The MPLS WG Archive

[Sasha Vainshtein <Sasha@AXERRA.com>]

Hi,
	The reordering issue has been addressed in
<draft-ietf-diffserv-new-terms-04.txt>,
	"New Terminology for Diffserv" with an explicit reference to work 
	on MPLS Support of Differentiated Services.
	 Section 5 of this I-D introduces the notion of an Ordering
Aggregate (OA) as 
	<quote> A set of Behavior Aggregates that share an ordering
constraint. 
	 The set of PHBs that are applied to this set of Behavior Aggregates

	constitutes a PHB scheduling class. <end of quote>
     	
	I suggest that <draft-ietf-mpls-diff-ext-08.txt> should be updated
to 
	allow only grouping of multiple OAs (and not BAs as it does) into
	a single E-LSP. The current I-D version explicitly states
	that L-LSP is established for a given (OA, FEC) class but is  
	ambiguous when it comes to E-LSPs. 

	Nabil, in his message in this thread, has noticed that RFC 2597
	defines AF<x><y> (y=1,2,3) as an OA for any fixed value of x (1-4). 
	The suggested modification would prohibit configurations like one
described
	in the original message. 
______________________________________________
With best regards,
Sasha Vainshtein
mailto: sasha@axerra.com
phone: +972-3-7659993 (office)
fax:      +972-3-6487779 (office)


>>-----Original Message-----
>>From: N S S Kishore Kankipati [mailto:kishore_iitb@yahoo.com]
>>Sent: Thursday, April 05, 2001 3:39 PM
>>To: flefauch@cisco.com; liwwu@cisco.com
>>Cc: mpls@UU.NET
>>Subject: Diff-Serv over MPLS
>>
>>
>>hi all	
>>   Could any of you please explain about the following
>>sentence in the draft-ietf-mpls-diff-ext-0.8.txt.
>>
>>section 1.2-- Exp-Inferred-PSC LSPS (E-LSP)
>>
>>"A single LSP can be used to support up to eight BAs
>>of
>>a given FEC, regardless of how many OAs these BAs
>>span."
>>
>>A small doubt
>>  Suppose PHBs related to a PSC have been assigned to
>>different E-LSPs (say AF11 to one LSP and AF12 to
>>another LSP)and first few (say 1-10)Packets belonging
>>to a microflow have been assigned to AF11 and later
>>packets (say 10-15) to AF12. 
>>Is it not possible for the packets in AF12 LSP to get
>>transferred before the packets in AF11 LSP? If that is
>>the case the ordering constraint is violated i.e
>>packets are reordered. (I think this may happen in 
>>the following case- if the LSPs are on different 
>>interfaces of a router and  there may be some packets
>>which are required to be served in the AF11 while the
>>packets in AF12 may get immediately served as there
>>are
>>no packets before these which require service).
>> 
>>thanks
>>kk
>>
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