Layer 3 in 5G Networks

By Erez Aviv 9 min read

5G brings with it many benefits. But before we can leverage those benefits some challenges need to be addressed. When it comes to transport networks, the focus is often on higher capacity, greater resiliency, and advanced network slicing features.

Network slicing is a fundamental capability of 5G and can only be achieved when using Layer 3. Slice implementation applies the same principles of virtualization across the provider’s entire network architecture. Slicing allows providers to allocate network resources according to the unique demands of each individual slice whether it’s minimum throughput, lower latency, or packet delivery priority. All this is required by eMBB, mMTC, and uRLLC 5G service types.

Watch Erez Aviv, Product Line Manager talk about a growing need for Layer 3 networking, its requirements, protocols and benefits.


Full transcript:

Dudy: Hi, we are back with the Backhaul Lounge. Today we have with us Erez. Erez is a PLM at Ceragon and a great networking expert. Hi Erez.

Erez: Hi Dudy.

Dudy: Thanks for joining. We’re going to talk today about Layer 3 and specifically the need for Layer 3 networking in 5G environments, in 4.5G environments, and this growing need as you evolve your network.

Erez: Looking at the 5G era, and looking about all the new use cases and the new services that 5G is bringing with it like the URLLC, mMTC and eMBB, you see a growing need for Layer 3 and the main reason is that you need some kind of orchestration, to have end-to-end services.

When you’re using Layer 2, most likely you will not have the capacity and capability to have end-to-end services all over the way. When you are using Layer 3 you have some kind of quality of service being done from the core network towards the edge, towards the tail, that we’re seeing that there is a growing need going towards the edge network that requires this kind of services being done with an orchestrator on top.

Dudy: So, basically, you’re talking about different services and use cases of 5G and the need for service orchestration. What you’re basically saying is that now we will need to use Layer 3 in more areas in the network then, we used to have in previous generations. So, as we move towards the tail of the network, we will start to see Layer 3 requirements there.

What exactly are the benefits in terms of scalability and manageability, and simplicity of the network, when you move from Layer 2 networking to Layer 3?

Erez: So, when you’re dealing with Layer 2 it means that you need to create a service from one point to another point, and then you need to go and do it again repeatedly, and often it will not be done automatically.

When you’re dealing with Layer 3, any network elements coming into the network automatically will have a service, which means that the Layer 3 will handle it and will connect it automatically. Beside that, there is a lot of densification coming for with 5G. You’re talking about mass deployments and a huge amount of nodes getting into the network, such as automated vehicles, such as IoTs – a lot of different services coming into the network into the same infrastructure. You need to connect them first of all automatically, and secondly you need to make sure that each and every segment and each and every

layer will get the exact capabilities and capacities that it needs from the same infrastructure layer. Doing it with Layer 2 is almost impossible, but with Layer 3 it can be done quite easily.

Dudy: So what you’re describing is basically network slicing, as a solution for service orchestration. What I understand from you is that network slicing is possible but not scalable or cost-efficient to implement in a Layer 2 environment.

Erez: Correct, so, the main drive for 5G use cases and to give the exact and specific capabilities to each and every service is based on network slicing. To have network slicing, you need some kind of orchestration on top. The main idea of network slicing is that you have the same infrastructure, the same physical network, but you are taking each and every slice, a logical slice to each and every service.

That means if you need a very low-latency service, like URLLC that 5G speaks about, you will take specific infrastructure from your network, and on them you’ll build the required service and this can only be done with Layer 3.

It’s more than that – When you have more and more services coming into the network, you will have some kind of congestion building on these networks, and to handle this congestion and to do it automatically you need Layer 3, and this comes with a very important feature called “Path Computation”.

The idea of Path Computation is once you created the service, probably it will be served by the network for sure, but having more and more services on top of it, then you can reach a point of congestion, and you want your network to be flexible enough to have some kind of reroute of these services into different paths to avoid this congestion.

Dudy: OK, that’s interesting Erez. Now we talked about Layer 3 in general terms. Are there any specific protocols that we would use in 5G with regards to Layer 3 because in the past we used to have some IGP protocols like OSPF and IS-IS. Then we evolved into IP/MPLS. What is the next step in the evolution?

Erez: So, looking at the Layer 3 era, the IP/MPLS is like the king of the neighborhood. This is a protocol being started in the early 90’s and it’s implemented most commonly and in most of the elements in the network when we’re dealing with Layer 3.

The main problem with IP/MPLS is that it’s very complicated. It’s very complicated because you need to involve a lot of protocols on it. So, beside the idea of having labels and to do the routing and the quality of service based on the labels that the MPLS insert into the packets, you will need some kind of protocol to distribute these labels. This is the LDP or RSVP-TE. And. Of course there is the inter gateway protocol such as OSPF and IS-IS. So, you have quite a lot of protocols to handle this IP/MPLS. I think in early 2014, Cisco came with a very unique and nice protocol means called “Segment Routing”.

Segment routing takes all the benefits of the IP/MPLS, and makes it much simpler. The idea is that we already have the IGP protocols, meaning the OSPF or the IS-IS. So why not use these protocols, also for the distribution of the labels? By this we will eliminate the LDP or the RSVP-TE. What we are left with is all the benefits of the IP/MPLS, with a very simple implementation of the segment routing.

Dudy: Excellent, Thank you very much Erez. To conclude, I would say that if you are out there gearing up for 5G, you will need to think about your Layer 3 strategy. You will see Layer 3 networking in more and more places in your network and you will also see an evolution of your Layer 3 protocols, from IP/MPLS to a more scalable and simplified protocols like segment routing.

Thank you very much for joining us. Thank you for watching and stay tuned for our next chapter of the Backhaul Lounge. Thank you very much.

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