Section 9. Carriers' Carriers Best, R.
On Wed, Oct 31, 2012 at 11:17 PM, Lucy yong <[email protected]> wrote: > Another silly question, What does CSC stand for? > Lucy > >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On Behalf Of Robert >> Raszuk >> Sent: Wednesday, October 31, 2012 5:07 PM >> To: Lucy yong >> Cc: [email protected]; [email protected]; [email protected]; >> [email protected]; [email protected] >> Subject: Re: comment on draft-fang-l3vpn-virtual-pe-framework-01 >> >> Hi Lucy, >> >> To your below question the answer is yes. This is a flavor of CSC >> which standard 4364 supports just fine. >> >> Best regards, >> R. >> >> > For another scenario is that, if a WAN VPN is used to interconnect DC >> provider underlying networks at different sites, i.e. PE-CE case, DC >> provider should be able to build a L3VPN among vPEs at DC sites >> directly, in which it seems necessary to have a tunnel between a pair >> of vPEs. This makes that DC GW and WAN VPN are not aware of DC L3VPN >> existence, which creates a true virtual environment. vPE host address >> /32 is required to advertised from one CE to another CE, will RFC4364 >> support this? >> >> >> >> >> >> On Wed, Oct 31, 2012 at 10:59 PM, Lucy yong <[email protected]> >> wrote: >> > Hi, Eric, Robert, and Ali, >> > >> > Thank you very much for the explanations. They are very helpful. >> > >> > You are right. The label switch path in the text means the VPN label. >> Individual labels are used over each segment and swapped at ASBR in >> option B. This is not related to underlying tunnel mechanism at all. >> ASBR1 is the next hop for the PE1, a tunnel is terminated at ASBR. >> Option A, B, C are about VPN interworking (or say virtual overlay >> network). >> > >> > For another scenario is that, if a WAN VPN is used to interconnect DC >> provider underlying networks at different sites, i.e. PE-CE case, DC >> provider should be able to build a L3VPN among vPEs at DC sites >> directly, in which it seems necessary to have a tunnel between a pair >> of vPEs. This makes that DC GW and WAN VPN are not aware of DC L3VPN >> existence, which creates a true virtual environment. vPE host address >> /32 is required to advertised from one CE to another CE, will RFC4364 >> support this? >> > >> > Regards, >> > Lucy >> > >> > >> > >> > >> > >> > >> > >> >> -----Original Message----- >> >> From: Eric Rosen [mailto:[email protected]] >> >> Sent: Wednesday, October 31, 2012 3:45 PM >> >> To: Lucy yong >> >> Cc: Robert Raszuk; [email protected]; [email protected]; >> >> [email protected]; [email protected] >> >> Subject: Re: comment on draft-fang-l3vpn-virtual-pe-framework-01 >> >> >> >> I think there's a misunderstanding of the sentence from RFC4364: >> "This >> >> procedure requires that there be a label switched path leading from >> a >> >> packet's ingress PE to its egress PE." >> >> >> >> If a VPN packet is traveling the following path: >> >> >> >> PE1--->P1--->ASBR1--->ASBR2--->P2--->PE2 >> >> >> >> where the ASBRs are supporting option B, then there is necessarily >> an >> >> LSP >> >> consisting of the following sequence of routers: >> <PE1,ASBR1,ASBR2,PE2>. >> >> What makes this sequence of routers an LSP is that they all operate >> on >> >> the >> >> "VPN label". (See section 3.15 of RFC 3031 for the precise >> definition >> >> of >> >> "Label Switched Path". Note that "LSP" is defined relative to the >> >> position >> >> of a particular label in the stack of a particular packet.) PE1 >> pushes >> >> on >> >> the label, ASBR1 swaps it with a label assigned by ASBR2, ASBR2 >> swaps >> >> it >> >> with a label assigned by PE2, PE2 pops it. We could call this the >> "VPN >> >> LSP", because it follows the path of distribution of a VPN-IP route. >> >> >> >> The cited text is intended to distinguish option B from option A; in >> >> option >> >> A, the sequence <PE1,ASBR1,ASBR2,PE2> is not an LSP, because ASBR2 >> does >> >> not >> >> distribute labels to ASBR1. >> >> >> >> > which requires two SPs pre-provisioning process that may not apply >> to >> >> > here. >> >> >> >> The LSP exists by virtue of the distribution of the labeled VPN-IP >> >> routes. >> >> >> >> Note that, although <PE1, ASBR1, ASBR2, PE2> is an LSP according to >> the >> >> definition in RFC 3031, each router in the sequence only has to know >> >> which >> >> router is next in the sequence; the ingress router does not need to >> >> know how >> >> to reach to the egress router. Also, there is no requirement that >> an >> >> LSP is >> >> used to carry packets from PE1 to ASBR1, or from ASBR2 to PE2. >> Either >> >> or >> >> both of those "hops" could be via a GRE tunnel, or any other method >> of >> >> transport. >> >> >> >> It's true that in a typical deployment, there is a "top-level" LSP >> >> <PE1,P1,ASBR1> and another "top-level" LSP <ASBR2,P2,PE2>. Neither >> of >> >> these >> >> is the VPN LSP; rather, each is used to carry packets from one >> member >> >> of the >> >> VPN LSP to the next member in sequence. But option B is independent >> of >> >> how >> >> packets get between adjacent members of the VPN LSP. >> >> >> >> > WAN may use MPLS LSP tunnel and DC may use IP based tunnel. >> >> >> >> That is compatible with RFC4364 option B, because the LSP >> >> <PE1,ASBR1,ASBR2,PE2> still exists. >> >> >> >> > This will be an issue when use IP GRE tunnels. >> >> >> >> It's only an issue if you want to have a single GRE tunnel that goes >> >> from >> >> PE1 to PE2. If that is what you want, then you should probably be >> >> using >> >> option C. Option B does not tell the ingress PE who the egress PE >> is. >> >> (Well, not unless RFC 6513/6514 is also in use ...) >> >> >> >> > Option C request set up two LSP tunnel, one from ingress PE to >> egress >> >> PE, >> >> > second from ingress PE to ASBR to solve the issue in IGP. >> >> >> >> In option C, the "VPN LSP" would be <PE1,PE2>. If one wants to use >> >> MPLS to >> >> move the packets from PE1 to PE2, one needs a "top-level" LSP like >> >> <PE1,P1,ASBR1,ASBR2,P2,PE2>; but this is not the "VPN LSP". I think >> >> you >> >> interpreted the text from RFC 4364 as requiring this top-level LSP >> for >> >> option B, but it is only intended to require the VPN LSP >> >> <PE1,ASBR1,ASBR2,PE2>. >> >> >> >> I'm not sure whether this makes things any clearer or not ...
