Networking Research – Vision and Opportunities

1
Networking Research Vision and Opportunities

• Henning Schulzrinne
• Dept. of Computer Science
• Columbia University
• hgs_at_cs.columbia.edu

2
Overview

• Network research topics
• will focus on L3 and above
• mostly on software
• optical and electronic switch work continues
• systems perspective
• Some samples of IRT research
• location-based services
• service creation
• network reliability
• End-to-end QoS estimation

3
Networking is getting into middle years
4
Technologies at 30 years

• Other technologies at similar maturity level
• air planes 1903 1938 (Stratoliner)
• cars 1876 1908 (Model T)
• analog telephones 1876 1915 (transcontinental
  telephone)
• railroad 1800s -- ?

5
Maturing network research

• Old questions
• Can we make X work over packet networks?
• All major dedicated network applications (flight
  reservations, embedded systems, radio, TV,
  telephone, fax, messaging, ) are now available
  on IP
• Can we get M/G/T bits to the end user?
• Raw bits everywhere any media, anytime,
  anywhere
• New questions
• Dependency on communications ? Can we make the
  network reliable?
• Can non-technical users use networks without
  becoming amateur sys-admins? ? auto/zeroconfigurat
  ion, autonomous computing, self-healing networks,
  
• Can we prevent social and financial damage
  inflicted through networks (viruses, spam, DOS,
  identity theft, privacy violations, )?

6
Standardization

• Really two facets of standardization
• public, interoperable description of protocol,
  but possibly many (Tanenbaum)
• reduction to 1-3 common technologies
• LAN Arcnet, tokenring, ATM, FDDI, DQDB, ?
  Ethernet
• WAN IP, X.25, OSI ? IP
• Have reached phase 2 in most cases, with RPC
  (SOAP) and presentation layer (XML) most recent
  'conversions'

7
Observations on progress

• 1960s military ? professional ? consumer
• now, often reversed
• Oscillate convergence ? divergence
• continued convergence clearly at physical layer
• niches larger ? support separate networks
• Communications technologies rarely disappear (as
  long as operational cost is low)
• exceptions
• telex, telegram, semaphores ? fax, email
• X.25 OSI, X.400 ? IP, SMTP
• analog cell phones

8
History of networking

• History of networking non-network applications
  migrate
• postal intracompany mail, fax ? email, IM
• broadcast TV, radio
• interactive voice/video communication ? VoIP
• information access ? web, P2P
• disk access ? iSCSI, Fiberchannel-over-IP

9
Transition of networking

• Maturity ? cost dominates
• can get any number of bits anywhere, but at
  considerable cost and complexity
• casually usable bit density still very low
• Specialized ? commodity
• OPEX ( people) dominates
• installed and run by 'amateurs'
• need low complexity, high reliability

10
Network evolution

• Only three modes, now thoroughly explored
• packet/cell-based
• message-based (application data units)
• session-based (circuits)
• Replace specialized networks
• left to do embedded systems
• need cost(CPU network) lt 10
• cars
• industrial (manufacturing) control
• commercial buildings (lighting, HVAC, security
  now LONworks)
• remote controls, light switches
• keys replaced by biometrics

11
Commercial access cost (T1)
12
Transit cost (OC-3, NY London)
13
Disk storage cost (IDE)
14
Research directions

• Whats promising/interesting two different
  axes
• Intellectual merit ? interesting analysis,
  broadly applicable,
• Satisfies practical needs ? may not be a
  scientific breakthrough
• Related, but Ill (mostly) ignore
• Whats fashionable/hot"

15
Whats fashionable (and not)

• Judging from Infocom submissions and NSF panels
• Security of any sort
• Peer-to-peer networks
• Ad-hoc and sensor networks
• Overlay networks
• Network measurements
• Whats not
• QoS scheduling, admission control,
• Active networks
• (Native) multicast

16
Observations on network research

• Frustration with inability to change network
  infrastructure in less than 10 -- 20 year
  horizons
• IPv6
• Layer-3 multicast
• QoS
• Security
• Network research community has dismal track
  record for new applications
• web, IM, P2P, vs. video-on-demand
• Disconnect from standardization
• Few attempts to bring research work into
  standards bodies
• Standards bodies slow to catch up (e.g., P2P)

17
Network research

• Old goal "new universal network"
• IP, OSI, ATM
• New goal "niche networks"
• may claim universality
• peer-to-peer, ad hoc, sensor, mesh,
• New research community realizations
• difficulty in rolling out new network ?
  incrementalism
• spectrum issues (open spectrum, SDR, )

