OTT  and  the  future  of  the  PSTN  Henning  Schulzrinne  

FCC  

2  

PSTN:  The  good  &  the  ugly  The  good   The  ugly  

Global  Connectivity  (across  devices  and  providers)  

Minimalist  service  

High  reliability  (engineering,  power)  

Limited  quality  (4  kHz)  

Ease  of  use   Hard  to  control  reachability  (ring  at  2  am)  

Emergency  usage   Operator  trunks!  

Universal  access  (HAC,  TTY,  VRS)  

No  universal  text  &  video  

Mostly  private  (protected  content  &  CPNI)  

Limited  authentication  Security  more  legal  than  technical  (“trust  us,  we’re  a  carrier”)  

Relatively  cheap  (c/minute)  

Relatively  expensive  ($/MB)  

The  OTT  to  “traditional”  spectrum    

Non-­‐interconnected  VoIP  

• Not  interconnected  

Interconnected  VoIP  

• Bidirectional  connectivity  to  E.164  numbers  • 911  • CALEA  • USF  

Video  relay  service  

• Multimedia  for  Deaf  &  HoH  • Can  reach  any  E.164  number  via  relay  

QoS-­‐enabled  VoIP  

• [technical  possibility]  • Can  reach  any  telephone  number  • QoS  as  commercial  service  

Facilities-­‐based  VoIP  

• “specialized  service”  • often,  logical,  not  physical  separation  (“service  flow”)  • e.g.,  MVPD  service  

Traditional  Analog/TDM  POTS  

• needs  no  explanation  

user-­‐initiated  resource  reservation  (RSVP,  NSIS,  DOCSIS  3)  

 

*  Universality  *  reachability  à  global  numbering  &  interconnection  *  media  à  HD  audio,  video,  text  *  availability  à  universal  service  regardless  of  *  geography  *  income  *  disability  

*  affordability  à  service  competition  +  affordable  standalone  broadband  *  Public  safety  *  citizen-­‐to-­‐authority:  emergency  services  (911)  *  authority-­‐to-­‐citizen:  alerting  *  law  enforcement  *  survivable  (facilities  redundancy,  power  outages)  

*  Quality  *  media  (voice  +  …)  quality  *  assured  identity  *  assured  privacy  (CPNI)  *  accountable  reliability  

4  

What  are  key  attributes?  

*  Technology  *  wired  vs.  wireless  *  but:  maintain  quality  if  substitute  rather  than  supplement  

*  packet  vs.  circuit  *  “facilities-­‐based”  vs.  “over-­‐the-­‐top”  *  distinction  may  blur  if  QoS  as  a  separable  service  

*  Economic  organization  *  “telecommunication  carrier”  

5  

What  is  less  important?  Signaling   Media  

Analog   circuit  (A)   circuit  (A)  

Digital   circuit  (D)   circuit  (D)  

AIN   packet  (SS7)  

circuit  (D)  

VoIP   packet  (SIP)  

packet  (RTP)  

6  

OTT:  access  to  broadband  

Chart  1Households  With  Access  to  the  

Fixed  Broadband  Speed  Benchmark  by  Technology

0% 20% 40% 60% 80% 100%

Fiber

Other Copper

Fixed Wireless

DSL

Cable

Any Fixed

Eighth  Broadband  Progress  Report,  August  2012  

7  

Advertised  vs.  actual  2012  

Measuring Broadband America

Chart 1: Average Peak Period and 24-Hour Sustained Download Speeds as a Percentage of Advertised, by Provider—April 2012 Test Data

0%

20%

40%

60%

80%

100%

120%

140%

AT&T

Cablevision

CenturyLink

Charter

Comcast

Cox

Frontier

Insight

Mediacom

Qwest

TimeWarner

Verizon�Fiber

Verizon�DSL

Windstream

Actual/�

Advertised�spee

d�(%

)

24Ͳhr�MonͲSun 7pmͲ11pm�MonͲFri

As shown in Chart 2, upload performance in the April 2012 test data is much less affected than download performance during peak periods. While in 2011 almost all ISPs reached 90 percent or above of their advertised upload rate, in 2012 most ISPs improved to deliver above 100 percent of their advertised rate, even during peak periods.

