Re: [vnrg] Layering vs. virtualization

[Pedro Andrés Aranda Gutiérrez <[e-mail]>]

Hi Monique

I was just trying to add my 10^-9 cents to Roland's question. The issue 
of administrative boundaries is IMvvvHO orthogonal to Roland's question.
I'm happy to discuss it too, but let's keep them separated.

Cheers,/PA

On 29/07/10 10:40, Monique Morrow (mmorrow) wrote:
> Further to layering vs virtualization is the issue of "control"  : implication of administrative domains  [inter-domain] -- or is it relevant?
>
> Monique
>
>
> -----Original Message-----
> From: [e-mail] on behalf of Pedro Andrés Aranda Gutiérrez
> Sent: Thu 7/29/2010 1:28 AM
> To: [e-mail]
> Subject: Re: [vnrg] Layering vs. virtualization
>
> Hi,
>
> Roland is really making an interesting point here. IMHO, we have to
> say which layer we are talking about. Examples I see:
>
> L1: DWDM; different lambdas are different virtual networks at L1
>
> L2: 802.1q
>
> L2.5:   the venerable ATM and MPLS nowadays
>
> Cheers,/PA
>
> On 29/07/10 10:20, Roland Bless wrote:
>> Hi,
>>
>> I thought a little bit more on that topic, e.g., whether IP
>> on top of Ethernet itself is a virtualization technique and I
>> think that it is not - longer rationale below. First, I want to second
>> what Aaron said: we should consider network technologies other
>> than IP in the substrate as well as in the virtual network. So
>> sometimes it is easier to think of some abstract substrate technology
>> instead of IP as substrate.
>>
>> However, I think one difference between "layering" and virtualization
>> is as follows:
>> when you put another protocol layer on top, you usually have to
>> do it in the "end-system"/at the end points, i.e., IP nodes are
>> sitting at L2 end points whereas L2 nodes (e.g., switches) are
>> transparent for L2 end points.
>> Same in L3 (letting the control plane aside for this moment):
>> routers as L3 network nodes are largely transparent for
>> the end-systems (except for first/last-hop routers),
>> i.e., a transport connection at L4 is normally
>> terminated in L3 end-systems. So in this way neither IP is a virtual
>> network on top of Ethernet nor is a TCP connection on top of IP, but I
>> would consider IP as an overlay and abstraction technique (it mainly
>> abstracts from different L2 networks in its substrate).
>>
>> In contrast, a virtualization technique in/at L2 involves mechanisms
>> within the L2 nodes, e.g., support of VLAN tagging.
>> A real network virtualization technique at layer 3 would require,
>> e.g., partitioning of a L3 node/a router; lets consider that you are
>> running a different protocol than IP in a partition.
>> The "hard part" now is getting/demultiplexing from the substrate
>> to the virtual parts of the router. There are various ways to do it
>> depending on the substrate's capabilities.
>> So using a dedicated physical L2 port would be one possibility,
>> using VLANs over a shared L2 cable would be another. If the substrate
>> is on higher layers MPLS LSPs or L3 tunnels etc. can be used.
>>
>> Sometimes it also helps to think on addressing the virtual resources
>> from the control plane inside the substrate. Basically you have
>> to address a VNet (denoting a specific virtual network),
>> a Virtual Node, and a specific Virtual Interface inside the
>> Virtual Node, e.g., in order to connect a substrate link/tunnel
>> to a specific interface of this particular virtual node.
>> However, it is not required that VNet-IDs, Virtual Node IDs,
>> or Virtual Link/Interface IDs are literally carried in substrate
>> data packets since there could be link-specific mapping techniques using
>> available multiplexing mechanisms, e.g., VLAN-tags.
>> In analogy one can denote such link-specific identifiers for VNets as
>> "VNet-Tags". A VNet-Tag identifies a virtual link in a link-specific
>> context. In absence of multiplexing support in the substrate, it may be
>> required to use an explicit shim header that carries the
>> VNet-Tag in order to allow proper demultiplexing of virtual networks on
>> a shared substrate link.
>>
>> To keep a long story short: when talking about virtualization
>> we must be specific which layer is actually virtualized or do we
>> consider layer 3 only?
>>
>> Regards,
>>    Roland
>> _______________________________________________
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>> https://www.irtf.org/mailman/listinfo/vnrg
>
> --
> Pedro A. Aranda Gutiérrez       Telefónica I+D
> Technology Specialist           New Network Technologies
> mailto: [e-mail]             C/Emilio Vargas,6
> Tlf: [phone]            E-28043 Madrid
>
> "Fragen sind nicht da, um beantwortet zu werden.
>    Fragen sind da, um gestellt zu werden" Georg Kreisler
> http://www.mendeley.com/profiles/pedro-a-aranda-gutierrez
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-- 
Pedro A. Aranda Gutiérrez	Telefónica I+D
Technology Specialist		New Network Technologies
mailto: [e-mail]		C/Emilio Vargas,6
Tlf: [phone]            E-28043 Madrid

"Fragen sind nicht da, um beantwortet zu werden.
  Fragen sind da, um gestellt zu werden" Georg Kreisler
http://www.mendeley.com/profiles/pedro-a-aranda-gutierrez