[DB]

No Bob, high speed serial communications that are byte oriented commonly use HDLC (though it doesn’t have to be byte oriented) which does not have start bits and stop bits on each byte. Instead it uses zero stuffing. If there are 5 or more consecutive ones it inserts a zero in order to protect what’s called a flag byte which has 6 consecutive ones with zeros on each end. The flag bytes are what provide both frame alignment and bit alignment.

See: http://en.wikipedia.org/wiki/HDLC

So the actual overhead is dependent on the data being sent over the link. In practice I believe it typically adds about 3% to the overhead. There’s additional overhead in the IP packets due to headers (routing information) and other encapsulating packet structures like Ethernet that are commonly used in network communications.

[Bob]

There’s additional overhead in the IP packets due to headers (routing information) and other encapsulating packet structures like Ethernet that are commonly used in network communications.

Thanks for the link. The packet overhead is probably the reason that using a divide-by-10 seems to work out so close for the conversion.