WAN Performance Analysis – A Study on the ... - Talari Networks

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24 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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A  Talari  Networks  White  Paper
 
A  Talari  White  Paper
 
WAN  Performance  Analysis  

 
 
A  Study  on  the  Impact  of  Windows  7  
 
Test  results  demonstrating  WAN  performance  changes  due  to  
upgrading  to  Windows  7  and  the  network  architecture  and  
performance  optimization  technologies  that  can  be  applied  to  
improve  that  performance.
 
Analysis  on  the  Impact  of  Windows  7  on  WAN  Performance
 
2
 
 
©  20
11
 
Talari  Networks  Inc.
 
 
Introduction  
 
When  to  migrate  and  why?  This  is  the  question  faced  by  many  organizations  considering  a  
transition  to  Windows  7.  This  is  especially  true  given  that  many  
bypassed  Windows  Vista  
entirely,  instead  sticking  with  the  tried  and  trusted  XP  platform.    
 
Gartner  says  most  organizations  should  be  eliminating  Windows  XP  by  the  end  of  2012.    
Michael  Silver,  vice  president  and  distinguished  analyst  at  Gartner  recently  s
tated,  "Windows  7  
has  been  getting  positive  reviews,  and  many  clients  report  that  they  have  plans  to  start  their  
production  deployments,  but  there  are  some  that  are  still  undecided  about  when  to  start  and  
how  quickly  to  do  the  migration."

For  those  organiz
ations  that  rely  on  a  Wide  Area  Network  (WAN),  this  paper  examines  how  
major  improvements  in  the  underlying  network  technologies  used  in  the  Windows  7  impact  
performance  over  the  WAN  when  compared  to  Windows  XP.  It  looks  specifically  at  how  the  
Server  Mess
age  Block  (SMB,  often  referred  to  as  Common  Internet  File  System,  CIFS)  protocol  
version  2.1  in  Windows  7  has  been  enhanced  to  make  it  work  more  efficiently  over  a  WAN.
 
Test  Methodology
 
and  Results
 
 
To  benchmark  the  differences  in  performance  we  compared  t
he  times  taken  to  transfer  a  40  
Megabyte  non
-­‐
compressible  file  over  a  link  with  20Mbps  of  capacity  with  different  round  trip  
times  (RTT)  ranging  from  50ms  to  250ms  and  different  packet  loss  rates  ranging  from  0%  to  
5%.  
 
The  test  also  looked  at  how  the  perf
ormance  of  both  Windows  XP  and
 
Windows  7  was  
improved  using  
Talari’s  
Mercury  appliances
 
to  make  the  WAN  performance  more  predicable  
and  reliable.
 
The  results  demonstrated  that  Windows  7  performs  consistently  better  on  the  WAN  than  
Windows  XP  for  file  trans
fers.    Using  
Talari  technology
 
improved  the  performance  of  Windows  
XP  by  as  much  as  a  factor  of  7.  With  Windows  7  plus  
Talari,  
however,  the  results  were  even  
more  dramatic,  with  performance  improving  by  as  much  as  75  times  that  of  Windows  XP.
 
Windows  7  Imp
act  on  WAN  Round  Trip  Times  
 
Server  Message  Block  (SMB),  often  referred  to  as  Common  Internet  File  Systems  (CIFS),  is  a  
client
-­‐
server  protocol  that  was  originally  designed  to  work  on  small  local  area  networks.    As  the  
name  suggests  it  is  a  block
-­‐
oriented  p
rotocol  where  the  client  makes  requests  and  the  server  
responds.  This  is  in  contrast  with  streaming  or  windowed  protocols  that  can  send  large  
amounts  of  data  represented  by  the  window  size  before  requiring  some  form  of  handshake  to  
indicate  that  the  data  w
as  received  successfully.    CIFS/SMB  is  often  described  as  a  ‘chatty’  
protocol  that  requires  a  large  number  of  request  and  response  sequences  to  accomplish  any  
given  task.  Wide  area  networks  introduce  latency  and  severely  impact  the  performance  of  SMB  
as  th
e  round  trip  time  (RTT)  from  sending  a  request  to  receiving  a  response  is  multiplied  by  a  
large  number  of  transactions.
 
With  Microsoft  SMB  1.0  in  Windows  XP  many  IT  managers  incorporated  
performance  
enhancing
 
products  into  their  networks  to  make  SMB  1.0  pe
rform  better  on  the  WAN  by  
terminating  SMB  request  and  responses  locally  to  hide  large  round  trip  times  from  protocol.  
Analysis  on  the  Impact  of  Windows  7  on  WAN  Performance
 
3
 
 
©  20
11
 
Talari  Networks  Inc.
 
