Transmission

1. 0000
Frame Relay Technology

2. Technologies Overview 2
Frame Relay History
• Before frame relay era, large organizations were
interconnected by:
X.25 Leased Lines
Long network processing time Point to point connectivity
Low bandwidth (max. 64kbps) Expensive, there is no
Charge per traffic bandwidth sharing
Required multiple port routers
Fixed price

3. Technologies Overview 3
Frame Relay History
• As the 1980’s came to close a new demands from the
wide area network switching began to appear:
• Growth in high speed, high speed throughput
application.
• Sophistication of the end user devices, equipment with
processing ability.
• This new wide area switching technology required
high speed, low delay, port sharing and bandwidth
sharing on a virtual circuit basis.
• These characteristics implemented in Frame Relay
make Frame Relay ideal solution for the burst traffic
sources found in LAN-WAN internetworking.

4. Technologies Overview 4
What is Frame Relay?
• Frame Relay is a high-speed communication
technology, which enables to send information over
the WAN by dividing the information into frames and
packets.
• Frame Relay is not a single physical connection
between two end points, but a logical path is defined
within the network.No Bandwidth is allocated to the
path until actual data needs to be transmitted. Then,
the Bandwidth within the network is allocated on a
packet-by-packet basis, This logical path called VC
(Virtual Circuit).

5. Technologies Overview 5
E
C
A
Router
Router
Router
Frame Relay Network
DLCI101
DLCI102
DLCI103
LAN 1
LAN 2
LAN 3
D
B
Frame Relay Network

6. Technologies Overview 6
Frame Relay Network (cont.)
User Node
Router
User Node
Router
User Node
Router
User Node
Router
FR
switch
Network Node
FR
switch
FR
switch
NNI
Network to Network Interface
UNI
User to Network Interface
• Network nodes (FR switches)
• User nodes (usually routers)

7. Technologies Overview 7
Data Link Control Identifier
• Logical connection with pre-defined bandwidth from
56KBps to E1/T1 and even T3
• Many logical connections can co-exist on a single
physical line
• DLCI no. is attached to data frames in order to tell the
network how to route the data

8. Technologies Overview 8
VC Parameters
• Each VC has several parameters needed to be
configured:
• CIR (Committed Information Rate)
• CIR is the "worst-case" throughput that the frame relay network
provider attempts to guaranty
• CIR bandwidth is guaranteed. In overload situations, transmission
will occur over a reasonable time span (usually over a span of
seconds)
• Transmission is monitored using "leaky bucket algorithm."
• Bc (Burst Committed)
• Value which indicated how many bits can be transmitted at a
certain time interval and the system obligate to transmit them.
• Be (Burst Exceeded)
• The amount of bits which were transmitted over the Bc at the
defined time interval.
• Tc (Time Committed)
• The time interval.

9. Technologies Overview 9
Leaky Bucket Algorithm
• When buying a CIR, one is getting a timed buffer
(bucket) in each switch port along the PVC. This
bucket has two dimensions:
• A diameter measured in seconds called committed time
(Tc)
• A height called committed burst (Bc) measured in
Kbytes
• One can only send Bc frames or less during every Tc
period
(CIR = Bc/Tc)
• The power of Frame Relay consists in a second
bucket: its diameter is also Tc. Its height is typically
equal to Bc and is known as excess burst (BE) - (for
CIR=0 excess rate =Be/Tc)

10. Technologies Overview 10
Leaky Bucket Algorithm (cont.)
Bc+BeBc

11. Technologies Overview 11
VC Parameters
To
To+Tc
Time
Bits
Bc+Be
Bc
Access
Rate
CIR
Frame 1
within CIR
Frame 2
within CIR
Frame 3
within CIR
Frame 4
marked DE
Frame 5
Discarded

12. Technologies Overview 12
VC parametersBit Rate
[Kbps]
Time
[sec.]
Bc+Be
Tc
CIR
Dicarded
DATA

13. Technologies Overview 13
Frame Relay Packet Structure
• Frame Relay Header: 2 bytes of FR address and control
• Information Field: User’s data
• FCS: 32 bits of Cyclic Redundancy Check (CRC)
• Flag : 2 identical bytes made of 6 ones and 2 zeros.

14. Technologies Overview 14
Frame Relay Theory
• Congestion Notification Mechanism is helping us to
avoid a situation where a node reaches a certain point
which it can’t deliver data any more due to a sever
congestions. In Frame Relay there are several ways
to avoid congestions:
• Explicit Congestion Notification
• Discard Eligibility

15. Technologies Overview 15
• Explicit Congestion Notification
Congestion
FECN – Forward Explicit Congestion Notification
BECN – Backward Explicit Congestion Notification
C
B
A
Router
Router
Frame Relay Network
LAN 1
LAN 2
Frame Relay Theory

16. Technologies Overview 16
Frame Relay Theory
• Discard Eligibility
• Due to the use of the CIR which is an obligation for the
quality of service to the customer, in case of a problem
any frame which is send through the network above the
CIR can be discarded. And will not effect the guarantied
Quality of Service.

