Re: [CCAMP] Overlay model framework and context

Lou Berger <lberger@labn.net> Wed, 19 December 2012 15:54 UTC

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Date: Wed, 19 Dec 2012 10:53:50 -0500
From: Lou Berger <lberger@labn.net>
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To: Daniele Ceccarelli <daniele.ceccarelli@ericsson.com>
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Cc: CCAMP <ccamp@ietf.org>
Subject: Re: [CCAMP] Overlay model framework and context
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Daniele,
	If ONI is a superset (i.e., covers all cases), what's the difference.
So the terminology options are:

For the signaling+routing(normal case):
	LB) customer interface with signaling and routing
	DC) ONI with signaling and routing
For the UNI case:
 	LB) customer interface with UNI
	DC) ONI with UNI

Right?

Lou

On 12/19/2012 10:32 AM, Daniele Ceccarelli wrote:
>  Lou, it's just a matter of convenience.
> 
> Why should is say: 
> "customer interface/link between an OE and an OC in the overlay model context supporting both signaling and routing message exchange that is called UNI when only signaling is supported"
> 
> ...when i could simply say: ONI? :)
> 
> BR
> Daniele
> 
>> -----Original Message-----
>> From: Lou Berger [mailto:lberger@labn.net] 
>> Sent: mercoledì 19 dicembre 2012 16.09
>> To: Daniele Ceccarelli
>> Cc: CCAMP
>> Subject: Re: [CCAMP] Overlay model framework and context
>>
>> Daniele,
>> 	see below.
>>
>>
>> On 12/19/2012 5:56 AM, Daniele Ceccarelli wrote:
>>> Hi Lou,
>>>
>>> Plese find replies in line.
>>>
>>> BR
>>> Daniele
>>>
>>>> -----Original Message-----
>>>> From: Lou Berger [mailto:lberger@labn.net]
>>>> Sent: lunedì 17 dicembre 2012 20.45
>>>> To: Daniele Ceccarelli
>>>> Cc: CCAMP
>>>> Subject: Re: [CCAMP] Overlay model framework and context
>>>>
>>>>
>>>> Daniele,
>>>> 	Thanks for getting this on-list discussion going.  I have some 
>>>> comments and questions:
>>>>
>>>> - So what's a "client layer network" in this context?  Perhaps you 
>>>> mean OC or "(overlay) customer layer"?
>>>
>>> Yes. The terms client layer and server layer are 
>> reminescences to be corrected.
>>>
>>>>
>>>> - So what's a "server layer network" in this context?  Perhaps you 
>>>> mean OE or "(overlay) provider layer"?
>>>
>>> Again correct
>>>
>>>>
>>>> - For OC, I'd thing referring back to a CE in the VPN context, and 
>>>> likewise to a PE for an OE, is helpful context.
>>>
>>> In the case of the interface we generally define the ONI as 
>> an overlay 
>>> interface that in a particular case is called UNI.
>>
>> I have no idea what this means.  I suspect it relates to 
>> comments below, so will discuss there.
>>
>>> I would
>>> apply the same method: those nodes are called Overlay Customer and 
>>> Overlay Edge and in the particular case of VPNs they are the 
>> CE and PE 
>>> respectively. What about that?
>>>
>>
>> How about:
>>
>> An OC is analogous to an L3VPN CE, and an OE is analogous to 
>> an L3VPN PE (with a provider based VPN).
>>
>>>>
>>>> - As you mention in the Appendix, (from the OC perspective) 
>> there is 
>>>> no difference between a virtual and real node (and 
>> presumably link as 
>>>> well).  Given this and your comment in 8, that the ONI can take the 
>>>> form of a UNI or include both signaling and routing (i.e., a 
>>>> peer/I-NNI or
>>>> E-NNI) what value is there in introducing the ONI term?  
>> Said another 
>>>> way, there's no specific term for the interface between a CE and PE 
>>>> in L3VPNs, so why do we need to introduce one in this context?
>>>
>>> We gave a name to the UNI, why don't giving to the ONI?
>>
>> Because redundant/unnecessary terminology only obfuscates.
>>
>> Why not customer interface/link? This has been sufficient for L3VPNs.
>>
>>>
>>>>
>>>> I think this same comment probably holds for the O-NNI 
>> (e.g., what's 
>>>> the name of the interface between providers which support L3VPN 
>>>> handoffs?)...
>>>
>>> I would suggest giving a name to that interface also in 
>> order to distinguish between an "internal" and an "external" 
>> link when multiple overlay provider network domains are present.
>>>
>>
>> How about inter-provider interface/link? Again, this has been 
