Network Diversity and Survivability - Spectrum · What is network diversity and survivability? As discussed in the introduction, diversity and survivability are important concepts

Network Diversity and Survivability: Five ways to evolve to true diversityWHITE PAPER 2016

An Independent Analysis Published on Behalf of Time Warner Cable, Inc.

Copyright © 2016 iGillottResearch Inc. | www.igr-inc.com

Copyright © 2016 iGillottResearch Inc.2 Copyright © 2016 iGillottResearch Inc. 3

Executive Summary ...................................................................................................................... 2

Different Types of Network Diversity ........................................................................................... 4

How Network Diversity is Implemented ....................................................................................... 6 Baseline Network Architecture ............................................................................................. 6 Step 1: Dual Entrance Facilities ............................................................................................ 7 Step 2: Diverse Hubs and Routes ......................................................................................... 8 Step 3: Dual Hubs, Diverse Routes and Dual Entrance Facilities ......................................... 8

Step 4: True Access Diversity ............................................................................................... 9 Step 5: Access Diversity — ENNI POP ............................................................................... 10

Network Failover and Mean Time to Recovery ................................................................... 11

Leveraging Time Warner Cable’s Network for Diversity and Survivability ................................. 12

Conclusion .................................................................................................................................. 14

About Time Warner Cable Business Class Carrier Services ....................................................... 15

About iGR ................................................................................................................................... 15

TABLE OF CONTENTS

Reliable network connectivity is critical for most businesses and enterprises today, from retail stores depending on fast, dependable Internet access for credit card verification to insurance companies reliant upon continuous access to product and pricing databases. Hospitals, manufacturing locations, hotels, restaurants and financial institutions all need Internet and data center access in order to operate their businesses. Rather than simply viewed as a “nice to have,” guaranteed connectivity to customers, corporate offices, data centers and the Internet is now “mission critical.” If a connection is lost, it may be impossible for many modern businesses to continue operating.

Guaranteed network connectivity does not happen by accident. Networks are carefully designed and implemented to ensure that they are diverse and survivable — two related and very important concepts used in network design and deployment. Network diversity ensures that there are alternative paths available for network traffic in the event of a failure, while network survivability is the ability of a network to maintain service connection after a failure. The goal, of course, is that the end users are completely unaware of any network issues or failures.

EXECUTIVE SUMMARY


There are three types of network diversity: carrier diversity, access diversity and transport diversity. Carrier diversity is when an enterprise selects two different carriers to provide network connectivity. Access diversity refers to the capability of a network to provide backup protection for a local access circuit. Lastly, transport diversity provides alternative transmission paths in the network core or cross-market section of the connection.

Some telecom service providers will talk about “redundancy” in the same terms as “network diversity,” but these two terms are not synonymous. For example, a network could have redundant fiber connections, but if the fibers are both in the same conduit then there is no network diversity.

Network diversity ensures continuity of telecom services to a specific location, building or premises. Since all businesses today rely on some type of Internet or data connectivity, service continuity is vital. Diversity provides several benefits:

•Protectionfortheentireconnection,ensuringcontinuousconnectivity

•Availabilityofalternativeaccessanddistinctanddiversecentralofficesfromtheprimary telco

•Provisionofanalternativephysicallong-haulconnection

•Connectiondiversityinthecaseoffailureoftheprimarytelco’sinfrastructure

Designing and building a network with diversity and survivability is not simply a case of adding redundant equipment – several important considerations must be taken into account:

•Geography

•Varietyoftelecomserviceproviders

•Useofredundantequipmentandelectronics

•Uniformityinnetworkdesignandbuild

Each of the major components of the network (customer premises equipment, building access, street manhole or pole, local circuit to the hub or CO, the hub or CO itself and the connections back to the ENNI or POP) must be designed and built with diversity and survivability in mind. For example, if dual hubs/COs are used but are connected to the customer premises through a single manhole or pole on the street, then there is still a potential single point of failure in the network (separate manholes or poles must be used).

This paper will demonstrate five ways to design and implement a more diverse network.


What is network diversity and survivability?As discussed in the introduction, diversity and survivability are important concepts used in network design and deployment. Network diversity ensures that there are alternative separate paths available for network traffic in the event of a failure, while network survivability is the ability of a network to maintain service connection after a failure. This section will discuss the benefits of network diversity as well as the major design considerations.

There are three different types of network diversity:

•Carrierdiversityiswhenanenterpriseselectstwodifferentcarrierstoprovidenetworkconnectivity. The assumption is that if one network fails, the backup carrier will be able to provide service. However, this assumption is flawed, since many carriers share some parts of their networks.

