ForeRunner
ATM Switch Network Configuration Manual
3 - 15
Con
figurin
g an
Em
ul
ated
LAN
Configuring an Emulated LAN
When the third DLE peer server receives the LE-ARP response, it passes it directly to LEC 9
(which sent the original query)
➑
. The third DLE peer server also caches the registration infor-
mation for LEC 1 so that other local LECs do not have to go through the entire process again.
However, this cache ages out over time. LEC 9 can now open a connection to LEC 1, and send
its IP ARP response
➒
, as shown in Figure 3.11.
Figure 3.11 -
LE-ARP Response Delivered and LEC 9 Contacts LEC 1
3.4.2.2 Advantages of DLE
As mentioned earlier, using DLE provides solutions to the problems of using a single server.
3.4.2.2.1
Load Sharing
DLE peer servers distribute the circuit and processing load. The number of LANE LECs is no
longer limited by the number of circuits one LES/BUS platform can maintain, since many
platforms can support a single ELAN. Also, more VCs are available for use by other applica-
tions.
3.4.2.2.2
Improved Performance for Remote LECs
With DLE, broadcast delivery and LE-ARP resolution across peer servers can take a little
longer than if all LECs were connected to a single server, since extra processing steps and
transmissions are needed. However, ELANs with groups of LECs in different locations can be
designed for higher performance by providing a DLE peer server with each group. Broadcasts
and address resolution within each group will improve.
3.4.2.2.3
Fault
Tolerance
Perhaps the most important advantage of DLE is fault tolerance. In a single server ELAN, the
server can be a single point of failure. If the server fails, endstations in the ELAN are unable to
discover each other through broadcast queries and unable to resolve MAC addresses into
ATM addresses. Increased network reliability, therefore, requires that ELANs have backups
for LES and BUS functions. To illustrate this point, the single server model is again discussed.
Eng LEC 4
Eng LEC 5
Eng LEC 6 Eng LEC 7
Eng LEC 8
Eng LEC 9
Eng LEC 1
Eng LEC 2
Eng LEC 3
➑
➒
LES/BUS 1
Eng
LES/BUS 2
Eng
LES/BUS 3
Eng
Summary of Contents for forerunner series
Page 6: ......
Page 16: ...TOC 10 ForeRunner ATM Switch Network Configuration Manual Table of Contents ...
Page 20: ...LOF 4 ForeRunner ATM Switch Network Configuration Manual List of Figures ...
Page 22: ...LOT 2 ForeRunner ATM Switch Network Configuration Manual List of Tables ...
Page 30: ...viii ForeRunner ATM Switch Network Configuration Manual Preface ...
Page 144: ...3 58 ForeRunner ATM Switch Network Configuration Manual Configuring an Emulated LAN ...
Page 180: ...6 12 ForeRunner ATM Switch Network Configuration Manual ATM Forum PNNI ...
Page 220: ...9 6 ForeRunner ATM Switch Network Configuration Manual Configuring Timing ...
Page 300: ...D 24 ForeRunner ATM Switch Network Configuration Manual Configuring FramePlus Modules ...
Page 308: ...Acronyms 8 ForeRunner ATM Switch Network Configuration Manual Acronyms ...
Page 346: ...Glossary 38 ForeRunner ATM Switch Network Configuration Manual Glossary ...
Page 352: ...Index 6 ForeRunner ATM Switch Network Configuration Manual Index ...