A system handles timing information within a packet-switched network. The system classifies packets for processing depending on the packet type. After classification, a new timestamp value may be produced depending on the packet classification. The new timestamp value may use a timestamp value from the received packet, a value from a local clock, and an offset value. The timestamp value may be written into the packet, depending on the packet classification, and checksum-type fields may additionally be updated in the packet. In some embodiments, multiple physical layer circuits are integrated with a local clock circuit.