Q&A on Delivering the ‘Optimal Mobile Backhaul Experience’ Webinar

Recently we conducted a webinar on Delivering the ‘Optimal Mobile Backhaul’ Experience – which generated many interesting and insightful questions on wireless backhaul implementation challenges, solutions, and future roadmap. We received more questions than we were able to answer in the allotted time, so we decided to answer all the questions through this blog. We hope these responses are informative for those of you seeking to better understand the nuances of building robust wireless backhaul networks. You can access the webinar archive by clicking here.

Q.  Why do you say MPLS can’t provide SONET like resiliency? The Fast ReRoute mechanism has been standardized and widely used for many years now and provides an excellent way to provide path level redundancy and resiliency in the network.

Yes, you are right. The Fast ReRoute mechanisms have been standardized and widely deployed. The key difference lies in the specification and standardization. The standard for Fast ReRoute does not specific any time limits for service outages or how to break up the outage between failure detection and service restoration times. Because of these lacunae, standardized hardware or software components have not emerged and it is left to each individual vendor to address this in proprietary ways. This is a key issue that has been addressed in the MPLS-TP standards by specifying time limits on outages and explaining the breakup between failure detection and service restoration times.

Q. Why do you say that MPLS doesn’t have established OAM methods? What about Fast ReRoute, VCCV, BFD, and LSP-Ping? Don’t these provide a good set of OAM tools?

OAM comprises continuity check, connectivity verification, route tracing, fault management, and performance management. BFD, LSP Ping, and VCCV standards address continuity check, connectivity verification, and route tracing but do not address fault and performance management. These are necessary to monitor service levels and compliance to service guarantees. So, the support for OAM is partial with the existing methods and a key issue that is being addressed by MPLS-TP.

Q.  What makes packet microwave appealing? It seems just the same as Ethernet or MPLS with an additional microwave overhead. Does packet microwave provide any advantages if there is already a fiber installation available?

The key advantages of packet microwave are the reuse of the existing installed base in several parts of the world and the ease of a new installation in a greenfield environment by avoiding the logistics of cable layouts. In areas where an existing fiber installation is available or there is no existing microwave installed base, packet microwave does not offer any significant advantages over the other technologies.

Q: Isn’t MPLS-TP the same thing as MPLS? What big difference does it make whether or not the transport network assumes usage of IP/routing or not?

MPLS-TP improves upon the established fundamentals of MPLS which have served very well for traffic engineering and core network requirements. As Ethernet expands its reach from the enterprise to the access and core networks everywhere, requiring an additional IP layer for transporting customer traffic over carrier networks causes unnecessary overheads and is a burden. This is not an issue when the IP layer is used only for signaling and when the data path uses plain MPLS over Ethernet. However, if MPLS is carried in IP like in GRE, then using the mandatory minimum 40 byte IP header on each user packet (when user packets which are predominantly in the 128 byte length category) poses close to a 30% overhead. Avoiding this directly translates into a 30% increased capacity and more efficient use of network resources. Apart from this, the existing MPLS standards do not address the OAM and service availability requirements for transport networks. By defining standards for OAM and service availability in transport networks, MPLS-TP improves upon the MPLS technology, while leveraging the benefits of MPLS fully.

Q.  Many backhaul networks are built using MPLS L3-VPN technology today. Is there any reason or benefit to consider MPLS-TP?

If the network usage is far lesser than the available capacity, and service growth is small, there is no benefit from using MPLS-TP. As an operator’s consumer base grows and the network is expected to reach its capacity, MPLS-TP promises significant benefits through more efficient utilization of the network capacity and the standardization of tools and techniques to monitor service levels and enforce service guarantees.

Q.  In a backhaul network using MPLS L3-VPN technology today, can MPLS-TP usage be added incrementally? Can the benefits of MPLS-TP alone be added without having to change everything in all the nodes?

The OAM and service resiliency aspects can be improved by applying MPLS-TP incrementally in an existing MPLS network without having to relay the network or change switches etc. Increase in capacity utilization, however, requires changes in at least the software, if not in the hardware design of the installed switching elements. The cables and connections can, however, continue to be used without changes.

Q.  You say provider bridging is not scalable and is limited to 4K services. Why does a backhaul network need more than this number?

