Re: Question about logical link in Link bundling

[Maarten Vissers <mvissers@lucent.com>]

Man Wing,

An OC12 interface port (when connect to another OC12 interface port)
provides what is called a "topological link" in ITU-T Rec. G.852.2 to
its client (HOVC/STS) layer network. This topological link supports one
or more HOVC/STS link connections, as expressed in terms defined in
G.853.8 "pre-provisioned adaptation management":

- pamMaxProvisionableCapacity: The pamMaxProvisionableCapacity attribute
provides the value that represents the maximum capacity that could be
provisioned for a link from the server trail of this link. However, this
maximum may not be provisioned for this link if several links are
supported by the same server trail: in this case, they are sharing the
maximum capacity.

- pamPotentialLinkCapacity: The pamPotentialLinkCapacity attribute
provides a value that represents the potential capacity that could be
provisioned on a link from the capacity that has not already been
provisioned from the server trail of this link.

- pamProvisionedLinkCapacity: The pamProvisionedLinkCapacity attribute
provides the capacity provisioned on a link.

- pamAvailableLinkCapacity: The pamAvailableLinkCapacity attribute
represents the provisioned capacity that is not assigned.

For an OC12, the following may be supported:

- example 1 - STS1, STS3c and STS12c supported:
pamMaxProvisionableCapacity:	STS1: 12;	STS3c: 4;	STS12c: 1
pamPotentialLinkCapacity: 	STS1: 12;	STS3c: 4;	STS12c: 1
pamProvisionedLinkCapacity:  	STS1: 0;	STS3c: 0;	STS12c: 0
pamAvailableLinkCapacity:  	STS1: 0;	STS3c: 0;	STS12c: 0

- example 2 - only STS3c supported:
pamMaxProvisionableCapacity:	STS1: 0;	STS3c: 4;	STS12c: 0
pamPotentialLinkCapacity: 	STS1: 0;	STS3c: 4;	STS12c: 0
pamProvisionedLinkCapacity:  	STS1: 0;	STS3c: 0;	STS12c: 0
pamAvailableLinkCapacity:  	STS1: 0;	STS3c: 0;	STS12c: 0

- example 3 - STS1 and STS12c supported:
pamMaxProvisionableCapacity:	STS1: 12;	STS3c: 0;	STS12c: 1
pamPotentialLinkCapacity: 	STS1: 12;	STS3c: 0;	STS12c: 1
pamProvisionedLinkCapacity:  	STS1: 0;	STS3c: 0;	STS12c: 0
pamAvailableLinkCapacity:  	STS1: 0;	STS3c: 0;	STS12c: 0

The above examples are assuming an initial situation in which none of
the link connections is already providing service. For the case 1 STS1
and 1 STS3c link connection are providing service example 1 would have
its parameters presented as:

- example 1 - STS1, STS3c and STS12c supported and 1 STS1 and 1 STS3c
link connection used:
pamMaxProvisionableCapacity:	STS1: 12;	STS3c: 4;	STS12c: 1
pamPotentialLinkCapacity: 	STS1: 6;	STS3c: 2;	STS12c: 0
pamProvisionedLinkCapacity:  	STS1: 1;	STS3c: 1;	STS12c: 0
pamAvailableLinkCapacity:  	STS1: 2;	STS3c: 0;	STS12c: 0

See for more examples my ASTN layer network architecture document.

Note that DS3's, T1's, etc are not visible at this point in the layer
network structure. 
The HOVC/STS layer network deals with VC3/STS1, VC4/STS3c,
VC-4-4c/STS12c, VC-4-16c/STS48c, VC-4-64c/STS192c and VC-4-256c/STS768c
signals and groups of these signals (AUG-X/STSG-X, groups supporting
virtual concatenation, other groups).
In addition, these signals may be terminated in trail termination points
(TTP) within an Access Group (AG), providing access to its client
signals. Such client signals can be a e.g. DS3, E4, ATM, ethernet, IP,
MPLS and LOVC/VT signals.

For the case the HOVC/STS layer network connects two STS1 or two VC4
ports, the STS1 or VC4 path that is now present provides e.g. a LOVC/VT
topological link to the LOVC/VT layer network. 
Alternatively, if the payload would have been ATM, it would have
provided a ATM VP topological link to the ATM VP layer network. 
For the case the payload would have been DS3, it would have provided a
DS3 link connection to e.g. a customer.

In the LOVC/VT layer network T1's are not directly visible either. It
are the VC11/VT1.5, VC12, VC3 signal and groups of these signals. Only
when such signal is terminated in a TTP within an AG in this layer
network, access to its client signals (e.g. a T1) is provided.

So for the LOVC/VT layer entwork, STS1 and VC4 are the interface ports
providing LOVC/VT (topological) links. some examples:

For a VC4, the following may be supported:

- example 1 - VC11/VT1.5, VC12 and VC3 supported:
pamMaxProvisionableCapacity:	VC11/VT1.5: 84;	VC12: 63;	VC3: 3
pamPotentialLinkCapacity: 	VC11/VT1.5: 84;	VC12: 63;	VC3: 3
pamProvisionedLinkCapacity:  	VC11/VT1.5: 0;	VC12: 0;	VC3: 0
pamAvailableLinkCapacity:  	VC11/VT1.5: 0;	VC12: 0;	VC3: 0

