atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Telecom Service & Providers FRAME RELAY (FR/IFR/ATM/IMA)

Good day fellow technicians,

Starting in-house, where would you start troubleshooting frame relay (FR/IFR/ATM/IMA), if you were with AT&T? What would you expect to see from the cloud as well as some of the fals and trouble readings. What does the cloud tell you? How do you read information coming from the cloud? What are the readings from the customer? Directions of INGRESS/EGRESS. Who is who from the companies standpoint?

Thank you,

Elsevier Lippincott

Frame relay operates at layer 2 of the OSI model, which means it works very different then IP. When you order a frame relay circuit you are given a PVC (Permanent Virtual Circuit) that has a numaricFrame relay operates at layer 2 of the OSI model, which means it works very different then IP. When you order a frame relay circuit you are given a PVC (Permanent Virtual Circuit) that has a numeric identifier called a DLCI. This DLCI number is locally significant which means the numbers can be the same on both sides. The DLCI numbers are typically mapped to IP address. The local circuit has no way of knowing what the far end DLCI number is. There is a process by which local DLCI number can be acquired and it is called iARP (inverse ARP). LMI is kind of a keepalive messaging service that frame relay communicates with. It send all kinds of information to the adjacent switch and the DLCI numbers are some of the information. I have run a debug from a DS-3 circuit in my NOC to see what raw LMI looks like coming in from the phone company.

May 17 20:08:25: Serial1/0(in): Status, myseq 62, pak size 13
May 17 20:08:25: RT IE 1, length 1, type 1
May 17 20:08:25: KA IE 3, length 2, yourseq 61, myseq 62
May 17 20:08:35: Serial1/0(out): StEnq, myseq 63, yourseen 61, DTE up
May 17 20:08:35: datagramstart = 0x3F4658D4, datagramsize = 13
May 17 20:08:35: FR encap = 0xFCF10309
May 17 20:08:35: 00 75 01 01 01 03 02 3F 3D
May 17 20:08:35:
May 17 20:08:35: Serial1/0(in): Status, myseq 63, pak size 13
May 17 20:08:35: RT IE 1, length 1, type 1
May 17 20:08:35: KA IE 3, length 2, yourseq 62, myseq 63
May 17 20:08:45: Serial1/0(out): StEnq, myseq 64, yourseen 62, DTE up
May 17 20:08:45: datagramstart = 0x3F2019D4, datagramsize = 13
May 17 20:08:45: FR encap = 0xFCF10309
May 17 20:08:45: 00 75 01 01 00 03 02 40 3E
May 17 20:08:45:
May 17 20:08:45: Serial1/0(in): Status, myseq 64, pak size 229
May 17 20:08:45: RT IE 1, length 1, type 0
May 17 20:08:45: KA IE 3, length 2, yourseq 63, myseq 64
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 101, status 0x0 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 102, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 103, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 104, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 105, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 106, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 107, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 108, status 0x0 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 109, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 110, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 111, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 112, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 113, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 114, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 115, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 116, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 117, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 118, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 119, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 120, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 121, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 122, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 123, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 124, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 125, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 126, status 0x2 , bw 768000
May 17 20:08:45: PVC IE 0x7 , length 0x6 , dlci 127, status 0x2 , bw 768000
May 17 20:08:55: Serial1/0(out): StEnq, myseq 65, yourseen 63, DTE up
May 17 20:08:55: datagramstart = 0x3F465294, datagramsize = 13
May 17 20:08:55: FR encap = 0xFCF10309
May 17 20:08:55: 00 75 01 01 01 03 02 41 3F
May 17 20:08:55:

Notice all of the DLCI number acquired also note the myseq is incrementing.

Frame relay differs significantly from a typical point-to-point circuit significantly insofar as with frame you “share” the pipe with many other subscribers. Since the pipe is a PVC it is not like communications is possible between people on the same switch, unless the phone company sets up PVCs like that due to customer request. The ILEC owns the frame switch and gives a certain amount (CIR – Committed Information Rate) to its subscribers. The CIR is a commitment, usually they will give you burstable speed also. There might be 100 frame switches between a-z and that is a don’t care, as long as the phone company does its mapping correct you are good to go. This is what is known to the subscriber, the “cloud” is not his concern.



Your question was from a carrier perspective so let me give you some perspective from that. The phone company controls all of the internal mapping, usually this is done from DS-1 to DS-3 and so on.

Troubleshooting:

1) Determine if you getting LMI. Do a debug frame-relay lmi from exec mode. If you are telneted make sure you have term mon on. There are different flavors of LMI but the newer IOSs will autodetect it.
2) Make sure you are using the correct encapsulation type. The two main ones are IETF and Cisco.
3) Make sure your network topology is configured appropriately for the network. The two main ways are point-to-point and point-to-multipoint. Point-to-point is much easier to configure if you are not comfortable use that.
4) Make sure your mapping is correct. Do a show frame-relay map and show frame-relay pvc and a show ip interface brief.

This is the very basics of frame I hope this helps.

Greg

I am not going to bombard this site with lengthy gratitudes, but WOW! I am truly thankful to you, Greg, for unselfishly departing many years of knowledge with me. Please, visit the T-1, CSU and Dsu site and add your expertise.

Again, thank you.

Elsevier Lippincott

No problem any time. I hope this information was beneficial.