Subject: Re: [vnrg] way forward on VNRG definitions

From: Martin Röhricht <[email-masked]>
Date: Wed, 30 Jun 2010 14:55:59 +0200

Dear Joe,

On 08.06.2010 18:57 Joe Touch wrote:
> As a starting point, we would like to have everyone on the list answer the
> following questions. We would prefer short text rather than full paragraphs
> extracted from any I-D or other document.
> -----------------------------------------------------
>
> Starting questions:
>
> 1. how do you define VNs?

A VN is a network that appears to its users as an ordinary network by 
providing ordinary interfaces and services but which is actually 
decoupled from the physical substrate.

> 	1.a. what are the key components?

Virtual nodes, virtual links, management entities

> 	1.b. what is the relationship between these components?

An arbitrary number of virtual links may be spanned between an arbitrary 
number of virtual nodes.  A physical node may be equipped with multiple 
virtual nodes.  Virtual links are controlled by management entities 
residing on physical nodes and acting as mediators between pyhsical and 
virtual nodes.

> 	1.c. what is the characteristic behavior/capability of the
> 	resulting system?

The resulting virtual network provides its users the illusion of using a 
dedicated (physical) network with a set of guaranteed resources.  It 
should provide its services isolated from other virtual or physical 
networks that actually run on the same hardware.  Network management 
operations should be performed transparent for the network's users, e.g. 
by migrating nodes or links in the physical substrate.

> 2. what are VNs used for?

VNs may be used to provide a dedicated network for its users which 
operates isolated from any other network traffic.  They may be used to 
bring out completely new network architectures and protocols.  They may 
be used to optimize resource utilization either via aggregating or via 
distributing resources used for a virtual network.

> 3. what are they key challenges?
>
> for each challenge:
> 	- define the challenge
> 	- explain why it is hard
> 	- provide some references to those working on solutions

- Instantiation of virtual nodes and virtual links.  How can we a
  priori determine whether a virtual node exists or is actively running?
- Inter-domain-wide operation across multiple administrative domains.
  Comparable to the issues in QoS research we may be able to easily
  provide dedicated services to users within our domain, but providing
  these services inter-domain-wide may have some technical or business
  constraints.
- Dynamic and on-demand instantiation of virtual networks.  Instead of
  using a manual or semi-manual (e.g. script-based) configuration of
  virtual networks, it may be desirable to use signaling protocols for a
  dynamic and on-demand management of virtual networks.
- Network topologies. Talking about virtual networks, we may wish to
  not only control some virtual nodes and virtual links, but also create
  virtual network topologies, such as full-meshed networks, rings,
  trees, etc.
- Attachment of end-users---are they part of the virtual network? How
  do we cope with the mobility of end-users, again inter-domain-wide?
- Aggregation---to what level can we aggregate traffic by still
  preserving isolation and by not losing flexibility to migrate virtual
  nodes and virtual links to another location?
- Security---how can security be achieved?  Is it an integrated part of 
the virtual network architecture and transparent to its users?
- AAA---using virtual network resources breaks down to actually using
  physical resources of one or more network operators.  How do we
  provide authentication, authorization, and accountability?  How do we
  provide these AAA services inter-domain-wide?
- Are Quality-of-Service guarantees an inherent requirement for virtual
  networks? If yes, to what extent?
- Providing the users the opportunity to create completely new network
  architectures and protocols inside their virtual networks---how do we
  cope with interoperability?  Or do we run the risk of creating an
  »inverse Internet«?

That's it for now.

Martin

---

From: Didier Colle <[email-masked]>
Date: Tue, 13 Jul 2010 12:28:53 +0200

Dear Martin, all,

>  these services inter-domain-wide may have some technical or business
I tend to disagree with this point.
The abstraction as part of the virtualization should hide whether 
resources belong to one or multiple domain.
Scenario I am thinking of: global network service provider X and global 
network service provider Y obtain guaranteed virtual resources from 
virtual infrastructure provider P who aggregates and VIRTUALIZES 
resources (probably also partly virtual resources) obtained from local 
infrastructure provider A and in another local infrastructure provider 
B. Those local infrastructure providers might also deliver virtual 
resources directly to local service providers xa, xb, ya and yb.

