Tema 1: Tecnologías de red. - GRC
Download
Report
Transcript Tema 1: Tecnologías de red. - GRC
Tema 1:
Tecnologías de red.
Estructura de Internet
Redes “core”
SONET
DWDM
Redes de acceso
Redes cableadas: Ethernet et al.
Redes inalámbricas: IEEE 802.11, UMTS et al.
Transmisión de Datos Multimedia –
http://www.grc.upv.es/docencia/tdm
– Master IC 2007/2008
Transmisión de Datos Multimedia - Master IC 2007/2008
What’s the Internet: “nuts and bolts” view
End systems
Host computer
Network applications
Access networks
Local area networks
communication links
router
server
mobile
local ISP
Network core:
routers
network of networks
regional ISP
company
network
2
workstation
Transmisión de Datos Multimedia - Master IC 2007/2008
3
Internet structure: network of networks
roughly hierarchical
at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T, Cable and
Wireless), national/international coverage
treat each other as equals
Tier-1
providers
interconnect
(peer)
privately
Tier 1 ISP
Tier 1 ISP
NAP
Tier 1 ISP
Tier-1 providers
also interconnect
at public network
access points
(NAPs)
Transmisión de Datos Multimedia - Master IC 2007/2008
Tier-1 ISP: e.g., Sprint
Sprint US backbone network
DS3 (45 Mbps)
OC3 (155 Mbps)
OC12 (622 Mbps)
OC48 (2.4 Gbps)
Seattle
Tacoma
Stockton
San Jose
Cheyenne
Kansas City
New York
Pennsauken
Relay
Wash. DC
Chicago
Roachdale
Anaheim
Atlanta
Fort Worth
Orlando
4
Transmisión de Datos Multimedia - Master IC 2007/2008
Internet structure: network of networks
“Tier-2” ISPs: smaller (often regional) ISPs
Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs
Tier-2 ISP pays
tier-1 ISP for
connectivity to
rest of Internet
tier-2 ISP is
customer of
tier-1 provider
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
5
Tier-2 ISP
NAP
Tier 1 ISP
Tier-2 ISP
Tier-2 ISPs
also peer
privately with
each other,
interconnect
at NAP
Tier-2 ISP
Transmisión de Datos Multimedia - Master IC 2007/2008
Internet structure: network of networks
“Tier-3” ISPs and local ISPs
last hop (“access”) network (closest to end systems)
local
ISP
Local and tier3 ISPs are
customers of
higher tier
ISPs
connecting
them to rest
of Internet
Tier 3
ISP
Tier-2 ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
local
local
ISP
ISP
6
local
ISP
NAP
Tier 1 ISP
Tier-2 ISP
local
ISP
Tier-2 ISP
local
ISP
Transmisión de Datos Multimedia - Master IC 2007/2008
Internet structure: network of networks
a packet passes through many networks!
local
ISP
Tier 3
ISP
Tier-2 ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
7
local
ISP
Tier-2 ISP
local
local
ISP
ISP
NAP
Tier 1 ISP
Tier-2 ISP
local
ISP
Tier-2 ISP
local
ISP
Transmisión de Datos Multimedia - Master IC 2007/2008
Network Access Points (NAPs)
Note: Peers in this context are
commercial backbones..droh
Source: Boardwatch.com
8
Transmisión de Datos Multimedia - Master IC 2007/2008
MCI/WorldCom/UUNET Global Backbone
Source: www.lightreading.com
9
Transmisión de Datos Multimedia - Master IC 2007/2008
The situation in Europe
See: http://www.geant2.net/server/show/nav.1368
1
0
Transmisión de Datos Multimedia - Master IC 2007/2008
Standards
Mandatory vs. voluntary
Allowed to use vs. likely to sell
Example: health & safety standards UL listing for electrical
appliances, fire codes
Telecommunications and networking always focus of standardization
1865: International Telegraph Union (ITU)
1956: International Telephone and Telegraph Consultative Committee
(CCITT)
Five major organizations:
1
1
ITU for lower layers, multimedia collaboration
IEEE for LAN standards (802.x)
IETF for network, transport & some applications
W3C for web-related technology (XML, SOAP)
ISO for media content (MPEG)
Transmisión de Datos Multimedia - Master IC 2007/2008
1
2
Who makes the rules? - ITU
ITU = ITU-T (telecom standardization) + ITU-R (radio) +
development
