1. CEG 2400 FALL 2012 Chapter 6 Network Hardware, Switching, and Routing 1

2. NICs (Network Interface Cards) Connectivity device (Common to every networking device) –Transceiver Transmits and receives data Enable device transmission Operates at the Physical and Data Link layer –Issue data signals –Assemble and disassemble data frames –Interpret physical addressing information Determines if client can transmit data Do not analyze information –Added by Layers 3 through 7 OSI model protocols 2

3. NICs (Network Interface Cards) NIC dependencies –Access method (EX. Ethernet) –Network transmission speed (1 Gbps) –Connector interfaces (RJ-45) –Method of connecting to the computers motherboard 3

4. How NICs connect Bus - signaling pathway in computer –Motherboard uses bus to transmit data to computer’s components Memory, processor, hard disk, NIC –Differ according to capacity Defined by data path width and clock speed –Data path size Parallel bits transmitting at any given time Proportional to attached device’s speed 4

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6. How NICs connect Expansion slots- Multiple electrical contacts on motherboard Expansion card (expansion board) –Circuit board for additional devices (NIC, sound card) –Inserts into expansion slot –Device connects to computer’s main circuit or bus –Computer centrally controls device 6

7. 7 Expansion Slots

8. How NICs connect Multiple bus types –PCIe bus: most popular expansion board NIC PCIe (Peripheral Component Interconnect Express) –32-bit bus –Maximum data transfer rate: 1 Gbps –Introduced in 2004 8 PCIe expansion board NIC

9. 9 Bus Types

10. How NICs connect Externally attached NICs –Simple installation into a variety of slots PCMCIA USB CompactFlash FireWire –Installing and configuring software may be required On-Board NICs –Connect device directly to motherboard –Advantages Saves space Frees expansion slots 10

11. How NICs connect 11 A USB NIC

12. How NICs connect 12 Motherboard with on-board NICs

13. Modular Interfaces –Changes network interfaces on connectivity devices –Hot-swappable components - Can be changed without disrupting operations GBIC (Gigabit interface converter) –May contain RJ-45 or fiber-optic cable ports –Now mostly Obsolete SFPs (small form-factor pluggable) –Provide same form factor as GBIC Allow more ports per inch 13

14. Modular Interfaces 14 SFP (small form-factor pluggable) transceiver for use with fiber connections GBIC (Gigabit interface converter) with an RJ-45 port

15. Repeaters and Hubs Repeaters –Operate in Physical OSI model layer –No means to interpret data –Just regenerates signal Hub –Repeater with more than one output port –Typically contains multiple data ports Patch cables connect printers, servers, and workstations –Most contain uplink port 15

16. Bridges Device that connect two network segments Operate at Data Link OSI model layer Single input and single output ports Protocol independent Analyze incoming frames and makes decisions on where to direct them by MAC address Filtering database –Contains known MAC addresses and network locations Not common anymore 16

17. Bridges 17 A bridge’s use of a filtering database

18. Switches Connectivity devices that subdivide a network into segments Traditional switches –Operate at Data Link OSI model layer Modern switches –Can operate at Layer 3 or Layer 4 (blurs line between switches and routers) Switches interpret MAC address information (just like bridge) Common switch components –Internal processor, operating system, memory, ports 18

19. 19 PC connecting to a Switch

20. Switches Advantages –Better performance and security Disadvantages –Can be overwhelmed by heavy traffic Four switching methods exist –Two basic methods discussed 1.Cut-through mode 2.Store-and-forward mode 20

21. Switching Methods Cut-through mode –Switch reads frame’s header only –Forwarding decision made before receiving entire packet Uses frame header: first 14 bytes which contains destination MAC address –Cannot verify data integrity using frame check sequence Cannot detect corrupt packets 21

22. Switching Methods Cut-through mode (cont’d.) –Advantage: speed –Disadvantage Data buffering (switch flooded with traffic) –Best use Small workgroups needing speed Low number of devices 22

23. Switching Methods Store-and-forward mode –Switch reads entire data frame into memory –Checks for accuracy before transmitting information (frame check) –Transmit data more accurately than cut-through mode –Slower than cut-through mode because reads entire frame –Best uses Larger LAN environments –Can transfer data between segments running different transmission speeds 23

24. VLANs VLANs (virtual local area networks) –Concept of partitioning a physical network –Logically separate networks not physical Groups ports into broadcast domain Broadcast domain –All nodes can reached each other by a broadcast message Collision domain –Data packets can collide with one another when being sent on a shared medium 24

25. 25 A simple VLAN design

26. VLANs Advantage of VLANs –Flexible Ports from multiple switches or segments grouped Any end node type (PCs, printers) can belong to VLAN –Reasons for using VLAN Separating user groups Isolating connections Identifying priority device groups Grouping legacy protocol devices Separating large network into smaller subnets 26

27. VLANs Switch typically preconfigured –One default VLAN –Cannot be deleted or renamed Create additional VLANs –Indicate to which VLAN each port belongs Maintain VLAN using switch software Potential problem –Cutting off group from rest of network 27

28. Show vlan command 28

29. Trunking –Switch’s interface carries traffic of multiple VLANs Trunk –Single physical connection between VLAN data separation (tag) –Frame contains VLAN identifier in header 29