18
Infrastructure research questions Scaling,
Reliability, Security

• Scaling
• no major changes for 20 years (link-state, DV,
  etc.)
• two-layer (intra/inter) ? other routing paradigms
• Reliability
• reduce operator errors (e.g., XCONF effort in
  IETF)
• faster convergence in routing protocols (BGP ? up
  to 20-30 minutes!)
• Security
• secure routing protocols
• DOS prevention (pushback, source discovery)

19
Scaling practical issues

• Scaling is only backbone problem
• Depends on network evolution
• continuing addition of AS to flat space ? deep
  trouble
• additional hierarchy

20
QoS

• QoS is meaningless to users
• care about service availability ? reliability
• as more and more value depends on network
  services, can't afford random downtimes

21
Transport layer

• After XTP flop, flurry of new protocols SCTP,
  DDCP, UDP-lite
• fill in gaps in TCP/UDP
• flow control without reliability
• multiple logical streams with one flow control
  stream (cf. HTTP/1.1)
• Issues of very fat pipes
• single packet loss can wipe out effective
  throughput

22
Applications

• Transition of custom protocols to XML, SOAP?
• but this is the not the first try (DCE, SunRPC,
  COM, Java RMI, Corba, )
• Scalable event systems (research)
• Presence (SIP/SIMPLE, Jabber, )
• P2P systems
• Application-layer routing, multicast, discovery,

23
New applications

• New bandwidth-intensive applications
• Reality-based networking
• (security) cameras
• Distributed games often require only
  low-bandwidth control information
• current game traffic VoIP
• Computation vs. storage vs. communications
• communications cost has decreased less rapidly
  than storage costs

24
Security challenges

• DOS, security attacks ? permissions-based
  communications
• only allow modest rates without asking
• effectively, back to circuit-switched
• Higher-level security services ? more
  application-layer access via gateways, proxies,
• User identity
• problem is not availability, but rather
  over-abundance

25
Fundamental re-thinking

• "Hour glass" with single address space ? multiple
  gatewayed networks with separate address spaces
• diversity vs. uniformity
• Application-neutral connectivity ? filtered
  restricted (? tunneling over port 80)
• Send first, ask later ? permission-based
  networking
• old default no (mutual) authentication
• new only authenticated users/applications

26
Wildcards

• Quantum computing
• Teleportation

27
Ubiquitous SIP

• Henning Schulzrinne
• (with Stefan Berger, Stelios Sidiroglou, Kundan
  Singh, Xiaotao Wu, Weibin Zhao and the RPIDS
  authors)
• Columbia University IRT Lab
• Hewlett Packard March 2003

28
Overview

• What is ubiquitous computing?
• Core ubiquitous communications functionality
• Brief introduction to SIP
• Ubiquitous computing in SIP and SLP
• On-going work at Columbia

29
What is ubiquitous computing?

• Ubiquitous computing has as its goal the
  enhancing computer use by making many computers
  available throughout the physical environment,
  but making them effectively invisible to the
  user. (Weiser, 1993)
• Ubiquitous computing is not virtual reality, it
  is not a Personal Digital Assistant (PDA) such as
  Apple's Newton, it is not a personal or intimate
  computer with agents doing your bidding. Unlike
  virtual reality, ubiquitous computing endeavers
  to integrate information displays into the
  everyday physical world. It considers the nuances
  of the real world to be wonderful, and aims only
  to augment them. (Weiser, 1993)

30
Ubiquitous computing aspects

• Also related to pervasive computing
• Mobility, but not just cell phones
• Computation and communications
• Integration of devices
• borrow capabilities found in the environment ?
  composition into logical devices
• seamless mobility ? session mobility
• adaptation to local capabilities
• environment senses instead of explicit user
  interaction
• from small dumb devices to PCs
• light switches and smart wallpaper

31
Components of ubiquitous communications

• Service discovery ? discover devices
• Service mobility ? configuration information
  moves to new devices
• Event notification ? for context awareness
• Context-awareness ? location, user actions,
  location properties,

32
Example ubicomp projects

• Ambient Devices
• EU IST Disappearing Computer
• Project Aura, CMU ? user attention
• UNC office of real soon now
• augmented surfaces Reki99
• Microsoft Easy Living
• Oxygen, MIT
• Portolano, Univ. of Washington
• Endeavour, Berkeley
• CoolTown, HP Labs

