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From: daved@tsdiag.ccur.com (Dave Danielson)
Newsgroups: comp.dcom.lans
Subject: Re: X.25
Summary: just a bit more on the x.25 addresses
Message-ID: <644@tsdiag.ccur.com>
Date: 5 Dec 89 15:50:11 GMT
References: <2050001@hp-and.HP.COM> <1100@sumax.UUCP> <4586@dell.dell.com>
Organization: CONCURRENT,ENG. SERVICES,OCEANPORT NJ
Lines: 31

In article <4586@dell.dell.com>, mjhammel@Kepler.dell.com (Michael J. Hammel) writes:
> I couldn't remember if this was true so I looked it up in a manual I got
> in an X.25 class I took.  Now I'm more confused.  According to this text
> there is a Logical Channel Number of 8 bits and a Logical Channel Group
> Number of 4 bits.  Together these are used to maintain a call.  This would
> then allow upto 4095 maintained calls.  To establish a call there are 3
> fields:  the calling DTE address length field, the called DTE address
> length field, and the actual address field.  By this definition the
> address length can be any specified length (as long as the address fits
> between the 4th and 19th octets of the X.25 packet).  So in establishing
> the call the address field is quite large (a bit more than 8 bits), but
> as far as X.25 is concerned the logical addresses are no more than 8 bits
> or 12 bits if coupled with the group number.
> 
Mike, when you spoke of 8 bits you might have been thinking of
the link level (HDLC) addressing conventions which can be 8 bits
in normal mode or 16 bits in extended mode but as far as the
x.25 network level addresses go, they are 1-15 digits as
prescribed in the CCITT X.121 standard.  This is broken down:

       P  NNNN TTTTTTTT PP
       |   |     |      |- port id (2)
       |   |     |-terminal/station number (8)
       |   |-DNIC/Data Network Id Code (4)
       |-Prefix (1 - sim to the "1" for long distance)

Maybe this was unnecessary, but I thought I'd throw it in.
-- 
Dave Danielson -   CONCURRENT COMPUTER CORPORATION - Oceanport,NJ 07728
FAX   : 201/870-4249                                PHONE: 201/870-4137
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