The Network Hub

Nov 18 2014   9:32AM GMT

A VPLS Network procurement walkthrough

Robert Sturt Robert Sturt Profile: Robert Sturt

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Network

Organisations should never be forced into a features and benefits conversation with their prospective service providers. The majority of network designs produced by our BT Business partnership surrounds hybrid technologies, perhaps VPLS across data centres, layer 3 MPLS at branch sites, fibre services within the core and IPSec / SLL for remote users.  In certain sites, it makes sense to deliver a layer 3 capability, in others (such as data centres) VPLS is the clear option to deliver capability. In metropolitan areas, fibre is always a good option. This kind of features and benefits sales approach will result in missed requirements and essentially a MPLS or VPLS network solution which is not fit for purpose.

A good accompanying resource is the Techtarget version of my MPLS and VPLS step by step IT Managers procurement Mindmap which is available upon request.

The mindmap examines in detail the process and considerations to make vs your own business requirements. The overall complexity is dependent on not only your requirements today but also those which need to be predicted in the future. The IT team’s work is becoming more critical than ever to communicate needs as globalisation, security, application performance, user productivity and disaster recovery is driving a critical reliance on WAN connectivity. The ultimate goal, as ever, is to maximise uptime of resources and plan for scenario’s which are unlikely but would impact the business in a major way. The WAN may appear as though innovation is fairly stagnant, we don’t hear too much in the way of significant evolution and buzz around WAN connectivity. However, applications are evolving faster than they ever have before due to enhanced productivity, different ways of working and a desire to achieve efficiencies and this a competitive edge.

What is VPLS Ethernet

Virtual Private LAN Service networks provide the ability for companies to create a LAN structure between geographically separate sites. The traditional and default choice for IT Management is generally considered to surround layer 3 VPRn (Virtual Private Routed Network) – known as MPLS in the market place. We believe the growth of VPLS services is driven by the ubiquitous access of Ethernet coupled with private cloud based services. We will go on to to explain more about our findings later.

The key benefits of VPLS solutions surround a number of key points.

Perhaps the most popular discussion surrounds the ability to extend data centre connectivity (or essentially sites which contain resources) across geographical separation. The dream is to deliver global or national connectivity whilst maintaining a base level of configuration and thus avoiding IP address reconfiguration which is required with layer 3 networks (MPLS – Virtual Private Routed networks). We are aware that globalisation is growing with data centres located in far flung locations, the challenge of deploying applications is made easier with VPLS layer 2 WAN services. A VPLS solution will extend the deployment of your server clusters into different data centres protecting against major disruption.

In another scenario, service providers and enterprises often do not meet in terms of requirements vs capability. There are some businesses which are reluctant to allow a service provider access to their layer 3 management and routing, Perhaps the organisation is needing to serve an unsupported protocol which the service providers will not transport. In this example, the ability to layer on layer 3 is a clear advantage for VPLS based connectivity.

It would be remiss not to mention VLL (Virtual Leased Line) services as they are closely related. VLL’s are designed to emulate point to point  / multipoint fibre connectivity across an MPLS core network. The benefits are clear since MPLS provides the reach and emulation for circuits which would otherwise be too great in distance for dedicated fibre provision. 

In short:

VPLS provides any to any connectivity using pseudowires – Virtual Ethernet circuits provisioned as a full mesh topology

VLL – point to point or multipoint Ethernet pseudowires

A pseudowire is essentially point to point emulation of Ethernet.

One important distinction to make: VPLS is an evolution in terms of capability which is built and created on the shoulders of MPLS core networks. The majority of IT managers believe that VPLS is somehow a different platform to MPLS but the reality is, MPLS core networks are the foundation for layer 2 connectivity. In other words, today’s MPLS networks facilitate layer 2 and layer 3 connectivity.

Why VPLS 

Prior to VPLS becoming a mainstream technology, organisations were not only limited by distance related issues across layer 2 fibre but also dedicated high-speed data circuits equalled high costs. The telco’s already owned significant core networks with layer 3 capability, the addition of a layer 2 VPN capability made sense.

Some serious benefits to consider

An organisation with a private cloud (their own hosting facility) requires further virtual servers on the same LAN segment. However, space is running out fast. In this scenario, a further data centre could be added with a connection into VPLS. Once connected, further virtual servers are able to be installed which will appear on the same connected LAN as the older full data centre facility. The plus point is clearly demonstrated to surround seamless LAN connectivity. The added benefits of a geographically separated site surrounds disaster recovery and resilience since the loss of a DC will ultimately partially remove some connected hosts but not all of them which offers greater uptime.

