Frame Relay & ATM
description
Transcript of Frame Relay & ATM
![Page 1: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/1.jpg)
Frame Relay & ATM
1
Lecture 7
Paul Flynn
![Page 2: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/2.jpg)
2
Virtual Circuit SwitchingVirtual Circuit Switching
Digital Line Connection Identifier (DLCI)
Three Phases
Data Transfer Phase
Setup Phase
Teardown Phase
![Page 3: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/3.jpg)
3
Virtual circuit wide area network
Frame Relay does not provide flow or error control; they must be provided by the upper-layer protocols.
Frame Relay operates only at the physical and data link layers.
![Page 4: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/4.jpg)
4
A 'local identifier' between the DTE and the DCE, it identifies the logical connection that is multiplexed into the physical channel.
Value that specifies a PVC in a Frame Relay network.
In the basic Frame Relay specification, DLCIs are 'locally significant'.
In the LMI extended specification, DLCIs are 'globally significant' (DLCIs specify individual end devices).
The FR Switch maps the DLCIs between each pair of routers to create a PVC.
DLCI values are typically assigned by the Frame Relay service provider
DLCI(Data-link Connection Identifier)
![Page 5: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/5.jpg)
5
Frame Relay Interface types
• UNI: User-|Network Interface• NNI: Network-Network Interface
Frame Relaynetwork
Frame Relaynetwork
Frame Relaynetworkuser user
UNI UNINNI NNIPVC segment
Multi-network PVC
![Page 6: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/6.jpg)
666
Frame Relay Functions
![Page 7: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/7.jpg)
7
VCI
![Page 8: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/8.jpg)
8
VCI phases
![Page 9: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/9.jpg)
9
Switch and table
![Page 10: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/10.jpg)
10
Frame RelayLocal addressing
• DLCI (Data Link Connection Identifier) - identification of a virtual circuit• DLCI - of local (for a given port) meaning• there can be max. 976 VCs on an interface user-network
• DLCI values: 0 - LMI channel, 1-15 - reserved, 16-991 - available for VCs, 992-1007 - layer 2 management of FR service, 1008-1022 - reserved, 1023 - in channel layer management
A
B
C
To A: DLCI 121To B: DLCI 243
To A: DLCI 182To C: DLCI 121
![Page 11: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/11.jpg)
111111
Local Significance of DLCIsThe data-link connection identifier (DLCI) is stored in the Address field of every frame transmitted.
![Page 12: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/12.jpg)
12
Frame RelayFrame Relay
Architecture
Frame Relay Layers
FRAD
VOFR
LMI
![Page 13: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/13.jpg)
13
Frame Relay network
VCIs in Frame Relay are called DLCIs.
![Page 14: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/14.jpg)
14
Frame Relay layers
![Page 15: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/15.jpg)
15
Frame Relay frame
![Page 16: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/16.jpg)
16
Frame RelayGlobal addressing
• Extension proposed by “Group of Four”• Each end user access device FRAD is assigned a unique
DLCI number - a global addressTransmission to a given user goes over VC identified by a unique DLCI
• Current DLCI format limits number of devices to less than 1000
• Another addition to the standard - extended DLCI addresses
![Page 17: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/17.jpg)
17
Three address formats
![Page 18: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/18.jpg)
181818
LAPF Frame – Address Field
6-bits
4-bits
![Page 19: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/19.jpg)
19
FRAD
![Page 20: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/20.jpg)
20
Frame RelayFlow and congestion control
• There is no explicit flow control in FR; the network informs a user about congestion
• Congestion: FR frames are discarded from overflowed buffers of switching devices
• Congestion information:– FECN - Forward Explicit Congestion Notification– BECN - Backward Explicit Congestion Notification
• There are recommendations for access devices what to do with FECN and BECN (usually not implemented)
Transmission direction
BECN FECNFRAD
FRAD
![Page 21: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/21.jpg)
212121
Frame Relay Concepts
Queue
![Page 22: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/22.jpg)
222222
Frame Relay Concepts
![Page 23: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/23.jpg)
232323
Frame Relay Concepts
![Page 24: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/24.jpg)
DLCI-identifies logical connections on the Frame Relay switch to which the customer is attached
BECN-tells sending DTE device to reduce the rate of sending data.
