[rbridge] Should we optimize the common case?

Tue Nov 7 10:22:54 PST 2006

Looking at Silvano's proposed shim header---the only reason
we need the outer header is to distinguish between RBridge neighbors,
in the case of unicast, specifying next hop, and in the case of
multicast, specifying transmitter.

His format has two bytes after the Ethernet header portion of the shim
for TTL, and a bunch of reserved bits.

That leaves 10 bits. We can dynamically (through the IS-IS Hello)
give out, say, 4 bit link-local nicknames, and stick them there.

Then the only time we'd need an outer header is if there are more than,
say, 16 RBridges on the same link.

Radia

Silvano Gai wrote:

>I am not looking at TRILL for increased scalability, but for spanning
>tree replacement to get high bisectional bandwidth.
>
>-- Silvano
>
>  
>
>>-----Original Message-----
>>From: Gray, Eric [mailto:Eric.Gray at marconi.com]
>>Sent: Monday, November 06, 2006 10:38 AM
>>To: Silvano Gai; Eastlake III Donald-LDE008; rbridge at postel.org
>>Subject: RE: [rbridge] Should we optimize the common case?
>>
>>Silvano,
>>
>>	The assertion that only fortune 500 companies are interested in
>>TRILL is baseless and untrue.  One reason why you may believe this is
>>the case, is that you are making certain assumptions about complexity
>>and scale of the desired solution that are equally unfounded or false.
>>
>>	There is nothing that particularly prohibits definition of some
>>form of RBridge functionality that might be simple enough to deploy in
>>relatively small networks - where higher speed link are becoming more
>>common and wasting high speed links is also a problem.
>>
>>	The types of networks you're talking about cannot realistically
>>operate with plug & play devices, and greater scalability is
>>    
>>
>paramount.
>  
>
>>The work we're doing in this WG is aimed at simplistic, plug & play
>>deployment where increased scalability is a secondary consideration.
>>
>>--
>>Eric
>>
>>--> -----Original Message-----
>>--> From: rbridge-bounces at postel.org
>>--> [mailto:rbridge-bounces at postel.org] On Behalf Of Silvano Gai
>>--> Sent: Monday, November 06, 2006 1:51 AM
>>--> To: Eastlake III Donald-LDE008; rbridge at postel.org
>>--> Subject: Re: [rbridge] Should we optimize the common case?
>>-->
>>-->
>>--> Donald,
>>-->
>>--> The high end and the low end are extremely different.
>>-->
>>--> The customers interested in TRILL are the Fortune 500
>>--> companies. Large
>>--> Enterprise networks and large data centers used to run Financial,
>>--> Insurance, Health, Chemical, Oil, Information and manufacturing
>>--> companies.
>>-->
>>--> They have huge demand for high bandwidth and low latency.
>>-->
>>--> Each of these companies spends millions each year in
>>--> network operation
>>--> (OPEX) and millions in new equipment (CAPEX). In all of them OPEX
>>    
>>
>is
>  
>
>>--> much larger than CAPEX. They only buy major vendor
>>--> equipments and they
>>--> install them according to the recommended vendor design guideline.
>>--> Typically they have an internal certification lab in which
>>--> they test the
>>--> network configuration and the software releases before
>>--> putting them in
>>--> production networks.
>>-->
>>--> They have a very well defined concept of backbone ports and access
>>--> ports. All the backbone ports are in fiber at the highest
>>--> possible speed
>>--> (today 10 GE). For the access port they use a mix of fiber
>>--> and copper.
>>--> The backbone has a regular structure that matches the vendor
>>    
>>
>design
>  
>
>>--> guideline and the result of the certification experiment
>>--> they have done
>>--> independently.
>>-->
>>--> A network outage can cost millions/hour.
>>-->
>>--> There is no way you will see in one of these backbones a hub or
>>    
>>
>any
>  
>
>>--> other uncontrolled device. NEVER.
>>-->
>>--> That is the reason why I think this is the most important case for
>>--> TRILL.
>>-->
>>--> More inline.
>>-->
>>--> > -----Original Message-----
>>--> > From: rbridge-bounces at postel.org
>>--> [mailto:rbridge-bounces at postel.org]
>>--> On
>>--> > Behalf Of Eastlake III Donald-LDE008
>>--> > Sent: Sunday, November 05, 2006 10:20 PM
>>--> > To: rbridge at postel.org
>>--> > Subject: Re: [rbridge] Should we optimize the common case?
>>--> >
>>--> > Silvano,
>>--> >
>>--> > Why do you think that 90% of Rbridge deployment will be for this
>>--> unusual
>>--> > case? I mean, I have no problem with the belief that
