The MPLS WG Archive

[Yangguang Xu <xuyg@lucent.com>]

Hello All,

Traditionally, SONET/SDH run OSI stack over DCC, that's where the LAPD/DCC came
from. For IP traffic, PPP/HDLC/DCC is commonly used. Below is the introduction
of DCC from "ietf-koay-mpls-and-optical-00.txt". Details can be found at any
ANSI, Bellcore, ITU ... SONET/SDH document.

  "3.1  Line DCC-MS
   Line DCC or Multiplex-section DCC are the D4-D12 bytes in the overhead of a 
   SONET or SDH frame respectively. Being in the line or multiplex-section 
   overhead, they are passed thru repeaters in the span. Hence, DCC-MS should be 
   used for neighbor discovery when the link connection contains section 
   terminating regenerators.

   SDH customers should already be familiar with enabling multiplex-section DCC 
   for management traffic (ITU-T G.784 10/98). In this standard, Line DCC-MS is 
   recommended for routing management traffic and for communication between two 
   SONET/SDH line/MS terminating nodes when regenerators are in the span. 

   3.2  Section DCC-RS
   Section DCC or regenerator-section DCC are the D1-D3 bytes in the overhead of 
   a SONET or SDH frame respectively. The section overhead bytes are terminated 
   by regenerators. Since regenerators are not Network Control nodes, Section 
   DCC-RS can be used only if there are no regenerators in the span."
 
However, using in-band control channel always has bandwidth limitation.
Remember, DCC are fixed bytes and is not only used by control traffic. The
"control plane" (not the data plane) "network" (not only links) should start
from understanding its network level requirements (performance, security,
reliability and etc.) Which physical medium and its "default" layer 2 protocol
should meet the network level requirement and come naturally and conveniently. 

Yangguang


Riad Hartani wrote:
> 
> On this subject, the OIF UNI 1.0 specification (submitted for last call)
> describes, among other things, how to use SONET Line and/or Section DCC
> overhead bytes to transport various IP control plane messages (called IP
> Control Channel -IPCC-). For discovery of information required by the IP
> control plane, both DCC or J0 bytes may be used in the actual proposal.
> 
> For the IP control plane, the proposal requires IP packets to be
> encapsulated in PPP over HDLC-like framing with bit stuffing format. The
> spec also describes various aspects related to the selection and maintenance
> of IPCC parameters, as well as other ways of carrying IP control information
> in Sonet/WDM environments.
> 
> Hope this helps,
> 
> Riad
> 
> > -----Original Message-----
> > From: Alex Zinin [mailto:azinin@cisco.com]
> > Sent: Sunday, December 17, 2000 9:46 AM
> > To: Tony Przygienda
> > Cc: tli@procket.com; echang@pocketmail.com;
> > isis-wg@spider.juniper.net;
> > skatukam@cisco.com; mpls@UU.NET
> > Subject: Re: [Isis-wg] Question on DCC Architecture
> >
> >
> >
> > Tony,
> >
> > >>  A number of companies working in the SONET area already use or are
> > >>  planning to use DCC for IP control plane [I put MPLS list back ;),
> > >>  since this question is related to GMPLS and OTN-related work].
> > >>
> > >>  There are two types of IP encapsulation on DCC that I know of:
> > >>  LAP-D and PPP/HDLC. We use the second one in our SONET products.
> > >>
> > >>  I think writing up an IETF document describing this would
> > make sense.
> >
> > > First, this smells much like ISO thing to do so we'd need
> > an agreement/liason
> > > first from their side. That is obviously only worth
> > pursuiting if we have
> > > authors commiting to provide the cycles first.
> >
> > Hmmm... why do you think specification of *IP* encapsulation
> > over SONET DCC
> > using "PPP over HDLC-like framing" is something ISO should do?
> >
> > > Second, which workgroup ? One of the MPLS offsprings such
> > as GSMP ;-) ? What about
> > > a new one, IPSO (IP over SOnet) ? I'm joking but wouldn't
> > be surprised
> > > if the joke find takers ;-) ?
> >
> > Definitely not me ;)
> >
> > I think some kind of individual submission should be ok. I guess
> > the Internet Area is the one that logically hosts it.
> >
> > Thanks,
> >
> > Alex.
> >
> >
> > _______________________________________________
> > Isis-wg mailing list  -  Isis-wg@external.juniper.net
> > http://external.juniper.net/mailman/listinfo/isis-wg
> >