Friday, February 7, 2014

Control Plane Flow and Data Plane Flow - BGP RFC 3107


BGP 3107 Architecture for Large ISP-Telecoms covers how BGP RFC 3107 help service providers to share the VPN routes across the boundaries without sharing the PE routes. ABR(Area Border Router) plays a vital role, as it has to modified the BGP next hop attribute to self.



Once the iBGP next-hop is changed, there after we can see how the control and data flow will look like.


Control Flow



Next step is to see how the data flow will look like


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Tuesday, January 28, 2014

BGP 3107 Architecture for Large ISP-Telecoms


BGP Label Update: Carrier Support Carrier - RFC 3107 post was describing how BGP RFC 3107 help service provider to share the VPN routes across the boundaries without sharing the PE routes. BGP Label Update feature is mainly used during inter-AS communication so that the changes occurring in one network couldn't impact the other.

Now consider in case of LTE network, there are thousand of thousand of eNODEB with all IP connectivity. Telecom provider is using IGP+LDP within the single domain. In this case, all the routes of eNODEB will flood across the domain however which is not required. Even we can't perform the summarization on loopbacks to reduce the number of routes within single area. How the scalability of PE will work in this kind of network?

Probably, BGP-3107 based architecture can be utilized within single Service Provider domain also to carry PE reachability. BGP IPv4-label address-family sessions between PE and P routers. IGP+LDP still runs within areas but does not carry PE reachability across areas. Remote PE loopback is a BGP ipv4 labeled route in RIB and next-hop for BGP service prefix is a BGP 3107 route.


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Sunday, January 26, 2014

BGP Label Update: Carrier Support Carrier - RFC 3107


BGP Label Update allows you to set up a Virtual Private Network (VPN) network so that the autonomous system boundary routers (ASBRs) exchange IPv4 routes with Multiprotocol Label Switching (MPLS) labels of the provider edge (PE) routers. In this scenario, Route reflectors (RRs) exchange VPNv4 routes and ASBR get relaxed to store those routes.

This results in improved scalability and simplifies the configuration. By using this feature, you can use non MPLS network as transit network, this helps you to transport all the IPv4 routes with labels over non MPLS network.

When you issue the neighbor send-label command under BGP configuration, the routers advertise to each other that they can then send MPLS labels with the routes. If the routers successfully negotiate their ability to send MPLS labels, the routers add MPLS labels to all outgoing BGP updates. This eliminates the need for using any label distribution protocol between the LSRs.(IS LDP Required For VPNv4 Labels)



In the above scenario, route reflector can reflect the IPv4 routes and MPLS labels learned from the ASBR to the PE routers in the VPN. This is accomplished by enabling the ASBR to exchange IPv4 routes and MPLS labels with the route reflector. The route reflector also reflects the VPNv4 routes to the PE routers in the VPN. ASBRs exchange IPv4 routes and MPLS labels for the PE routers by using EBGP.

MPLS labels are included in the update messages. Routers exchange the following types of BGP messages:
1. Open Messages
2. Update Messages
3. Keepalive Messages
4. Notification Messages

Out of four, Update Messages contains the Network Layer Reachability Information (NLRI), which has IP addresses of the usable routes. The update message also includes path attributes and the lengths of both the usable and unusable paths. Labels for VPNv4 routes are encoded in the update message as specified in RFC 2858. The labels for the IPv4 routes are encoded in the update message as specified in RFC 3107.

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