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EXP Computer S200 Figure 49. Before Local Termination Example, Figure 50. After Local Termination Example

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Bridging 101

T0008-16F Release 5.2M

LLC2 Local Termination

Before Local

Termination Without Local Termination, networks face significant problems with bandwidth

usage and session timeouts due to polling overhead between the host and termin al, as

well as network delays.

For example, Figure49 shows a terminal session on a source route bridged Token

Ring LAN connected to a host without Local Termination. During the terminal

session, LLC2 polls, such as ACKs and keepalives, are exchanged between the host

and the terminal session, causing:

• Inefficient use of the WAN bandwidth

• Increased session timeouts

• Ongoing tuning of network parameters to fix session timeouts

Figure 49. Before Local Termination Example

You can increase timer values to reduce the number of session timeouts experienced

on a network, but configuring large numbers of stations makes such a solution

impractical. Moreover, it does not solve the problem with “keepalives” slowing

down network traffic.

After Local

Termination The best solution to such network traffic problems is to locally terminate the LLC2

session at the Token Ring interface, as shown in Figure 50.

Figure 50. After Local Termination Example

Using LLC2 LT, you can spoof traffic on a Token Ring LAN, reducing the polling

overhead by minimizing session timeouts. Ack and “keepalive” messages traverse

the network between spoofers; they are controlled in frequency by the WAN

parameters.

