Page "Asynchronous Transfer Mode" Paragraph 13

Following the initial design of ATM, networks have become much faster.

A 1500 byte ( 12000-bit ) full-size Ethernet frame takes only 1. 2 µs to transmit on a 10 Gbit / s network, reducing the need for small cells to reduce jitter due to contention.

Some consider that this makes a case for replacing ATM with Ethernet in the network backbone.

However, it should be noted that the increased link speeds by themselves do not alleviate jitter due to queuing.

Additionally, the hardware for implementing the service adaptation for IP packets is expensive at very high speeds.

Specifically, at speeds of OC-3 and above, the cost of segmentation and reassembly ( SAR ) hardware makes ATM less competitive for IP than Packet Over SONET ( POS ); because of its fixed 48-byte cell payload, ATM is not suitable as a data link layer directly underlying IP ( without the need for SAR at the data link level ) since the OSI layer on which IP operates must provide a maximum transmission unit ( MTU ) of at least 576 bytes.

SAR performance limits mean that the fastest IP router ATM interfaces are STM16-STM64 which actually compares, while POS can operate at OC-192 ( STM64 ) with higher speeds expected in the future.