•Accessdiversityreferstothecapabilityofthenetworktoprovidebackupprotectionforthe local access circuit that connects the customer location to the carrier’s hub (or wire center).

•Transportdiversityprovidesalternativetransmissionpathsinthenetworkcoreorcross-market section of the connection.

‘Redundancy’ and ‘diversity’ mean different thingsIt is important to understand that “redundancy” is not the same thing as “diversity.” For example, a network may have redundant fiber connections, but if the physical fibers are both in the same conduit then there is no route diversity.

Similarly, if redundant circuit access equipment is located in the same data center or CO as the primary access equipment, there is no location redundancy. Building a fully redundant and survivable network, therefore, involves more than simply duplicating the network connections and equipment.

Benefits of access and transport diversityBut why is network diversity needed? What specific benefits do access and transport diversity provide to the end user? In the simplest terms, network diversity ensures continuity of telecom services to a location, which is obviously important for businesses that rely on connections to data centers, the Internet or other enterprises for their revenue. But network diversity is also used to connect hospitals to doctors and specialists at remote locations, for example, and therefore may directly impact quality of life. And in the case of a catastrophe or failure at the business’s main location, network diversity is an important element in an effective disaster recovery plan.

DIFFERENT TYPES OF NETWORK DIVERSITY


From a network perspective, diversity provides several benefits:

•Protectionfortheconnectiontothebuildingorenterpriseinthelastmileandthroughout the whole network, ensuring continuous connectivity

•Offersanalternativephysicalconnection(access)fromtheprimarytelecomnetworkor telco

•Providesanalternativephysicallong-haulconnection

•Connectiondiversityinthecaseoffailureoftheprimarytelco’slastmile,metropolitanand/or long-haul infrastructure. This functions as “insurance” for a network outage.

Design considerationsThere are several important considerations when designing a diverse and survivable network:

•Geography–thereshouldbeatleasttwodiversetransmissionpathsforthenetworktraffic. For example, if we consider a transcontinental network, one path should take a southern route and the other a northern route.

•Hubs,POPSorCOsshouldbefromdifferentproviders.Ideally,atleasttwohubsshouldbe used from the service provider that supports separate circuit transmission paths.

•Redundantequipmentandelectronicsshouldbeprovidedbothwithinthecustomerandservice provider networks. At the customer premises, the equipment should be located in different closets in different parts of the building.

•Uniformityinnetworkdesignandbuild—auniformplatform,constructedwithconsis-tent technology and ownership, translates into effective control over potential problems by limiting the variables all parties face when troubleshooting network components. For example, the network architecture and physical build should look the same in New York as it does in Los Angeles to ease problem solving.


HOW NETWORK DIVERSITY IS IMPLEMENTED

CustomerPremises

Local Hub orCentral Office

Streetmanholeor pole

Singlepremisedevice

Pointof entry

Single circuit unprotectedTo POP/HeadendENNI location, etc.

Building a diverse, survivable network is more complicated than simply selecting a backup tele-com service provider or deploying redundant network equipment. This section will show how to build a diverse network and where the potential points of possible failure are.

BASELINE NETWORK ARCHITECTUREBefore discussing the evolution to a fully diverse, survivable network, we need to start with the baseline network design (Figure 1A). In this network, a single circuit is connected to a single manhole or pole on the street and then to the customer premises. The premises’s termination equipment and electronics are represented by the blue box in the customer building.

•Theorangetrianglesshowthepotentialpointsofnetworkvulnerabilityandfailure:

- A single network hub or CO is used, which is connected to the POP/headend, ENNI location, etc.

- A single circuit is used, which is unprotected.

- There is a single point of entry into the customer premises from the manhole or pole.

- In the customer premises, there is a single network termination device.

FIGURE 1A: Non-Diverse Access, Single Building Point of Entry

Indicates point of potential vulnerabilitySource: Time Warner Cable, 2016


Step 1: Dual entrance facilitiesThe first step in the network evolution is to use a second entrance into the customer premises (Figure 1B). While this gives a diverse route into the building, note that potential vulnerabilities still exist with the single network termination device and with the single manhole or pole. And while two circuits connect the hub to the manhole/pole, a single hub/CO is still used.

Also, the two circuits follow the same route and could therefore both be cut at the same time by a single incident. The two circuits are configured as “active/active” with no protection switching.

FIGURE 1B: Dual Entrance Facilities

Indicates point of potential vulnerability Source: Time Warner Cable, 2016

CustomerPremises


Primaryentrance

2 fibersTwo circuits

“active/active”

To POP/HeadendENNI location, etc.

