Enabling Resilience in Virtualized RANs with Atlas
Enabling Resilience in Virtualized RANs with Atlas
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DOI：
10.1145/3570361.3613276
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发表时间：
2023-10
期刊：
影响因子：
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通讯作者：
Jiarong Xing;Junzhi Gong;Xenofon Foukas;Anuj Kalia;Daehyeok Kim;Manikanta Kotaru
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文献类型：
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作者：
Jiarong Xing;Junzhi Gong;Xenofon Foukas;Anuj Kalia;Daehyeok Kim;Manikanta Kotaru
虚拟化无线接入网络 (vRAN) 允许在商用服务器而不是专有硬件上运行 RAN 处理，正在蜂窝网络中得到采用。实现较低 RAN 层的 vRAN 的“分布式单元 (DU)”的两个属性（实时期限和黑盒性质）使得在不造成长期服务中断的情况下提供升级和故障转移等弹性功能具有挑战性。这些属性妨碍了使用现有的弹性技术，例如用于典型工作负载的虚拟机迁移或状态复制。本文介绍了 Atlas，这是第一个为 DU 提供弹性的系统。 Atlas 的核心见解是重新利用现有的无线弹性蜂窝机制，即切换和小区重选，为 DU 提供软件弹性。对于升级等计划内的弹性事件，我们设计了一种新技术，通过同一无线电同时为新旧 DU 的小区提供服务，并使用这些小区之间的切换来迁移用户设备。对于计划外故障，我们确定了现有 RAN 协议中在 DU 故障后扰乱小区重选的缺陷，并展示了如何使用 DU 和更高层之间的中间盒来消除这些中断。我们对最先进的 5G vRAN 测试床的评估表明，Atlas 在弹性事件期间实现了对蜂窝连接的最小干扰，同时产生的开销也很低。
Virtualized radio access networks (vRANs), which allow running RAN processing on commodity servers instead of proprietary hardware, are gaining adoption in cellular networks. Two properties of the vRAN's "Distributed Unit (DU)" that implements the lower RAN layers---its real-time deadlines and its black-box nature---make it challenging to provide resilience features such as upgrades and failover without long service disruptions. These properties preclude the use of existing resilience techniques like virtual machine migration or state replication that are used for typical workloads. This paper presents Atlas, the first system that provides resilience for the DU. The central insight in Atlas is to repurpose existing cellular mechanisms for wireless resilience, namely handovers and cell reselection, to provide software resilience for the DU. For planned resilience events like upgrades, we design a novel technique that simultaneously serves cells from both the old and new DUs via the same radio, and uses handovers between these cells to migrate user devices. For unplanned failures, we identify deficiencies in existing RAN protocols that disrupt cell reselection after DU failure, and show how we can eliminate these disruptions using a middlebox between the DU and higher layers. Our evaluation with a state-of-the-art 5G vRAN testbed shows that Atlas achieves minimal disruption to cellular connectivity during resilience events, while incurring low overhead.