FECN-tells receiving DTE device to implement congestion avoidance procedures
FRAMES
BECN FECN
![Page 25: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/25.jpg)
25
Frame RelayParameters of a UNI interface
• Physical speed - just clock rate• Guaranteed bandwidth parameters
– CIR: Committed Information Rate– BC: Committed Burst Size
• Extended bandwidth parameters– EIR: Extended Information Rate– BE: Extended Burst Size
• TC: Measurement IntervalUsertraffic
192kbps
64kbps
EIR
CIR
256kbps
time
![Page 26: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/26.jpg)
26
Frame RelayCIR and EIR - how does it work
• BC = TC * CIR
• BE = TC * EIR
Frame 1 Frame 2 Frame 3 Frame 4 Frame 5Within CIR Within CIR Marked DE Marked DE Discarded
Bits
BC+BE
BC
T0
T0+TC
Time
CIR
CIR + EIR
Clock rate
![Page 27: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/27.jpg)
27
CIR (Committed Information Rate - The rate at which a Frame Relay network agrees to transfer information under normal conditions, averaged over a minimum increment of time. CIR, measured in bits per second, is one of the key negotiated tariff metrics.
Local access rate - The clock speed (port speed) of the connection (local loop) to the Frame Relay cloud. It is the rate at which data travels into or out of the network.
Committed Burst (Bc) - The maximum number of bits that the switch agrees to transfer during any Committed Rate Measurement Interval (Tc).
Excess Burst - The maximum number of uncommitted bits that the Frame Relay switch will attempt to transfer beyond the CIR. Excess Burst is dependent on the service offerings available by your vendor, but is typically limited to the port speed of the local access loop.
Glossary
![Page 28: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/28.jpg)
28
ECN (Forward explicit congestion notification) - When a Frame Relay switch recognizes congestion in the network, it sends an FECN packet to the destination device indicating that congestion has occurred.
BECN (Backward explicit congestion notification) - When a Frame Relay switch recognizes congestion in the network, it sends a BECN packet to the source router instructing the router to reduce the rate at which it is sending packets.
DE (Discard Eligibility indicator) - When the router detects network congestion, the FR switch will drop packets with the DE bit set first. The DE bit is set on the oversubscribed traffic; that is, the traffic that was received after the CIR was met.
More Terms
![Page 29: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/29.jpg)
292929
Data Link Control Identifier
• The 10-bit DLCI associates the frame with its virtual circuit
• It is of local significance only - a frame will not generally be delivered with the same DLCI with which it started
• Some DLCI’s are reserved
![Page 30: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/30.jpg)
30
Frame Relay Local Management Interface - LMI
• LMI - a signaling protocol used on an interface: end user - network (UNI)
• Implementation optional (everybody implements it...)• Usage:
– notification about: creation, deletion, existence of PVCs on a given port– notification about status and availability of PVCs– periodic checks of integrity of physical connection
• Planned extensions:– dynamic (SVC) channel creation and deletion– congestion notification
• Also planned: LMI for network-network interface (NNI)
![Page 31: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/31.jpg)
31
A signalling standard between the CPE device and the FR Switch that is responsible for managing the connection and maintaining "status" between the devices.
Set of enhancements to the basic Frame Relay specification. LMI includes support for:
• 'keepalive mechanism', which verifies that data is flowing; • 'multicast mechanism', which provides the network server
with its local DLCI and the multicast DLCI; • ‘global addressing', which gives DLCIs global rather than
local significance in Frame Relay networks; • 'status mechanism', which provides an on-going status
report on the DLCIs known to the FR Switch.
LMI(Local Management Interface)
![Page 32: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/32.jpg)
32
The main purpose for the LMI process is: (management of the connection) – PVC status - What is the operational status of the various PVCs that the
router knows about? – Transmission of 'keepalive' packets - Insure that the PVC stays up and
does not shut down due to inactivity.
