The DLCI value is not stored contiguously within the Address field of the
Frame Relay frame, but rather is subdivided into two separate components—one
containing the DLCI high-order bits, and the other containing DLCI low-order
bits.
A frame relay address field can be two, three, or four bytes in length. In
each case, the frame relay address field will contain:
- DE (Discard Eligible) bit information
- FECN (Forward Explicit Congestion Notification) information
- BECN (Backward Explicit Congestion Notification) information
- C/R (Command Response) information
- and EA (Extended Address) bits used to identify the length of the
Frame Relay address field that can be either two, three, or four
bytes in length.
Frame relay address field formats are as follows:
Two Byte Format
8 7 6 5 4 3 2 1
----------------------------------------------------------
| | | |
| DLCI (high order) | C/R | EA |
| | | |
----------------------------------------------------------
| | | | | |
| DLCI (low order) | FECN | BECN | DE | EA |
| | | | | |
----------------------------------------------------------
Three Byte Format
8 7 6 5 4 3 2 1
----------------------------------------------------------
| | | |
| DLCI (high order) | C/R | EA |
| | | |
----------------------------------------------------------
| | | | | |
| DLCI | FECN | BECN | DE | EA |
| | | | | |
----------------------------------------------------------
| | | |
| DLCI (low order) or DL-CORE Control | D/C | EA |
| | | |
----------------------------------------------------------
Four Byte Format
8 7 6 5 4 3 2 1
----------------------------------------------------------
| | | |
| DLCI (high order) | C/R | EA |
| | | |
----------------------------------------------------------
| | | | | |
| DLCI (low order) | FECN | BECN | DE | EA |
| | | | | |
----------------------------------------------------------
| | |
| DLCI | EA |
| | |
----------------------------------------------------------
| | | |
| DLCI (low order) or DL-CORE Control | D/C | EA |
| | | |
----------------------------------------------------------
If you issued a "show frame-relay map" command on a Cisco router, you'll
notice two hexadecimal values that follow the DLCI number - the first is the
DLCI as it is configured on the router, the second is the value as it
appears within the address header when separated into the high- and
low-order bits.
Serial0 (up): ip 10.0.1.100 dlci 104(0x68,0x1880), broadcast
Just a bit of interesting trivia... oh how I love Frame Relay!
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Tony van Ree
Sent: February 7, 2001 3:11 PM
To: Giuseppe Albucci; [EMAIL PROTECTED]
Subject: Re: help about frame relay
Hi,
Chatting with one of the frame guys beside me he tells me there is an
extended DLCI range available in the header. This is made up of an extra 2
octets. These are the 'upper DLCI field' the normal DCLI lives in the
'lower dlci field'
There is a white paper at
http://www.ins.com/knowledge/whitepapers/frame0798.asp
Teunis,
Hobart, Tasmania
Australia
On Wednesday, February 07, 2001 at 11:05:17 AM, Giuseppe Albucci wrote:
> Hi, a need some information about "upper DLCI field" ad "lowerDLCI field".
>
>
> Thanks
>
> Giuseppe Albucci
> Product Manager Networking & Nortel
> Global Knowledge Network Italia
> Tel: +39 06 68194816
> Fax: +39 06 68194880
> http://www.globalknowledge.it
> mailto:[EMAIL PROTECTED]
>
>
>
> _________________________________
> FAQ, list archives, and subscription info:
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>
>
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