Having said that, doing is much harder than saying a couple of words. 
Still I believe the abstraction and aggregation features of 
virtualization should enable overcoming multi-domain issues.
You are right, business constraints can probably not be solved by 
virtualization (probably not by any technical solution...). Having said 
that: what is the business scenario in which a provider delivers virtual 
network instances but putting in place business constraints preventing 
extensions to other domains?

Kind regards,

Didier

Martin Röhricht wrote:
> An arbitrary number of virtual links may be spanned between an 
> arbitrary number of virtual nodes.  A physical node may be equipped 
> with multiple virtual nodes.  Virtual links are controlled by 
> management entities residing on physical nodes and acting as mediators 
> between pyhsical and virtual nodes.
>
> The resulting virtual network provides its users the illusion of using 
> a dedicated (physical) network with a set of guaranteed resources.  It 
> operations should be performed transparent for the network's users, 
> e.g. by migrating nodes or links in the physical substrate.
>
> bring out completely new network architectures and protocols.  They 
> may be used to optimize resource utilization either via aggregating or 
> via distributing resources used for a virtual network.
>
> - Security---how can security be achieved?  Is it an integrated part 
> of the virtual network architecture and transparent to its users?
> _______________________________________________
> vnrg mailing list
> [email-masked]
> https://www.irtf.org/mailman/listinfo/vnrg

-- 
Didier Colle
Ghent University - IMEC - IBBT
Department of Information Technology (INTEC)
Gaston Crommenlaan 8 bus 201, B-9050 Gent (Ledeberg)
Email: [email-masked]
MSN: [email-masked]
Skype: didiercolle
Tel. +32 9 331 4970
Fax. +32 9 331 4899
Mobile: +32 473 295655
WWW: www.ibcn.intec.UGent.be

---

From: Joe Touch <[email-masked]>
Date: Wed, 14 Jul 2010 16:51:34 -0700

Hi, all,

Speaking as an *individual* contributor (i.e., with my RG-chair hat "off"):

I define them as composed of virtual routers, virtual hosts, and virtual 
links.

A virtual link is the easiest to define - it is a tunnel over some 
existing network path, i.e., with an additional layer of encapsulation 
that is used solely for the VN, but which is otherwise not needed.

A virtual host is a source or sink of packets on a virtual link.

A virtual router forwards packets between virtual links.

Note that nothing about these definitions specifies a boundary, i.e., 
inside a single machine, etc. I don't think those boundaries are 
meaningful in the base Internet anyway.

I.e., IMO, virtual has nothing per se to do with "logical". I.e., a set 
of devices on a network that source/sink packets with a single network 
address act as a single logical host. That's not 'virtual' to me, though 
most 'virtual' things tend to be logical, not all logical things are 
virtual.

> 	1.a. what are the key components?

See above; virtual link, virtual router, and virtual host.

> 	1.b. what is the relationship between these components?

See above; hosts source/sink packets, and routers forward them. When a 
router sources/sinks packets, IMO it acts as a host on the network for 
those messages.

> 	1.c. what is the characteristic behavior/capability of the

I think that the defining characteristic of a VN is that it allows an 
existing network to concurrently emulate another, distinct and separate 
network.

> 2. what are VNs used for?

Protection: keeping concurrent uses of a network from interfering with 
each other.

Abstraction: presenting the application (whether user layer, routing, 
etc.) with a simpler or desired topology that need not match the 
physical connections. E.g., as with DHTs, hypercubes, rings, etc. This 
also includes presenting a topology that is either much larger or 
smaller than the physical, i.e., that doesn't match in scale either.