FEDERAL COMMUNICATIONS COMMISSION | JULY 2012 | STATE OF U.S. BROADBAND 17

Measuring  Broadband  America,  July  2012  

Significantly  better  than  2011  

Measuring  Broadband  America,  July  2012  

9  

Latency  by  technology  Measuring Broadband America

Chart 10: Average Peak Period Latency in Milliseconds, by Technology—April 2012 Test Data

0

10

20

30

40

50

60

70

0.512�Mbps

1�Mbps

2�Mbps

4�Mbps

6�Mbps

8�Mbps

12�Mbps

16�Mbps

20�Mbps

24�Mbps

28�Mbps

35�Mbps

50�Mbps

Advertised�Speed�(Mbit/s)

Average

�Laten

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Cable DSL Fiber

Charts 11.1-11.5 displays average web page loading39 time by speed tier for the April 2012 test data period. Web pages load much faster as broadband speed increases, but beyond 10 Mbps, performance increases for basic web browsing lessen dramatically. There also appear to be differences in web loading times by service provider at these higher speeds. The data indicate that a consumer subscribing to a 10 Mbps speed tier is unlikely to experience a significant performance increase in basic web browsing—i.e., accessing web pages, but not streaming video or using other high-bandwidth applications such as video chat—by moving to a higher speed tier. These results are largely consistent with and show no significant improvement over 2011 results. Web page download speeds at higher rates are limited by intrinsic factors (e.g. service architectures, latency and protocol effects) and not easily improved at the current time. Research is ongoing to improve overall Internet service performance and future improvements in performance may be possible. Note that in Charts 11.1-11.5, lower bars indicate shorter load time, and therefore better performance.

FEDERAL COMMUNICATIONS COMMISSION | JULY 2012 | STATE OF U.S. BROADBAND 30

Measuring  Broadband  America,  July  2012  

*  Packet  loss  *  VoIP:  <  1-­‐5%  acceptable  *  Video:  loss  à  lower  

throughput  *  Home  networks  *  “Buffer  bloat”  in  gateways  *  “don’t  download  that  video,  

I’m  on  the  phone!”  *  Reliability?  

Other  QoS  impairments  

(a) Download throughput is mostly consistent, with some excep-tions.

(b) Upload throughput is consistent across ISPs.

Figure 7: Consistency of throughput performance: The averagethroughput of each user is normalized by the 95th percentile valueobtained by that user. (SamKnows)

“speed test” measurement taken at the wrong time could likelyreport misleading numbers that do not have much bearing on thelong-term performance.

5.3 Effect of Traffic Shaping on ThroughputISPs shape traffic in different ways, which makes it difficult to

compare measurements across ISPs, and sometimes even acrossusers within the same ISP. We study the effect of PowerBoost 3across different ISPs, time, and users. We also explore how Com-cast implements PowerBoost.

Which ISPs use PowerBoost, and how does it vary across ISPs?The SamKnows deployment performs throughput measurementsonce every two hours; each measurement lasts 30 seconds, and eachreport is divided into six snapshots at roughly 5-second intervals forthe duration of the 30-second test (Section 4). This measurementapproach allows us to see the progress of each throughput mea-surement over time; if PowerBoost is applied, then the throughputduring the last snapshot will be less than the throughput during thefirst. For each report, we normalize the throughput in each periodby the throughput reported for the first period. Without Power-Boost, we would expect that the normalized ratio would be closeto one for all intervals. On the other hand, with PowerBoost, weexpect the throughput in the last five seconds to be less than thethroughput in the first five seconds (assuming that PowerBoost lastsless than 30 seconds, the duration of the test). Figure 9 shows theaverage progression of throughput over all users in an ISP: the av-erage normalized throughput decreases steadily. We conclude thatmost cable ISPs provide some level of PowerBoost for less than 30seconds, at a rate of about 50% more than the normal rate. Ca-blevision’s line is flat; this suggests that either it does not providePowerBoost, or it lasts well over 30 seconds consistently, in whichcase the throughput test would see only the PowerBoost effect. The

(a) The biggest difference between peak and worst performance isabout 40%.