30. VLANs and Trunking 30 Trunk for multiple VLANs

31. VLAN and Trunking 31

32. STP (Spanning Tree Protocol) IEEE standard 802.1D Operates in Data Link layer Prevents traffic loops –Calculating paths to avoid potential loops –Artificially blocks links completing loop Three steps –Select root bridge based on Bridge ID (lowest mac number) –Examine possible paths between network bridge and root bridge –Disables links not part of shortest path 32

33. 33 Enterprise-wide switched network

34. 34 STP-selected paths on a switched network

35. STP (Spanning Tree Protocol) History –Introduced in 1980s Original STP too slow responding to changes –RSTP (Rapid Spanning Tree Protocol) Newer version IEEE’s 802.1w standard Cisco and Extreme Networks –Have proprietary versions No enabling or configuration needed –Included in switch operating software 35

36. Content and Multilayer Switches Blurring lines between switches and routers Layer 3 switch (routing switch) - Interprets Layer 3 data Layer 4 switch - Interprets Layer 4 data Content switch (application switch) –Interprets Layer 4 through Layer 7 data Advantages of interpreting higher layers –Advanced filtering –Keeping statistics –Security functions Disadvantage – Cost, standards 36

37. Routers Multiport connectivity device –Integrates LANs and WANs Operate at Network layer (Layer 3) –Directs data between network nodes and from one segment or network to another –Uses logical addressing, Protocol dependent Slower than switches and bridges –Need to interpret Layers 3 and higher information Traditional stand-alone LAN routers –Being replaced by Layer 3 routing switches 37

38. Router Characteristics and Functions Intelligence –Determine shortest, fastest path between two nodes –Connects dissimilar network types Large LANs and WANs –Routers indispensable Router components –Internal processor, operating system, memory, input and output jacks, management control interface 38

39. Router Characteristics and Functions Multiprotocol routers –Multiple slots –Accommodate multiple network interfaces Inexpensive routers –Home, small office use Router capabilities –Interpret Layer 3 addressing –Determine best data path –Reroute traffic 39

40. 40 Routers

41. Router Types and Terms Interior router –Directs data between nodes on a LAN Exterior router –Directs data between nodes external to a LAN Border routers –Connect autonomous LAN with a WAN Routing tables (database) –Maintain information where hosts are and how to reach them Static routing –Router configured to use specific path between nodes Dynamic routing –Automatically calculates best path between nodes 41

42. 42 The placement of routers on a LAN

43. Routing Protocols How to decide on best path –Path is decided by routing protocol Routing metric factors –Number of hops –Throughput on potential path - Transmission speed –Delay on a potential path - Current network activity –Load (traffic) –Maximum transmission unit (MTU) –Reliability of potential path - Unavailable link –Cost (assigned by administrator) 43

44. Routing Protocols Router Convergence Time (con’t) –The time the router takes to recognize best path after change or network outage event 44

45. Routing Protocols 45 Summary of common routing protocols

46. Routing Protocols Distance-vector type routing protocols - RIP, RIPv2, BGP –Determine best route based on distance to destination –Factors Hops, latency, network traffic conditions RIP (Routing Information Protocol) –Only factor is number of hops between nodes Limits 15 hops –Type of IGP (Interior Gateway Protocol) Can only route within internal network –Slower and less secure than other routing protocols 46

47. Routing Protocols RIPv2 (Routing Information Protocol Version 2) –Generates less broadcast traffic, more secure than RIP –Cannot exceed 15 hops –Less commonly used BGP (Border Gateway Protocol) –Type of EGP (Exterior Gateway Protocol) –Most complex (choice for Internet traffic) –Communicates using BGP-specific messages –Many factors determine best paths –Configurable to follow policies 47

48. Routing Protocols Link-state type routing protocol – OSPF and IS-IS –Routers share information Each router independently maps network, determines best path OSPF (Open Shortest Path First) –Interior or border router use –No hop limit –Complex algorithm for determining best paths –Each OSPF router Maintains database containing other routers’ links 48

49. Routing Protocols IS-IS (Intermediate System to Intermediate System) –Codified by ISO –Interior routers only! –Supports two Layer 3 protocols IP ISO-specific protocol –Much less common than OSPF 49

50. Routing Protocols Hybrid type routing protocol - EIGRP –Link-state and distance-vector characteristics –EIGRP (Enhanced Interior Gateway Routing Protocol) Most popular Cisco network routers only! –EIGRP benefits Fast convergence time, low network overhead Easier to configure and less CPU-intensive than OSPF Supports multiple protocols Accommodates very large, heterogeneous networks 50

51. Gateways and Other Multifunction Devices Gateway –Combination of networking hardware and software –Connects two systems that use different formatting, communications protocols, architecture –They repackages information –Can reside on servers, microcomputers, connectivity devices, mainframes Popular gateways –Firewall, E-mail gateway, Internet gateway, voice/data gateway, LAN gateway 51

52. Summary Network adapter types vary (NIC) Repeaters - Regenerate digital signal Hubs Bridges can interpret the data they retransmit Switches subdivide a network –Create VLANs –Trunking Routers –Various routing protocols Gateways 52

53. End of Chapter 6 Questions 53