Re: Update to OSPF Hello procedure[draft-kou-ospf-immediately-replying-hello-00.txt]

Zengjie Kou <kouzengjie@HUAWEI.COM> Sat, 31 December 2005 08:29 UTC

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From: Zengjie Kou <kouzengjie@HUAWEI.COM>
Subject: Re: Update to OSPF Hello procedure[draft-kou-ospf-immediately-replying-hello-00.txt]
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Hi,Mitchell

    Please see inline for answers to your questions.


----- Original Message ----- 
From: "Erblichs" <erblichs@EARTHLINK.NET>
To: <OSPF@PEACH.EASE.LSOFT.COM>
Sent: Friday, December 30, 2005 12:09 PM
Subject: Re: Update to OSPF Hello procedure[draft-kou-ospf-immediately-replying-hello-00.txt]


> Kou,
> 
> 1) A few extra hellos? You will force a matrix number
>    of hellos? With 10 routers, you will need 90 hellos.
>    With 100 routers, we have 9900 hellos I think, if
>    we need to respond to each nbr's hello. Where we have
>    2x the number of router's hellos in the standard method
>    with MC hellos (20 and 200). Oh, yours are with ms of
>    each other and the standard hellos are spread along the
>    hello interval.
> 
1.) Immediate Hello can be enable or disable.
2.) On broadcast and NBMA networks, Immediate Hello expedite link recovery when a link goes down then up and does bring a few extra hellos(with 10 routers, will need 27(9*3) hellos ).

At the moment of router booting, the Immediate Hello is not fit. So, we can disable it.

> 2)
> I disagree, this can effect DR election.
> 
> How? Assume their is a disagreement as to whom
> should be elected DR in the normal method. Now, with
> that quick hello, the faster router tells the other
> routers not just whom he choose, but who is the DR.
> 
> Anytime before DR is elected, Y informs that X is the DR,
> then OSPF says X is the DR. You are saving on avg
> 1/2 hello interval time.
> 
> Now, why can their be a disagreement? Simply, a late
> hello informing about a new router with a higher priority
> before the DR is elected.
> 
> With the current method, we give an extra few secs, just
> to allow everyone to make up their own private decision, then 
> publicise the decision, and if their is a disagreement after
> recieving the multiple public hellos, then resolve it.
> 
> Yes, some implimentations ignore hellos with DR announcement
> after election has begun. But some don't. And I am refering
> to the later ones.
> 
> Now, it gets complicated. Assume that 2 routers who accept
> the fast hello and the interruption of the DR process. Won't
> they form a full ADJ if one or both are the DR / BDR? Now,
> the 3rd guy heard a hello from the highest priority router
> and accepted him as the DR? Aren't you needlessly trying
> to sync the LSDBs with the wrong DR?
> 
> Mitchell Erblich
> 
> 
> 
Sorry, I don't know what is your question.
1)Why is DR election  interrupted? Why is DR election wrong? With two routers, one is DR, another is BDR, their hello packets include DR/BDR information.

Thanks
Kou.

> Zengjie Kou wrote:
>> 
>> Hi,Manav
>>     I don't find any harm except a few additional hello packets before the state reaches "ExStart".
>> 
>>     The Immediate Hello do not affect which router will be elected DR. It only expedite the election.
>> 
>> thanks
>> kou.
>> 
>> ----- Original Message -----
>> From: "Manav Bhatia" <manav_bhatia06@YAHOO.CO.UK>
>> To: <OSPF@PEACH.EASE.LSOFT.COM>
>> Sent: Thursday, December 29, 2005 7:27 PM
>> Subject: Re: Update to OSPF Hello procedure[draft-kou-ospf-immediately-replying-hello-00.txt]
>> 
>> > So whats the harm in this?
>> >
>> > If you wanted a particular router to become the DR then you would have given it a higher priority.
>> > The fact that you havent done that implies that you dont really care which router becomes the DR.
>> >
>> > Manav
>> > --- Nitin Kakkar <nitink@HUAWEI.COM> wrote:
>> >
>> >> Suppose there are n routers on a Link and all of them come up almost
>> >> simultaneously.
>> >>
>> >> Seems like the routers which were fractionally faster to send hello will be
>> >> picked for DR/BDR election !!!
>> >>
>> >>
>> >>
>> >> May be you can think of  immediately replying to hello packet "Only when DR
>> >> is already elected on the link".
>> >>
>> >>
>> >>
>> >> Rgds
>> >>
>> >> Nitin
>> >>
>> >>
>> >>
>> >> -----Original Message-----
>> >> From: Mailing List [mailto:OSPF@PEACH.EASE.LSOFT.COM] On Behalf Of
>> >> Kouzengjie
>> >> Sent: Thursday, December 29, 2005 7:51 AM
>> >> To: OSPF@PEACH.EASE.LSOFT.COM
>> >> Subject: Update to OSPF Hello
>> >> procedure[draft-kou-ospf-immediately-replying-hello-00.txt]
>> >>
>> >>
>> >>
>> >> A New Internet-Draft is available from the on-line Internet-Drafts
>> >> directories.
>> >> The draft can be found here:
>> >> http://www.ietf.org/internet-drafts/draft-kou-ospf-immediately-replying-hell
>> >> o-00.txt
>> >>
>> >>
>> >>
>> >>  This memo documents an extension of the OSPF protocol to reach
>> >>    "ExStart" state more quickly. Currently, the OSPF behavior requires
>> >>    the Hello Packet to be sent between the neighbors every
>> >>    HelloInterval. This document proposes to generalize the use of
>> >>    Immediately Replying Hello which could reduce the time required to
>> >>    reach the OSPF "ExStart" state and  expedite the routing table
>> >>    convergence.
>> >>
>> >>
>> >
>> >
>> >
>> >
>> > ___________________________________________________________
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