Sharing: allowing a single set of resources to be concurrently used for 
multiple, separate purposes.

NB: these are identical to the reasons why virtual memory is useful

 > 	- provide some references to those working on solutions

Challenge: mapping logical components onto virtual ones - which I 
consider the 'provisioning' step of a conventional physical network.

Why it's hard: like any mapping, this is a distributed resource 
allocation problem, difficult to optimize fully, and challenging to 
coordinate without requiring global locks.

Who's working on this: this is known as "mapping" VNs, and many groups 
have worked on it over the years; it's also one of the least interesting 
problems, IMO, since it is not particularly new in the virtual domain 
(i.e., it exists in physical networks too)

--

Challenge: Clean, clear architecture supporting VNs.

Why it's hard: done wrong, VNs require users to reimplement some 
protocols at the user layer (e.g., as with DHTs, DTNs, etc. - usually 
transport protocols). done wrong, VNs also require extraordinary 
measures to restore existing capabilities, such as traceroute, ping, etc.

Who's working on this: our group (X-Bone), Violin, Akari (IMO)

--

---

From: Sangjin Jeong <[email-masked]>
Date: Thu, 15 Jul 2010 16:59:41 +0900

This is the fourth trial to send a response message because I got an error
when sending the previous trials and the message was not archived in the vnrg
mail archive.

I apologize if you have received multiple copies of this mail.

-----------------------------------
Dear Joe,

I hope it is not too late.

On Wed, Jun 9, 2010 at 1:57 AM, Joe Touch <[email-masked]> wrote:
> Hi, all,
>
> (speaking as co-chair)
>
> One of the challenges with starting with full text ("prose") is a tendency
> to
> edit the text, to focus on what to change, rather than on either what's
> missing,
> or shifts in perspective that would require substantial revision.
>
> To avoid that, Martin and I propose that we begin by each providing
> definitions
> and perspectives, rather than all try to wordsmith any single suggestion.
>
> Please DO NOT merely edit the posts of others. Once we see where people
> stand in
> their own voice, we can decide how best to move forward.
>
> Please send your responses by Jun 30 if possible.
>
> Joe (as VNRG co-chair)
>

A VN is a logical partition of a (physical/logical) network and its
capability is the same as or subset of the network. Also, the VN may expand
its capability by aggregating the capabilities of multiple networks. From the
user's point of view, the VN can be seen as a non-virtualized network.

>         1.a. what are the key components?

The key components of VNs include traditional network elements, such as hosts,
routers, links, etc. In addition to them, methods for creating and managing
the VNs are also included.

>         1.b. what is the relationship between these components?

The VN management methods create logical partitions in the components and
connect those partitions in order to construct a VN. The VN can be
connected with non-virtualized components.

>         1.c. what is the characteristic behavior/capability of the

Basically, users can see the VN as a non-virtualized dedicated network, so
they can perform any actions such as deploy new services, network
architectures, etc. as if they own the dedicated network.

> 2. what are VNs used for?

VNs can be used for the same purposes as non-virtualized networks without
interfering other VNs' operation while sharing the key components among VNs.
Therefore, the coexistence of multiple VNs is possible.

>         - provide some references to those working on solutions

- Performance: virtualization layer would be necessary for creating and
managing the VNs, so the performance of the VNs is not as good as the
non-virtualized network. So, how to reduce the performance degradation is a
challenge.

- Scalability: how many VNs can be simultaneously exist? how many key
components can be connected?

- Isolation: multiple VNs coexist over the key components, so isolation among
the VNs is the challenge. The isolation includes various aspects such as
security isolation, performance isolation, etc.

- Flexibility: after creating a VN based on user's requirements, the
requirements can be changed. In that case, it will be necessary to modify the
capability of the VN. The update of VN's capability may be done dynamically
and without interrupting the operation of the current VN.

- Management: how to provide independent management functions for each
VNs

Regards,
Sangjin