33
Ubiquitous computing using SIP whats different?

• Traditionally, focus on closed environments (lab,
  single company, home, )
• Often, proprietary protocols ? self-contained
  environment
• Here,
• operate across Internet (? no Corba)
• trusted, semi-trusted and untrusted participants
• use standard protocol mechanisms where possible
• make minimal assumptions on homogeneity
• respect user privacy

34
What is SIP?

• Session Initiation Protocol ? protocol that
  establishes, manages (multimedia) sessions
• also used for IM, presence event notification
• uses SDP to describe multimedia sessions
• Developed at Columbia U. (with others)
• Standardized by IETF, 3GPP (for 3G wireless),
  PacketCable
• About 60 companies produce SIP products
• Microsofts Windows Messenger (4.7) includes SIP

35
Basic SIP message flow
36
SIP trapezoid
37
SIP event notification

• Named events
• Typically, used for events within conferences
  (Alice joined) and call legs (e.g., call
  transfer)
• Supports arbitrary notification bodies, typically
  XML

SUBSCRIBE sipalice_at_vmail.example.com SIP/2.0 To
ltsipalice_at_example.comgt From ltsipalice_at_example.c
omgttag78923 Call-Id 1349882_at_alice-phone.example
.com Contact ltsipalice_at_alice-phone.example.comgt
NOTIFY sipalice_at_alice-phone.example.com
SIP/2.0 Event message-summary Subscription-Stat
e active Messages-Waiting yes Message-Account
sipalice_at_vmail.example.com Voice-Message 2/8
(0/2)
38
SIP event architecture

• Does not try to route notifications (application
  layer multicast) as in SIENA
• Filtering at PA under discussion (for
  low-bandwidth devices)
• rate
• content
• But most ubicomp notification groups are probably
  small
• and message volume not likely to provide much
  bandwidth saving via network-based filtering
• Greatly simplifies trust model no intermediaries
  that need to inspect content
• can encrypt via S/MIME
• However, can build redistribution exploders and
  list subscriptions (subscribe to
  engineering_at_hp.com)

39
SIP presence architecture
REGISTER
SUBSCRIBE
watcher
PA
Alice
NOTIFY
Bob
lt?xml version"1.0" encoding"UTF-8"?gt ltppresence
xmlnsp"urn" entity"presalice_at_example
.com"gt ltptuple id"sg89ae"gt ltpstatusgt
ltpbasicgtopenlt/pbasicgt lt/pstatusgt
ltpcontactgttel09012345678lt/pcontactgt lt/ptuplegt
lt/ppresencegt
PUAs
PUBLISH
40
Session mobility

• Walk into office, switch from cell phone to desk
  phone
• call transfer problem ? SIP REFER
• related problem split session across end devices
• e.g., wall display desk phone PC for
  collaborative application
• assume devices (or stand-ins) are SIP-enabled
• third-party call control

41
Session mobility via 3PCC
pc42
INVITE speakerphone maudio cpc42
192.0.2.1
INVITE pc42 mvideo c192.0.2.7 maudio c192.0.2.
1
INVITE display mvideo cpc42
192.0.2.7
42
How to find services?

• Two complementary developments
• smaller devices carried on user instead of
  stationary devices
• devices that can be time-shared
• large plasma displays
• projector
• hi-res cameras
• echo-canceling speaker systems
• wide-area network access
• Need to discover services in local environment
• SLP (Service Location Protocol) allows querying
  for services
• find all color displays with at least XGA
  resolution
• slp//example.com/SrvRqst?public?typeprinter
• SLP in multicast mode
• SLP in DA mode
• Need to discover services before getting to
  environment
• is there a camera in the meeting room?
• SLP extension find remote DA via DNS SRV

43
Service Location Protocol (SLP)

• Version 2 standardized June 1999

SrvRqst
SA
UA
SA
SrvRply
SrvReg
DA
SrvReg
SrvRqst
DAAdvert
44
SLP attribute example
45
Other service location mechanism

• DNS SRV/NAPTR
• DNS TXT records (Apple Rendezvous) ? DNS-SD
• UPnP uses SSDP
• multicast HTTP over UDP

