Gopi, Lyndon, Attached is a short document describing some virtual concatenation and LCAS details. There can be different architectures, each with its specific characteristics with respect to sequence numbers. When there is no flexibility at the two virtconc end points (e.g. combination of figures 1 and 4), the path setup process (either network management or control plane) has only one way to connect the VC-n trail termination fucntions together; otherwise no transmission. When there is flexibility in both virtconc end points (e.g. figure 3 based adaptation or figure 3/4 based adaptation and figure 2 (IIa) architecture), the path setup process can connect any two VC-n trail termination fucntions together; the adaptation sink (receiver) will be able to follow automatically. Sequence identifiers don't need to be provisioned under connection management control (network management or control plane). These numbers are under control of the network element. For the case of no flexibility these numbers need to be known by the connection management process (network management or control plane) in order to be able to connect the correct VC-n trail termination functions. For the case of flexibility, connection management can ignore these sequence identifiers completely. Network elements will take care of correct ordering of received streams. For the case one end is flexible and the other end has no flexibility, I need to do a further check... Regards, Maarten "Ong, Lyndon" wrote: > > Hi Juergen, > > I was wondering about this, if the order of the VC-Ns is specified > twice (once by the automated path setup, and again by the > sequence number in the overhead) this could provide an additional > consistency check or it could be a source of error. For automated > path setup, might it not be better to leave the > sequence number out of the GMPLS/ASON signaling and have it only in the > overhead? Then there is no need for a consistency check. > > Thanks, > > Lyndon > > -----Original Message----- > From: Heiles Juergen [mailto:juergen.heiles@siemens.com] > Sent: Wednesday, November 06, 2002 8:41 AM > To: 'gopi@india.tejasnetworks.com'; ccamp@ops.ietf.org > Cc: sjtrowbridge@lucent.com; Bernstein, Greg; Anup@jasminenetworks.com; > mvissers@lucent.com > Subject: AW: Virtual concatenation: a clarification on sequence numbers > > Gopi, > > the sequence number always reflects the order of the VC-Ns within a virtual > concatenation and is never provisioned directly. In a SDH/SONET environment > with TMN provisioning and without LCAS the order is set by the TMN at the > source and sink. If the sink receives sequence numbers in the wrong order it > will alarm. With LCAS the order can change dynamical for example if one VC > fails and is removed from the group and later on added again. In case of > automatic path setup (GMPLS/ASON) this process has to define the order of > the VCs and as such the sequence numbers. > > Regards > > Juergen > > > -----Ursprüngliche Nachricht----- > > Von: gopi@india.tejasnetworks.com > > [mailto:gopi@india.tejasnetworks.com] > > Gesendet: Mittwoch, 6. November 2002 14:58 > > An: ccamp@ops.ietf.org > > Cc: sjtrowbridge@lucent.com; GregB@ciena.com; > > Anup@jasminenetworks.com; > > mvissers@lucent.com > > Betreff: Virtual concatenation: a clarification on sequence numbers > > > > > > [ post by non-subscriber. with the massive amount of spam, > > it is easy to > > miss and therefore delete mis-posts. so fix subscription > > addresses! ] > > > > hi.. > > > > I was going through the thread > > http://ops.ietf.org/lists/ccamp/ccamp.2001/threads.html#00295 > > subject: "concatenation extensions in sonet/sdh" > > > > I needed a small clarification on virtual concatenation sequencing > > > > Sequence number is sent by the transmitter and receiver checks for > > the sequence number to perform interleaving. > > > > IS this sequence number "Provisioned"(on both terminating > > equipments) ? > > OR > > Is it automatically assigned by the transmitting equipment in some > > sequence and the receiver synchronizes with the > > transmitters sequence number? > > > > > > I read the following relevant standards on virtual > > concatenation, but couldn't > > clearly understand how the receiver knows the sequencing of the > > individual links. > > + T1X1.5/2001-062(Synchronous Optical Network (SONET) - Basic > > Description including Multiplex Structure, Rates and Formats, > > put up on ftp.t1.org/..../1X150620.DOC) > > + G.707, G.783(virtual concatenation) > > + G.7042(LCAS) > > > > Thanx in advance > > Gopi > > > > > > > >
Attachment:
lcas-model.pdf
Description: Adobe PDF document
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