SAs periodically need to refresh their service advertisements before lifetimes expire. If a DA is handling an extremely heavy load from many UAs and SAs, frequent refreshes can cause the DA to become overloaded. If the DA becomes overloaded, UA requests start to time out and are then dropped. UA request timeouts have many possible causes. Before you assume that DA overload is the problem, use a snoop trace to check the lifetimes of service advertisements that are registered with a service registration. If the lifetimes are short and reregistrations are occurring often, the timeouts are probably the result of frequent reregistrations.
A service registration is a reregistration if the FRESH flag is not set. See Chapter 11, SLP (Reference) for more information on service registration messages.