The MPLS WG Archive

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

Hi,


>    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."
> 

This means that an E-LSP can support up to 8 PHBs. But the number of PSCs that can be supported is not fixed, because it depends on the type of PSCs. For example you could support 4 PSCs (= 8 PHBs) as following: AF1x, AF2x, EF, DF

Or you could support only one PSC like CS (= 8 PHBs): CSx

So the Max. number of OAs is variable but the Max number of BAs is fixed= 8.

> 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. 

Although this can be done in theory, but you should not do it, becasue of the reordering problem that you mentioned.

Yours,
-Shahram


>