Telindus 1031, Руководство пользователя и справочник

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Telindus 1031 Router Chapter 6
User manual Configuring the WAN encapsulation protocols
85
6.3.5 Configuring CIR and EIR
Refer to 6.3.1 - Introducing Frame Relay on page 78 for an introduction on CIR and EIR.
As said before, CIR is the data rate which the user expects to pass into the Frame Relay network with
few problems. Note that the CIR is unrelated to the actual bit rate of the physical connection. A user could
have a physical connection operating at 2 Mbps, but a CIR across this physical connection of only 64
kbps. This would mean that the user’s average data rate would be 64 kbps, but data bursts up to 2 Mbps
would be possible (EIR).
You can configure the CIR and EIR using the cir and eir elements of the frameRelay structure within the
dlciTable . Refer to telindus1031/g703[ ]/channel[ ]/frameRelay/dlciTable/frameRelay on page 190 .
Important remarks
• Be careful not to over-dimension the CIR. I.e. do not let the sum of the CIRs of the DLCIs exceed the
bandwidth of the physical connection.
• When you do exceed the total bandwidth of the physical connection, then the Telindus 1031 Router
first buffers the data. However, when the buffers of the Telindus 1031 Router are completely filled up,
it has to discard the “excess” data.
Examples
Suppose you have a 2
Mbps physical connection
towards the Frame Relay
service provider and you
define 2 DLCIs:
• Suppose you assign to
both DLCIs a CIR of 1
Mbps and an EIR of 0.
⇒
In that case you have per DLCI a guaranteed bandwidth of 1 Mbps and no bursts are allowed.
• Suppose you assign to both DLCIs a CIR of 512 kbps and an EIR of 512 kbps.
⇒
In that case you have per DLCI a guaranteed bandwidth of 512 kbps and you allow bursts up to 1
Mbps. This means that if on both DLCIs a burst up to 1 Mbps occurs at the same time, the speed
of the physical connection (2 Mbps) is still not exceeded (so no data is discarded). If however
somewhere else on the network a congestion occurs, it is possible that some of the “excess” data
is discarded (refer to
What is the Discard Eligible bit? on page 79 ).
• Suppose you assign to both DLCIs a CIR of 1 Mbps and an EIR of 1 Mbps.
⇒
In that case you have per DLCI a guaranteed bandwidth of 1 Mbps and you allow bursts up to 2
Mbps. Obviously, this means that if on both DLCIs a burst up to 2 Mbps occurs at the same time,
the speed of the physical connection (2 Mbps) is exceeded and some data is discarded. In that
case the principle of first come, first served is applied. I.e. the DLCI on which the burst occurred
first its data is passed on to the Frame Relay network. If however somewhere else on the network
a congestion occurs, it is still possible that some of the “excess” data is discarded.
• Suppose you assign to both DLCIs a CIR of 2 Mbps and an EIR of 0.
⇒
In that case you over-dimensioned your CIR. You can not guarantee 2 Mbps of bandwidth for both
DLCIs, due to the bandwidth limit of 2 Mbps on the physical connection. Also in this case the prin-
ciple of first come, first served is applied. I.e. the DLCI which sends data first gets its data onto the
Frame Relay network.
Frame Relay
network
LAN 2 Mbps connection
DLCI 16
DLCI 17