Subject: draft-hsingh-6man-enhanced-dad-02.txt - loopback text

From: Eli Dart <[email-masked]>
Date: Tue, 01 Nov 2011 13:37:58 -0700

Hi all,

In the terminology section, there is the following text describing Loopback:

    o  Loopback - A function in which the router's interface to the
       network is looped back, resulting in interface unavailability for
       regular data traffic forwarding.  See more details in section 9.1
       of [RFC1247].  Loopback function is commonly used to gain
       information on the quality of this interface, by employing
       mechanisms such as ICMPv6 pings, bit-error test etc.  Loopback
       function may be done locally or remotely.

I suggest the replacement of the above text with the following text:

Loopback - A function in which the router's interface (or the circuit to 
which the router's interface is connected) is looped back or connected 
to itself.  Loopback causes packets sent by the interface to be received 
by the interface, and results in interface unavailability for regular 
data traffic forwarding.  See more details in section 9.1 of [RFC1247]. 
  The Loopback function is commonly used in an interface context to gain 
information on the quality of the interface, by employing mechanisms 
such as ICMPv6 pings, bit-error tests, etc.  In a circuit context, it is 
used in wide area environments including optical dense wave division 
multiplexing (DWDM) and SONET/SDH for fault isolation (e.g. by placing a 
loopback at different geographic locations along the path of a wide area 
circuit to help locate a circuit fault).  The Loopback function may be 
employed locally or remotely.

I have looked briefly for a reference in standards for Loopback in a 
circuit context, and haven't found one yet.  However, I like the new 
text because it captures the notion that a circuit might be in loopback 
and therefore cause the interface to receive traffic it sent, where the 
current text (as well as its reference) covers only the interface case.

Comments welcome.

Thanks,

		--eli

-- 
Eli Dart                                            NOC: (510) 486-7600
ESnet Network Engineering Group (AS293)                  (800) 333-7638
Lawrence Berkeley National Laboratory
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