Subject: Re: [IP-Optical] GMPLS - Hierarchies

From: John Ellson <[email-masked]>
Date: Thu, 07 Dec 2000 09:13:07 -0500

Nuno,

The service being provided by a switched network provider between two
UNIs is a Link with one or more Link-connections providing capacity.
Once a Link-Connection has been provided it can be considered
by the user as a fixed resource which can be used to provide larger
composite connections.

Internal to the provider's domain the Link, in general, may be further
partitioned into Link-Subnet-Link, and Subnets can be partitioned
into Subnet-Link-Subnet, so a Link as provided to a User may
infact consist of an arbitrarily long alternating sequence
of Link-Subnet and a terminating Link.  As a minimum, all Links
provided by a Switched network can be composed
into:  Link-Subnet-Link.
The end Links could reasonably be called Access Links, but they are
not fundamentally different from any other Link. 

External to the provider's domain, the Link may be just a part of an
even longer composite Link, for example if one provider is just handing
off to another provider.

This is all partitioning.  i.e. this is all at one network layer
without any terminations or adaptations.  

At the limit of Link partitioning, the link-connections of a single
link may be provided by one or more parallel trails in a server layer.
e.g. A Link comprised of 6 Link-Connections may have 4 Link-Connections
provided by one Trail and 2 provided by another.  i.e. the relationship
between a Link and a Trail is not, in general, 1:1.

So the relationship between a Link provided to a 
user, and a trail in some server layer, is highly indirect and
is rarely 1:1.  This is why it makes no sense to talk about
the technology of the server layer when requesting
a connection in a client layer. 

When we are talking about partitioning, we should be talking 
about SNPs (Subnetwork Points), not TTPs of CTPs.
In connection management we presume that SNPs are also
TTPs or CTPs in real equipment, but during the establishment of a
connection within one layer the details of multiplexing 
can be abstracted away by use of SNPs.

SNPs are aliases, that is they carry a different name for the
same object instance.  Thus CTPs and TTPs have a name based
on physical containment that allows an operator to find
the smallest-replaceable-units during maintenance.  SNPs
on the other hand, carry a name that is convenient to
connection-setup.  e.g. labels.   Since Subnets can be nested,
a single CTP or TTP instance can have many SNP aliases.  One
for each of the nested Subnets.

e.g. The TTP: Net1,NE3,Board6,TTP2  may have SNP aliases:
2076, 949-2076, and 732-949-2076 if we have a hierarchical 
namespace.   Its also possible, in principle, that the SNPs
have names that  are unrelated to each other.

An SNP is the shared point on the boundary of a Subnet that
is at the junction of a Subnet-Connection inside the
subnet, and a Link-Connection outside the Subnet.  In any
connection operation, the Link-Connections represent the
fixed resource and the Subnet-Connection the flexibility.
(This is not saying that Link-Connections are inflexible,
only that a Link-Connection is static during the operation
to form a longer connection.)

I hope this helps

John Ellson

Nuno Silva wrote:
> 
> Neil et all,
> 
>  Under the scope of G.805 (March 2000), do you think it makes sense to model
> an LSP as a Network Connection, composed by a concatenation of SNCs and LCs
> (if so, what would be the subnetwork connections, the link connections, the
> TTPs and CTPs), or as an IP trail?
> 
>  TTPs - are the IP interfaces/ports?
>  CTPs- are the labels?
>  LCs - are the connections/associations between 2 labels in two different
> LSRs?
>  SNCs- are the forwarding tables in the LSRs and LERs? (a connection between
> the TTP and CTP in the LER, or a connection between CTPs in the LSRs)?
> 
>  So the question is indeed, is the functional architecture defined in G.805
> applicable to the MPLS/MPlambaS worlds?
>  How does this cope with G.cls (connectionless) work?
> 
>  Thanx ahead. Nuno.
> 
> 
> Nuno Carvalho Silva
> PT Inovação, SGR
> 
> Phone: + 351 234 403 394
> Fax: + 351 234 424 160
> E-mail: [email-masked]
> 
> > -----Original Message-----
> > From: [email-masked] [SMTP:[email-masked]]
> > Sent: Wednesday, December 06, 2000 10:07 PM
> > To:   [email-masked]; [email-masked]; [email-masked]
> > Cc:   [email-masked]
> > Subject:      RE: [IP-Optical] GMPLS - Hierarchies
> >
> > <snipped>
> >
> > > Furthermore a LSP -at least for circuit switching - doesn't have to
> > start
> > > and end at the trail termination where you extract your payload.
> >       NH=> I fudamentally disagree *if* we are adhering to functional
> > arch.
> > >  A LSP could be used only for a sub part of the overall connection, e.g.
> > a
> > > DS1 signal starts in a user domain with tradional TMN path setup or even
> > > manual connections, the DS1 comes to a operator which uses GMPLS for
> > path
> > > -setup (in this case a permanent connection set-up by himself as the
> > user
> > > doesn't support the UNI). The LSP starts in the middleof the overall DS1
> > > connection and no access to the paylaod of the DS1 is requried at that
> > > point.
> >       NH=> The DSI signal is 'an LSP' in its own right......it is, after
> > all, a clear layer network trail entity.  The fact that it may be served
> > (on
> > link connections, which are a partition of the end-end DS1 trail) by lower
> > layer "LSPs" (which could be a DS3, VC4, ODU, etc.......and which
> > themselves
> > are trails *but* only between their points of source/sink) is
> > academic.....the DS1 trail is completely unaware of this, and the layering
> > recursion of client_links=>server_trails can recurse many times.......its
> > stops at the duct network.
> >       Your example *must*, and indeed does, fit this.
> >       neil
> >
> > >
> >
> > _______________________________________________
> > IP-Optical mailing list
> > [email-masked]
> > http://lists.bell-labs.com/mailman/listinfo/ip-optical
> 
> _______________________________________________
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---

