> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On > Behalf Of Phil Griffin > Sent: Saturday, November 17, 2001 9:30 AM > To: [EMAIL PROTECTED] > Subject: Re: [ASN.1] itu-t (0) recommendation (0) h (8) 245 > version (0) 2 > > > Just my opinion. But a receiver should rarely need to > decode an OID. OIDs are constants usually tied to > processing semantics (as with an algorithm identifier) > and used as a switch in an application. > > Once you've encoded each OID you expect at a given
Right...but one should keep in mind that encoding an OID value requires CPU cycles as well as its decoding. So there is always a tradoff. Convenience from handling OID values in encoded form comes from much easier comparison since all you need to do is to know the length of the encoded OID value and its start address, as opposed to individually decoding and comparing the OID arcs. Nick > point in your application and defined these encodings > in your application as a list of known hex blobs, all > you need do to determine that a given OID hex blob you > receive in a message is some particular OID is to just > compare the encoded OID blob receive against your set of > expected OID constants. > > Decoding the blob you receive is a waste of effort. It > gains you little unless you perhaps intend to display > the value, or reformat the encoding, say from BER into > the XER dotted format, and pass it along for further > processing. > > Phil Griffin > > > > William Of Ockham wrote: > > > > What does it mean to "evaluate" an object identifier, I mean, > > "resolve" it? > > > > I'm curious to know how the recipient uses an object > identifier once > > he's got it. > > > > William > > > > --- "Sathya[IT]" <[EMAIL PROTECTED]> wrote: > > > Hi Justin, > > > > > > Long ago, back in 1986, ASN.1 specification considered a > wastage of > > > octets to use 2 bytes for the first 2 roots. So they > juxtaposed both > > > into a single octet using the formula Root * 40 + Second > root. This > > > was due to the fact that there ar only 3 root nodes > (ITU-T, ISO and > > > Joint ISO-ITU). Since the values of OID are encoded in > 7Bit encoded > > > Integer. We can have only 128 values for this juxtaposed > integer to > > > be represented in a single octet. 128/3 is approx. 40. > The first 40 > > > is given to ITU-T, the next 40 to ISO and the rest to > joint iso-itu. > > > This also explains why the second level arc cannot have > more than 40 > > > siblings. > > > > > > Hope this will clarify your doubt. > > > > > > regards, > > > > > > Sathya Narayanan S > > > RPG Cellular Services Limited > > > GSM : +91 98410 48051 > > > > > > > -----Original Message----- > > > > From: Hwang, Justin > > > > Sent: Thursday, November 15, 2001 10:13 PM > > > > To: '[EMAIL PROTECTED]' > > > > Subject: RE: [ASN.1] itu-t (0) recommendation (0) h > (8) 245 version > > > > (0) 2 > > > > > > > > Hi, > > > > > > > > I never decode OBJECT ID before, so please > > > > help me with the following questions. > > > > > > > > > itu-t (0) recommendation (0) h (8) 245 version (0) 2 > > > > > 1) 40 * 0 + 0 = 0 > > > > > > > > ===> Why 40? where 40 comes from? and why only 1 byte for both > > > > "itu-t (0) recommendation (0)"? why not 2 bytes? 1 byte (0) for > > > > itu-t and other byte > > > > (0) for recommendation? > > > > > > > > > 2) 8 > > > > > 3+4) 245 = 11110101B => 1 0000001 0 1110101 = F1 75 > > > > > > > > ===> How "11110101B" is converted to "1 0000001 0 1110101"? > > > > > > > > > 5) 0 > > > > > 6) 2 > > > > > > > > > > > > Thanks! > > > > > > > > Justin > > > > > > > > > > > > -----Original Message----- > > > > From: Sathya[IT] [mailto:[EMAIL PROTECTED]] > > > > Sent: Thursday, November 15, 2001 3:35 AM > > > > To: [EMAIL PROTECTED] > > > > Subject: RE: [ASN.1] itu-t (0) recommendation (0) h (8) 245 > > > > version (0) 2 > > > > > > > > > > > > Hi Bernd, > > > > > > > > While I encode this, the octets turn out to be 00 08 81 75 00 02 > > > > > > > > I dont understand how you arrived at f1 instead of 81. > Is there a > > > > significance for the deviation? > > > > > > > > regards, > > > > > > > > Sathya Narayanan S > > > > RPG Cellular Services Limited > > > > GSM : +91 98410 48051 > > > > > > > > > -----Original Message----- > > > > > From: Bernd Kunze > > > > > Sent: Monday, November 05, 2001 9:15 PM > > > > > To: '[EMAIL PROTECTED]' > > > > > Subject: RE: [ASN.1] itu-t (0) recommendation (0) h (8) 245 > > > > > version > > > > > (0) 2 > > > > > > > > > > Hi, > > > > > > > > > > itu-t (0) recommendation (0) h (8) 245 version (0) 2 > > > > > > > > > > 1) 40 * 0 + 0 = 0 > > > > > 2) 8 > > > > > 3+4) 245 = 11110101B => 1 0000001 0 1110101 = F1 75 > > > > > 5) 0 > > > > > 6) 2 > > > > > > > > > > => 00 08 F1 75 00 02 > > > > > > > > > > Bernd > > > > __________________________________________________ > > Do You Yahoo!? > > Find the one for you at Yahoo! Personals http://personals.yahoo.com > >
