TIP Spells Out What WAN SDN Controllers MUST Do

Emir Halilovic, Principal Analyst

Summary Bullets:

  • TIP MUST intends to accelerate SDN adoption in the WAN by defining requirements for WAN SDN based on real-life operator use cases.
  • The resulting architecture is open and will likely help fill the gap most vendors are unwilling or unable to address: the hierarchical controller space.

From the onset of attempts to implement SDN into telco WAN infrastructure, operators have faced two obstacles that severely limited its usefulness: lack of multi-vendor support and inability to control legacy environments. Telco equipment vendors have not been able to come up with a technical consensus that would solve these issues, for various reasons. Instead, most WAN SDN implementations have so far been restricted to one vendor’s equipment or have entailed costly integration of multiple vendors’ equipment under one domain controller. The results of these developments have so far been underwhelming; the market landscape remains fragmented, SDN adoption is slow, and the costs are high due to custom integration and operational support overhead.

The ‘Mandatory Use Case Requirements for SDN for Transport’ (MUST) workstream within the Telecom Infra Project’s (TIP) Open Optical and Packet Transport project group intends to solve obstacles for WAN SDN implementation by defining the SDN architecture, use-case implementation, and interfaces for communication between different elements of the solution, from network elements to the OSS layer. The group includes prominent Tier 1 operators Deutsche Telekom, MTN, Orange, Telefonica, Telia, and Vodafone. The work is divided into domain-specific workstreams focusing on the packet, optical, and – eventually – microwave domains.

SDN Architecture and Work So Far

TIP MUST also made one important technology choice right at the onset: its reference architecture includes often overlooked hierarchical controller function. The hierarchical controller role is crucial, because most of the multi-vendor and multi-domain capabilities of the whole SDN solution will rely on it. However, most network equipment vendors focus on developing domain controllers or develop proprietary hierarchical controllers for multi-domain operations in single-vendor environments, leaving the hierarchical control function space wide open.

So far, TIP MUST has produced detailed technical requirements for IP southbound and optical northbound SDN interfaces, going far beyond the usual list of APIs by specifying protocols, paths, and models to be used, as well as the relevant use cases and SDN functionality. In the future, the group will establish workstreams addressing the hierarchical controller and microwave domain controller and develop northbound and southbound API requirements for IP and optical controllers, respectively.

Getting the Vendor Buy-In

With TIP’s various workstreams underway, the ball is now with telecoms equipment vendors that, after all, are supposed to translate TIP requirements into palpable results. So far, the workstream does not include any vendors, which is par for the course as TIP MUST’s work should be distinct from vendors’ technology choices and preferences. TIP should, however, seek ways for including vendors into its activities – either by publicly acknowledging support for MUST’s work or developing a mechanism for certifying vendor solutions’ MUST compliance.

The situation with hierarchical controllers is also interesting. Very few ‘hardware-independent’ vendors of hierarchical controllers exist in the marketplace, and for good reasons: due to lack of standards and diverse operator requirements, hierarchical control vendors are equal parts software developers and services companies, with long implementation cycles and high costs attached to each deployment. If successful, TIP MUST could open the way for innovation in hierarchical controller space and create a viable market niche for independent software developers.

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