With  Windows  7  and  SMB  2.1,  Microsoft  has  made  enhancements  to  the  protocol  itself  to  
reduce  the  ‘chattiness’.  A  summary  of  the  specific  
enhancements  can  be  found  in  
Jose  Baretto’s  
Blog
.
 
The  SMB  2  specification  is  also  available  publically  on  the  
MSDN  website
.
 
When  comparing  the  performance  of  Windows  XP,  using  SMB  1
.0,  and  Windows  7  using  
SMB2.1,  the  results  
demonstrated  that  SMB2.1  has  effectively  fixed  the  RTT  problem.  
 
 
Figure  
1
 

 
Impact  of  RTT  on  the  transfer  time  of  a  40MByte  non
-­‐
compressible  file  over  a  single  
20Mbps  link  with  Windows  XP  and  Windows  7
 
The  test  
compared  the  perfo
rmance  of  both  Windows  XP  and  Windows  7  under  different  
network  impairments.    Specifically  we  compared  the  times  taken  to  transfer  a  40MByte  non
-­‐
compressible  file  over  a  link  with  20  Mbps  of  capacity  with  different  RTT  ranging  from  50ms  to  
250ms  and  differ
ent  packet  loss  rates  ranging  from  0%  to  5%.  
 
As  
Figure  
1
 
clearly  shows,  even  with  a  small  RTT  of  50ms  Windows  7  transferred  the  40MByte  
file  3  times  faster  than  Windo
ws  XP.    As  the  RTT  increased  the  time  taken  to  transfer  the  same  
file  increased  only  modestly  for  Windows  7  whereas  the  time  taken  on  Windows  XP  increases  
dramatically.  In  this  test,  with  an  RTT  of  250ms,  Windows  7  is  eight  times  faster  than  Windows  
XP.
 
Al
l  shared  IP  networks  exhibit  packet  loss;  in  fact  it  is  required  for  TCP/IP  flow  control  to  work.  
TCP/IP  is  constantly  trying  to  find  the  rate  at  which  it  begins  to  see  congestion  resulting  in  
packet  loss  by  sending  more  packets  than  the  network  can  handle
.
 
WAN
 
congestion  can  happen  on  the  first  mile  and  last  mile  links  that  often  have  significantly  
less  capacity  than  the  networks  they  interconnect,  or  at  routers  in  the  middle  of  the  network  
where  many  TCP/IP  flows  are  competing  for  bandwidth.  
 
53
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193
18
19
24
0
50
100
150
200
250
50 ms RTT, 0% loss
100 ms RTT, 0% loss
250 ms RTT, 0% loss
File Transfer Time (s)
XP
Win 7
Analysis  on  the  Impact  of  Windows  7  on  WAN  Performance
 
4
 
 
©  20
11
 
Talari  Networks  Inc.
 
As  can  be  se
en  in  
Figure  
2
,  loss  has  even  more  impact  on  the  performance  of  SMB  for  both  
Windows  XP  and  Windows  7.  
 
 
Figure  
2
 

 
Impact  of  Packet  Loss  Ra
te  on  the  transfer  time  of  a  40MByte  non
-­‐
compressible  file  over  a  
single  20Mbps  link  with  Windows  XP  and  Windows  7
 
With  just  a  packet  loss  rate  of  1%  the  performance  of  Windows  XP  drops  by  a  factor  of  4.5  and  
8.5  respectively.  Windows  7  does  a  much  better  
job  than  XP  at  zero  loss,  which  impacts  this  
ratio.  Overall  Windows  7  is  much  better  than  Windows  XP  under  loss.
 
Impact  of  
Talari  
Appliances
 
on  Windows  7  and  Windows  XP  
Performance
 
Enterprises  can  dramatically  improve  Windows  XP  and  Windows  7  performance  by  
incorporating  Talari’s  
Mercury  appliances
 
into  their  infrastructure
.    
Talari  brings
 
a  
revolutionary  approach  to  
enhancing
 
Enterprise  WANs.  Unlike  
other  performance  enhancing  
devic
es
 
that  focus
 
on  compression
 
application  acceleration
,  
Talari
 
optimizes  a  
low  cost,
 
higher
-­‐
bandwidth  network  fabric  for  all  applications.
 
 
 
Talari  
makes  the  WAN  look  to  each  TCP  
application  as  if  it  were  a  zero
-­‐
packet
-­‐
loss  WAN  with  the  occasional  bout  of  j
itter
-­‐
something  
TCP  and  TCP
-­‐
based  applications  are  designed  to  expect  and  accommodate  without  incident.
 
 
The  effect  of  
Talari
’s  loss  mitigation  technology  can  be  clearly  seen  in  
Figure  
3
 
and  
Figure  
4
,  
when  comparing  the  performance  of  Windows  XP  and  Windows  7  for  the  same  40MByte  file  
transfer  under  both  increasing  RTT  and  loss.
 
