Update protocol.md
Update protocol.md

- byte order
- csum function
Zirpon/tchannel,hustxiaoc/tchannel,bunnyblue/tchannel,hustxiaoc/tchannel,chenwenbin928/tchannel,vanloswang/tchannel,davewhat/tchannel,bunnyblue/tchannel,sasa233/tchannel,savaki/tchannel,davewhat/tchannel,sasa233/tchannel,vanloswang/tchannel,RyanTech/tchannel,savaki/tchannel,vanloswang/tchannel,RyanTech/tchannel,RyanTech/tchannel,benfleis/tchannel,bunnyblue/tchannel,sasa233/tchannel,Zirpon/tchannel,hustxiaoc/tchannel,Zirpon/tchannel,chenwenbin928/tchannel,savaki/tchannel,i/tchannel,chenwenbin928/tchannel,i/tchannel,benfleis/tchannel,benfleis/tchannel,i/tchannel