Variable-size multipacket segments in buffered crossbar (CICQ) architectures

Abstract

Abstract-Buffered crossbars can directly switch variable size packets, but require large crosspoint buffers to do so, especially when jumbo frames are to be supported. When this is not feasible, segmentation and reassembly (SAR) must be used. We propose a novel SAR scheme for buffered crossbars that uses variable-size segments while merging multiple packets (or fragments thereof) into each segment. This scheme eliminates padding overhead, reduces header overhead, reduces crosspoint buffer size and is suitable for use with external, modern DRAM buffer memory in the ingress line cards. We evaluate the new scheme using simulation, and show that it outperforms existing segmentation schemes in buffered as well as unbuffered crossbars. We also study how the size of the maximum segment affects system performance.

Packet mode scheduling in buffered crossbar (CICQ) switches

“…We model variable size transfer units at the switch interfaces and the core, so in order to keep track of time we follow the discrete event simulation approach [15]. Information relative to the simulator can be found in [12].…”

“…A subsequent observation was that buffered crossbars can directly switch variable-size packets [6] [11]. Doing so, without any segmentation, eliminates the need for speedup to cope with cell-padding overhead; in turn, the lack of speedup eliminates egress queueing, and the lack of segmentation eliminates reassembly buffers, thus reducing cost [12].…”

“…Buffered crossbars that use no segmentation at all have a limitation: the required buffer size per crosspoint is at least one maximum-size packet plus one round-trip-time (RTT) worth of data [12]. That buffer space becomes expensive in high valency switches (the number of crosspoint buffers equals the square of the port count), and in switches supporting large packets (e.g.…”

Providing flow based performance guarantees for buffered crossbar switches

“…The simulation results demonstrate that the proposed architecture outperforms unbuffered crossbar switches. A segmentation and reassembly (SAR) scheme was proposed in [9]. It uses variable size segments while merging multiple packets into each segment.…”

TCP/IP Jumbo Frames Network Performance Evaluation on A Test-bed Infrastructure

“…Jumbo frames and its impact on TCP packet processing is the subject of research in [4] and it is shown that jumbo frames can form a substantial component in data transfer. Performance under maximum-segment sizes is discussed in [5] and shown that segment size does affect performance. The impact of using jumbo frames in field-buses and multimedia applications to enhance performance is presented in [6].…”