http://www.itu.int
14 study groups
produce Recommendations:
E: overall network operation, telephone service (E.164)
G: transmission system and media, digital systems and networks (G.711)
H: audiovisual and multimedia systems (H.323)
I: integrated services digital network (I.210); includes ATM
V: data communications over the telephone network (V.24)
X: Data networks and open system communications
Y: Global information infrastructure and internet protocol aspects
Transmisión de Datos Multimedia - Master IC 2007/2008
1
3
ITU
Initially, national delegations
Members: state, sector, associate
Membership fees (> 10,500 SFr)
Now, mostly industry groups doing work
Initially, mostly (international) telephone services
Now, transition from circuit-switched to packet-switched universe &
lower network layers (optical)
Documents cost SFr, but can get three freebies for each email
address
Transmisión de Datos Multimedia - Master IC 2007/2008
IETF
IETF (Internet Engineering Task Force)
see RFC 3233 (“Defining the IETF”)
Formed 1986, but earlier predecessor organizations (1979-)
RFCs date back to 1969
Initially, largely research organizations and universities, now mostly
R&D labs of equipment vendors and ISPs
International, but 2/3 United States
meetings every four months
about 300 companies participating in meetings
but Cisco, Ericsson, Lucent, Nokia, etc. send large delegations
1
4
Transmisión de Datos Multimedia - Master IC 2007/2008
IETF
Supposed to be engineering, i.e., translation of well-understood
technology standards
make choices, ensure interoperability
reality: often not so well defined
Most development work gets done in working groups (WGs)
specific task, then dissolved (but may last 10 years…)
typically, small clusters of authors, with large peanut gallery
open mailing list discussion for specific problems
interim meetings (1-2 days) and IETF meetings (few hours)
published as Internet Drafts (I-Ds)
1
5
anybody can publish draft-somebody-my-new-protocol
also official working group documents (draft-ietf-wg-*)
versioned (e.g., draft-ietf-avt-rtp-10.txt)
automatically disappear (expire) after 6 months
Transmisión de Datos Multimedia - Master IC 2007/2008
1
6
IETF process
WG develops WG last call IETF last call approval (or not)
by IESG publication as RFC
IESG (Internet Engineering Steering Group) consists of area
directors – they vote on proposals
areas = applications, general, Internet, operations and management,
routing, security, sub-IP, transport
Also, Internet Architecture Board (IAB)
provides architectural guidance
approves new working groups
process appeals
Transmisión de Datos Multimedia - Master IC 2007/2008
1
7
IETF activities
general (3): ipr, nomcom, problem
applications (25): crisp, geopriv, impp, ldapbis, lemonade, opes,
provreg, simple, tn3270e, usefor, vpim, webdav, xmpp
internet (18) = IPv4, IPv6, DNS, DHCP: dhc, dnsext, ipoib, itrace,
mip4, nemo, pana, zeroconf
oam (22) = SNMP, RADIUS, DIAMETER: aaa, v6ops, netconf, …
routing (13): forces, ospf, ssm, udlr, …
security (18): idwg, ipsec, openpgp, sasl, smime, syslog, tls,
xmldsig, …
subip (5) = “layer 2.5”: ccamp, ipo, mpls, tewg
transport (26): avt (RTP), dccp, enum, ieprep, iptel, megaco,
mmusic (RTSP), nsis, rohc, sip, sipping (SIP), spirits, tsvwg
Transmisión de Datos Multimedia - Master IC 2007/2008
1
8
RFCs
Originally, “Request for Comment”
now, mostly standards documents that are well settled
published RFCs never change
always ASCII (plain text), sometimes PostScript
anybody can submit RFC, but may be delayed by review (“end run
avoidance”)
see April 1 RFCs (RFC 1149, 3251, 3252)
accessible at http://www.ietf.org/rfc/ and http://www.rfc-editor.org/
Transmisión de Datos Multimedia - Master IC 2007/2008
1
9
IETF process issues
Can take several years to publish a standard
