10GbE WAN Data Transfers for Science High Energy/Nuclear Physics (HENP) SIG Fall 2004 Internet2 Member Meeting Yang Xia, HEP, Caltech yxia@caltech.edu September 28, 2004 8:00 AM – 10:00 AM

Agenda Introduction 10GE NIC comparisons & contrasts Overview of LHCnet High TCP performance over wide area networks Problem statement Benchmarks Network architecture and tuning Networking enhancements in Linux 2.6 kernels Light paths : UltraLight FAST TCP protocol development

Introduction High Engery Physics LHC model shows data at the experiment will be stored at the rate of 100 – 1500 Mbytes/sec throughout the year. Many Petabytes per year of stored and processed binary data will be accessed and processed repeatedly by the worldwide collaborations. Network backbone capacities advancing rapidly to 10 Gbps range and seamless integration into SONETs. Proliferating GbE adapters on commodity desktops generates bottleneck on GbE Switch I/O ports. More commercial 10GbE adapter products entering the market, e.g. Intel, S2io, IBM, Chelsio etc.

InfiniBand and 4xTwinax cables IEEE 802.3ae Port Types Port Type Wavelength and Fiber Type WAN/ LAN Maximum Reach 10GBase-SR 850nm/MMF 300m 10GBase-LR 1310nm/SMF (LAN-PHY) 10km 10GBase-ER 1550nm/SMF 40km 10GBase-SW WAN 10GBase-LW (WAN-PHY) 10GBase-EW 10GBase-CX4 InfiniBand and 4xTwinax cables 15m 10GBase-T Twisted-pair 100m The 10-Gigabit Ethernet distances are defined as 300 meters for short reach (SR), 10 km for long reach (LR), and 40 km for extended reach (ER).

10GbE NICs Comparison (Intel vs S2io) Standard Support: 802.3ae Standard, full duplex only 64bit/133MHz PCI-X bus 1310nm SMF/850nm MMF Jumbo Frame Support Major Difference in Performance Features: S2io Adapter Intel Adapter PCI-X Bus DMA Split Transaction Capacity 32 2 Rx Frame Buffer Capacity 64MB 256KB MTU 9600Byte 16114Byte IPv4 TCP Large Send Offload Max offload size 80k Partial; Max offload size 32k

LHCnet Network Setup 10 Gbps transatlantic link extended to Caltech via Abilene and CENIC. NLR wave local loop is in working progress. High-performance end stations (Intel Xeon & Itanium, AMD Opteron) running both Linux and Windows We have added a 64x64 Non-SONET all optical switch from Calient to provision a dynamic path via MonALISA, in the context of UltraLight.

LHCnet Topology: August 2004 StarLight CERN Glimmerglass Alcatel 7770 Procket 8801 Alcatel 7770 Procket 8801 Juniper M10 Cisco 7609 Cisco 7609 Juniper M10 Linux Farm 20 P4 CPU 6 TBytes Linux Farm 20 P4 CPU 6 TBytes 10GE 10GE 10GE LHCnet tesbed LHCnet tesbed Juniper T320 Juniper T320 10GE American Partners 10GE European Partners Internal Network Caltech/DoE PoP - Chicago OC192 (Production and R&D) CERN - Geneva Services: IPv4 & IPv6 ; Layer2 VPN ; QoS ; scavenger ; large MTU (9k) ; MPLS ; links aggregation ; monitoring (Monalisa) Clean separation of production and R&D traffic based on CCC. Unique Multi-platform / Multi-technology optical transatlantic test-bed Powerful Linux farms equipped with 10 GE adapters (Intel; S2io) Equipment loan and donation; exceptional discount NEW: Photonic switch (Glimmerglass T300) evaluation Circuit (“pure” light path) provisioning

LHCnet Topology: August 2004 (cont’d) GMPLS controlled PXCs and IP/MPLS routers can provide dynamic shortest path set-up and path setup based on priority of links. Optical Switch Matrix Calient Photonic Cross Connect Switch

Problem Statement To get the most bangs for the buck on 10GbE WAN, packet loss is the #1 enemy. This is because of slow TCP responsive from AIMD algorithm: No Loss: cwnd := cwnd + 1/cwnd Loss: cwnd := cwnd/2 Fairness: TCP Reno MTU & RTT bias Different MTUs and delays lead to a very poor sharing of the bandwidth.

Internet 2 Land Speed Record (LSR) IPv6 record: 4.0 Gbps between Geneva and Phoenix (SC2003) IPv4 Multi-stream record with Windows: 7.09 Gbps between Caltech and CERN (11k km) Single Stream 6.6 Gbps X 16.5 k km with Linux We have exceeded 100 Petabit-m/sec with both Linux & Windows Testing on different WAN distances doesn’t seem to change TCP rate: 7k km (Geneva - Chicago) 11k km (Normal Abilene Path) 12.5k km (Petit Abilene's Tour) 16.5k km (Grande Abilene's Tour) Monitoring of the Abilene Traffic in LA:

Internet 2 Land Speed Record (cont’d) Single Stream IPv4 Category

Primary Workstation Summary Sending Station: Newisys 4300, 4 x AMD Opteron 248 2.2GHz, 4GB PC3200/Processor. Up to 5 x 1GB/s 133MHz/64bit PCI-X slots. No FSB bottleneck. HyperTransport connects CPUs (up to 19.2GB/s peak BW per processor), 24 SATA disks RAID system @ 1.2GB/s read/write Opteron white box with Tyan S2882 motherboard, 2x Opteron 2.4 GHz , 2 GB DDR. AMD8131 chipset PCI-X bus speed: ~940MB/s Receiving Station: HP rx4640, 4x 1.5GHz Itanium-2, zx1 chipset, 8GB memory. SATA disk RAID system

