Nortel Web OS 10.0, Application Manual

Page: 471 / 482

212777-A, February 2002
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Glossary
DIP (Destination IP
Address) The destination IP address of a frame.
Dport (Destination
Port) The destination port (application socket: for example, http-80/https-443/DNS-53)
NAT (Network
Address Translation) Any time an IP address is changed from one source IP or destination IP address to another
address, network address translation can be said to have taken place. In general, half NAT
is when the destination IP or source IP address is changed from one address to another.
Full NAT is when both addresses are changed from one address to another. No NAT is
when neither source nor destination IP addresses are translated. Virtual server-based load
balancing uses half NAT by design, because it translates the destination IP address from
the Virtual Server IP address, to that of one of the real servers.
Preemption
In VRRP, preemption will cause a Virtual Router that has a lower priority to go into
backup should a peer Virtual Router start advertising with a higher priority.
Priority
In VRRP, the value given to a Virtual Router to determine its ranking with its peer(s). Min-
imum value is 1 and maximum value is 254. Default is 100. A higher number will win out
for master designation.
Proto (Protocol) The protocol of a frame. Can be any value represented by a 8-bit value in the IP header
adherent to the IP specification (for example, TCP, UDP, OSPF, ICMP, and so on.)
Real Server Group A group of real servers that are associated with a Virtual Server IP address, or a filter.
Redirection or
Filter-Based Load
Balancing
A type of load balancing that operates differently from virtual server-based load balancing.
With this type of load balancing, requests are transparently intercepted and “redirected” to
a server group. “Transparently” means that requests are not specifically destined for a Vir-
tual Server IP address that the switch owns. Instead, a filter is configured in the switch.
This filter intercepts traffic based on certain IP header criteria and load balances it.
Filters can be configured to filter on the SIP/Range (via netmask), DIP/Range (via net-
mask), Protocol, SPort/Range or DPort/Range. The action on a filter can be Allow, Deny,
Redirect to a Server Group, or NAT (translation of either the source IP or destination IP
address). In redirection-based load balancing, the destination IP address is not translated to
that of one of the real servers. Therefore, redirection-based load balancing is designed to
load balance devices that normally operate transparently in your network—such as a fire-
wall, spam filter, or transparent Web cache.
RIP (Real Server)
Real Server IP Address. An IP addresses that the switch load balances to when requests
are made to a Virtual Server IP address (VIP).