworking strategies can be employed to improve performance. • Internet has about 400 million hosts* and is still growing exponentially! • TCP/IP is the lingua franca of the Internet. Internet domain survey, January, 2001 -- http://www.isc.org/ds/