Linux Tuning Parameters PCI-X Bus Parameters: (via setpci command) Maximum Memory Read Byte Count (MMRBC) controls PCI-X transmit burst lengths on the bus: Available values are 512Byte (default), 1024KB, 2048KB and 4096KB “max_split_trans” controls outstanding splits. Available values are: 1, 2, 3, 4 latency_timer to 248 Interrupt Coalescence: It allows a user to change the CPU-affinity of the interrupts in a system. Large window size = BW*Delay (BDP) Too large window size will negatively impact throughput. 9000byte MTU and 64KB TSO

Linux Tuning Parameters (cont’d) Use sysctl command to modify /proc parameters to increase TCP memory values.

10GbE Network Testing Tools In Linux: Iperf: Version 1.7.0 doesn’t work by default on the Itanium2 machine. Workarounds: 1) Compile using RedHat’s gcc 2.96 or 2) make it single threaded UDP send rate limits to 2Gbps because of 32-bit date type Nttcp: Measures the time required to send preset chunk of data. Netperf (v2.1): Sends as much data as it can in an interval and collects result at the end of test. Great for end-to-end latency test. Tcpdump: Challenging task for 10GbE link In Windows: NTttcp: Using Windows APIs Microsoft Network Monitoring Tool Ethereal

Networking Enhancements in Linux 2.6 2.6.x Linux kernel has made many improvements in general to improve system performance, scalability and hardware drivers. Improved Posix Threading Support (NGPT and NPTL) Supporting AMD 64-bit (x86-64) and improved NUMA support. TCP Segmentation Offload (TSO) Network Interrupt Mitigation: Improved handling of high network loads Zero-Copy Networking and NFS: One system call with: sendfile(sd, fd, &offset, nbytes) NFS Version 4

TCP Segmentation Offload Must have hardware support in NIC. It’s a sender only option. It allows TCP layer to send a larger than normal segment of data, e,g, 64KB, to the driver and then the NIC. The NIC then fragments the large packet into smaller (<=mtu) packets. TSO is disabled in multiple places in the TCP functions. It is disabled when sacks are received, in tcp_sacktag_write_queue, and when a packet is retransmitted, in tcp_retransmit_skb. However, TSO is never re-enabled in the current 2.6.8 kernel when TCP state changes back to normal (TCP_CA_Open). Need to patch the kernel to re-enable TSO. Benefits: TSO can reduce CPU overhead by 10%~15%. Increase TCP responsiveness. p=(C*RTT*RTT)/(2*MSS) p: Time to recover to full rate C: Capacity of the link RTT: Round Trip Time MSS: Maximum Segment Size

Responsiveness with and w/o TSO Path BW RTT (s) MTU Responsiveness (min) With Delayed ACK (min) Geneva-LA (Normal Path) 10Gbps 0.18 9000 38 75 Geneva-LA (Long Path) 0.252 74 148 (Long Path w/ 64KB TSO) 10 20 LAN 0.001 1500 428ms 856ms Geneva-Chicago 0.12 103 205 1Gbps 23 46 45 91 1 2

The Transfer over 10GbE WAN With 9000byte MTU and stock Linux 2.6.7 kernel: LAN: 7.5Gb/s WAN: 7.4Gb/s (Receiver is CPU bound) We’ve reached the PCI-X bus limit with single NIC. Using bonding (802.3ad) of multiple interfaces we could bypass the PCI X bus limitation in mulple streams case only LAN: 11.1Gb/s WAN: ??? (a.k.a. doom’s day for Abilene)

UltraLight: Developing Advanced Network Services for Data Intensive HEP Applications UltraLight (funded by NSF ITR): a next-generation hybrid packet- and circuit-switched network infrastructure. Packet switched: cost effective solution; requires ultrascale protocols to share 10G  efficiently and fairly Circuit-switched: Scheduled or sudden “overflow” demands handled by provisioning additional wavelengths; Use path diversity, e.g. across the US, Atlantic, Canada,… Extend and augment existing grid computing infrastructures (currently focused on CPU/storage) to include the network as an integral component Using MonALISA to monitor and manage global systems Partners: Caltech, UF, FIU, UMich, SLAC, FNAL, MIT/Haystack; CERN, Internet2, NLR, CENIC; Translight, UKLight, Netherlight; UvA, UCL, KEK, Taiwan Strong support from Cisco and Level(3)

“Ultrascale” protocol development: FAST TCP Based on TCP Vegas Uses end-to-end delay and loss to dynamically adjust the congestion window Achieves any desired fairness, expressed by utility function Very high utilization (99% in theory) Compare to Other TCP Variants: e.g. BIC, Westwood+ Capacity = OC-192 9.5Gbps; 264 ms round trip latency; 1 flow BW use 30% BW use 40% BW use 50% BW use 79% Linux TCP Linux Westwood+ Linux BIC TCP FAST

Summary and Future Approaches Full TCP offload engine will be available for 10GbE in the near future. There is a trade-off between maximizing CPU utilization and ensuring data integrity. Develop and provide cost-effective transatlantic network infrastructure and services required to meet the HEP community's needs a highly reliable and performance production network, with rapidly increasing capacity and a diverse workload. an advanced research backbone for network and Grid developments: including operations and management assisted by agent-based software (MonALISA) Concentrate on reliable Terabyte-scale file transfers, to drive development of an effective Grid-based Computing Model for LHC data analysis.