Three types of LMIs are supported: 1. cisco - LMI type defined jointly by Cisco, StrataCom, Northern Telecom,
and DEC (frame relay forum) 2. ansi - Annex D defined by ANSI standard T1.617 3. q933a - ITU-T Q.933 Annex A
LMI encapsulation types: – IETF Encapsulation Type – Cisco Encapsulation Type
LMI
![Page 33: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/33.jpg)
333333
Local Management Interface (LMI)
• Three types of LMIs are supported by Cisco routers:
Cisco — The original LMI extensions
Ansi — Corresponding to the ANSI standard T1.617 Annex D
q933a — Corresponding to the ITU standard Q933 Annex A
![Page 34: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/34.jpg)
Frame Relay Map The term map means to “map” or bind a
Layer 2 address to a Layer 3 address. An ARP table maps MACs to IPs in a LAN In ISDN, we use the dailer-map command to map
SPIDs to IP addresses In Frame Relay, we need to map the data link
layer’s DLCI to the IP address We use the frame-relay map command
![Page 35: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/35.jpg)
Frame Relay Map The Frame Relay switch builds a table of
incoming/outgoing ports and DLCIs. The router builds a Frame Relay Map through Inverse
ARP requests of the switch during the LMI exchange process.
The Frame Relay Map is used by the router for next-hop address resolution.
![Page 36: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/36.jpg)
36
Frame RelayIARP
• FRADs know DLCIs of available PVCs (through LMI), but don’t know IP addresses of other ends
• IP addresses for given DLCIs are obtained automatically; mapping IP-DLCI is generated - dynamic mapping
• IARP can be switched of; static maps have to be generated by FRAD user
![Page 37: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/37.jpg)
373737
Configuring Basic Frame Relay
![Page 38: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/38.jpg)
383838
Configuring a Static Frame Relay Map
![Page 39: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/39.jpg)
393939
Reachability Issues with Routing Updates in NBMA
![Page 40: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/40.jpg)
404040
Reachability Issues with Routing Updates in NBMA
By default, a Frame Relay network provides nonbroadcast multiaccess (NBMA) connectivity between remote sites. An NBMA environment is treated like other multiaccess media environments, where all the routers are on the same subnet.
![Page 41: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/41.jpg)
414141
Frame Relay Subinterfaces
![Page 42: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/42.jpg)
424242
Configuring Point-to-Point Subinterfaces
![Page 43: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/43.jpg)
434343
Verifying Frame Relay
• The show interfaces command displays information regarding the encapsulation and Layer 1 and Layer 2 status. It also displays information about the following:
The LMI type The LMI DLCI The Frame Relay data terminal equipment/data circuit-terminating equipment (DTE/DCE) type
![Page 44: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/44.jpg)
444444
The show interface Command
LMI Type
LMI DLCI
LMI Status
![Page 45: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/45.jpg)
454545
The show frame-relay lmi Command
![Page 46: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/46.jpg)
464646
The show frame-relay pvc Command
![Page 47: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/47.jpg)
474747
The show frame-relay map Command
![Page 48: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/48.jpg)
484848
Troubleshooting Frame Relay The debug frame-relay lmi Command
PVC Status0x2 – Active0x0 – Inactive0x4 – Deleted
![Page 49: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/49.jpg)
49
ATMATM
Design Goals
Problems
Architecture
Switching
Layers
![Page 50: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/50.jpg)
50
Multiplexing using different frame sizes
A cell network uses the cell as the basic unit of data exchange. A cell is defined as a small, fixed-sized
block of information.
![Page 51: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/51.jpg)
51
Multiplexing using cells
![Page 52: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/52.jpg)
52
ATM multiplexing
![Page 53: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/53.jpg)
53
Architecture of an ATM network
![Page 54: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/54.jpg)
54
TP, VPs, and VCs
![Page 55: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/55.jpg)
55
Example of VPs and VCs
Note that a virtual connection is defined by a pair of numbers: the VPI and the VCI.
![Page 56: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/56.jpg)
56
Connection identifiers
![Page 57: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/57.jpg)
57
Virtual connection identifiers in UNIs and NNIs
![Page 58: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/58.jpg)
58
An ATM cell
![Page 59: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/59.jpg)
59
Routing with a switch
![Page 60: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/60.jpg)
60
ATM layers
![Page 61: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/61.jpg)
61
ATM layers in endpoint devices and switches
![Page 62: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/62.jpg)
62
ATM layer
![Page 63: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/63.jpg)
63
ATM headers
![Page 64: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/64.jpg)
64
AAL1
![Page 65: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/65.jpg)
65
AAL2
![Page 66: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/66.jpg)
66
AAL3/4
![Page 67: Frame Relay & ATM](https://reader034.fdocuments.us/reader034/viewer/2022052212/56815598550346895dc37615/html5/thumbnails/67.jpg)
67
AAL5