Abstract: In the present invention, a service network includes, when user terminals are divided by area, subscriber accommodation nodes that accommodate the user terminals present in the respective areas and relay nodes that perform relay of information among the subscriber accommodation nodes. The congestion control system further includes an edge router that routes a processing request for a communication service received from each of the user terminals to each of the subscriber accommodation nodes on the service network side as a control message and a congestion control server that controls congestion states of the subscriber accommodation nodes and the relay nodes. The subscriber accommodation node detects, when congestion occurs or it is likely that congestion occurs in the subscriber accommodation node because of a large number of control messages from the edge router, the occurrence of the congestion or the likelihood of occurrence of congestion and notifies the congestion control server to that effect.

Abstract: An electrophotographic photoreceptor having a photosensitive layer containing a butadiene compound represented by general formula ##STR1## wherein A.sub.1 to A.sub.4 are alkyl group, and a hydrazone compound represented by general formula ##STR2## wherein B.sub.1 and B.sub.2 are alkyl, phenyl, benzyl or methoxyphenyl groups, R.sub.1 is hydrogen, alkyl, alkoxy or benzyloxy groups and R.sub.2 is alkyl, phenyl or benzyl groups. The photoreceptor can suppress the photo-deterioration due to cyclic operation and is useful in the field of copying printers.