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LMP & neighbor discovery
Hello all,
I found the concept of neighbor discovery mentioned several times in
previous discussions on this list. However, I did not find a final
conclusion on how this neighbor discovery is done. Correct ?
Could you please check my understanding below ?
In my mind, reading the incoming 'access point identifier' [ITU-G.707]
and subsequent LMP 'link property correlation' form a perfect fit. By
simply encoding the sending node's IP address and local access point
number in the access point identifier (see e.g. [OIF.2000.159.01]), the
receiver can discover the data link (linkConnection in ITU terminology).
Subsequent 'link property correlation' could then a.o. check on bi-
directional fibering, matching data link properties and grouping of data
links into TE links.
Example: the following figure shows 4 network elements of which 2 terminate
the data link (TTPs, T) and two are transparent to the data link (CTPs, C).
E.g. NE-1 and NE-4 are SONET/SDH multiplexers; NE-2 and NE-3 are transparent
optical cross connects. The data link in this example is STM-N/OC-N.
+------+ +------+ +------+ +------+
| T-|--->--|-C C-|--->--|-C C-|--->--|-T |
| | A | | B | | C | |
| | | | | | | |
| NE-1 | | NE-2 | | NE-3 | | NE-4 |
+------+ +------+ +------+ +------+
NE-2 should, when it wants to discover data link B, connect a test-set that
sends an access point identifier to identify the sending connection point C
in NE-2. This test-signal should be send long enough for NE-3 to detect and
read the test-signal (a fixed, agreed upon timer is needed). NE-3 will
continuously scan all its not discovered input ports for a discovery signal.
At some point, it will detect the test-signal on data link B.
+------+ +------+ +------+ +------+
| T-|--->--|-C C-|--->--|-C C-|--->--|-T |
| | A | / | B | \ | C | |
| | | T | | T | | |
| NE-1 | | NE-2 | | NE-3 | | NE-4 |
+------+ +------+ +------+ +------+
When NE-3 has read the access point identifier in the test signal, data
link B is discovered. Subsequent link property correlation can then be
invoked.
Discovery of data link A is similar, except that the access point identifier
is continuously sent. Discovery of data link C is also similar, except that
the access point identifier is continuously monitored. In other words, there
is no need for a sending respectively monitoring 'test-set' in NE-1 and NE-4.
Data link type Access point identifier to be used
-------------- ----------------------------------
STM-N, OC-N J0
STS-1/3/.../VC-3/4/... J1
VT-1.5/VC-11/12 J2
Notes:
- I understand that LMP's link verification procedure is more efficient for
*already discovered* data links. It does not need the continuous scanning
on received access point identifiers in undiscovered CTPs (in the example:
in NE-3).
- Discovering the address of the sending access point might also go via a 'name
server'. This can, for example, be useful in case the address of this access
point can not be encoded in the limited length of the access point identifier.
B.t.w., could you please explain why the linkSummary and linkSummaryAck messages
have to go over a point-to-point control channel ? Is it also possible to
use the generic DCN network (MCN/SCN, can be IP-based, see ITU-G.7712) ?
In the latter case, we could simply use the normal UDP service of that network
to transport the linkSummary and linkSummaryAck messages ? Is implementation
of the LMP's 'control channel management' mandatory ?
Thanks !
Michiel
--
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| Michiel van Everdingen |
| Systems Engineer |
| Lucent Technologies - Optical Networking Group |
| Botterstraat 45, 1271 XL Phone : +31 35 687 4883 |
| P.O. Box 18, 1270 AA Fax : +31 35 687 5976 |
| Huizen, The Netherlands mailto:MvanEverdingen@lucent.com |
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