As the mobile subscriber base continues to rise exponentially, the number of operators seeking to service these consumers has also been increasing. Cell towers commonly house antennas for multiple operators. Each operator must use a separate set of service identifiers through a common, shared, transport network. Each operator also needs to differentiate customer and application traffic through the network. The 4K limit constrains the number of services that each operator can use through the network. The greater issue with the provider bridging technology is the proliferation of customer MAC addresses into the provider network which severely hogs precious resources in the service provider’s network elements.

Q.  When do you think MPLS-TP will be standardized? Isn’t it risky to start implementing it now?

The basic mechanism of transport using MPLS labels remains the same. The use of MPLS-TP identifiers and the specifications for OAM and service resiliency have seen a lot of advancements and are nearing standardization. These can be expected to be standardized within 2012. The risk in implementing these standards (or pre-standards) is fairly low given the widespread adoption happening currently.

Q.  When you say Ethernet/IP based packet backhaul, you mean any L2 (legacy ATM or FR) or L3 using one of the flavors of PWE (pseudo-wire)?

The traffic being transported is L2 (legacy ATM / FR, or Ethernet) as pseudo wires (PWE3). The transport network is either Ethernet (L2) or IP (L3).

Q. How can mobile backhaul help an upstart MVNO be successful in countries like Brazil and China?

Mobile backhaul poses requirements to change the existing network and therefore creates opportunities for new players to enter into an existing consumer base. The fundamental philosophy in mobile backhaul is the use of a shared packet network instead of mobile service provider specific leased lines for the traffic between the base stations and base station controllers. This fits in very nicely with the MVNO model of using/leasing infrastructure from 3rd parties to service a consumer base.

Q.  I need to know how to create the protocols for mobile communication?

There are 2 types of protocols. The 1st type is the protocols between the mobile user and the base station as well as the base station and the base station controller. These are addressed by forums like the 3GPP, LTE etc. The 2nd type is the protocols that enable the networking infrastructure between the base station and the base station controller. These are addressed by the IEEE, IETF, and ITU-T. There are numerous white papers on these on various websites. Some are also available at http://www.aricent.com for a quick understanding of the various technologies.

Q. From the management point of view, wouldn’t IP/MPLS and MPLS-TP make more sense than deploying Carrier Ethernet in the backhaul and MPLS in the core?

MPLS-TP is definitely more efficient in the core of the transport network. In the backhaul, Carrier Ethernet promises better capacity utilization than IP/MPLS. Management solutions will be adapted to or will emerge to cater to the most efficient ways of utilizing the network.

Q. Has Aricent installed its ISS software in West Africa?

Aricent has installed other software for operators in West Africa., but not directly installed the ISS (Intelligent Switch Solution) in West Africa.

Q. What is the outlook for the use of Solar and Wind technologies for RAN and other networking infrastructure?

We understand this question is about using solar or wind energy to power cell towers, cell site routers and other networking equipment. As network equipment proliferates, and energy needs grow, reliance on traditional energy sources like coal, water, petroleum or gas is not sufficient or viable. There are only 4 choices for energy in the future – solar, wind, nuclear, and geo-thermal. Wind energy, being dependent on the vagaries of the environment, and its inherent limits on capacity, will not be sufficient in the long term, though being a good option in the short term. Nuclear energy has inherent dangers as is evident from the Chernobyl and Fukushima experiences. Solar energy is a viable long term option and will definitely find greater adoption. Geo-thermal energy will also emerge as a viable choice in the future as the methods and technologies to tap it in an economical manner are developed.

Q. Since too many important features of MPLS are disabled in MPLS-TP, what do you think is the main "USP" for MPLS-TP?

The key benefits of MPLS-TP are:

(a)  Much higher utilization of network capacity

(b)  Standardization of OAM tools and techniques

(c)  Standardization of mechanisms for service availability guarantees

Q.  What is biggest challenge you see in Mobile Backhaul growth?

The biggest challenge in the current scenario is the delivery of QoS consistently. QoS techniques play a vital role in enhancing the user experience for the end consumer. This directly relates to growth in the operator’s consumer base and thereby growth in the operator’s revenues and margins.

Q.  What technologies are Aricent's ISS solution committed to support in the near to long term?

Aricent’s ISS solution is committed to support MPLS-TP, provider bridging, packet microwave, and datacenter Ethernet technologies in the near to long term. The commitment is based on a strong understanding of technology and market trends, together with the commitment to adapt to changes in these trends and network requirements.

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