Complementary solutions include sending scripts to the navigator intended to ping the
chosen server, reverting to another one in case of timeouts. Additionally, IP takeover techniques
(Damani et al., 1997), as will be mentioned later on, may enhance responsiveness
to higher levels.
Whichever the mechanism is used to route requests, and following the general operation
scheme depicted in Figure 4, a thick blue arrow represents the interaction between a particu-
Figure 4. General operation over a WAN
Web
Application
HTTP
HTTP
Replica.1.
Web
Application
HTTP
Replica.2.
HA
module
Web
Application
HTTP
Replica.3.
Client
HTTP
(ip: x.x.x.x)
DNS
(dot.com)
DNS
DNS.
Server.
IP:.x.x.x.x. IP:.y.y.y.y. IP:.z.z.z.z.
dot.com:
...x.x.x.x.
y.y.y.y
z.z.z.z
??¦
http://dot.com
HA
module
HA
module
Gald??mez
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of Idea Group Inc. is prohibited.
lar client and Replica 1, chosen as the service entry point. The client will interact with that
replica as if the service was not replicated. However, the HA-module at that node, when it
receives the client request, instead of giving it to its attached Web application, will multicast
the request to the other HA-modules.
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