M-SEARCH HTTP/1.1 S uuidijklmnop-7dec-11d0-a76
5-00a0c91e6bf6 Host 239.255.255.250reservedSSDPp
ort Man "ssdpdiscover ST gefridge MX
3 HTTP/1.1 200 OK S uuidijklmnop-7dec-11d0-a765
-00a0c91e6bf6 Ext Cache-Control no-cache"Ext",
max-age 5000 ST gefridge USN
uuidabcdefgh-7dec-11d0-a765-00a0c91e6bf6 AL
ltblenderixlgtlthttp//foo/bargt
46
Service mobility

• Allow access to service parameters anywhere
  payphone problem
• address book
• incoming call rules
• source name (SIP From)
• Existing solutions
• SIM card ? cumbersome to change
• synchronization (e.g., Palm) ? not suitable for
  borrowed devices
• Server-based services ? easier with SIP
  (service-routing), if carrier allows
• Emerging solutions for SIP systems
• Small user token (smart card, RFID, i-button)
  identifying user
• Temporarily download configuration from home
  server

47
Location-based services

• 3 major factors for services and personalization
• universal persona (certs, IM, email, SIP) ?
• time (NTP) ?
• space ? not much yet
• Most location-based services
• "find nearest X"
• customized popup ads eagerly await!
• 911
• We focus on computational, network and
  communication services in the environment
• current and future locations

48
Locations

• Geographic location
• latitude, longitude, altitude, velocity, heading
• Civil location (? postal location!)
• street address, city
• some countries are a bit difficult
• Categorical
• office, library, theater, hospital,
• Behavioral
• public location, don't expect privacy
• silence is encouraged, don't ring the phone

49
Determining locations

• SIP entities are often far away from physical
  user or his current network (intentionally)
• For many devices, cant afford hardware to
  determine location
• different precision requirements
• in Fayette County (within driving distance of
  service or person)
• on campus
• in room 815
• in corner, talking to Bob
• GPS doesnt work indoors, but Assisted GPS
  (A-GPS) may
• Use location beacons BlueTooth, 802.11
• 802.11 requires overlapping APs
• may not offer network connectivity
• see our 7DS project offer local content
  location
• Physically close by network entities
• DHCP (same broadcast domain)
• PPP (tail circuit)
• Not always true with VPNs, but end system knows
  that its using a VPN

50
DHCP for locations

• modified dhcpd (ISC) to generate location
  information
• use MAC address backtracing to get location
  information

8020abd5d
DHCP server
CDP SNMP 8020abd5d ? 458/17
DHCP answer staDC locRm815 lat38.89868
long77.03723
458/17 ? Rm. 815 458/18 ? Rm. 816
51
Determining locations

• For many devices, cant afford hardware to
  determine location
• Implementing BlueTooth-based location sensor
  networks
• CU 7DS project offer local content location
• Developing programmable active badges with IR and
  RF capabilities

52
DHCP for locations

• Proposal DHCP extensions for geographic and
  civil location
• geographic resolution (bits), long/lat, altitude
  (meters or floors)
• civil
• what end system, switch or DHCP server
• hierarchical subdivisions, from country to
  street, landmark name, occupant
• Also, some LAN switches broadcast port and switch
  identification
• CDP for Cisco, EDP for Extreme Networks
• Can also use backtracking via SNMP switch tables
• locally implemented for emergency services (Perl
  sip-cgi script)

53
Location-based services

• Services
• Location-aware call routing
• do not forward call if time at callee location
  is 11 pm, 8 am
• only forward time-for-lunch if destination is on
  campus
• contact nearest emergency call center
• do not ring phone if Im in a theater
• send delivery_at_pizza.com to nearest branch
• Location-based events
• subscribe to locations, not people
• Alice has entered the meeting room
• subscriber may be device in room ? our lab stereo
  changes CDs for each person that enters the room
• Person location events
• Were implementing SIP, caller-preferences and
  CPL extensions for these services

54
SIP extensions for location-based services

• Location information is highly sensitive
• complete tracking of person
• stalkers and burglars would kill for this
  information
• IETF GEOPRIV principle target can control
  dissemination of location information
• restrict time of day, information (location,
  heading, velocity) resolution, number of times
  queried, destination, retention,
• Alice is in time zone MET may be ok for
  strangers, but Alice is at 41.872833 N,
  087.624417 W, heading NE at 45 mph is not
• GEOPRIV still defining application scenarios
• in many cases, easiest to include location
  information in-band with protocol, as this
  avoids delegating authorization
• otherwise, need to give access key to database to
  recipient
• we propose adding SIP Location header field

