Suppose RG1=(PE1,PE2) using label space 1~5, RG2=(PE2, PE3) using label space 6~10. So PE2 is in 2 RGs. But, PE1 can well use label space 6~10 for other RG, say RG3 and PE3 can use label space 1~5 for RG4.
Thanks, Mingui >-----Original Message----- >From: Jakob Heitz [mailto:[email protected]] >Sent: Friday, November 29, 2013 1:54 PM >To: Mingui Zhang >Cc: [email protected]; [email protected] >Subject: Re: Why we consider the method of "label sharing for fast PE >protection" > >I any PE is part of 2 RGs, then those RGs can not have overlapping label >spaces. > >-- >Jakob Heitz. > > >On Nov 28, 2013, at 6:16 PM, "Mingui Zhang" <[email protected]> >wrote: > >> Hi Bruno, >> >> So you suppose the label used in an RG cannot be used again out of the RG. >That is not correct. >> Please find my comments inline [Mingui]. >> >> <snip> >>> [Bruno2] Let's assume: >>> - 5 PE in the group, hence sharing the same range of labels (e.g., 1~1100). >>> - 5 VPNs in connect to this group of PE, 2 of which being dual-homed >>> (VPN1 & VPN2). >>> >>> With label sharing: >>> Label:1 2 3 4 5 >>> >>> PE1 VPN1 x x x x >>> PE2 VPN1 VPN2 x x x >>> PE3 x VPN2 x x x >>> PE4 x x VPN3 x x >>> PE5 x x x VPN4 VPN5 >>> >>> All labels marked as "x" are burned/lost because of the label sharing. >> >> [Mingui] Not true. Where we got this constraint? For an explicitly example, >PE4 can well use label 1,2,4,5. >> >> [Mingui] I anticipate you assume PE1~PE5 are forming an RG, so that once a >label is used it is used across the RG. I need to point out that the unit of >"RG" is >independent of PEs. It depends on the VPN connections. I saw Zhou Peng has >already given examples on this point. >> >> <snip> >> >>> [Bruno2] not always. There is public/ietf example for this: >>> draft-l3vpn-legacy-rtc-00 >> >> [Mingui] It's designed to be incrementally deployable in the network. The >> trick >is confined in the RG. Other P and PE routers are unaware of the change. >> >> [Mingui] I guess you may change to imagine the scenario that operator >> need a legacy PE and a label sharing PE form an RG. Let's consider the >> analogy that the operator interconnects two switches using LAG while >> one of them does not support LAG at all. :) >> >> [Mingui] Thanks for continuing the discussion. I think the discussion about >> label >ranges reservation in another thread is related to our discussion. To my >understanding, the conclusion is that it's not OK to require a label block to >be >supported across multiple PEs. A possible escape is to resort to a higher-layer >authorized entity out of the RG to assign the label. >> >> Thanks, >> Mingui
