Re: Not understanding something in LLC
Guy Harris <[email protected]> Thu, 29 Jun 2006 03:20:03 -0700
| Newsgroups | gmane.network.ethereal.devel |
|---|---|
| Message-ID | <[email protected]> |
Eduardo Escudero Sánchez wrote: > But i dont understand. If you go to teh standard 802.2-1998 to the > 5.4.2.1 <http://5.4.2.1> for example (Format of the I - PDU) you can see > in the drawing that the bits are numbered from 1 to 16 and teh only > indication it gives you is that the bit numbered with 1 is the least > significant byte so one can deduce from here that the most significant > bit of teh conrol field is teh bit numbered with 16 so the first byte of > the control field will be the byte whose eight bits are the last eigth > bits of the drawing. So you can not go to the last bit of the first byte > to see the type of frame because you will be seeing the value of the P/F > bit, dont you? If bits are transmitted in the order in which they're shown in 5.4.2.1; the only way in which bit 1 would be the low-order bit of the *second* octet of a 2-octet control field would be if the second octet were transmitted first. That seems unlikely to be the case. Note that the control field is two octets, not a single 16-bit quantity; see 3.3.2 "Control field": The control field shall consist of one or two octets that shall be used to designate command and response functions, and shall contain sequence numbers when required.