The MPLS WG Archive

[Eric Rosen <erosen@cisco.com>]

Eric> I think the IP header already  contains a field which the user can set
Eric> to signal diffserv support to the service provider.  Or are you saying
Eric> that it  is important to  be able to  signal diffserv on  a per-packet
Eric> basis for non-IP packets?

Juha> i as a service provider don't have any idea what packets my customer is
Juha> carrying over the l2 circuits between their sites.  it is beneficial for
Juha> the customer if it can tell in the exp field how it wants the packets to
Juha> be treated when they cross my network. 

What is the customer application for  which the customer is likely to have a
CE  device   that  will  mark   individual  non-IP  packets   with  diffserv
information?

Eric> This suggests  that the  backbone should run  MPLS, rather  than Frame
Eric> Relay, and I'd certainly agree with  that, but I don't see why this is
Eric> an issue vis. a  vis. CE-CE LSPs.  Of course, if two  CEs want to send
Eric> each  other  MPLS packets,  they  can send  them  over  any data  link
Eric> whatsoever.

Juha> if the  customer uses mpls  for its internal  stuff and has an  lsr ce
Juha> device, it would be very stupid if i as the provided would need to ask
Juha> the  customer  to encapsulate  their  mpls  packets  into frame  relay
Juha> packets when they are send to other sites.

Not many  customers use  MPLS for  their internal stuff.   Do you  foresee a
significant migration of  MPLS into the enterprise?  Or  are you thinking of
other service providers as the customers. 

In any  event, if two routers are  connected by a serial  link, MPLS packets
between the  routers get encapsulated into  (most likely )  PPP packets.  If
two  routers are connected  by an  ethernet link,  MPLS packets  between the
routes get encapsulated into ethernet  frames.  If two routers are connected
by a  frame relay  link, MPLS packets  between the routers  get encapsulated
into frame relay frames.  If two  routers are connected by an ATM link, MPLS
packets between  the routers get encapsulated  in AAL5 frames.   In fact, it
looks like in all the common  cases, MPLS packets get encapsulated in a data
link frame when being sent from one system to another. 

Are all these cases "very stupid"?  If not, how do they differ from the case
you are considering?