see draft-ietf-problem-issue-statement
Relies on authors and editors to keep moving
often, busy people with “day jobs” spurts three times a year
Lots of opportunities for small groups to delay things
Original idea of RFC standards-track progression:
Proposed Standard (PS) = kind of works
Draft Standard (DS) = solid, interoperability tested (2 interoperable
implementations for each feature), but not necessarily widely used
Standard (S) = well tested, widely deployed
Transmisión de Datos Multimedia - Master IC 2007/2008
2
0
IETF process issues
Reality: very few protocols progress beyond PS
and some widely-used protocols are only I-Ds
In addition: Informational, Best Current Practice (BCP),
Experimental, Historic
Early IETF: simple protocols, stand-alone
TCP, HTTP, DNS, BGP, …
Now: systems of protocols, with security, management,
configuration and scaling
lots of dependencies wait for others to do their job
Transmisión de Datos Multimedia - Master IC 2007/2008
Other Internet standards organizations
ISOC (Internet Society)
legal umbrella for IETF, development work
IANA (Internet Assigned Numbers Authority)
assigns protocol constants
NANOG (North American Network Operators Group)
(http://www.nanog.org)
operational issues
holds nice workshop with measurement and “real world” papers
RIPE, ARIN, APNIC
regional IP address registries dole out chunks of address space to
ISPs
routing table management
2
1
Transmisión de Datos Multimedia - Master IC 2007/2008
2
2
ICANN
Internet Corporation for Assigned Names and Numbers
manages IP address space (at top level)
DNS top-level domains (TLD)
ccTLD: country codes (.us, .uk, …)
gTLDs (.com, .edu, .gov, .int, .mil, .net, and .org)
uTLD (unsponsored): .biz, .info, .name, and .pro
sTLD (sponsored): .aero, .coop, and .museum
actual domains handled by registrars
Tema 1:
Tecnologías de red.
Estructura de Internet
Redes “core”
SONET
DWDM
Redes de acceso
Redes cableadas: Ethernet et al.
Redes inalámbricas: IEEE 802.11, UMTS et al.
Transmisión de Datos Multimedia –
http://www.grc.upv.es/docencia/tdm
– Master IC 2007/2008
Transmisión de Datos Multimedia - Master IC 2007/2008
2
4
IP and Traditional Transport
In the 80’s, software based routers were interconnected via
relatively slow links
56K (early 80’s),
to fractional T1, to full T1,
to T3
This was layered over core TDM infrastructure
Which was intended for voice and circuits
Generally, data folks ignored TDM folks, and vice versa
Transmisión de Datos Multimedia - Master IC 2007/2008
Time Division Multiplexing
Source 1
Source 2
Source 3
MUX
Time
Slot1
Time
Slot2
Time
Slot3
Time
Slot4
TimeS
lot5
TimeS
lot6
SyncB
it
Source 4
Source 5
Source 6
2
5
Sync
Bit
Multiplexed Bit Stream
Sum of sources = Total MUX’d bit stream
Time
Slot1
Time
Slot2
Transmisión de Datos Multimedia - Master IC 2007/2008
2
6
SONET & SDH
SONET - Synchronous Optical NETwork
ANSI/Bellcore standard
SDH - Synchronous Digital Hierarchy
ITU (European) standard
Both standards are practically identical
Standards for a synchronous digital transmission system of TDM
traffic over fiber networks.
Standards based system for data rates above a T3.
Transmisión de Datos Multimedia - Master IC 2007/2008
2
7
SONET/SDH Hierarchy
STS - Synchronous Transport Signals
51.84Mbps - base level of SONET hierarchy
STM - Synchronous Transport Module
155.52Mbps - base level of SDH hierarchy
Exactly equal to STS-3
STS
OC
STS-1
STS-3
STS-12
STS-48
STS-192
STS-768
OC-1
OC-3
OC-12
OC-48
OC-192
OC-768
STM
STM-1
STM-4
STM-16
STM-64
STM-256
Bit Rate
(Mbps)
51.84
155.52
622.08
2488.32
9953.28
39813.12
Transmisión de Datos Multimedia - Master IC 2007/2008
2
8
STS/OC/STM
STS-n and OC-n are identical OC-n names are used for optical interconnects
STS-n names are used for electrical interconnects
OC-n is exactly n times the rate of an OC-1 signal.