17. Technologies Overview 17
Frame Relay Theory
• Local Management Interface (LMI)
• The LMI is a connection status mechanism, this status
information is accomplished on unique DLCI using
special management frames.
• The management frames monitors the status of the
connection and provide the following information:
• Weather the interface is still active.
• The valid DLCIs defines in the interface.
• The status of each VC (Congested or not, etc.).
• There are 3 versions of LMI specifications:
• LMI – Defined by the Frame Relay Forum.
• Annex A – Defined by ITU-T(CCITT).
• Annex D- Defined by ANSI.

18. Technologies Overview 18
Frame Relay Advantages
• Frame Relay benefits over alternative technologies:
• Lower cost of ownership
• Well-established and widely adopted standards that
allow open architecture and plug-and-play service
implementation.
• Low overhead, combined with high reliability.
• Network scalability, flexibility and disaster recovery.
• Interworking with other new services and applications,
such ATM.

19. Frame Relay Technology in
WALKair 1000

20. Technologies Overview 20
Frame Relay traffic parameters
• Committed Information Rate (CIR)
• The bandwidth defines for a VC.
• Bc = Burst Committed
• Maximum number of committed bits to be transmitted over
time interval (Tc).
• Be = Burst Excess
• Number of excess bits that will be transmitted over time
Interval (Tc).
• Tc = Time interval
• Time measurement based on the amount of bandwidth is
available for data to burst on to the network.
For better performance it is recommended that the TC will be
1/8 sec.

21. Technologies Overview 21
Data Flow in WALKair
HDLC
DRIVER
DLCI
16
DLCI
17
CIRCIR EXSEXS
TX Q
DATA TRANSMITTED
OVER THE AIR
WALKair
Congestion
Ind.
WALKair
DATA RECEIVED
FROM THE AIR
RX Q HDLC
DRIVER
DATA to
FR DEVICE
DATA from
FR DEVICE

22. Technologies Overview 22
Relay
BS
TS
TS
FRAD
FRAD
FR
switch
FRAD
m*DLCI's
max(m)=200
n*DLCI's
max(n)=30
Frame
Relay
Network
DLCI 101
DLCI 102
FR
switch

23. Technologies Overview 23
Frame Relay
DLCI 20
FR
Networ
k
BS
TS1
TS2
FRAD
FRAD
FR switch
FR switch
FRAD
DLCI 17
DLCI 18 DLCI 18
DLCI 17
DLCI 19
DLCI 19
10BaeT
10BaeT

24. Technologies Overview 24
Congestion Notification
TSBS
Uplink Congestion
TS congested with traffic
towards the air link
FR
Switch
Router
BS congested with traffic
towards the FR switch
TSBS
Downlink Congestion
BS congested with traffic
towards the air link
FR
Switch
Router
TS congested with traffic
towards the FR router

25. Technologies Overview 25
Physical Layer Parameters Configuration
• Data rate [n*64kbps]
• Protocol [v.35 / x.21]
• Operating mode [DCE / DTE]
• Timing mode [internal / external]
• Clock mode [standard / inverse]
• Administrative status [enable / disable]

26. Technologies Overview 26
Protocol Parameters Configuration
• Signaling protocol [ ansit1617annexd / ccitt AnnexA /
LMI]
• Port type [UNI / NNI]

27. Technologies Overview 27
Service Parameters Configuration
• DLCI [16 ..995]
• Cir/Bc/be [0..4095, 0..4095, 0..4095] kbps
• BS port number [0/1/2]
• TS customer ID
• TS port number [0/1/2]
• Administrative status [enable/disable]

28. Technologies Overview 28
Frame Relay Attributes in WALKair
• DLCI
• 979 DLCI(s) with 2 octets long
• Same set at BS and TS's
• Maximum DLCI(s) per TS port is 30
• Maximum DLCI(s) per BS’BU port is 250
• CIR
• CIR (BS port) = CIR (all TS’s) <= 2mbps/4mbps
• Recommendation: TS_CIR to be a boundary of n*64 kbps
• BC=CIR/8 ; BE=(MIR-CIR)/8

29. Technologies Overview 29
Management Protocol Configuration
• WALKair supports all the relevant items of frame relay
NNI MIB RFC 1604, including all statistic information.
• Traps will be send to the EMS whenever there is a
change in the operational status in 3 levels:
• Physical link (up or down).
• FR port (up or down).
• DLCI (up or down).

30. Certified Alvarion System
Engineer - CASE
Frame Relay Technology

31. Technologies Overview 31
Adding FR service
• Stage 1:
• Configure the telecom port (physical layer) both in the
BS and TS.

32. Technologies Overview 32
Adding FR service (cont’)
•Stage 2:
•Configure the Logical Port:
Signaling protocol
•ANSI 1617 Annex D
•CCITT Annex A
•LMI
Port type
•U-UNI
•N-NNI
•T-UNI
From the FR interface menu add interface

33. Technologies Overview 33
Adding FR service (cont’)
• Stage 3:
Adding the DLCI and the connection
• DLCI [16 .. 995]
• Cir/Bc/Be [0..4095, 0..4095, 0..4095] kbps
• BS port number [0/1/2]
• TS customer ID
• TS port number [0/1/2]
• Administrative status [enable/disable]

34. Technologies Overview 34
Adding FR service (cont’)