 
53
238
364
885
18
152
222
457
0
100
200
300
400
500
600
700
800
900
1000
50 ms RTT, 0% loss
50 ms RTT, 1% loss
50 ms RTT, 2% loss
50 ms RTT, 5% loss
File Transfer Times (s)
XP
Win 7
Analysis  on  the  Impact  of  Windows  7  on  WAN  Performance
 
5
 
 
©  20
11
 
Talari  Networks  Inc.
 
 
Figure  
3
 

 
Impact  of  Talari’s  
 
loss  mitigation
 
technology  
 
on  the  transfer  time  of  a  40Mbyte  non
-­‐
compressible  file  over  a  single  20Mbps  link  with  Windows  XP  and  Windows  7
 
 
 
Figure  
4
 

 
Relative  impact  of  T
alari’s  
loss  mitigation  
 
technology  
on  the  transfer  time  of  a  40Mbyte  
non
-­‐
compressible  file  over  a  single  20Mbps  link  with  Windows  XP  and  Windows  7  compared  to  
Windows  XP  alone
 
 
Loss  mitigation  is  able  to  help  the  performance  of  Windows  XP  file  transfers  by  reducing  the  file  
transfer  times  by  as  much  as  a  factor  
of  
7.    With  the  new  protocols  in  Windows  7,  
Talari’s
 
loss  
mitigation  
technology  
works  extremely  well  for  a  combined  solu
tion  that  has  consistent  
performance  over  a  wide  range  of  network  conditions.  This  results  in  reducing  the  file  transfer  
time  by  as  much  as  a  factor  of  75.
 
How  
Talari  Technology
 
Improves  WAN  Performance
 
In  this  controlled  test  only  a  single  link  is  used  so
 
that  consistent  data  could  be  compared.  In  
real  life  deployments  of  Talari  technology,  diverse  sources  of  bandwidth  would  allow  much  of  
53
448
1600
3180
18
293
1073
2232
58
132
386
457
20
22
27
42
0
500
1000
1500
2000
2500
3000
3500
50 ms RTT, 0% loss
100 ms RTT, 1% loss
250 ms RTT, 2% loss
250 ms RTT, 5% loss
File Transfer Times (s)
XP
Win 7
XP + Talari
Win 7 + Talari
1.0x
1.0x
1.0x
1.0x
2.9x
1.5x
1.5x
1.4x
0.9x
3.4x
4.1x
7.0x
2.7x
20.4x
59.3x
75.7x
0.0x
10.0x
20.0x
30.0x
40.0x
50.0x
60.0x
70.0x
80.0x
50 ms RTT, 0% loss
100 ms RTT, 1% loss
250 ms RTT, 2% loss
250 ms RTT, 5% loss
Speed-up Factor
XP
XP to Win 7
XP + Talari
Win 7 + Talari
Analysis  on  the  Impact  of  Windows  7  on  WAN  Performance
 
6
 
 
©  20
11
 
Talari  Networks  Inc.
 
the  loss  to  be  avoided  altogether  by  favoring  the  better  performing  paths.  This  will  result  in  
even  better  overall  file
 
transfer  times.  
 
In  a  network  with  redundant  links,  
Talari  combines
 
multiple  IP  networks  into  a  single  network  
fabric  with  the  aim  of  increasing  the  amount  of  bandwidth  available  at  each  remote  office  
location  and  as  a  means  to  provide  physical  redundancy
 
should  any  individual  link  fail.
 
This
 
allows  an  enterprise  to  build  a  
WAN  that  is
 
very  reliable  and  predictable  in  the  way  that  it  
performs.  
 
This  also  results  in  
dramatic  perform
ance  improvements  
as  well  as  increased  reliability.  This  is  
because  Talari  a
ctively  uses  
all  available  links,  monitoring  the  health  and  performance  of  all  
links  in  order  to  make  real  time  adjustments  to  optimize  network  performance.
 
There  are  two  key  technologies  that  allow  
Talari  
to  deliver  these  benefits.
 
Multipath  Network  
Spect
rometry  
With  Multipath  Network  Spectrometry,  the  characteristics  
of  every  WAN  link,  network  path  and  traffic  flow  are  monitored  precisely  and  continuously.  
This  yields  detailed  data  about  instantaneous  loss,  latency  and  jitter  
throughout  the  network,  
allowing  for  sub
-­‐
second  changes  in  path  selection.
 
 
Resilient  Multipath  Connectivity
 
A
ll
 
of  the  possible  paths  through  the  network  
are  monitored  
and
 
utilized  to  improve  the  
performance  for  
all
 
applications  by  maximizing  the  use  of  available  
bandwidth  and  
mitigating  
the  effects  of  packet  
loss
.    Lost  packets  can  be  detected  and  re
-­‐
transmitted  before  the  higher  layer  applications  respond  by  scaling  back  their  transmission  
rates.  This  delivers  predictable  performance  throughout,  regardless  of  transient  congest
ion  or  
network  outages.  
To  
TCP/IP  based  applications,
 
a  network  using  Talari  technology  
looks  like  a  
zero  loss  network  with  occasional  bouts  of  jitter.
 
