Understanding EoMPLS WAN Technology

Just another New Type of lease line. Understanding EoMPLS WAN Technology will explain why the Ethernet almost dominated both networks types – LAN and WAN. Ethernet over Emulation Multi-Protocol Label Switching (EMPLS) responded to the exponential growth of the internet over the passed years, MPLS became the preferred backbone by ISP providers to provide your business/home with either Internet or Private virtual leased line.

Ethernet as WAN Technology

There is no doubt that Ethernet became the king of LAN networks, IEEE improvement for Ethernet standards made it suitable for WAN technology as well, E.g. Ethernet Fiber 1000BASE-LX standard uses single-mode 9u fiber-cable with support for 5-km cable length; the 1000BASE-ZX supports even longer 70-km cable length.

So, IEEE improvements in cabling distance for fiber-ethernet links, made ethernet technology the king in WAN networks too.

Moving Forward

As we know it, the phone cables were already there, hence, serial link connections can be used, however, when Fiber such FIOS or Time Warner cable was evolved, new cable infrastructure should be used instead of phone cables to serve more robust internet.

It’s interesting to mention that Ethernet can run over Coax, UTP , and up to the latest type of fiber technology cable. However, Ethernet went through a lot of development by IEEE team to make it suitable for 100Mb, 1Gb, 10Gb, or even 100Gb. Cable type are different though among the different speed used.

Nowadays, many WAN Services Providers (SP) offer their WAN services based on Ethernet Technology. SPs offer wide variety of these ethernet WAN services using different names. But all of them use a similar model based on ethernet used between the customer site and the SP’s network as shown in the image below.

As you can see, the concept of lease line still there, however, the technology was replaced suing Ethernet instead. So, instead of using Channel Service Unit (CSU) device or the CSU WAN card at the customer site, the customer simply uses the Router Ethernet port.

As with CSU at the customer side, Ethernet Point of Service (POP) is being used instead of Central Office (CO) as it used to be when leased line was used. FYI –  CSU and CO technology is absolute, but still used in study martial to map the Old Technology concept to new one.

As seen in the upper image, Customer’s Router Ethernet Internet port will be connected to the closest ISP POP which can be on the building’s roof or at the end of the block using either a fiber cable, or a UTP cable to fiber Modem, then the Modem connects to the POP.

Remember, that Ethernet is just a Language, and as long as the physical standards understand it, Ethernet simply works.

Ethernet WAN as Layer 2 Services

I won’t go through the complex part of ISP infrastructure such MPLS which beyond this article. But, since we are talking about WAN Ethernet type, Ethernet over Emulation Multi-Protocol Label Switching (MPLS) is the Back Bone of WAN Technology used nowadays by ISPs.

Ethernet emulations is a general term, meaning, that the service (EoMPLS) acts like as if there is Long Fiber Ethernet cable or straight link connected between R1 and R2 as shown below, but the reality is: the ethernet signal is going through the MPLS infrastructure and switched back to the customer site through either a dedicated virtual circuit, or shared circuit. A dedicated circuit would be equal to an old private lease line.

The EoMPLS service provides:

• A point-to-point connection between two customer devices (Private line)
• Behave as if a Straight Fiber Ethernet link existed between two Routers

If you imagine two routers with single Ethernet link between them, you will understand what this particular EoMPLS service does. The following figure shows how R1 and R2 connected through EoMPLS similar to the previous figure, but Fiber-Optic is being used instead of old serial link cable. I have included a serial link connection for comparison.

Routing IP Packets using EoMPLS

As you probably guessed, Ethernet MAC Address System with Ethernet Header and Trailer are used in each encapsulation and discarded in each de-encapsulation process, EoMPLS WAN is no difference than Ethernet LAN in that regard.

Each Router discards the MAC address (Ethernet Data-Link Header and Trailer) and adds its new set. The following steps where the upper PCs talk to each describe the process:

Step 1: Send IP packet to R1, Ubuntu encapsulate the IP packet in an Ethernet frame that has the destination MAC address of R1.

Step 2: R1 applies FCS, de-encapsulates the IP packet from the Ethernet frame, discard the old frame (Old Header and Trailer), and encapsulates the IP packet into new Ethernet frame, using new header and trailer. R1 includes a destination MAC address of R2’s f0/0 interface, and a source MAC address of R1’s f0/0 interface. finally, R1 forwards the frame over the EoMPLS service to R2 as a next-hop.

Step 3: R2 applies FCS, de-encapsulates the IP packet from the Ethernet frame, discard the Old frame, encapsulates the IP packet into a new Ethernet frame that has destination MAC address of WinXP, and forwards the Ethernet frame to WinXP PC.

Ways to Access the Internet

There are too many ways to connect to the internet such Satellite, 4G, Fiber, Cable, T1, and so on. I believe Fiber such FIOS, Cable, and 4G are the most known WAN technologies used to gain access to the internet. T1 and DSL are still heavily used by small business, however, slowly are switching to Fiber and Cable.

Largest WAN Ever Exist

Internet is simply one huge TCP/IP network. In fact, the name “Internet” comes from the core network layer protocol: Internet Protocol. The internet includes many LANs, and because the Internet spans the globe, it of course needs WAN links to connect all these different LANs or ISP sites together.

As a network of networks, the Internet is actually owned by countless companies and people. The Internet includes most every enterprise TCP/IP network and huge number of home-based networks, as well as a huge number of individuals from their phones and other wireless devices.

Thanks to BGP routing protocol which made it possible to connect different ISP’s Networks together around the world. For instance, your home Router connect to the ISP closest Router using static route, the closest Router might be part of OSPF network owned by your ISP; another ISP Networks might be running EIGRP which connect to a third ISP Networks, and so on.

At the edge of these ISPs, BGP routing protocol must be used to let ISPs and their Customers communicate with each other regardless what Routing Protocol the ISP infrastructure is using.

WAN Links are Internet Access Links

Digital Subscriber Line (DSL)

Interestingly, too many people still using dail-up, but moving to DSL if you can’t give up your PSTN line (RJ11 Phone line) is better choice since there is no difference in price. DSL uses the same phone infrastructure, but doesn’t replace PPP (T1) leased lines or EoMPLS lines since DSL support asymmetric speeds most of the time.

DSL Access Multiplexer (DSLAM)

In order to serve the customer with phone and internet service, ISP Central Office (CO) DSLAM splits the single-pair cable to 2 channels: One goes out to the data over an Internet Router, and another one goes out to the phone switch called Public Switch Telephone Network (PSTN).

Cable Faster Internet

Since a Coax cable is being used for TV signal, why not using the same Cable for internet connection as well. Ethernet runs the MAN network, and most customers were able to use Asymmetric Rate speed such DSL connection, now why not offering customers faster internet speed than DSL but using Coax cables instead of PSTN cables? Yes, I believe, in new buildings, phone cables are being replaced by Coax cables, so TV, Internet, and Phone service are being provided using a one Coax cable.

Note: It’s good to remember that Cable and DSL Internet connections use asymmetric rate, meaning, the downstream is faster than the upstream, which makes it suitable for most home consumers. Symmetric rate on the other hand is used by T1 and Fiber such FiOS, for example, the down and upload stream are equal speed which makes T1 and FiOS more suitable for some businesses needs such Internal Private Cloud.

Subject Related

By Wikipedia MPLS | Router Ally MPLS | Cisco Learning | MPLS as a Service | How to Master CCNA | Cisco CCNA Simplified | Cisco CCNA in 60 Days | R&S ICND1 and ICND2 | Network Warrior | CCNA R&S Study Guide | R&S 200-120 Official Guide | Routing and Switching Guide