Scapy is a well known packet manipulation framework developed in Python. It could be quite useful for people want to understand network at people level. Though it is used mostly by security engineers or penetration testers but i also suggest for Network Engineers apart from using Wireshark. Below are the few resources from where you can learn about it.
1. You can start with Unofficial Guide to learn Scapy : Download Link
2. Then start with official tutorials : http://www.secdev.org/projects/scapy/doc/usage.html
3. You can also refer Scapy cheat sheet for review or while working.
(from packetlife by Jermy Strectch)