With  these  two  underlying  technologies,  
Talari
 
appliances  use  end
-­‐
to
-­‐
end  algorithms  to  match  
the  state  o
f  the  network  with  the  needs  of  different  traffic  types  and  adapt  using  real  time  traffic  
engineering.  This  ensures  that  the  optimal  path  is  chosen  for  every  packet.  
 
Talari  appliances  implement
 
QoS  and  use  the  class  of  service  information  associated  with  
each  
flow  or  configured  in  a  policy  rule  as  part  of  the  path  selection  criteria.  Unlike  other  boxes  that  
implement  QoS  and  can  only  prioritize  which  traffic  goes  out  on  the  local  link  first;  
Talari
 
uses  
this  QoS  information  to  choose  the  path  that  gets  the
 
packet  to  the  destination  in  the  shortest  
possible  time,  which  is  ultimately  what  matters  most.  
 
Analysis  on  the  Impact  of  Windows  7  on  WAN  Performance
 
7
 
 
©  20
11
 
Talari  Networks  Inc.
 
Even  though  packets  can  follow  any  number  of  paths  to  the  destination,  the  connection  between  
two  locations  appears  as  a  single  highly  reliable  link  called  a  
“conduit”.    
In  a  Talari
 
conduit  there  
can
 
be  up  to  10  classes  of  service,
 
and  per  fl
ow  classification  inside  the  
appliance  determines  
which  class  to  use  for  each  traffic  flow.  So  
there  is
 
a  lot  of  flexibility  on  how  the  bandwidth  is  
used  
among
 
real
-­‐
time  tr
affic,  interactive  and  bulk  
transfer  application  flows
.
 
The  packets  within  
a  conduit  are  also  secured  using  128
-­‐
bit  AES  encryption.
 
This  makes  it  a  viable  alternative  to  either  add  bandwidth  to  existing  private  network  
connections  such  as  MPLS  or  replace  t
hose  expensive  connections  altogether  with  much  less  
expensive  Internet  links.
 
Conclusion
 
By  fixing  the  RTT  problem  in  SMB/CIFS,  Windows  7  certainly  holds  
one
 
of  the  keys  to  building  a  
faster  WAN  and  this  fact  alone  may  be  reason  enough  to  switch  over  from  Windows  XP  sooner  
rather  
than  later.
   
But  
a
s  companies  move  to  centralized  data  centers,  backhaul  cloud
-­‐
driven  
Internet  traffic  through  the  WAN  to  the  data  cente
r,  move  more  video  and  voice  traffic  across  
their  corporate  WAN  network,  and  adjust  to  
increasing
 
requirements  for  document  retention,  
pressure  is  mounting  to  continue  to  increase  
bandwidth  without  corresponding  increases  in  
cost
.  
Moving  to  Windows  7  alone  will  not  free  up  enough  bandwidth  to  
accommodate
 
this  
additional  demand.
 
With  Talari,  companies  c
an  add  inexpensive  Internet  connections  to  increase  bandwidth,  while  
still  achieving  the  performance  and  quality  of  service  they  have  come  to  expect  from  a  
traditional  WAN  connection.  
 
For  example,  u
sing  Talari,  a  site  with  a  DSL  connection  plus  a  Cable  Mo
dem  connection,  
together  costing  $100  per  month  can  achieve  four  nines  reliable  connection  back  to  the  data  
center.  Compare  this  to  using  an  MPLS  network  with  a  T1  link  at  the  site  costing  $750  per  
month.  The  key  difference  is  that  the  remote  office  now  ha
s  perhaps  
5  to  15  times  as  much  
bandwidth,  for  a  fraction  of  the  cost.
 
This  is  game  changing  for  businesses  that  rely  on  applicat
ions  that  run  over  the  WAN  as
 
remote  
offices  can  benefit  from  an  order  of  magnitude  more  reliable  bandwidth  at  a  fraction  of  th
e  
traditional  cost.  
 
 
 
 
References
:
 
Jose Baretto’s Blog
-

SMB2, a complete redesign of the main remote file protocol for Windows

http://blogs.technet.com/b/josebda/archive/2008/12/05/smb2
-
a
-
complete
-
redesign
-
of
-
the
-
main
-
remote
-
file
-
protocol
-
for
-
windows.aspx

SMB 2.0 Specification

http://msdn.microsoft.com/en
-
us/library/cc246482(PROT.13).aspx


 
Talari  Networks.  
 
20195  Stevens  Creek  Blvd.  Suite  220,  
 
Cupertino  CA
 
95014
 
http://www.talari.com