>> sufficient for L3VPNs.
>>
>> Lou
>>
>>>>
>>>> Much thanks,
>>>> Lou
>>>>
>>>> On 12/17/2012 6:17 AM, Daniele Ceccarelli wrote:
>>>>> Dear CCAMPers,
>>>>>
>>>>> In the last weeks several off-line discussions on the
>>>> Overlay model framework and related works took place. Some 
>>>> discussions led to some sort of agreemet among a small group of 
>>>> people, some others to a set a viable options, some others 
>> to totally 
>>>> open issues. I tried to summarize the output of such discussions 
>>>> below so to progress the discussions into a single thread on the WG 
>>>> ML.
>>>>>
>>>>> Please note that the aim of this mail is not to present a
>>>> well shaped and conclusive idea to the WG but rather to provide the 
>>>> basis for starting a discussion from a barely shaped idea (step 1) 
>>>> instead of starting it from scratch (step 0).
>>>>>
>>>>> In addition you can find attached a slide depicting a
>>>> proposal of the overlay scenario.
>>>>>
>>>>> Thanks,
>>>>> Daniele
>>>>>
>>>>> + Disclaimer:
>>>>>  1. Packet opto integration is often considered but the work
>>>> can be extented to any type of SC. Eg. TDM over LSC.
>>>>>
>>>>> + Terminology:
>>>>>
>>>>>  1. Virtual Link: A virtual link is a potential path between
>>>> two virtual or real network elements in a client layer network that 
>>>> is maintained/controlled in and by the server domain control plane 
>>>> (and as such cannot transport any traffic/data and protected from 
>>>> being de-provisioned) and which can be instantiated in the 
>> data plane 
>>>> (and then can carry/transport/forward traffic/data) preserving 
>>>> previously advertised attributes such as fate sharing information.
>>>>>  2.  Virtual Node: Virtual node is a collection of zero or
>>>> more server network  domain nodes that are collectively represented 
>>>> to the clients as a single node that exists in the client layer 
>>>> network and is capable of terminating of access, inter-domain and 
>>>> virtual links.
>>>>>  3.Virtual Topology: Virtual topology is a collection of one
>>>> or more virtual or real server network domain nodes that 
>> exist in the 
>>>> client layer network and are interconnected via 0 or more virtual 
>>>> links.
>>>>>  4. Overlay topology:  is a superset of virtual topologies
>>>> provided by each of server network domains, access and inter-domain 
>>>> links.
>>>>>  5. Access Link: Link between OC and OE. GMPLS runs on that
>>>> link. It can support any of the SCs supported by the GMPLS.
>>>>>  6. Overlay Customer (OC): Something like the CN in RFC4208
>>>> teminology  but (i) receiving virtual topology from the 
>> core network 
>>>> and requesting the set up of one of them or (ii) requesting the 
>>>> computation and establishment of a path accordingly to gien 
>>>> constraints in the core network and receiving the parameters 
>>>> characterizing such path. (ii) == UNI.
>>>>>  7. Overlay Edge (OE): Something like the EN in RFC4208 but
>>>> able to deal with (i) and (ii) above.
>>>>>  8. ONI : Overlay network interface: Interface allowing for
>>>> signaling and routing messages exchange between Overlay and  Core 
>>>> network. Routing information consists on virtual topology  
>>>> advertisement. When there is no routing adjacency across the  
>>>> interface it is equivalent to the GMPLS UNI defined in 4208.
>>>> Signaling messages are compliant with RFC4208. Information  related 
>>>> to path carachteristics, e.g. TE-metrics, collected  SRLG, 
>> path delay 
>>>> etc, either passed from OE to OC via  signaling after the LSP 
>>>> establishment in the core network or from OC to OE to be 
>> used as path 
>>>> computation constraints, fall  under the definition of 
>> signaling info 
>>>> and not routing info).
>>>>>  9. O-NNI (name to be found,maybe reused): Interface on the
>>>> links between different core networks in the overlay model 
>>>> environment, i.e. Between border OEs. Same features of the 
>> ONI apply 
>>>> to this interface. Could it be an E-NNI? A ONI? A new name 
>> is needed?
>>>>>
>>>>> + Statements
>>>>>  1. In the context of overlay model we are aiming to build
>>>> an overlay
>>>>> topology for the client network domains  2. The overlay
>>>> topology is comprised of:
>>>>>     a) access links (links connecting client NEs to the
>>>> server network domains). They can be PSC or LSC.
>>>>>     b) inter-domain links (links interconnecting server
>>>> network domains)   
>>>>>     c) virtual topology provided by the server network
>>>> domains. Virtual Links + Virtual Nodes (TBD) + Connectivity Matrix 
>>>> (with a set of parameters e.g. SRLG, optical impairments, delay etc 
>>>> for each entry) describing connectivity between access links and 
>>>> virtual links.
>>>>>  3. In the context of overlay model we manage  hierarchy  
>> of overlay 
>>>>> topologies with overlay/underlay relationships  4. In the 
>> context of 
>>>>> overlay model multi-layering and inter-layer relationships
>>>> are peripheral at best, it is all about horizontal network 
>>>> integration  5. The overlay model assumes one instance for 
>> the client 
>>>> network and a separate instance for the server network and 
>> in the ONI 
>>>> case the server network also surreptitiously participates in the 
>>>> client network by injecting virtual topology information into it.
>>>>>  6. L1VPN (and LxVPN) in general is a service provided over
>>>> the ONI (it falls under the UNI case as no routing adjacency is in 
>>>> place between OC and OE).
>>>>>
>>>>> + Open issues/questions
>>>>>  
>>>>>  1. PCE-PCEP - do we need to include considerations about
>>>> PCE and PCEP into the overlay framework context?
>>>>>  2. BGP-LS needs to be considered
>>>>>  3. Should potentials be included? E.g. I2RS?
>>>>>
>>>>> + Appendix:
>>>>> Some notes on the Virtual Node:
>>>>> 1.      Virtual Link Model along, sadly, does not scale 
>>>> because of N**2 problem. IP over ATM and single-segment PWs 
>> have the 
>>>> same issue, that's why people invented multi-segment PWs
>>>>> 2.      The only way to avoid full-mesh of Virtual Links is 
>>>> by having intermediate nodes interconnecting Virtual Links in the 
>>>> middle of the virtual topology
>>>>> 3.      These intermediate nodes cannot be real server 
>>>> domain switches, because, generally speaking:
>>>>>   a)Real switches belong to different layer network;
>>>>>   b)Real switches are named from different naming space
>>>>>   c)real switches individually may not have sufficient
>>>> resources to terminate virtual links (while a group of real 
>> switches 
>>>> collectively will have)
>>>>>   d)Presenting a group of real switches as a single virtual
>>>> node have better scalability qualities
>>>>> 4.      Even if you map a virtual node on a single real 
>>>> node, you need to keep in mind that real server domain 
>> switches are, 
>>>> generally speaking, blocking switches and as such must expose their 
>>>> connectivity matrices
>>>>> 5.      If you want to compute SRLG-disjoint paths that 
>>>> could potentially go through a real server domain switch, the 
>>>> latter's connectivity matrix must expose "internal" SRLGs, so that 
>>>> the two services traversing the switch will not simultaneously fail 
>>>> if a single internal element shared by the services fails
>>>>> 6.      If you walk through all cases that need to be 
>>>> addressed when you are traffic engineering topologies with blocking 
>>>> switches, you will understand that there is absolutely no 
>> difference 
>>>> between a virtual node and real blocking real node.
>>>>> 7.      Even in case of pure VL model, client NEs connected 
>>>> to server network domain must be upgraded so that they could 
>>>> understand the connectivity matrices advertised by the border nodes 
>>>> describing connectivity constraints between access links 
>> and virtual 
>>>> links they terminate.
>>>>>
>>>>>
>>>>>  
>>>>> ===================================
>>>>> DANIELE CECCARELLI
>>>>> System & Technology - PDU Optical & Metro
>>>>>
>>>>> Via E.Melen, 77
>>>>> Genova, Italy
>>>>> Phone +390106002512
>>>>> Mobile +393346725750
>>>>> daniele.ceccarelli@ericsson.com
>>>>> www.ericsson.com
>>>>>
>>>>> This Communication is Confidential. We only send and receive
>>>> email on
>>>>> the basis of the term set out at www.ericsson.com/email_disclaimer
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> CCAMP mailing list
>>>>> CCAMP@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/ccamp
>>>>>
>>>>
>>>
>>>
>>>
>>
> 
> 
>