STM-1 signal is exactly 3 times the rate of an STS-1 signal
STM-n is exactly n times the rate of an STM-1 signal
Transmisión de Datos Multimedia - Master IC 2007/2008
2
9
ADM, Terminal, Repeater
SONET/SDH terminal - a mux/demux that creates a SONET signal
and terminates paths.
SONET/SDH ADM (Add/Drop Multiplexer) - a mux/demux that can
separate individual STS-n signals from a higher level signal.
SONET/SDH repeater- a physical level regenerator that also
terminates section level overhead to allow section level
management.
Transmisión de Datos Multimedia - Master IC 2007/2008
SONET/SDH - Path/Section/Line
In Sonet/SDH systems a strong designation of levels of overhead
are kept.
Section is lowest level
Repeater to repeater
Line is middle layer
Path is top/longest layer
from entrance to SONET system to exit of SONET system
Path
Line
Section
Line
Section
Section
Line
Section
Section
T3
T3
OC-n
OC-n
Repeater
T3
3
0
OC-n
Terminal
Multiplexer
OC-n
Repeater
Add/Drop
Multiplexer
OC-n
T3
Add/Drop Terminal
Multiplexer Multiplexer
Transmisión de Datos Multimedia - Master IC 2007/2008
SONET/SDH - Section & Line Overhead
The section overhead is the first 3 rows of the first 3 columns (9
bytes) per frame.
The line overhead is the lower 6 rows of the first 3 columns (18
bytes) per frame.
An STS-1 frame consists of 810 bytes (octets) sent in 125µs.
810 * 8 * 8000 = 51.84Mbps
The 810 bytes are arranged as 90 columns x 9 rows
3 columns are overhead
87 columns are actual data
Section
Overhead
Line
Overhead
A1
A2
C1
B1
E1
F1
D1 D2
D3
H1
H2
H3
B2
K1
K2
D4 D5
D6
D7 D8
D9
D10 D11 D12
3
1
Z1
Z2
Z3
87 columns
STS-1 Payload
Transmisión de Datos Multimedia - Master IC 2007/2008
STS concatenated signals
Multiple STS-1s can be grouped together into a single higher bit
rate facility.
Extra overhead bytes are ignored.
Technically, any number of STS-1s can be grouped, but the only
groupings normally supported are:
STS-3C, STS-12C, STS-48C
Generally a grouping must fall on a boundary of the same size
inside of the OC-n carrier
A STS-3C must fall on a boundary of 3
STS-12C must fall on a boundary of 12
Typically used for situations where ATM or Packets are sent over a
SONET network.
3
2
3
3
Transmisión de Datos Multimedia - Master IC 2007/2008
Traditional View of Routers and Links
Transmisión de Datos Multimedia - Master IC 2007/2008
Reality has always been more complex
Terminal
Multiplexer
Terminal
Multiplexer
SONET/SDH
ADM
SONET/SDH
DCS
SONET/SDH
ADM
SONET/SDH
DCS
Terminal
Multiplexer
SONET/SDH
ADM
Terminal
Multiplexer
3
4
SONET/SDH
ADM
SONET/SDH
DCS
SONET/SDH
ADM
Terminal
Multiplexer
SONET/SDH
ADM
Terminal
Multiplexer
Transmisión de Datos Multimedia - Master IC 2007/2008
3
5
Optical Fiber Evolution
Fiber is better than copper wire
Purity – low attenuation and distortion
Multimode
Longer distances,fiber
lower bit error rates
Higher
frequency
– massive
bandwidth
Low
cost –signals
LEDs,
not lasers
Single-mode
fiber
Different
wavelengths
– massive
bandwidth
Many
wavelengths
(modes)
One to
wavelength
– small
core fiber
Immunity
noise
Non-zero
dispersion
shifted
Dispersion – limits bandwidth and distance
Less
interference
anddistances
loss
Security
– difficult
to tap
Optimized
for
longer
Light pulses spread out
Greater
distance (up to 100 km)
Small
size
and weight
