Christian, 

The SDWAN use case  is about grouping a set of nodes in geographically 
different locations to be one TTZ zone being treated as one Virtual Node. 

Linda

-----Original Message-----
From: Christian Hopps <[email protected]> 
Sent: Saturday, July 11, 2020 6:42 AM
To: Linda Dunbar <[email protected]>
Cc: Christian Hopps <[email protected]>; LEI LIU <[email protected]>; Huaimo Chen 
<[email protected]>; [email protected]; [email protected]
Subject: Re: [Lsr] Request WG adoption of TTZ



> On Jul 10, 2020, at 4:39 PM, Linda Dunbar <[email protected]> wrote:
> 
> I also support the adoption of TTZ draft.
> 
> The Virtual Zone concept would be very useful for the Overlay networks. The 
> proposed TTZ can group a set of nodes not geographically together into one 
> virtual area to scale virtual overlay networks with lots of nodes. Those kind 
> overlay networks are getting more momentum in SDWAN and CDN environment.

I'm not sure I follow this use-case. The intent of TTZ is to treat a bunch of 
nodes as a single node (or subset of nodes in early work) to reduce the 
link-state DB size and flooding requirements, AFAICT.

Thanks,
Chris.
[As WG member]


> 
> Linda Dunbar
> 
> From: Lsr <[email protected]> On Behalf Of LEI LIU
> Sent: Friday, July 10, 2020 12:42 PM
> To: Huaimo Chen <[email protected]>
> Cc: [email protected]; [email protected]
> Subject: Re: [Lsr] Request WG adoption of TTZ
> 
> I support the adoption of the TTZ draft.
> 
> The operation on TTZ is simple. Smooth transferring between a zone and a 
> single node will improve customer experience. The work on TTZ should be moved 
> forward.
> 
> Thanks,
> Best regards,
> 
> Lei
> 
> On Thu, Jun 18, 2020 at 8:38 PM Huaimo Chen <[email protected]> wrote:
> Hi Chris and Acee, and everyone,
> 
> 
> 
>     I would like to request working group adoption of "Topology-Transparent 
> Zone"
> 
> (TTZ for short) https://datatracker.ietf.org/doc/draft-chen-isis-ttz/ .
> 
> 
> 
>     This draft comprises the following solutions for helping to improve 
> scalability:
> 
>         1) abstracting a zone to a single pseudo node in IS-IS,
> 
>         2) abstracting a zone to a single pseudo node in OSPF,
> 
>         3) abstracting a zone to zone edges' full mess in IS-IS, and
> 
>         4) transferring smoothly between a zone and a single pseudo node.
> 
>     A zone is a block of an area (IS-IS L2 or L1 area, OSPF backbone or
> 
> non-backbone area).
> 
> 
> 
>     When a network area becomes (too) big, we can reduce its size in the sense
> 
> of its LSDB size through abstracting a zone to a single pseudo node or
> 
> abstracting a few zones to a few pseudo nodes.
> 
> 
> 
>     While a zone is being abstracted (or transferred) to a single pseudo node,
> 
> the network is stable. There is no or minimum service interruption.
> 
> 
> 
>     After abstracting a few zones to a few pseudo nodes, if we want to 
> reconstruct
> 
> them, we can transfer (or roll) any of the pseudo nodes back to its zone 
> smoothly
> 
> with no or minimum service interruption.
> 
> 
> 
>     We had a prototype implementation of abstracting a zone to zone edges' 
> full
> 
> mess in OSPF. The procedures and related protocol extensions for transferring
> 
> smoothly from a zone to zone edges' full mess are implemented and tested.
> 
> A zone (block of an OSPF area) is smoothly transferred to its edges’ full mess
> 
> without any routing disruptions. The routes on every router are stable while
> 
> the zone is being transferred to its edges' mess. It is very easy to operate
> 
> the transferring.
> 
> 
> 
>     There are two other drafts for improving scalability: "Area Proxy for 
> IS-IS"
> 
> (Area Proxy for short) and "IS-IS Flood Reflection" (Flood Reflection for 
> short).
> 
> 
> 
>     "Area Proxy" https://tools.ietf.org/html/draft-li-lsr-isis-area-proxy-03
> 
> abstracts an existing IS-IS L1 area to a single pseudo node.
> 
> 
> 
>     "Flood Reflection" 
> https://tools.ietf.org/html/draft-przygienda-lsr-flood-reflection-01
> 
> abstracts an existing IS-IS L1 area to its edges' connections via one or more
> 
> flood reflectors.
> 
> 
> 
>     We believe that TTZ has some special advantages even though
> 
> Area Proxy and Flood Reflection are very worthy. We would like
> 
> to ask for working group adoption of TTZ.
> 
> 
> 
> Best Regards,
> 
> Huaimo
> 
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