(b) The standard deviation of throughput measurements increasesduring peak hours, most significantly for ISPs that see lowerthroughputs at peak hours.

(c) Loss increases during peak hours for Cox. Other ISPs do not seethis effect as much.

Figure 8: Time of day is significant: The average downloadthroughput for Cablevision and Cox users drops significantly dur-ing the evening peak time. Throughput is also significantly morevariable during peak time. (SamKnows)

gradual decrease, rather than an abrupt decrease, could be becausePowerBoost durations vary across users or that the ISP changesPowerBoost parameters based on network state. From a similaranalysis for uploads (not shown), we saw that only Comcast andCox seem to provide PowerBoost for uploads; we observed a de-crease in throughput of about 20%. Dischinger et al. [12] also re-ported PowerBoost effects, and we also see that it is widespreadamong cable ISPs. For the DSL ISPs (not shown), the lines are flat.

Takeaway: Many cable ISPs implement PowerBoost, whichcould distort speedtest-like measurements. While some people maybe only interested in short-term burst rates, others may be more in-terested in long-term rates. Any throughput benchmark should aimto characterize both burst rates and steady-state throughput rates.

Do different users see different PowerBoost effects? Using BIS-Mark, we study Comcast’s use of PowerBoost in depth. Accord-ing to Comcast [9], their implementation of PowerBoost provides

140

S.  Sundaresan  et  al,    Broadband  Internet  Performance:  A  View  From  the  Gateway,  ACM  SIGCOMM  2011  

Broadband  virtuous  cycle  fixed  

broadband  investment  

cellular  broadband  (backhaul)  

broadband  availability  

applications  (incl.  OTT)  

adoption  (relevance,  

value)  

OI  principles  

Open  Internet  Principles  

Transparency.  Fixed  and  mobile  broadband  providers  must  disclose  the  network  management  practices,  performance  characteristics,  and  terms  and  conditions  of  their  broadband  services;  

No  blocking.  Fixed  broadband  providers  may  not  block  lawful  content,  applications,  services,  or  non-­‐harmful  devices;  mobile  broadband  providers  may  not  block  lawful  websites,  or  block  applications  that  compete  with  their  voice  or  video  telephony  services  

No  unreasonable  discrimination.  Fixed  broadband  providers  may  not  unreasonably  discriminate  in  transmitting  lawful  network  traffic.  

12  

Going  forward  

*  Interconnected  VoIP:  done  *  CALEA,  USF,  E911  *  Part  4  outage  reporting  

*  In  progress  *  Intercarrier  compensation:  IP  interconnection  

expectation  +  transition  to  bill-­‐and-­‐keep  *  NG911,  better  location  *  video  relay  services,  CVAA  

*  To  do  *  numbering  &  databases  *  security  model  (robocalls,  text  spam,  vishing)  *  VoIP  interconnection  model  

…  ,  we  expect  all  carriers  to  negotiate  in  good  faith  in  response  to  requests  for  IP-­‐to-­‐IP  interconnection  for  the  exchange  of  voice  traffic.  The  duty  to  negotiate  in  good  faith  has  been  a  longstanding  element  of  interconnection  requirements  under  the  Communications  Act  and  does  not  depend  upon  the  network  technology  underlying  the  interconnection,  whether  TDM,  IP,  or  otherwise.  Moreover,  we  expect  such  good  faith  negotiations  to  result  in  interconnection  arrangements  between  IP  networks  for  the  purpose  of  exchanging  voice  traffic.