From: Maarten Vissers <[email-masked]>
Date: Thu, 07 Dec 2000 15:22:24 +0100

All:

As both G.805 and GMPLS are describing the same physical network, there
must be a unique relation between the terminology in the two cases. I
see it as our duty to discover and describe this relation; otherwise I
foresee problems when the transport plane (derived from G.805) and the
control plane (derived from GMPLS) are to interconnect.

A) Transport view 

When you look at today's transport network, you can identify the
following:
- user network (might be as small as a single network element)
- network operator network.

From the network operator's perspective, the user connects via a fiber
(let's limit to this medium for this purpose). The network operator will
now transport the complete or only a part of the signal on this fiber. 

In either case, the network operator doesn't provide the trail or
network connection. The trail and network connection start in the user
network.
As such, the network operator provides transport via a subnetwork
connection.

	Example of complete signal transport: transport of an 
	STM-N/OC-N signal including all of its overhead. E.g. STM-N
	signal is mapped into the payload of the ODUk.
	Other example is the transport of a DS1 via the payload of 
	a VT1.5 signal, or an E1 via the payload of a VC-12 signal.
	As the ODUk, VT1.5 and VC-12 start in the operator's network,
	the ODUk, VT1.5 and VC-12 trail and network connection start
	in the operator's network. These are the server layer trails
	and network connections.

	Example of transport of a part of the signal: transport of
	a VC-4 or STS-1; in this case the STM-N/OC-N signal on the
	fiber is terminated and the VC-4 or STS-1 is extracted and
	passed through.

In network management these DS1 and E1 subnetwork connections are often
referred to as DS1 and E1 circuits.
We could formalise this terminology, allowing us to start talking about
VC-4 circuit, STS-1 circuit, STM-N/OC-N circuit. Something to consider?

B) Monitoring view

A network operator may decide that the transport of the signal through
his subnetwork connection ("circuit") has to be monitored. The
subnetwork connection can therefore be extended with tandem connection
(ATM: segment) monitor functionality. 

For SDH/SONET and ATM one tandem connection level is defined. 
For OTN, 6 levels of tandem connection are defined in G.709. 
For MPLS, ... levels of tandem connection are proposed in the MPLS OAM
activity (Neil can you provide the number here) in draft Y.17oam.1.

Tandem connections can be nested, and perhaps even overlapping (under
discussion at the moment in Q.11/15).

-----

What has helped me in the past, is to formalize the relationships. I
have used BNF for this (refer e.g. to Annex C/EN 300 417-1-1
(http://webapp.etsi.org/pda/home.asp?wki_id=7959)).

Perhaps we can use BNF (or similar tool) again to formalise the
relationships in GMPLS.

Regards,

Maarten

---- copy of annex C/EN 300 417-1-1 --------

Annex C (informative):	Network "production rules"

The relationship between trails, (sub-)network connections, link
connections, atomic functions, and reference points can be described by
means of the "production rules" of a network. This kind of formalism can
also be found in software language specifications. One of the methods
used to describe a language is the Backus-Naur Form (BNF) 23) . This
shows the decomposition and partitioning processes described in § 3 of
ITU-T Recommendation G.803 [28].

<trail>			::=	AP <termination> <network connection>
					<termination> AP

<network connection>	::=	TCP <sub-network connection *> TCP

<sub-network connection *>	::=	<sub-network connection *> CP <link
connection> CP
					<sub-network connection *>
				| <simple connection>
				| <tandem connection>

<link connection>		::=	<adaptation> <trail> <adaptation>
				| Transmission_Medium

<simple connection>		::=	Degenerate_Connection
				| Matrix_Connection (C)

<adaptation>			::=	Adaptation (A)

<termination>		::=	Trail_Termination (TT)

<tandem connection>	::=	<Dadaptation> AP_D <Dtermination> TCP_D
					<sub-network connection *> TCP_D
					<Dtermination> AP_D <Dadaptation>

<sub-network connection *>	::=	<sub-network connection * > CP <link
connection>
					CP <sub-network connection *>
				| <simple connection>

<Dadaptation>		::=	Domain_Monitoring_Adaptation (D_A)

<Dtermination>		::=	Domain_Monitoring_Trail_Termination (D_T)

		AP_D:		Domain Monitoring Access Point
		CP_D:		Domain monitoring Connection Point
		TCP_D:	Domain Monitoring Termination Connection Point
		TM:		Transmission_Medium

The <sub-network connection> shows the recursion, which terminates when
the <simple connection> is selected. This <simple connection> represents
the cross-connection on an individual matrix, or an inflexible (fixed)
connection for the case where a matrix is not present. It is represented
by the (flexible) connection function or an (inflexible) line.

