IETF Open Shortest Path First general discussion

Richard Ogier | 7 Dec 2007 19:52

Re: OSPF-MDR options

Philippe,

The MDR draft gives some guidance regarding the options, e.g., that 
uniconnected adjacencies and partial-topology LSAs should be used to 
minimize overhead, but I agree that it would be good to include a better 
explanation of parameter choices.

The default configuration is recommended for most scenarios.  The 
optional configurations are included either because some people have 
expressed a preference to use full-topology adjacencies and LSAs (which 
also simplifies the protocol), or to provide greater scalability 
(LSAFullness = 0) or greater robustness (AdjConnectivity = 2).  More 
experimentation is needed to evaluate the benefits of these optional 
configurations.

I expect that the configuration will be selected before deployment 
depending on the scenario, and not changed during operations based on 
automatic scenario recognition.  However, if one chooses to change the 
parameters during operations, a nice property of OSPF-MDR is that each 
router can change its options independently of the other routers (as 
discussed in my previous message).

BTW, I noticed an error in the "corrected" paragraph of my previous 
message: "LSAFullness" should be changed to "AdjConnectivity", as follows:

Thus, the only case in which interoperability is an issue is if some 
routers use adjacency reduction while others do not.  This can be 
handled by adding an option bit for adjacency reduction to the Hello 
TLV, and always forming an adjacency with a neighbor that has selected 
AdjConnectivity = 0 (no adjacency reduction).  With this option bit,

(Continue reading)

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Thomas, Matthew R | 7 Dec 2007 20:18

RE: OSPF-MDR options

Thanks Philippe for that last clarification. It took me back to the drawing board to make sure I understood
the Fullness :o) With the type of scarios needing to be covered these features seem to be a minimum
required. The fact that the routers can independently change and still work together is very useful.

Matthew

________________________________

From: Richard Ogier [mailto:ogier <at> earthlink.net]
Sent: Fri 07/12/2007 18:52
To: Philippe Jacquet
Cc: ospf <at> ietf.org
Subject: Re: [OSPF] OSPF-MDR options

Philippe,

The MDR draft gives some guidance regarding the options, e.g., that
uniconnected adjacencies and partial-topology LSAs should be used to
minimize overhead, but I agree that it would be good to include a better
explanation of parameter choices.

The default configuration is recommended for most scenarios.  The
optional configurations are included either because some people have
expressed a preference to use full-topology adjacencies and LSAs (which
also simplifies the protocol), or to provide greater scalability
(LSAFullness = 0) or greater robustness (AdjConnectivity = 2).  More
experimentation is needed to evaluate the benefits of these optional
configurations.

I expect that the configuration will be selected before deployment

(Continue reading)

headers

Thomas, Matthew R | 7 Dec 2007 20:23

FW: OSPF-MDR options

Sorry I meant "Thanks Richard".. my turn for a typo..

________________________________

From: Thomas, Matthew R
Sent: Fri 07/12/2007 19:18
To: Richard Ogier; Philippe Jacquet
Cc: ospf <at> ietf.org
Subject: RE: [OSPF] OSPF-MDR options

Thanks Philippe for that last clarification. It took me back to the drawing board to make sure I understood
the Fullness :o) With the type of scarios needing to be covered these features seem to be a minimum
required. The fact that the routers can independently change and still work together is very useful.

Matthew

________________________________

From: Richard Ogier [mailto:ogier <at> earthlink.net]
Sent: Fri 07/12/2007 18:52
To: Philippe Jacquet
Cc: ospf <at> ietf.org
Subject: Re: [OSPF] OSPF-MDR options

Philippe,

The MDR draft gives some guidance regarding the options, e.g., that
uniconnected adjacencies and partial-topology LSAs should be used to
minimize overhead, but I agree that it would be good to include a better
explanation of parameter choices.

(Continue reading)

headers

Richard Ogier | 24 Jan 2008 19:54

OSPF-MDR welcomes comments

All,

I encourage people to read and send comments for the OSPF-MDR draft:
http://www.ietf.org/internet-drafts/draft-ogier-manet-ospf-extension-10.txt

So far, the following changes are planned for the February 25 deadline:

1. Add an option bit to the Hello TLV, which indicates whether
AdjConnectivity = 0 (no adjacency reduction).
A router always forms an adjacency with a bidirectional neighbor
that has set this bit.  As a result, interoperability is achieved
even if each router chooses AdjConnectivity and LSAFullness
independently of the other routers.

2. Clarify the rationale for selecting parameter values and
the fact that different routers need not select the same
parameter values for the new MDR parameters.

3. In the algorithm descriptions, instead of using the term
"neighbor" as an abbreviation for "bidirectional neighbor",
use the term "bi-neighbor".

Richard