- example 2 - VC12 and VC3 supported:
pamMaxProvisionableCapacity:	VC11/VT1.5: 0;	VC12: 63;	VC3: 3
pamPotentialLinkCapacity: 	VC11/VT1.5: 0;	VC12: 63;	VC3: 3
pamProvisionedLinkCapacity:  	VC11/VT1.5: 0;	VC12: 0;	VC3: 0
pamAvailableLinkCapacity:  	VC11/VT1.5: 0;	VC12: 0;	VC3: 0


- example 1 - VC11/VT1.5, VC12 and VC3 supported and 1 VC12 and 1 VC3
link connection:
pamMaxProvisionableCapacity:	VC11/VT1.5: 84;	VC12: 63;	VC3: 3
pamPotentialLinkCapacity: 	VC11/VT1.5: 52;	VC12: 39;	VC3: 1
pamProvisionedLinkCapacity:  	VC11/VT1.5: 0;	VC12: 1;	VC3: 0
pamAvailableLinkCapacity:  	VC11/VT1.5: 0;	VC12: 2;	VC3: 0


Now consider that there is one OC12 and one OC48 connection between the
two network elements. This would create an additional HOVC/STS
topological link supported by the OC48 connection. Assume that this OC48
supports from STS1 to STS48c, then the HOVC/STS link (i.e. the "bundle"
in GMPLS terminology) would be characterised as follows:

- example 1b - STS1, STS3c and STS12c supported on OC12 and STS1 to
STS48c supported on OC48:
pamMaxProvisionableCapacity:	STS1: 60; STS3c: 20; STS12c: 5;	STS48c: 1
pamPotentialLinkCapacity: 	STS1: 60; STS3c: 20; STS12c: 5;	STS48c: 1
pamProvisionedLinkCapacity:  	STS1: 0;  STS3c: 0;  STS12c: 0;	STS48c: 1
pamAvailableLinkCapacity:  	STS1: 0;  STS3c: 0;  STS12c: 0;	STS48c: 1

If instead of one VC4 also one STS1 path is present, an additional
LOVC/VT topological link would be provided by the STS1 path to the
LOVC/VT layer network. If this STS1 supports VT1.5 only, the LOVC/VT
link (i.e. the "bundle" in GMPLS terminology) would be characterised as
follows:

- example 2b - VC12 and VC3 supported on VC4 and VT1.5 on STS1:
pamMaxProvisionableCapacity:	VC11/VT1.5: 28;	VC12: 63;	VC3: 3
pamPotentialLinkCapacity: 	VC11/VT1.5: 28;	VC12: 63;	VC3: 3
pamProvisionedLinkCapacity:  	VC11/VT1.5: 0;	VC12: 0;	VC3: 0
pamAvailableLinkCapacity:  	VC11/VT1.5: 0;	VC12: 0;	VC3: 0

Hope this helps understanding the multi layer aspects as well as
"bundling".

Regards,

Maarten


"Fong, Man Wing" wrote:
> 
> Bala,
> 
> Correct me if I am wrong. For my understanding, a channelized OC-12
> interface can support 12 channels (12 logical DS3 interfaces). Some even
> capable of defining logical interface within those DS3 channel to support
> T1. Then, each logical DS3 interfaces can create a (logical) link to the
> remote routers' DS3 interfaces. The original used of the channelized OC-12
> interface is to reduce the cabling and additional equipment cost and labor
> cost at the central location. Since it is a channelized interface, I
> believe, it would not allow the user to use it as an OC-12c interface. By
> applying link bundling on that, now you can size your pipe whatever you want
> upto the maximum BW (in this case, it will be STS-12c). In addition, using
> O-UNI, you will get a true bandwidth on demand.
> 
> Just a thought.
> 
> Man Wing
> 
>  -----Original Message-----
> From:   Bala Rajagopalan [mailto:BRaja@tellium.com]
> Sent:   Tuesday, May 08, 2001 3:24 PM
> To:     'Fong, Man Wing'; mpls@UU.NET; 'Kireeti Kompella'
> Cc:     ccamp@ops.ietf.org
> Subject:        RE: Question about logical link in Link bundling
> 
> Hello,
> 
> I'm a bit confused by the question. If you
> had a channelized OC-12 link, wouldn't you
> just advertise it with suitable Min Reservable
> Bw values to indicate that it can carry lower
> granularity traffic? In other words, why would
> you introduce the notion of a "logical" link
> in this case?
> 
> REgards,
> 
> Bala Rajagopalan
> Tellium, Inc.
> 2 Crescent Place
> P.O. Box 901
> Oceanport, NJ 07757-0901
> Tel: (732) 923-4237
> Fax: (732) 923-9804
> Email: braja@tellium.com
> 
> > -----Original Message-----
> > From: Fong, Man Wing [mailto:MFong@WhiteRockNetworks.com]
> > Sent: Monday, April 30, 2001 3:31 PM
> > To: mpls@UU.NET; 'Kireeti Kompella'
> > Cc: ccamp@ops.ietf.org
> > Subject: Question about logical link in Link bundling
> >
> >
> > Hi All,
> >
> > From "draft-kompella-mpls-bundle-05.txt", it indicates that
> > multiple links
> > between two LSRs can be bundled as a single link to improve
> > the routing
> > scalability. Apparently, it can be used to bundle multiple links from
> > multiple physical interfaces (e.g. multiple T1s, DS3s, OC-12s, OC-48s,
> > etc...) to be a single link. However, can it be used to
> > bundle logical links
> > like T1s in channelized T3, or DS3s, STS-3c in channelized
> > OC-12 interface?
> >
> > Thanks.
> >
> > Regards,
> > Man Wing
> >
> >
> >
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