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Any Questions?. Ch 13- Frame Relay Concepts. Frame Relay Overview Frame Relay Addressing Network Layer Concerns with Frame Relay Controlling Speed and Discards in the Frame Relay Cloud. Do I know this?. Go through the Quiz- 5 minutes.

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  1. Any Questions?

  2. Ch 13-Frame Relay Concepts • Frame Relay Overview • Frame Relay Addressing • Network Layer Concerns with Frame Relay • Controlling Speed and Discards in the Frame Relay Cloud

  3. Do I know this? Go through the Quiz- 5 minutes

  4. 1. Which of the following is a protocol used between the Frame Relay DTE and the Frame Relay switch? a. VC b. CIR c. LMI d. Q.921 e. DLCI f. FRF.5 g. Encapsulation

  5. 1. Which of the following is a protocol used between the Frame Relay DTE and the Frame Relay switch? a. VC b. CIR c. LMI d. Q.921 e. DLCI f. FRF.5 g. Encapsulation Answer: C

  6. 2. Which of the following statements about Frame Relay are true? a. The DTE typically sits at the customer site. b. Routers send LMI messages to each other to signal the status of a VC. c. A frame’s source DLCI must remain unchanged, but the frame’s destination DLCI is allowed to change, as the frame traverses the Frame Relay cloud. d. The Frame Relay encapsulation type on the sending router should match the encapsulation type on the receiving router for the receiving router to be able to understand the frame’s contents.

  7. 2. Which of the following statements about Frame Relay are true? a. The DTE typically sits at the customer site. b. Routers send LMI messages to each other to signal the status of a VC. c. A frame’s source DLCI must remain unchanged, but the frame’s destination DLCI is allowed to change, as the frame traverses the Frame Relay cloud. d. The Frame Relay encapsulation type on the sending router should match the encapsulation type on the receiving router for the receiving router to be able to understand the frame’s contents. Answer: A &D

  8. 3. What does DLCI stand for? a. Data-link connection identifier b. Data-link connection indicator c. Data-link circuit identifier d. Data-link circuit indicator Answer: A

  9. 4. Router R1 receives a frame from router R2 with DLCI value 222 in it. Which of the following statements about this network is the most accurate? a. 222 represents Router R1. b. 222 represents Router R2. c. 222 is the local DLCI on R1 that represents the VC between R1 and R2. d. 222 is the local DLCI on R2 that represents the VC between R1 and R2.

  10. 4. Router R1 receives a frame from router R2 with DLCI value 222 in it. Which of the following statements about this network is the most accurate? a. 222 represents Router R1. b. 222 represents Router R2. c. 222 is the local DLCI on R1 that represents the VC between R1 and R2. d. 222 is the local DLCI on R2 that represents the VC between R1 and R2. Answer: C

  11. 5. A Frame Relay planning diagram shows the number 101 beside R1, 102 by R2, 103 by R3, and 104 by R4. No other DLCIs are listed. The lead network engineer tells you that the planning diagram uses global DLCI addressing and that a full mesh of VCs exists. Which of the following are true? a. Frames sent by R1 to R2, as they cross R2’s access link, have DLCI 102. b. Frames sent by R1 to R2, as they cross R2’s access link, have DLCI 101. c. Frames sent by R3 to R2, as they cross R3’s access link, have DLCI 102. d. Frames sent by R3 to R1, as they cross R3’s access link, have DLCI 102.

  12. 5. A Frame Relay planning diagram shows the number 101 beside R1, 102 by R2, 103 by R3, and 104 by R4. No other DLCIs are listed. The lead network engineer tells you that the planning diagram uses global DLCI addressing and that a full mesh of VCs exists. Which of the following are true? a. Frames sent by R1 to R2, as they cross R2’s access link, have DLCI 102. b. Frames sent by R1 to R2, as they cross R2’s access link, have DLCI 101. c. Frames sent by R3 to R2, as they cross R3’s access link, have DLCI 102. d. Frames sent by R3 to R1, as they cross R3’s access link, have DLCI 102. Answer: B&C

  13. 6. FredsCo has five sites, with routers connected to the same Frame Relay network. Virtual circuits (VC) have been defined between each pair of routers. What is the fewest subnets that FredsCo could use on the Frame Relay network? a. 1 b. 2 c. 3 d. 4 e. 5 f. 10

  14. 6. FredsCo has five sites, with routers connected to the same Frame Relay network. Virtual circuits (VC) have been defined between each pair of routers. What is the fewest subnets that FredsCo could use on the Frame Relay network? a. 1 b. 2 c. 3 d. 4 e. 5 f. 10 Answer: A

  15. 7. BarneyCo has five sites, with routers connected to the same Frame Relay network. VCs have been defined between each pair of routers. Barney, the company president, will fire anyone who configures Frame Relay without using point-to-point subinterfaces. What is the fewest subnets that BarneyCo could use on the Frame Relay network? a. 1 b. 4 c. 8 d. 10 e. 12 f. 15

  16. 7. BarneyCo has five sites, with routers connected to the same Frame Relay network. VCs have been defined between each pair of routers. Barney, the company president, will fire anyone who configures Frame Relay without using point-to-point subinterfaces. What is the fewest subnets that BarneyCo could use on the Frame Relay network? a. 1 b. 4 c. 8 d. 10 e. 12 f. 15 Answer: D

  17. 8. R1 sends a Frame Relay frame over a VC to router R2. About the same time, a Frame Relay switch notices that too many packets are trying to exit the Frame Relay network over the access link connected to R2. Which of the following is the most likely result that could be caused by this scenario? a. R1 eventually receives a frame with BECN set. b. R1 eventually receives a frame with FECN set. c. R1 eventually receives a frame with DE set. d. None of the other answers is correct.