55
RPIDS rich presence data

• Basic IETF presence (CPIM) only gives you
• contact information (SIP, tel URI)
• priority
• open or closed
• Want to use presence to guide communications

watcher
everything
PA
PUA
watcher
"vague"
PUBLISH
watcher
NOTIFY
CPL
INVITE
56
Aside SIP caller preferences

• SIP core philosophy many devices, one identifier
• Address people, not plastic

57
Aside SIP caller preferences

• But caller sometimes has preferences among
  devices
• SIP caller guides call routing
• I hate voicemail!
• I hate people!
• I prefer voicemail
• Multilingual lines
• Caller proposes, callee disposes

sipisabel_at_a.comlanguages"es" sipisabel_at_a.coml
anguages"en"q0.2
INVITE sipsales_at_a.com Accept-Contact
languages"en"
REGISTER
INVITE
sipbob_at_a.comlanguages"en"
58
RPIDS Rich presence data

• Integrates caller preferences information into
  presence announcements
• ltactivitygt on-the-phone, away, appointment,
  holiday, meal, meeting, steering, in-transit,
  travel, vacation, busy, permanent-absence
• ltplacetypegt home, office, public
• ltprivacygt public, private, quiet
• ltfromgt, ltuntilgt status validity
• ltidlegt activity for device
• ltrelationshipgt family, associate, assistant,
  supervisor
• ltclassgt labeling and grouping
• lticongt, ltcardgt, ltinfogt labeling presentities

59
RPIDS example

• lttuple id"7c8dqui"gt
• ltstatusgt
• ltbasicgtopenlt/basicgt
• ltcontactgtsipsecretary_at_example.comlt/contactgt
• ltcapcapabilitiesgt ltcapfeature
  name"Media"gt
• ltcapvaluegtvoicelt/capvaluegt
• ltcapvalue negated"true"gtmessagelt/capval
  uegt
• lt/capfeaturegt
• lt/capcapabilitiesgt
• lt/statusgt
• lteprelationshipgtassistantlt/eprelationshipgt
• ltnotegtMy secretarylt/notegt
• lt/tuplegt

60
Event filtering

• Events are core attribute of ubiquitous computing
  systems
• tell devices about people actions
• tell people about device presence
• e.g., Alice has entered Room 815
• devices that know Alices preferences subscribe
  to Alice
• locations may also have presence
• e.g., for occupancy sensors, switches

61
Location filtering language

• SIP presence information will be updated using
  REGISTER and UPDATE
• Need to constrain
• who is allowed to see what detail ? presentity
  privacy
• who wants to see what detail
• how often
• what granularity of change
• Proposal to allow SUBSCRIBE to include frequency
  limitation
• Working on CPL-like language invoked (logically)
  at publication time
• classes of users, e.g., based on entry in my
  address book
• classes get mapped to restriction
• 12 bits of long/lat resolution, 6 bits of
  altitude resolution, 0 bits of velocity
• time zone only, category only
• watchers can then add filters that restrict the
  delivery
• location difference gt threshold
• entering or leaving certain area
• entering or leaving category or behavioral type

62
Columbia SIP servers (CINEMA)
Telephone switch
Local/long distance 1-212-5551212
rtspd media server
Quicktime
Single machine
RTSP
sipconf Conference server
RTSP clients
Department PBX
sipum Unified messaging
Internal Telephone Extn 7040
713x
sipd Proxy, redirect, registrar server
SQL database
SIP/PSTN Gateway
Web based configuration
SNMP (Network Management)
Extn 7134
H.323
Extn 7136
siph323 SIP-H.323 translator
NetMeeting
xiaotaow_at_cs
63
Location-based services in CINEMA

• Initial proof-of-concept implementation
• Integrate devices
• lava lamp via X10 controller ? set personalized
  light mood setting
• Pingtel phone ? add outgoing line to phone and
  register user
• painful needs to be done via HTTP POST request
• stereo ? change to audio CD track based on user
• Sense user presence and identity
• passive infrared (PIR) occupancy sensor
• magnetic swipe card
• ibutton
• BlueTooth equipped PDA
• IRRF badge (in progress)
• RFID (future)
• biometrics (future)

64
CINEMA system
65
All-SIP implementation
66
Service creation

• Promise of faster service creation
• traditionally, only vendors (and sometimes
  carriers)
• learn from web models

