MPLS BGP forwarding vs BGP Labelled Unicast (RFC 3107)

[nwekechampion]

Hey Guys,

Can anyone let me know the difference between MPLS BGP forwarding and BGP labelled unicast?

If both forward MPLS labels, what are the differences and unique use-cases?

[M02@rt37]

Hello @nwekechampion,

MPLS BGP forwarding and BGP labeled unicast are both involve the use of MPLS labels for forwarding packets. They are used in different contexts. 

MPLS BGP forwarding refers to the use of MPLS to forward IP packets in a network where BGP is the primary routing protocol. In this scenario, BGP is used to establish routing information among routers in a network, and MPLS is used to optimize the forwarding of packets based on that routing information. 

BGP is primarily responsible for routing decisions, while MPLS is used for efficient packet forwarding. MPLS labels are used to identify and forward packets along LSPs. These labels are assigned based on the routing information learned through BGP. MPLS BGP forwarding is typically used in service provider networks to provide services like MPLS VPNs, traffic engineering, and improved traffic handling. It allows for traffic engineering, enabling the network to route traffic along specific paths based on factors like link utilization and QoS requirements.

=> MPLS BGP forwarding focuses on optimizing the forwarding of IP packets in a network where BGP is the primary routing protocol.

On the other hand BGP labeled unicast is a specific extension of BGP that enables the exchange of labeled routing information. It involves the distribution of MPLS labels along with routing updates through BGP.

BGP labeled unicast extends BGP to carry MPLS label information for each route in the BGP update, allowing routers to make label-based forwarding decisions. It's comonly used in scenarios where BGP is the primary routing protocol, and MPLS is used to optimize forwarding. BGP labeled unicast is particularly useful in MPLS VPNs, where it enables the creation of VPN-specific LSPs. BGP labeled unicast allows for more precise control over MPLS label distribution and helps in building complex MPLS networks, such as hierarchical VPN services.

=> BGP labeled unicast extends BGP to carry MPLS label information and is used to create label-switched paths for specific purposes, such as MPLS VPNs. 

[nwekechampion]

Hi M02@rt37 ,

What is an example of a network where BGP is the primary protocol, well apart from EBGP.

From what I understand ibgp is used an overlay on IGP (OSPF /ISIS), hence not the primary protocol.

So could you provide some context/examples/use-cases to this statement:

"MPLS BGP forwarding focuses on optimizing the forwarding of IP packets in a network where BGP is the primary routing protocol"

Thanks

Champ

[M02@rt37]

Hello @nwekechampion 

In a service provider network, BGP is often chosen as the primary protocol for handling routing between different AS. Each AS represents a network domain, and BGP facilitates the exchange of routing information between these domains. Within each AS, the provider might use an IGP like OSPF or ISIS for internal routing.

MPLS is then employed to enhance the forwarding efficiency of IP packets within and between these ASs. BGP is responsible for distributing reachability information between ASs, and MPLS labels are assigned to packets to optimize their forwarding across the provider's network.

MPLS BGP forwarding is particularly relevant and beneficial in large-scale networks, especially service provider environments, where BGP is the primary protocol for interconnecting different autonomous systems.

[MHM Cisco World]

You have SP have AS and need to send traffic between two PE in same AS 

Here we use MPLS BGP

Assume this SP have two AS we need inter-AS options (A'B'C)

Here we need to push label between two AS so here we using bgp LU' there is connection between two AS and we run bgp and send label with each bgp prefix.

I.e. in simple words

MPLS BGP use vpnv4 with labels

BGP LU use ipv4 with labels

MHM