  18. 8. R1 sends a Frame Relay frame over a VC to router R2. About the same time, a Frame Relay switch notices that too many packets are trying to exit the Frame Relay network over the access link connected to R2. Which of the following is the most likely result that could be caused by this scenario? a. R1 eventually receives a frame with BECN set. b. R1 eventually receives a frame with FECN set. c. R1 eventually receives a frame with DE set. d. None of the other answers is correct. Answer: A

  19. Any Questions?

  20. Overview • PPP-usually enterprise will get a leased line from telco • Dedicated circuit • Each connection requires a physical interface • Frame-Relay lets you leverage the telco “cloud” • Can support multiple connections on same physical interface Pg 461

  21. Frame Overview • Multiaccess network • Multiple machines can connect • Nonbroadcast • Will not send data link brodcasts Pg 461

  22. Frame Components Pg 462

  23. Components • Leased line from Router to Frame Switch • Router is DTE • Switch is DCE • Router and Switch communicate with Local Management Interface • LMI • Connection from R1 to R2 is by Virtual Circuit • You share connection, but it seems like a leased circuit to your router Pg 462

  24. Key Terms Pg 463

  25. Any Questions?

  26. Standards • Cisco • IETF • ITU • ANSI Pg 464

  27. Virtual Circuits • Defines a logical path between tow Frame Relay DTEs • VC acts like a point-to-point connection • No true dedicated circuit • Share bandwidth with other frames • Bandwidth is assured with Committed Information Rate • CIR is assigned per VC Pg 465

  28. Frame VCs • Costs less since a single access link can support multiple VCs • 100 sites would need 4950 physical links • 100 sites need 4950 VCs but only 100 physical links • Permanent virtual Circuits (PVC) • Predefined by telco • Switched Virtual Circuit • Dynamically created on the fly Pg 465

  29. Full Vs. Partial Mesh • Full Mesh • Each location has a VC to each other location • Partial Mesh • Combination of multiple links and sinlge, point to point links • Hub and spoke Pg 465

  30. Partial Mesh • R1 has multiple connections • R2 only connects to R1 • No fully meshed Pg 466

  31. Any Questions?

  32. Virtual Circuits • Since a single access link can support multiple VCs, the system must be able to identify them • Data Link Connection Identifier (DLCI) • Identifies the link (VC) to the destination Pg 466

  33. LMI and Encapsulation • LMI is management between Router and Frame-Switch • Not and end to end link • Like a keepalive • Three choices • Cisco • ITU • ANSI Pg 467

  34. LMI • They perform a keepalive function between the DTE and DCE. If the access link has a problem, the absence of keepalive messages implies that the link is down. • They signal whether a PVC is active or inactive. Even though each PVC is predefined, its status can change. An access link might be up, but one or more VCs could be down. The router needs to know which VCs are up and which are down. It learns that information from the switch using LMI status messages. Pg 467

  35. LMI Pg 468

  36. Encapsulation • Describes the Header style • Like PPP or Ethernet Frame • Original Header didn’t have protocol Type field • Cisco and IETF both have solutions Pg 469

  37. Any Questions?

  38. Frame Relay Addressing • DLCI • There is only one DLCI field • No source and destination • Local Addressing • DLCI’s are locally significant • A DLCI can exist in mulitple places in the telco network, only has to be unique on access link (physical interface) • Remember-DLCI defines link to destination Pg 469

  39. DLCI Example • B and C can both use 40 • 40 refers to a VC to Router A Pg 470

  40. Frame Relay Global Addressing • Set up by telco/Provider • Gives a DLCI to each location • Thus the dlci identifies the destination • Program routers with the DLCI of the destination • Either mapping or inverse arp(see page 492-497) Pg 470

  41. Global Addressing Example Pg 471

  42. DLCI and Frame Switches • When a router sends the frame, the DLCI is the destination • En route, the Telco Frame Switches change this to the source • When a router receives a frame, the DLCI is the source • Can be used as reply-to address Pg 472

  43. DLCI Addressing Pg 472

  44. DLCI Global Addressing • If two VCs terminate at the same DTE, and a single DLCI is shown, it probably represents the global DLCI convention • If one DLCI is shown per VC, local DLCI addressing is depicted. Pg 473

  45. Any Questions?

  46. Network Layer issues • One subnet containing all Frame Relay DTEs • Usually Full Mesh • One subnet per VC • Hub and Spoke • A hybrid of the first two options • Partial Mesh Pg 474

  47. Full-Mesh addressing-Single Subnet Pg 474

  48. One Subnet per VC-Point to Points Pg 475

  49. Hybrid-Partial Mesh Pg 477

  50. Multipoint Subinterface • Terminate more than one VC • single subnet for point to pont • Shared subnet for meshed sections Pg 477

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