67
sip-cgi

• web common gateway interface (cgi)
• oldest (and still most commonly used) interface
  for dynamic content generation
• web server invokes process and passes HTTP
  request via
• stdin (POST body)
• environment variables ? HTTP headers, URL
• arguments as POST body or GET headers
  (?arg1var1arg2var2)
• new process for each request ? not very efficient
• but easy to learn, robust (no state)
• support from just about any programming language
  (C, Perl, Tcl, Python, VisualBasic, ...)
• Adapt cgi model to SIP ? sip-cgi
• RFC 3050

68
sip-cgi examples

• Block _at_vinylsiding.com
• if (defined ENVSIP_FROM ENVSIP_FROM
  "sip_at_vinylsiding.com")
• print "SIP/2.0 600 I can't talk right
  now\n\n"
• Make calls from boss urgent
• if (defined ENVSIP_FROM ENVSIP_FROM
  /sipboss_at_mycompany.com/)
• foreach reg (get_regs())
• print "CGI-PROXY-REQUEST reg SIP/2.0\n"
• print "Priority urgent\n\n"

69
Call Processing Language (CPL)

• XML-based language for processing requests
• intentionally restricted to branching and
  subroutines
• no variables (may change), no loops
• thus, easily represented graphically
• and most bugs can be detected statically
• termination assured
• mostly used for SIP, but protocol-independent
• integrates notion of calendaring (time ranges)
• structured tree describing actions performed on
  call setup event
• top-level events incoming and outgoing

70
CPL

• Location set stored as implicit global variable
• operations can add, filter and delete entries
• Switches
• address
• language
• time, using CALSCH notation (e.g., exported from
  Outlook)
• priority
• Proxy node proxies request and then branches on
  response (busy, redirection, noanswer, ...)
• Reject and redirect perform corresponding
  protocol actions
• Supports abstract logging and email operation

71
CPL example
72
CPL example

• lt?xml version"1.0" ?gt
• lt!DOCTYPE call SYSTEM "cpl.dtd"gt
• ltcplgt
• ltincominggt
• ltlookup source"http//www.example.com/cgi-bin
  /locate.cgi?userjones"
• timeout"8"gt
• ltsuccessgt
• ltproxy /gt
• lt/successgt
• ltfailuregt
• ltmail url"mailtojones_at_example.comSubjec
  tlookup20failed" /gt
• lt/failuregt
• lt/lookupgt
• lt/incominggt
• lt/cplgt

73
CPL example anonymous call screening

• ltcplgt
• ltincominggt
• ltaddress-switch field"origin" subfield"user"gt
• ltaddress is"anonymous"gt
• ltreject status"reject"
• reason"I don't accept anonymous calls" /gt
• lt/addressgt
• lt/address-switchgt
• lt/incominggt
• lt/cplgt

74
Service creation a comparison
75
Service creation for presence services
(work-in-progress)

• Accept or deny subscriptions
• Shape presence notifications
• different level of detail for family, friends and
  colleagues
• particularly important for geo data
• Subscriber can filter detail
• primarily, wireless bandwidth constraints
• rate limit notifications
• XPath?
• Mostly, condition/reaction ? CPL can be extended
  to most of these functions

76
Pushing context-sensitive data to users

• User with mobile device should get location
  information when entering city, campus or
  building
• flight and gate information
• maps and directions
• local weather forecast
• special advisories (choose security checkpoint
  2)
• Often does not require knowing user
• but interface with (e.g.) calendar
• Example Columbia implementation
• OBEX data exchange over BlueTooth
• PDA pushes current appointment or event name
• base station delivers directions and map

77
Summary ubiquitous computing using SIP

• SIP auxiliary protocols supports many of the
  core requirements for ubiquitous computing and
  communications
• mobility modalities terminal, user, session,
  service
• service negotiation for devices with different
  capabilities
• automatic configuration and discovery
• with SLP or similar
• event notification and triggered actions
• automatic actions event filtering, CPL, LESS
  (for end system services)
• SIP offers a loosely-coupled approach (cf. Jini
  or object models)
• Also need data push functionality
• Avoid tendency to assume SIP users are human
  want to interconnect different components and
  devices
• SIP device configuration needs automation, rather
  than screen-scraping

78
Network reliability and QoS measurements

• Henning Schulzrinne
• Columbia University, New York
• University of Cincinnati
• March 2003

79
Assessment of VoIP Service Availability

• Wenyu Jiang
• Henning Schulzrinne
• IRT Lab, Dept. of Computer Science
• Columbia University

