The MPLS WG Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Encapsulating MPLS in IP or GRE
Oops. Sent before I was done. In the approach described in http://www.ietf.org/internet-drafts/draft-ietf-ppvpn-gre-ip-2547-01.txt the tunnels between PE pairs are dynamic. No tunnel configuration required. In fact an implementation might chose to not even need to create a "tunnel" inteface if the tunnel header is viewed as an outbound encapsulation for a given BGP next hop. Much like there is no "interface" created for downstream label switching when using MPLS as the tunneling method between PEs. One descrepancy I see between the the dynamic approach of the above draft and draft-rosen-mpls-in-ip-or-gre-00.txt is the latter requires MTU path discovery for each "tunnel" destination. A static configured MTU or min MTU learned over the history of dynamic tunnels used would be prefered. In the customer's case mentioned below, by using the GRE tunnels made the customers creation of hierarchical VPNs (carrier's carrier) completely transparent to our service offer. They could use the existing service as defined without ordering or configuring anything special in our service network. Specifically, we did not have to certify, deploy, provision and support MPLS CE-to-PE. Instead it looks just like our standard IP service interface definition. Another application, perhaps less important, in the VPLS context when using BGP discovery and MAC address learning is that you do not need a label that is upstream PE specific (the label block method). You know which upstream PE sent the packet from the source address of the tunnel. Chris Chris Chase wrote: > This is the usage I find the most attractive. > Actually, we had a customer who wanted to do carrier's carrier to > create their own VPNs for their tenants. The approach taken was to > use GRE tunnels. The customer did not like having to create numerous > tunnel interfaces. > > > Mark Duffy wrote: > >> Hi Art, are you suggesting that there is something about the MPLS VPN >> case >> in particular that favors mpls-in-gre over mpls-in-ip? If so would you >> explain that? >> >> Thanks, Mark >> >> >> At 01:32 PM 8/15/02 -0700, Art King wrote: >> >> >>> Connecting MPLS VPN PE's over non-MPLS core in a Carrier is a >>> good example case for GRE usage. >>> >>> ----- Original Message ----- >>> From: "Eric Rosen" <erosen@cisco.com> >>> To: "Shahram Davari" <Shahram_Davari@pmc-sierra.com> >>> Cc: <mpls@UU.NET>; "Loa Andersson" <loa.andersson@utfors.se>; "George >>> Swallow" <swallow@cisco.com> >>> Sent: Wednesday, August 14, 2002 11:27 AM >>> Subject: Re: Encapsulating MPLS in IP or GRE >>> >>> >>> >>> >>>> In some cases you might already have a GRE tunnel through >>>> which you >>>> >>> >>> are >>> >>> >>>> supporting a routing adjacency. It should be possible to send MPLS >>>> >>> >>> packets, >>> >>> >>>> as well as IP packets, through such tunnels, and this >>>> requires >>>> >>> >>> an >>> >>> >>>> MPLS-in-GRE encapsulation. >>>> >>>> There are also other cases in which GRE tunnels (as opposed to IP >>>> >>> >>> tunnels) >>> >>> >>>> are commonly used, and you should be able to send MPLS packets >>>> >>> >>> through >>> >>> >>>> them. >>>> >>>> >>> >
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