SNA

FEP CC

LLC2

Keepalives/Acks

Before

SNA

FEP CC

LLC2

Keepalives/Acks

LLC2

Keepalives/Acks After

Contents

Main Notice Restricted Rights Notification for U.S. Government Users Restricted Rights Legend Notice Notice (continued) Proprietary Material Page Bridging Overview Figure 1. PathBuilder S200 Series Switch Bridge Combining Traffic from Serial Devices Page Page Page Bridging Features and Capabilities Figure 2. Example of Typical PathBuilder S200 Series Switch Bridging Application Ethernet LAN Figure 3. Frame Format for Ethernet Frames Figure 4. 802.3 Ethernet MAC Frame Format Example Figure 5. Ethernet Bridge Example Mixed LAN Bridging Figure 6. Example of Mixed LAN Bridging in PathBuilder S24x, 26x, and 27x Switch MAC Addressing LLC2 Local Termination Figure 7. Local Termination Example Autolearn for Local Termination Figure 8. Example of Local Termination Autolearn Filtering Spanning Tree Protocol Dual Ethernet LANs Basic Remote Bridging Examples Figure 9. PB S200s Connecting LANs via an X.25/Frame Relay Link Figure 10. Two-Port Bridges Connecting Multiple Token Ring LANs Figure 11. Example of Bridges in an SVC Arrangement Bridge Hardware Components in PathBuilder S200 Series Switches Figure 12. LAN Port Module and WAN Adapter Module (Logical View) Page Setting Up WAN Operation for Bridging Figure 13. Interface Connections Between WAN and LAN Page Configuring the PathBuilder S200 Series Switch for Bridging Operation Bridge Parameters Figure 14. Configure Bridge Parameters Page Page Page Bridge Link Parameters Figure 15. Configure Bridge Link Menu Page Page Page Page LAN Connection Table Figure 16. LAN Connection Table Menu Page Page Page Limiting Bridge Frame Sizes Figure 17. How Packet Size Affects Transit Delay Max Frame Size Line Speed Range (kbps) Configuring Translational Bridging 38 Bridging Configuring the PathBuilder S200 Series Switch for Bridging Operation Figure 18. Translational Bridging Example Figure 19. Translational Bridging Point-to-Point Example Bridge Frame Handling Configuring Source Route Bridging Operation Figure 20. LAN/WAN Bridge Links Used in PathBuilder S200 Series Switch LAN Network Page Connecting a Station to a Server in Source Route Bridging Figure 21. Example of a Station to Server Configuration Figure 22. Servers Destination MAC Address Not on LAN AAA Figure 23. All Route Explorer (ARE) Frame Searches the Network for the Server Figure 24. PathBuilder S200 Series Switch Transfers a Copy of ARE Frame to the Bridge Module Bridging 45 Configuring the PathBuilder S200 Series Switch for Bridging Operation Figure 25. WAN Adapter Transmits Each ARE Frame Across the WAN Figure 26. Server Responds with Specifically Routed TEST Frame If... Then... Transparent Bridging for Ethernet LANs Bridging 49 Transparent Bridging for Ethernet LANs Figure 27. How the Forwarder and Hardware Accelerator Process a Frame NO NO Figure 28. Relationship of Forwarder and Hardware Accelerator to LAN and WAN Handlers Page Page Forwarder Database and Spanning Tree Using Filters Page Transparent Bridge Configuration Parameters Figure 29. Transparent Bridge (TB) Forwarding Table Menu Bridge Filtering unnecessary MAC Address Filtering Parameter Action Parameter Action (continued) Parameter Value Action 60 Bridging Bridge Filtering Figure 30. MAC Address Filtering Action MAC Filtering Process Figure30 shows the MAC Filtering process. Figure 31. Example of a Frame Passing on a Bridge Link MAC Address Filtering Examples Figure 32. Example of Bridge Links Configured to Filter Selected MAC Address Frames Parameter Values Page Identifying Address Links for MAC Addressing Figure 33. Example of Address Links MAC Wildcard Filtering Figure 34. Example of How MAC Wildcard Filtering Works Configuring the MAC Address Filter Table Figure 35. MAC Address Filter Table Menu Page Page Page Protocol Filtering Configuring the Protocol Filter Table Figure 36. Configure Protocol Filter Table Menu Protocol SAP (hex value) Protocol OUI/IP (hex value) Page Figure 37. Protocol ID DSAP Located in LLC Field Figure 38. SNAP Protocol ID Parameter Action(s) NetBIOS Name Filtering Figure 39. NetBIOS Name Filtering Configuration Example Page Configuring NetBIOS Name Filtering Figure 40. Bridge Link Parameters Record Step Action Page Figure 41. Configure Bridge Menu Page Page Page NetBIOS Name Filtering Statistics Figure 42. Detailed Bridge Link Statistics NetBIOS Packet Formats Spanning Tree Protocol Entity (STPE) Configuration Menu STPE Control= AUTO STPE Control = MANUAL Page Page STPE Parameter Setting Considerations Figure 43. Example of a Bridge Network Figure 44. Example of Bridge ID and MAC Address 80-00 08-00-3E-02-53-8F MAC Address Bridge Priority Type of Network Speed STPE Path Cost Figure 45. Bridge Links Within Network Figure 46. Two Bridge Links Between B3 and B4 Page Spanning Tree Timers Page Bridge Forward Delay Timer Figure 47. Message Events in Network Page Page LLC2 Local Termination Figure 48. Local Termination Example Figure 49. Before Local Termination Example Figure 50. After Local Termination Example Figure 51. Example of Improper LT Configuration Figure 52. Example of Proper LT Configuration Type Name Description Figure 53. Example of LT Spoofing Local Termination spoofs: Local Termination does not spoof: Page Configuring Local Termination Step Action Step Action (continued) Result Page Page Page Page Page Deleting LT Configuration Records Mixed LAN Operation Figure 54. Example of Mixed LAN Bridging in PathBuilder S24x, 26x, and 27x Switch Page Step Action (continued) Result/Description Dual LAN Ethernet Figure 55. Example of Multiple Ethernet LAN Page Page LAN Server Subsystem Page Configuring the LSS Record Figure 56. LAN Server Subsystem (LSS) Record Menu Page Bridge Statistics Figure 57. The Bridge Statistics Menu Screen Spanning Tree Statistics Figure 58. Spanning Tree Status Page Bridging 127 Detailed Bridge Link Statistics Introduction Figure59 and Figure 60 show sample statistics screens. Figure 60. Detailed Bridge Link Statistics - Second Page Figure 59. Detailed Bridge Link Statistics - First Page Page Page Bridge Link Filter Summary Figure 61. Bridge Link Filter Summary Status Page Transparent Bridge Forwarding Table Statistics Figure 62. Transparent Bridge Forwarding Table Statistics Page Transparent Bridge Detailed Bridge Link Statistics Figure 63. Detailed Bridge Link Statistics (TB) - Second Page Term Description (continued) LAN Connection Statistics Figure 64. LAN Connection Statistics Menu Screen Figure 65. Detailed LAN Connection Statistics - First Page Figure 66. Detailed LAN Connection Statistics - Second Page Bridging 137 Page Page Figure 67. LAN Connection Summary Statistics LLC2 LT Session Summary Statistics Figure 68. Session Summary Statistics Screen Heading Description Page Bridging 143 LLC2 LT Detailed Session Statistics Figure 70. Detailed Session Statistics Screen - Page 2 Figure 69. Detailed Session Statistics Screen - Page 1 Heading Description Local Station Session Summary Heading Description (continued) Remote Spoofer Session Summary Heading Description (continued) Reset Statistics Page Appendix A Technical Support Country Data Rate Telephone Number Country Telephone Number Country Telephone Number Country Telephone Number Fax Number Index