80
Overview

• (on-going work, preliminary results, still
  looking for measurement sites, )
• Service availability
• Measurement setup
• Measurement results
• call success probability
• overall network loss
• network outages
• outage induced call abortion probability

81
Service availability

• Users do not care about QoS
• at least not about packet loss, jitter, delay
• FEC and PLC can deal with losses up to 5-8
• rather, its service availability ? how likely is
  it that I can place a call and not get
  interrupted?
• availability MTBF / (MTBF MTTR)
• MTBF mean time between failures
• MTTR mean time to repair
• availability successful calls / first call
  attempts
• equipment availability 99.999 (5 nines) ? 5
  minutes/year
• ATT 99.98 availability (1997)
• IP frame relay SLA 99.9
• UK mobile phone survey 97.1-98.8

82
Availability PSTN metrics

• PSTN metrics (Worldbank study)
• fault rate
• should be less than 0.2 per main line
• fault clearance ( MTTR)
• next business day
• call completion rate
• during network busy hour
• varies from about 60 - 75
• dial tone delay

83
Example PSTN statistics
Source Worldbank
84
Measurement setup
85
Measurement setup

• Active measurements
• call duration 3 or 7 minutes
• UDP packets
• 36 bytes alternating with 72 bytes (FEC)
• 40 ms spacing
• September 10 to December 6, 2002
• 13,500 call hours

86
Call success probability

• 62,027 calls succeeded, 292 failed ? 99.53
  availability
• roughly constant across I2, I2, commercial ISPs

87
Overall network loss

• PSTN once connected, call usually of good
  quality
• exception mobile phones
• compute periods of time below loss threshold
• 5 causes degradation for many codecs
• others acceptable till 20

88
Network Outages

• sustained packet losses
• arbitrarily defined at 8 packets
• far beyond any recoverable loss (FEC,
  interpolation)
• 23 outages
• make up significant part of 0.25 unavailability
• symmetric A?B ?? B?A?
• spatially correlated A?B ? ? A?X?
• not correlated across networks (e.g., I2 and
  commercial)

89
Network outages
90
Network outages
91
Outage-induced call abortion proability

• Long interruption ? user likely to abandon call
• from E.855 survey Pholding e-t/17.26 (t in
  seconds)
• ? half the users will abandon call after 12s
• 2,566 have at least one outage
• 946 of 2,566 expected to be dropped ? 1.53 of
  all calls

92
Conclusion

• Availability in space is (mostly) solved ?
  availability in time restricts usability for new
  applications
• initial investigation into service availability
  for VoIP
• need to define metrics for, say, web access
• unify packet loss and no Internet dial tone
• far less than 5 nines
• working on identifying fault sources and
  locations
• looking for additional measurement sites

93
Multimodal Wireless Networking From Message
Forwarding to Infrastructure Networks

• Henning Schulzrinne
• joint work with
• Maria Papadopouli and Stelios Sidiroglou
• Computer Science Department
• Columbia University
• http//www.cs.columbia.edu/IRT
• hgs_at_cs.columbia.edu

94
Outline

• Introduction
• A taxonomy of wireless networks
• Motivation
• Overview of 7DS
• Performance analysis on 7DS
• Conclusions
• Future work

95
Multimodal networking

• "The term multimodal transport is often used
  loosely and interchangeably with the term
  intermodal transport. Both refer to the transport
  of goods through several modes of transport from
  origin to destination." (UN)
• goods packaged in containers ? packets and
  messages
• Networking ? combine different modes of data
  transport that maximize efficiency

96
Multimodal networking

• Speed, cost and ubiquity are the core variables
• cf. pipelines, ships, planes, trucks
• Traditional assumption of value of immediacy from
  PSTN ? demise of Iridium

97
Access modalities
delay
bandwidth (peak)
98
Cost of networking
99
Wireless WAN access

• Spectrum is very expensive

• 3G bandwidth is very low (around 60 kb/s)

100
Limitations of 802.11

• Good for hotspots, difficult for complete
  coverage
• Manhattan 60 km2 ? 6,000 base stations (not
  counting vertical)
• With 600,000 Manhattan households, 1 of
  households would have to install access points
• Almost no coverage outside of large coastal cities