>>--> Rbridges would be
>>--> > better than bridges in this case but why shouldn't that be true
>>    
>>
>of
>  
>
>>--> less
>>--> > high end uses?
>>--> >
>>--> > A while ago on this list I posted a rhetorical question as to
>>    
>>
>why
>  
>
>>--> > Rbriges shouldn't eventually replace all bridges. No one posted
>>    
>>
>an
>  
>
>>--> > answer.
>>-->
>>--> This technology will start in the high end and move down to
>>--> the lower
>>--> end. How low will it goes is a good question.
>>-->
>>--> The low end is extremely cost sensitive. When we buys a switch or
>>    
>>
>a
>  
>
>>--> router on the Internet for 50-100$, the COGS cannot be more
>>--> that 15-30$,
>>--> even with low margins. This implies that few dollar more to
>>--> increase the
>>--> memory size or the processor speed are a big deal. Add software
>>--> development cost. Couple this with the fact that today we
>>--> have low cost
>>--> 1GE switches used by low-end users that have problems
>>--> pushing or pulling
>>--> more than few Mb/s. There is no bandwidth demand in the low end.
>>--> Spanning tree is just fine. Cost is the big issue. Moreover
>>--> there is the
>>--> huge issue of training home/small office installers in this new
>>--> technology.
>>-->
>>--> My 0.2 cents
>>-->
>>--> -- Silvano
>>-->
>>--> >
>>--> > Why not specify Rbridges more or less as we have been for
>>--> the common
>>--> > bridge case and, in the backbone case you are talking
>>--> about, just drop
>>--> > the MAC addresses on the point-to-point links within the
>>    
>>
>backbone?
>  
>
>>--> > Doesn't that produce less overhead than your proposal
>>--> below in both
>>--> the
>>--> > point-to-point and shared media cases?
>>--> >
>>--> > Donald
>>--> >
>>--> > -----Original Message-----
>>--> > From: rbridge-bounces at postel.org
>>--> [mailto:rbridge-bounces at postel.org]
>>--> On
>>--> > Behalf Of Silvano Gai
>>--> > Sent: Wednesday, November 01, 2006 9:07 PM
>>--> > To: rbridge at postel.org
>>--> > Subject: [rbridge] Should we optimize the common case?
>>--> >
>>--> >
>>--> > With 16 bit addresses the current TRILL overhead over
>>--> Ethernet is 20
>>--> > bytes. If we want to expand the RBridge addresses, it we
>>--> will go to
>>--> > 22-24 bytes.
>>--> >
>>--> > What customers are telling us is that they will deploy RBridges
>>    
>>
>by
>  
>
>>--> > creating an RBridge backbone in which all the links will be
>>    
>>
>10GE.
>  
>
>>--> >
>>--> > They will connect regular bridges and host to the
>>--> periphery of this
>>--> > backbone.
>>--> >
>>--> > They will not mix backbone ports with access ports, because this
>>--> screws
>>--> > up management, traffic engineering, debugging, and
>>--> troubleshooting.
>>--> > Regular network design, easy to understand, is very
>>--> important. Ports
>>--> are
>>--> > cheap, labor is expensive.
>>--> >
>>--> > I am totally convinced that this will account for 90+ % of TRILL
>>--> > deployment.
>>--> >
>>--> > I am wondering if it makes sense to have a solution
>>--> highly optimized
>>--> for
>>--> > such an environment.
>>--> >
>>--> > For example we can put the egress/ingress RBridge addresses in
>>    
>>
>the
>  
>
>>--> outer
>>--> > MAC addresses and define a TRILL shim header that
>>--> contains 1 byte of
>>--> hop
>>--> > limit and 1 byte reserved. For this common case we will get:
>>--> > 1) overhead of 16 bytes (4 to 8 bytes lower)
>>--> > 2) nickname = MAC address, i.e no hash collision
>>--> > 3) zero-conf achieved
>>--> >
>>--> > In the case we need to go over a shared media we will need to
>>    
>>
>add
>  
>
>>--> > another Ethernet encapsulation to carry the next hop
>>--> address, i.e. 14
>>--> > bytes
>>--> > - total overhead will be 30 bytes
>>--> >
>>--> > Summarizing:
>>--> > - current proposal 20-24 bytes overhead
>>--> > - new proposal on point to point: 16 bytes
>>--> > - new proposal on shared media: 30 bytes
>>--> >
>>--> > Comments?
>>--> >
>>--> > -- Silvano
>>--> >
>>--> >
>>--> > _______________________________________________
>>--> > rbridge mailing list
>>--> > rbridge at postel.org
>>--> > http://mailman.postel.org/mailman/listinfo/rbridge
>>--> >
>>--> > _______________________________________________
>>--> > rbridge mailing list
>>--> > rbridge at postel.org
>>--> > http://mailman.postel.org/mailman/listinfo/rbridge
>>-->
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>>-->
>>    
>>
>
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