Is Large MTU Beneficial to Cellular Core Networks?

Abstract

The Maximum Transmission Unit (MTU) refers to the largest packet size that can be transferred on a particular layer-3 network. As the dominance of Ethernet prevails, the "de-facto" standard MTU of 1500B has become universal in the wide-area networks. Unfortunately, the current MTU size overly limits the transmission performance especially when the underlying link speed rapidly increases while the CPU advancement stagnates. In this work, we investigate the potential impact of large MTU on fast-growing cellular core networks. First, we analyze the performance trend over the different MTU sizes on endpoint receivers as well as on User Plane Function (UPF) in a cellular core network that handles all data packets. Second, we present our dynamic MTU translation technique to transparently apply a large MTU inside a cellular core network without requiring update on other networks in the Internet. We observe that that large MTU is beneficial to both traffic endpoints and UPF, and our evaluation shows that dynamic packet merging scales the UPF performance by up to 4.9x, reaching 628 Gbps with only eight CPU cores.