101
Mobile data access

• Hoarding grab data before moving
• 802.11, 3G, BlueTooth wireless as last-hop
  access technology
• Ad-hoc networks
• Wireless nodes forward to each other
• Routing protocol determines current path
• Requires connected network, some stability
• Mobility harmful (disrupts network)
• 7DS networks
• No contiguous connectivity
• Temporary clusters of nodes
• Mobility helpful (propagates information)

102
A family of access points
103
Limitations of infostations wireless WAN

• Require communication infrastructure
• not available field operation missions,
  tunnels, subway
• Emergency
• Overloaded
• Expensive
• Wireless WAN access with low bit rates high
  delays

104
Our Approach 7DS

• 7DS Seven Degrees of Separation
• Increase data availability by enabling devices to
  share resources
• Information sharing
• Message relaying
• Bandwidth sharing
• Self-organizing
• No infrastructure
• Exploit host mobility

105
Examples of services using 7DS
news
WAN
events in campus, pictures
where is the closest Internet café ?
pictures, measurements
service location queries
schedule info
autonomous cache
106
Information sharing with 7DS
cache miss
Host C
WLAN
cache hit
data
Host B
Host A
107
Simulation environment
pause time 50 s mobile user speed 0 .. 1.5
m/s host density 5 .. 25 hosts/km2 wireless
coverage 230 m (H), 115 m (M), 57.5 m
(L) ns-2 with CMU mobility, wireless
extension randway model
querier
wireless coverage
dataholder
randway model
108
Simulation environment
pause time 50 s mobile user speed 0 .. 1.5
m/s host density 5 .. 25 hosts/km2 wireless
coverage 230 m (H), 115 m (M), 57.5 m
(L) ns-2 with CMU mobility, wireless
extension
querier
wireless coverage
1m/s
pause
mobile host
data holder
109
Simulation environment
pause time 50 s mobile user speed 0 .. 1.5
m/s host density 5 .. 25 hosts/km2 wireless
coverage 230 m (H), 115 m (M), 57.5 m
(L) ns-2 with CMU mobility, wireless
extension
wireless coverage
v1
110
Dataholders () after 25 min
high transmission power
P2P
Mobile Info Server
Fixed Info Server
2
111
Average delay (s) vs. dataholders ()
Fixed Info Server
one server in 2x2 high transmission power
4 servers in 2x2 medium transmission power
112
Average Delay (s) vs Dataholders ()Peer-to-Peer
schemes
high transmission power
medium transmission power
113
Fixed Info Serversimulation and analytical
results
high transmission power
Probability a host will acquire data by time t
follows 1-e-a?t
114
Message relaying with 7DS
WAN
Gateway
WLAN
Message relaying
Host B
Host A
115
Message relaying

• Take advantage of host mobility to increase
  throughput
• Hosts buffer messages forward them to a gateway
• Hosts forward their own messages to cooperative
  relay hosts
• Restrict number of times hosts forwards

116
Messages () relayed after 25 min (average
number of buffered messages 5)
2
117
7DS node
118
7DS Implementation

• Cache manager (3k lines)
• GUI server (2k lines)
• HTTP client methods (24k lines)
• Proxy server (1k lines)
• UDP multicast unicast (1k)
• Web client server (2k)
• Jar files used (xerces, xml,lucene, html parcer)

119
7DS implementation

• Initial Java implementation on laptop
• Compaq Ipaq (Linux or WinCE)
• Inhand Electronics
• ARM RISC board
• Low power
• PCMCIA slot for storage, network or GPS

120
7DS implementation
121
Message relayed to gateway after 25 min
2
122
Epidemic model

• Carrier is infected, hosts are susceptible
• Transmit to any give host with probability
  hao(h) in interval h
• Pure birth process
• Ttime until data has spread among all mobiles
• ET1/a S

N-1
i1
123
Conclusion

• Research in transition
• foundational ? operational
• universal ? niches
• Downward migration
• servers, PCs ? embedded systems
• professionals ? residential users
• IRT research examples
• location-based ubiquitous communication services
• network reliability
• multimodal networking

124
Other on-going IRT research topics

• Geographic service discovery
• Generic state signaling protocol (IETF NSIS)
• ./ ? ad-hoc web server rescue
• End system service creation (LESS)
• Black box QoS measurement and diagnosis
• Fully distributed multimedia conferencing
• Conferencing floor control
• MarconiNet multicast mobility
• Application-layer mobility

125
Application-focused research

• Event systems for medical environments
• Training for FAA flight controllers
• Enhanced presence systems
• CINEMA SIP-based telecom infrastructure