evaluating the networking performance of linux based home router platforms for multimedia services

Evaluating the Networking Performance of Linux-based

Home Router Platforms for Multimedia Services

Ingo Kofler, Robert Kuschnig, Hermann Hellwagner

Institute for Information TechnologyAlpen-Adria-Universitat Klagenfurt, Austria

WoMAN’11, Barcelona, July 2011

Ingo Kofler Linux-based Home Router Platform Evaluation

Motivation

Popularity of Linux-based network devices

No real-time OS but sufficient for home network deployments

Low development costs

Mature platform and code base

Availability of services and applications

Open platform for running additional multimedia services

What performance can be expected in terms of...

computing performance

memory throughput

application-layer networking throughput

... and where are the bottlenecks?


Examples of Multimedia ServicesIn-Network Adaptation of Scalable Video Content

Media-Aware Network Element (MANE) for H.264/SVC

Adapt scalable video directly on network device

Adaptation must be signaling-aware and stateful

Realized as proxy running as process in user space

Proxy adapts video bit rate according to wireless link conditions

Previous work → ACM NOSSDAV’08, ACM NOSSDAV’11


Examples of Multimedia ServicesServing Multimedia Content in the Home Network

Deployment as always-on home server

Storage attached via USB port

Serving videos, music and pictures to clients in the network

Open source server implementations available

Support for USB-based DVB devices for serving live content (DVB-T/S/C)


Examples of Multimedia ServicesSharing Social Content from Home

Using server at own premises to serve social content

To overcome privacy and copyright concerns in social networks

Recent work by Marcon et al. @ ACM NOSSDAV’11

Private content is stored on USB storage and served via HTTP

Proof-of-concept study indicates feasibility


Home Router PlatformsSoftware

openWrt Linux

Popular Linux distribution for embedded systems

Replacement for stock firmware

Supports a variety of network devices/models

Provides SDK for cross-compiling software

Large set of available software packages

Common software platform for comparison

Most recent release: Backfire 10.03 based on Linux 2.6.32 kernel

Deployed on representative router platforms

Running performance and network benchmarks


Home Router PlatformsHardware Specifications

Vendor/Model Linksys TP-Link UBNTWRT54GL WR1043ND RS Pro

System-on-a-chip BCM5352EL AR9132 AR7161CPU MIPS32 4Kc MIPS 24Kc MIPS 24KcCPU clock 200 MHz 400 MHz 720 MHzInst./Data-Cache 16 KB / 8 KB 64 KB / 32 KB 64 KB / 32 KBSDRAM size/clock 16 MB / 100 MHz 32 MB / 400 MHz 128 MB / 360 MHzFlash capacity 4 MB 8 MB 16 MB

Networking 100 Mbps 1 Gbps 1 GbpsWireless 802.11b/g 802.11b/g/n 802.11a/b/g/nMisc - USB USB, 3x mini-PCI


Platform EvaluationProcessing and memory performance

Determine processing performance and memory throughput

Comparison of results to modern system (Core i7 M620)

CoreMark benchmark

Focus on CPU performance using synthetic workloadList operation, matrix multiplication, state machine and CRCAlgorithms executed in a loopMetric: Number of loop iterations per second

STREAM copy

Part of the STREAM benchmark suiteCopies array content element-by-elementMetric: Megabytes per second


Platform EvaluationProcessing and memory performance

Vendor/Model Clock CoreMark CoreMark STREAM copy[MHz] absolute normalized [MB/sec]

WRT54GL 200 333 1.67 59TLWR 400 701 1.75 231RSPRO 720 1263 1.75 381Intel Core 2 Duo E8400 3000 8,651 2.88 4,055Intel Core i7 M620 2667 9,457 3.55 6,830

CoreMark: 7.5 to 28 times slower than modern desktop CPU (single core)

STREAM copy: 18 to 116 times slower


Platform EvaluationNetworking performance

Focus on application-layer performance

Evaluation using different traffic scenarios (UDP/TCP, incoming/outgoing)

Investigated impact of different parameters (block size, socket buffer)

Results obtained using iperf and netperf

Experiments performed with firewall rules disabled


Platform EvaluationOutgoing and Incoming TCP

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WRT54TLWRRSPRO

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WRT54TLWRRSPRO


Platform EvaluationOutgoing and Incoming UDP

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WRT54TLWRRSPRO

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WRT54TLWRRSPRO


Platform EvaluationObservations

Choice of block size significantly influences throughput

Cannot be observed on typical PC-based systems

High overhead per system call

Conclusion: avoid small packet sizes (UDP) and block sizes (TCP)

Application-layer throughput far below nominal link speed

WRT54 only achieves 29 Mbps outgoing UDP throughput

418 Mbps outgoing UDP throughput on RSPRO

Identify performance bottleneck using ftrace framework

Debugging and tracing facility in Linux kernel

Useful to determine function execution time

Execution traces of UDP sendto system call


Platform EvaluationImpact of netfilter

UDP sendto causes around 200 function calls in kernel

Nearly half of the functions caused by the netfilter component

Re-run evaluations using kernel without netfilter

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WRT54WRT54 w/o netfilterTLWRTLWR w/o netfilterRSPRORSPRO w/o netfilter

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WRT54WRT54 w/o netfilterTLWRTLWR w/o netfilterRSPRORSPRO w/o netfilter


Platform Evaluationftrace Results

Impact of netfilter

1/3 of execution time spent for netfilter code

Throughput increases up to 50 percent

netfilter used for many (often relevant) features like NAT, firewall, . . .

Further investigations

Measuring time-consuming functions of UDP sendto syscall

Aggregate function to certain blocks/task of networking stack

Evaluations performed with disabled netfilter code


Platform EvaluationDissecting the UDP sendto syscall

400 1450

Socket APIBuffer HandlingUDPIPBridge TxHardware Tx

UDP payload size [Byte]

Dur

atio

n [u

secs

]

05

1015

20

Significant part required

for buffer handling (buffer

allocation, copy from user

to kernel space)

Checksum calculation

done in software

Potential for

improvements by

offloading


Conclusions

Evaluation of Linux-based router platforms

Interesting platform for multimedia services

Deployment as Media-Aware Network Element

Modest application layer performance

Far below nominal link speed

Use large packet sizes (UDP) and large buffers (TCP)

Disable netfilter component if not really required

No hardware offloading, potential for improvements


evaluating the networking performance of linux based home router platforms for multimedia services

Technology

based home router platforms

platform evaluationprocessing

platform evaluationoutgoing

home networkdeployment

applications open platform

home server storage

multimedia services

usbbased dvb devices