Singlepremisedevice



Step 2: Diverse hubs and routesThe next step is to use diverse hubs and diverse routes for the two circuits to the street man-hole or pole (Figure 2). Now the circuits are more secure since both cannot be cut by a single incident (this assumes the two hubs or COs are in different locations and the circuits follow completely different routes).

Now the points of failure are the single serving manhole or pole and the customer premises equipment.

FIGURE 2: Access Diversity — Dual Hub/Single Entrance Facility


Step 3: Dual hubs, diverse routes and dual entrance facilitiesFigure 3 on the next page shows how the potential weakness of the single serving manhole or pole can be addressed: simply, two serving manholes/poles are used with separate (route diverse) entrances into the customer premises. Also note that each of the circuits has two fibers and are route diverse. In reality, there is also a connection between each of the man-holes/poles for full route diversity.

Now, the single point of potential failure is the customer premises termination equipment. Note that while this may be a single piece of equipment, it may have very high uptime metrics or have a redundant unit in the same rack.

CustomerPremises



Primaryentrance

2 fibersTwo diversely routedcircuits to dual hubs

“active/active”Single

premisedevice



FIGURE 3: Dual Hubs, Diverse Routes, Dual Entrance Facilities


Step 4: True access diversityThe final step in the network evolution is shown in Figure 4, when separate customer premises network termination units are shown, ideally housed in separate locations in the building. The network is now considered diverse and survivable.

FIGURE 4: Access Diversity: Dual Hubs, Diverse Routes, Dual Entrance Facilities

Source: Time Warner Cable, 2016

CustomerPremises



Primary entrance

Secondary entrance

2 fibers

2 fibers

Two diversely routedcircuits to dual hubs

“active/active”

SinglepremisedevicePrimary street

manhole or pole

Secondary streetmanhole or pole

2 fibers

2 fibers

CustomerPremises



Primary entrance

Secondary entrance

2 fibers

2 fibers

Two diversely routedcircuits to dual hubs

“active/active”

Diverse premise devices andelectronics

Primary streetmanhole or pole

Secondary streetmanhole or pole

2 fibers

2 fibers


PROTECTION AND DIVERSITYNow is a good time to discuss the difference between protection and diversity. In the network shown in Figure 4, if there is a failure in one of the circuits, the traffic will not automatically switch to the alternative route. To provide protection, one live circuit is used by the customer and the “standby” circuit is managed by TWC. If a failure occurs in the active circuit, TWC switches the traffic to the standby circuit. Note that some additional premises equipment and network configuration by TWC are required to support this working/protect scenario.

Step 5: Access diversity — ENNI POPThe network examples shown are all for the access network, from the local hubs or COs to the customer premises. But what about network diversity for the POP/ENNI sites and the long-haul network?

Figure 5 shows the primary and diverse access paths from the customer premises to the ENNI POP, with diversely routed circuits through diverse hubs. This gives a high availability network from the premises to the ENNI POP.

FIGURE 5: Access Diversity — ENNI POP


CustomerPremises



ACCESS NETWORK

POP/ENNISite

Dual pointsof entry

Primary path

Secondary path

NNIEdge

NNIEdge

ENNICustomerNetwork


NETWORK FAILOVER AND MEAN TIME TO RECOVERYMany telecom service providers will highlight the importance of network failover and offer this as an alternative to network diversity. This is not the case: network failover is not a viable alternative to a true diverse network, and the two should not be compared.

Network failover is simply the switching of traffic to an alternative link if the primary connection fails. In the case of failure of one fiber link, for example, the traffic will failover to another circuit. However, this alternative fiber may be in the same bundle as the failed link and will terminate in the same colocation facility or CO. If the fiber bundle is severed for some reason (for example, due to road construction), then both the primary link and the failover alternative will be cut and service will be lost.

This occurrence can, of course, be avoided if the telecom service provider uses separate routes for the active and standby fibers. But if they both terminate at the same colocation facility in the telecom network, this introduces a potential vulnerability. If there is a physical failure at that facility, service will be lost no matter how many separate fiber routes exist from the colocation to the customer premises.

The final issue with failover is the “mean time to recovery.” Simply, this is the time the network takes to failover from the active to standby circuits in the event of a failure. Sub-50 milliseconds failover time is a common benchmark as is “five nines” reliability — if the mean time to recovery exceeds 50 milliseconds, then the customer is likely to see a brief interruption in service, which may negatively impact internal systems and processes.


Time Warner Cable operates a nationwide network that is, importantly, totally independent of ILECinfrastructure.TWCservicescustomersin29statesand31U.S.metromarkets,withahighly redundant, secure and reliable hybrid-fiber coaxial network. The network has 150,000 fiberroutemilesacrosstheU.S.,connectingmorethan1,000POPs,18,000litcelltowersand70,000 fiber lit buildings. TWC’s network can be used as a primary communications network for enterprises,businessesandorganizationsacrosstheU.S.Inaddition,TWC’snetworkisaviablealternate CO and path option for those who already have a primary telecoms provider in place.

