TECHNICAL
This architecture enables the transition to software-based network functions on generic compute platforms which eases the introduction of PON to augment DOCSIS Networks. The link between head-end and node is now digital. The digital link allows adding software at the head-end, which can forward traffic by standard ethernet to be delivered from the access node over PON as well as DOCSIS. This was not possible in the past because the reach would have been too long for a PON network. Understanding Disaggregated Hardware Networking functions that were traditionally performed by an integrated CMTS, a chassis based DPoE system, or a BNG+OLT PON system are now distributed across multiple components in the network which perform more specialised functions. Three main areas for disaggregation have been identified: n Routing Engine: Performs all advanced routing functions, including IGP and EGP routing, VXLAN management, tunneling and L3 forwarding. This functionality is usually handed off to a dense, high performance L3 switch, or it can be also virtualised. n Cloud-Native Access Platform: Responsible for all subscriber QoS, filtering and classification, FCAPS functions, and MAC (in case of R-PHY). This functionality has become a prime candidate for virtualisation, it can run in off the shelf x86 high performance server clusters. Moreover, additional disaggregation could be possible by disaggregating management from the data plane. Much of the subscriber management functionality shares the same architecture for both DOCSIS and PON. n Physical Layer: Low powered devices that convert traffic into RF or light for last mile access.
through innovative solutions involving DOCSIS and PON access technologies co-located on the same edge access node. This combination is part of a DAA that hosts most network functions running in software at the MSO headend. Utilising this architecture provides a unified platform capable of providing both DOCSIS and PON with multiple benefits including a reduced time to market as operations and support teams do not have to be trained on multiple systems. With the exception of the PHY layer, the building blocks of DOCSIS and PON are very similar. This results in a unified software solution for DOCSIS and PON network access technologies.
Disaggregation and the Distributed Access Architecture
Overview
The standardisation of a DAA has triggered a major transformation in DOCSIS networks in recent years. The main variants of DAA and Remote-PHY, are shown in figure 1. For the R-PHY variant, DOCSIS MAC and PHY components are deployed separately on the access network head-end and node respectively.
Deploying Disaggregated Software
The advent of software containerisation has enabled the development of more flexible and resilient solutions. Rather than having a single, monolithic software platform, a disaggregated software
Figure 1: Distributed Access Architecture Variants
MARCH 2024 Volume 46 No.1
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