VPLS Extends VLANs into MPLS-VPNS

By Tom Cross

Technology Columnist

Virtual Private LAN Service — Service for Virtual Private Networks

The animated presentation can be found at: http://www.techtionary.com/podcasts/vpls/

Now for the English “non-acronym” version, Virtual Private LAN Service allows customers to create VLANs (Virtual Local-Area Networks) in a metro network or global network using IP (Internet Protocol) MPLS

(Multi-Protocol Label Switching) or VPNS (Virtual Private Network Service).

In CEO talk, this means you can connect all the branches in the same city without costing a lot and cities elsewhere “almost” as easily. In the animated presentation, you will see the differences between VPLS and VPNS. There are many others including training, availability, diversity, disaster recovery, application such as hub-spoke versus mesh networking and others. Check with your provider as your mileage may vary.

To begin with, let’s see the basic concept behind LAN switching. LAN switching is a Layer 2 (Datalink) concept of switching rather than routing which takes place at Layer 3 (Network). In LAN switching all packets are “flooded” to all locations until they find their destination. Nice idea if you have only a few sites. Originally known as TLS (Transparent LAN Service), Metro-Ethernet, Ethernet Private Line and now often called VPLS-Virtual Private LAN Service, here are some reasons why you should consider this service.

First, it is easy-to-implement with plug-and-play installation.
Next, LAN Switches are cheap.
Third, VPLS provides very flexible BOD-bandwidth on demand options.
Fourth, it is a great solution for same-city customers with many locations.

Here are some reasons against:

First, it doesn’t grow or scale well to tens of sites and hundreds of users.
Second, faster bandwidth doesn’t provide QoS or solve flooding of packets due to large applications.

In Layer 3 routing, only the packets that are destined for the other location are sent. That is, packets are routed based on the destination IP address.

Here are some reasons for routing:

First, it scales or grows essentially infinitely for customers with domestic and global locations.
Second, routing supports all kinds of IT systems new or legacy.
Third routing provides higher security.

Reasons against routing:

First, there is a high cost with routing and routing will always be more expensive than switching.
Second, routing is complex to manage.
Third, routing requires very knowledgeable and technical staff.

I didn’t forget VPLS, just needed a minute to get through the basics. VPLS uses MPLS to provide the “seamless” connections for VPLS. Shown in the presentation is the IP packet before and with the MPLS “label” attached or “tagged” on as it was originally called. MPLS consists of four elements, label bits, experimental bits, a stack bit and TTL (Time-To-Live) bits, which indicate the number of Label Switch Routers passed. Shown here is the “multi-protocol” part of MPLS and how it works with the other major networking protocols such as ATM

, Frame Relay, Ethernet and others.

As shown in the presentation MPLS is used to connect locations and VLANS together.

In the next slide are the three key access topologies — Ethernet-line for two sites, Ethernet-LAN for three or more sites and Ethernet-access for VPN/Internet. This makes implementation and configuration of VLANs really simple.

WHY VPLS – Summary

Here are a few business reasons:

Extends LAN infrastructure easily
Expands metro-net to global-net
Migrates Frame Relay to MPLS
Utilizes “pseudowire” approach
Needs “mesh’ connections
Connect call centers via SIP
Provides DR for data centers
Wants greater customer (less carrier) control
Has multi- and broadcast traffic
Building a CDN (Content Delivery Net)
Building an overlay multi-carrier network.

VPLS is a great solution for any customer with more than location.

This presentation is also included in TMC (News - Alert) University special course on Microsoft OCS (Office Communications Server) at ITEXPO.com. For more go here: http://www.tmcnet.com/voip/conference/west-08/tmc-university-microsoft-ocs.htm

This presentation is also included in online/onsite courses SIP 2.0c and for OCS-101 Office Communications Server per person (volume and site license discounts available). Discounts are also available to members of the SIP Forum (News - Alert) and MS Partners. For customizing, special discounts, website animations, technical/sales training, technical writing and other services, go to http://www.techtionary.com or please call Tom Cross (News - Alert) at 303-594-1694 or cross@gocross.com.

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