You have the desire and capability manage your own routed network. As the name suggest, the procurement of VPLS is at layer 2 which leaves layer 3 routing to be setup as required. Service providers set a base level of capability for MPLS.

We worked with a client recently which had decided to implement a cloud server cluster strategy for redundancy and scalability. With each cluster needing to reside in the same VLAN and network but with geographical separation for further redundancy, the organisation looked to VPLS. which enables extended VLAN. In addition, their data centres were encountering issues with power and cooling. The addition of a further datacenter allowed the client (as per point 1)

Consideration of VPLS vs MPLS

VPLS is built using a service provider product term called EVC’s (Ethernet Virtual Circuits). This is a marked difference when making a comparison to MPLS. The use of EVC’s is perceived as a scalability issue since, as networks grows, the network performance may be impacted meaning there is an ultimate ceiling in terms of how many EVCs each provider router may support. The majority of providers will brush over scalability since their core networks are, over time, increasing in their ability to scale which increases their ability to support greater EVC’s. In the majority of cases, there is no need to worry or be overly concerned but clarity should always be requested depending on which provider readers are considering.  On the counter point, MPLS (or rather layer 3 routed networks) are truly connectionless from the perspective of scalability.

VPLS network terminology

As I have previously mentioned, VPLS is a layer 2 VPN across an MPLS core network. When considering providers, procurement teams will often be faced with acronyms such as PE or P which refer to the edge and core devices within a network.

The PE device refers to the Provider Edge which is essentially the edge node into a service provider’s network. IT Managers are advised to understand the true PE capability of prospective service providers since PE coverage determines scale and diversity options. The P device is the ‘Provider’ core aggregation devices within the centre of their network used to scale the MPLS core network. 

VPLS Network Acronyms

Some thoughts regarding VPLS network procurement

In general, VPLS is sold as an unmanaged service with Ethernet handoff. With this said, in some instances, the provider will offer a managed service whether this is based on a Layer 3 switch or a router. As with any WAN procurement project, the advice is to carefully consider the service capability vs your specific requirements. The Mindmap not only details some of the specifics of VPLS but also the key vectors we know to matter across application performance, uptime, topology, strategy and budget. In general VPLS services should be viewed in the same way as the more traditional layer 3 from the perspective of SLA which includes latency, jitter and uptime guarantees. Clearly an unmanaged service creates a very different adds, moves and changes process vs managed services. The typical approach when making changes is often surrounded by ‘clunky’ processes which creates delay. One of the real plus points of VPLS, as we have mentioned within this article, is the ease of self managed services. We are seeing growth within the managed services sector where organisations are outsourcing the management to specialist organisations which overlay their services with the providers supplying the connectivity. This, we believe, is a major shift in thinking since the traditional approach is to use a single provider for connectivity and management. VPLS is creating an environment of adoption which creates a little more freedom when considering how to manage services on an ongoing basis.

All of the concerns surrounding MPLS procurement are essentially the same when considering VPLS. We are in effect talking about layer 3 vs layer 2 which both using an underlying MPLS core network.

We have written a fair amount of content on WAN procurement, both MPLS and VPLS but the core of our approach remains the same. It is clear that organisations which achieve better outcomes when they are able to align their business specifics vs the service provider capability. In short, if you consider applications (as an example), our approach to execute WAN procurement involves understand how the application performs today but also how performance may be increased to improve productivity. In some instances, improving application performance may not relate to the technical aspects of a capability but perhaps admin tasks such as adds, moves and changes. As organisations begin to understand how each provider might provide a capability which adds a competitive edge, the WAN becomes and enabler rather than the typical bottleneck.

Conclusion

VPLS is a growing technology which, in part, is due to the emergence of cloud based solutions, whether private or public. Server clusters often require geographical diversity, VPLS networks add a unique capability here. The ability to add, remove servers as required across a layer 2 Ethernet WAN with any to any connectivity. The simplicity of layer 2 is now available across the WAN offering seamless connectivity on a Global basis. As a counter point, layer 3 services offer an out of the box routed network supporting a standard capability. As I wrote toward the beginning of this article, we are finding most project result in a hybrid approach for design. This means that VPLS is a another building block for organisations to use in their pursuit of connectivity and cloud excellence.

Additional reading: MPLS Network long form article

WAN Service Providers long form article

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