The <link connection> shows the layering process, which terminates when
the Transmission_Medium is selected.

The concept of the <tandem connection> is introduced here because it is
considered to provide a rigid way of describing the property that is
required for the so-called tandem connection i.e. a sub-network
connection that can be monitored via an overhead dedicated for this
purpose.

---

From: Nuno Silva <[email-masked]>
Date: Thu, 7 Dec 2000 12:52:25 -0000

Neil et all, 

 Thanx ahead. Nuno.

Nuno Carvalho Silva
PT Inovação, SGR

Phone: + 351 234 403 394
Fax: + 351 234 424 160

---

From: Maarten Vissers <[email-masked]>
Date: Mon, 11 Dec 2000 10:44:55 +0100

Neil, Nuno,

I get the impression that a LSP is being used for both the trail and a
tandem connection (subnetwork connection). But also as a tributary slot
identifier. 

	Note - Tributary slot identifiers in other technologies are: 
	VPI, VCI, time slot, frequency slot (wavelength).

A tributary slot identifier is bound to a "link connection". 
A signal passing through from an incoming link connection (via a "matrix
connection" in a fabric) to an outgoing link connection may see a
tributary slot identifier change. E.g. VPI_in=124 => VPI_out=765,
timeslot_in=1, timeslot_out = 18, lambda_in = 15 => lambda_out = 63, and
label_in=5354 => label_out=678521.

TTP and CTP are terms defined in association with the information
modelling. 
*	A TTP in the information model is equivalent with a Trail Termination
function (_TT) and the common part of the Adaptation function (_A) in
the functional model. 
*	A CTP in the information model is equivalent with the Connection Point
at the Connection function (_C) and the client specific part of the
Adaptation function (_A) in the functional model.

A link connection (LC) starts at a CTP and ends at the next CTP:
	Link Connection: CTP - server layer trail - CTP

A matrix connection (MC) starts at a TTP/CTP and ends at the TTP/CTP at
the other end of the fabric (connection function):
	Matrix Connection: TTP/CTP - TTP/CTP

A matrix connection is the smallest subnetwork connection (SNC).
A subnetwork connection is in general defined as:
	SNC: SNC - LC - SNC, with the smallest SNC being a MC.

>  TTPs - are the IP interfaces/ports?

TTPs are the LSP termination points, where bits 20-31 of the MPLS label
are added/removed and the information in the payload of this MPLS packet
extracted.

>  CTPs- are the labels?

CTPs are the boundaries of the link connection. The 20-bit label value
is added/removed here. A link connection starts/ends at each LSR and
LER.

Associated with a CTP may be a tandem connection TTP. Such tandem
connection TTP adds another 32-bit MPLS label and associated MPLS OAM
packet flow.

>  LCs - are the connections/associations between 2 labels in two
>  different LSRs?

A LC is the connection between the egress of one LSR [or LER] and the
ingress of the next LSR [or LER].

>  SNCs- are the forwarding tables in the LSRs and LERs? (a connection
>  between the TTP and CTP in the LER, or a connection between CTPs in
>  the LSRs)?

The set of MCs (matrix connections) are the forwarding tables in the
LSRs and LERs.

Up to so far.

Regards,

Maarten

---

From: "Shun Yao" <[email-masked]>
Date: Thu, 14 Dec 2000 07:54:57 -0800

Hi!

My name is Shun Yao and I am a grad student at UC Davis working on optical
packet switching. I have the following questions regarding IP edge routers
and any insight, including useful URL's, is appreciated.

1. What's the state-of-art line speed and port-count on the higher bit-rate
side and lower bit-rate side of an edge router?

2. What's the price per-port of the fastest edge router available today?

2. Are edge router all 'north-south' routing type? (The routing only happens
between lower speed line cards and higher speed line cards but not among
themselves.)

3. The backbone ports (higher bit-rate ports), are they all based on SONET
interface? If so, how are the IP packets encapsulated inside an OC-192
frame? Are they contained in lower-rate virtual containers?

4. Is the number of higher bit-rate ports and lower bit-rate ports on an
edge router configurable?

5. Do most edge routers avalaible today incorporate MPLS?

Thanks a lot!

Shun

Networks Resarch Lab
University of California, Davis