1. 10GbE WAN Data Transfers for Science High Energy/Nuclear Physics (HENP) SIG Fall 2004 Internet2 Member Meeting
Yang Xia, HEP, Caltech
September 28, 2004
8:00 AM – 10:00 AM

2. 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

3. 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.

4. 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).

5. 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

6. 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.

7. 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

8. 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

9. 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.

10. 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:

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

12. Primary Workstation Summary
Sending Station:
Newisys 4300, 4 x AMD Opteron GHz, 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 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

13. 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

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

15. 10GbE Network Testing Tools
In Linux:
Iperf:
Version 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

16. 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

17. 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 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

18. 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

19. The Transfer over 10GbE WAN
With 9000byte MTU and stock Linux 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)

20. 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)

21. “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 Gbps; 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

22. 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.