Figure 6 below illustrates TWC’s national backbone fiber routes (in yellow) and the diversity of those long-haul routes. For example, traffic originating in Dallas has several different routes to New York.

FIGURE 6: Time Warner Cable Nationwide Network

LEVERAGING TIME WARNER CABLE’S NETWORK FOR DIVERSITY AND SURVIVABILITY



The following figure (Figure 7) illustrates TWC’s dense fiber footprint in the metro markets, using Manhattan as an example.

FIGURE 7: Time Warner Cable Manhattan Network Map

Figures 6 and 7 highlight several important aspects of Time Warner Cable’s fiber-rich metro network:

•TheTWCnetworkdoesnotshareaphysicalplantwithanILEC(asaCLECdoes)sodi-versity at the hub level is assured. An ILEC and CLEC, however, are likely to share some infrastructure (such as at the CO level) and so cannot ensure true network diversity.

•Asaresult,ifanILEC/CLECnetworkgoesdown,TWC’snetworkislikelytoremainoperational and vice versa. Therefore, network diversity may be provided to an enterprise by using TWC’s network in addition to ILEC/CLEC connectivity.

•Obviously,naturaldisasterscanimpactTWC’snetworkaswellatthatoftheILEC/CLEC in a specific area. If an alternate path is chosen for the primary and secondary networks, a diverse network can be built. An enterprise may leverage TWC’s metro fiber density and nationwide fiber network with careful route planning in conjunction with an ILEC/CLEC to achieve true route and hub diversity.



As this paper has discussed, reliable network connectivity is a “must-have” for most business-es and enterprises today, and guaranteed connectivity to customers, corporate offices, data centers and the Internet is now “mission critical.” If a connection is lost, it may be impossible for many modern businesses to continue operating.

But guaranteed network connectivity does not happen by accident — diverse and surviv-able networks are carefully designed and implemented. And there are three distinct types of network diversity: carrier diversity, access diversity and transport diversity. When all three are combined, a network ensures continuity of telecom services to a specific location, building or premises.

Of course, designing and building a network with diversity and survivability is not simply a case of adding redundant equipment — considerations such as geography, the variety of telecom service providers used, use of redundant equipment and uniformity of network design and build must all be taken into account. But the benefits of getting the design and deployment correct are significant.

The paper detailed the five steps to building a diverse and survivable network:

Step 1: Dual entrance facilities — use a second entrance into the customer premises.

Step 2:Usediversehubsandroutesforthetwocircuitsfromthepremisestothestreetmanhole or pole.

Step 3: Implement dual hubs, diverse routes and dual entrance facilities from two serving manholes/poles.

Step 4: True access diversity is achieved by adding separate customer premises network termination units, ideally housed in separate locations in the building.

Step 5: The final step is to add network diversity for the POP/ENNI sites and the long-haul network, with diversely routed circuits through diverse hubs. This gives a high availability network from the premises to the ENNI POP.

Time Warner Cable operates a nationwide network that is completely independent of the ILEC infrastructure. As physical plant is not shared with an ILEC (as a CLEC does), TWC’s network can ensure diversity at the hub level. In cases where TWC is not the primary network, the TWC network is a viable alternate hub and path option for those who already have a primary tele-coms provider in place — thus achieving a more diverse route for your customers.

CONCLUSION


ABOUT TIME WARNER CABLE BUSINESS CLASS CARRIER SERVICESTime Warner Cable Business Class is an industry-leading wholesale communications provider offering comprehensive coverage and capacity in more than 31 major metro markets across theU.S.DeliveringextensiveWholesaleEthernetAccessandTransport,WholesaleIPandCellTower Backhaul solutions across a reliable network infrastructure, Time Warner Cable Business Class is the one solution for all of your carrier needs. For more information, visit www.business.twc.com/carrier.

ABOUT IGRiGR is a market strategy consultancy focused on the wireless and mobile communications in-dustry. Founded by Iain Gillott, one of the wireless industry’s leading analysts, we research and analyze the impact new wireless and mobile technologies will have on the industry, on vendors’ competitive positioning, and on our clients’ strategic business plans.

A more complete profile of the company can be found at http://www.iGR-inc.com/.

DISCLAIMERThe opinions expressed in this white paper are those of iGR and do not reflect the opinions of the companies or organizations referenced in this paper.

Documents

Network Diversity and Survivability - Spectrum · What is network diversity and survivability? As discussed in the introduction, diversity and survivability are important concepts