EGP is not strictly a routing protocol, it is a reacha-
bility protocol. It tells only if nets can be reached
through a particular gateway, not how good the connec-
tion is. It is the standard by which gateways to local
nets inform the ARPAnet of the nets they can reach.
There is a metric passed around by EGP but its usage is
not standardized formally. Its typical value is value
is 1 to 8 which are arbitrary goodness of link values
understood by the internal DDN gateways. The smaller
the value the better and a value of 8 being unreach-
able. A quirk of the protocol prevents distinguishing
between 1 and 2, 3 and 4..., so the usablity of this as
a metric is as three values and unreachable. Within
NSFnet the values used are 1, 3, and unreachable. Many
routers talk EGP so they can be used for ARPAnet gateways.
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