Intramodal
– different
delay per mode
Optimized
for
higher bandwidth
Easier
installation
More expensive components – lasers
Typically
km
distance
Bundles
of fibers 2
in
samemaximum
space as point
copper
wire
Minimized
dispersion
shifted to 1550 nm
Minimized dispersion point at 1310 nm
Large
diameter
cores – for
multiple
modes
Suitable
for Erbium-based
optical
amplifiers
Not suitable for EDFA (Erbium Doped Fiber-optic
Silica-based
Initially flat profile
fibers have lowest attenuation at 1550 nm,
Amplifier)
1310end improves performance
not
Stepped
Transmisión de Datos Multimedia - Master IC 2007/2008
Wave Division Multiplexing
SONET/SDH ADM
Single Fiber
SONET/SDH ADM
SONET/SDH ADM
From One Wavelength Per
Fiber to Many
ADM
ADM
WDM Node
WDM Node
ADM
OT
OT
ADM
ADM
ADM
Single Fiber
ADM
ADM
OT = Optical Transponder
3
6
Transmisión de Datos Multimedia - Master IC 2007/2008
WDM System Elements
SONET/S
DH ADM
SONET/
SDH
ADM
SONET/
SDH
ADM
3
7
SONET/
SDH
ADM
SONET/
SDH
ADM
=
Regenerato
rs
SONET/
SDH
ADM
Laser
Output
l1
l1 … ln
OT
Transmisión de Datos Multimedia - Master IC 2007/2008
TDM and WDM Relationship
ln
TDM generates output from
sum of inputs into a single
bit stream
3
8
WDM changes TDM bit stream into
wavelengths between 1532 nm and
1560 nm
Transmisión de Datos Multimedia - Master IC 2007/2008
Dense and Ultra Dense WDM
l1
WDM 8 Lambdas
l2
l2
2.5 Gbps per lambda
l8
EDFA = Erbium Doped Fiber-optic Amplifier
3
9
l1
l8
Transmisión de Datos Multimedia - Master IC 2007/2008
Dense and Ultra Dense WDM
l1
l1
l2
l2
DWDM 40 Lambdas
l39
10 Gbps per lambda
l40
l40
EDFA = Erbium Doped Fiber-optic Amplifier
4
0
l39
Transmisión de Datos Multimedia - Master IC 2007/2008
Dense and Ultra Dense WDM
l1
l1
l2
l2
l3
UDWDM 192 Lambdas
40 Gbps per lambda
l190
l190
l191
l191
l192
4
1
l3
EDFA = Erbium Doped Fiber-optic Amplifier
l192
Tema 1:
Tecnologías de red.
Estructura de Internet
Redes “core”
SONET
DWDM
Redes de acceso
Redes cableadas: Ethernet et al.
Redes inalámbricas: IEEE 802.11, UMTS et al.
Transmisión de Datos Multimedia –
http://www.grc.upv.es/docencia/tdm
– Master IC 2007/2008
Transmisión de Datos Multimedia - Master IC 2007/2008
Los estándares 802.3 de IEEE
suplemento
año
descripción
802.3a
1985
Original 802.3: 10BASE-5 10BASE-2 10BROAD-36
802.3c
1986
Especificaciones de repetidores
802.3d
1987
FOIRL (enlace de fibra)
802.3i
1990
10Base-T Ethernet sobre par trenzado de cobre
802.3j
1993
10Base-F Ethernet sobre fibra
802.3u
1995
100Mbps Ethernet
802.3x e 802.3y
1997
operación full duplex
802.3z
1998
1000Base-X (Gigabit Ethernet)
802.3ab
1999
1000Base-T (GE sobre par trenzado)
802.3ac
1998
Extensiones de trama (hasta 1522 bytes) para VLANs
802.3ad
2000
link aggregation
802.3ae
2002
10 GE
802.3af
2003
PoE (Power over Ethernet). Hasta 15W
802.3ah
2004
Ethernet in First Mile
802.3an
10 Gbase-T (en draft)
Bridging en 802.1D
4
3
802.1w
Cambios y mejoras en el spanning tree
802.1s
Múltiples spanning trees
4
4
Transmisión de Datos Multimedia - Master IC 2007/2008
IEEE 802 standard
Transmisión de Datos Multimedia - Master IC 2007/2008
Estándares de ethernet sobre optico
ITU-T G.7041 Generic Framing Procedure (GFP)
ITU-T X.86 Link Access Protocol (LAPS)
ITU-T H.707 Virtual Concatenation (VCAT)
ITU-T G.7042 Link Capacity Adjustment Scheme (LCAS)
Otros:
IEEE 802.1X Port Based Network Access Control
IEEE 802.1D Ethernet switching
IEEE 802.1Q Virtual LAN (VLAN)
IEEE 802.1P Priorización de tráfico a nivel 2
IETF: MPLS Multi-Protocol Label Switching
IEEE 802.17 Resilient Packet Ring (RPR)
Ver:
http://grouper.ieee.org/groups/802/3/
http://grouper.ieee.org/groups/802/1/
4
5
Transmisión de Datos Multimedia - Master IC 2007/2008
4
6
Trama ethernet
Los datos trasmitidos se encapsulan en un contenedor, que se llama
trama
Este formato de trama DEFINE Ethernet
Históricamente, existen dos tipos de tramas:
»802.3 Framing usa en campo de longitud de trama (Length) despues del
campo de Source Address
»Ethernet II (DIX) Framing usa(ba) el campo de tipo de trama (type)
despues del campo Source Address
Ambos tipos de tramas están definidos y soportados dentro de IEEE
802.3
Transmisión de Datos Multimedia - Master IC 2007/2008
4
7
Trama ethernet
El tamaño de trama varía desde 64 a 1518 Bytes, excepto cuando
se usa el identificador (tag) de VLAN
Transmisión de Datos Multimedia - Master IC 2007/2008
802.1Q/P
3
User Priority
1
CFI
12
Bits of VLAN ID (VIDI) to identify possible VLANs
User Priority- Defines user priority, giving eight (2^3) priority levels. IEEE 802.1P defines the
operation for these 3 user priority bits.
CFI- Canonical Format Indicator is always set to zero for Ethernet switches. CFI is used for
compatibility reason between Ethernet type network and Token Ring type network. If a frame
received at an Ethernet port has a CFI set to 1, then that frame should not be forwarded as it is
to an untagged port.
VID- VLAN ID is the identification of the VLAN, which is basically used by the standard 802.1Q.
It has 12 bits and allow the identification of 4096 (2^12) VLANs. Of the 4096 possible VIDs, a
VID of 0 is used to identify priority frames and value 4095 (FFF) is reserved, so the maximum
possible VLAN configurations are 4,094.
Length/Type- 2 bytes. This field indicates either the number of MAC-client data bytes that are
contained in the data field of the frame, or the frame type ID if the frame is assembled using an
optional format.
Data- Is a sequence of nbytes (48=< n =<1500) of any value. The total frame minimum is
64bytes.
Frame check sequence (FCS)- 4 bytes. This sequence contains a 32-bit cyclic redundancy
check (CRC) value, which is created by the sending MAC and is recalculated by the receiving MAC
to check for damaged frames.
4
8
Transmisión de Datos Multimedia - Master IC 2007/2008
Servicios Metropolitanos
Algunos servicios son:
Conectividad Internet
Transparent LAN service (punto a punto LAN to LAN)
L2VPN (punto a punto o multipunto a multipunto LAN to LAN)
Extranet
LAN a Frame Relay/ATM VPN
Conectividad a centro de backup
Storage area networks (SANs)
Metro transport (backhaul)
VoIP
Algunos se están ofreciendo desde hace años. La diferencia está en
que ahora se ofrecen usando conectividad Ethernet !!
4
9
Casa
Residencial
Transmisión de Datos Multimedia - Master IC 2007/2008
Evolución de Ethernet
Acceso
Distribución Metro
ATM ADSL
T1/E1
FR
ATM
ATM
SONET/SDH
ATM
SONET/SDH
Optical Ethernet
EoMPLS
VPLS
EoRPR
NG-SONET(EoS)
Metro DWDM
Optical Ethernet
EoMPLS
VPLS
RPR
NG-SONET(EoS)
Metro DWDM
MDU
Global
Internet
STU
Empresa
MTU
IP ADSL
IP VDSL
EPON
EFM
Optical Ethernet
EoRPR
NG-SONET(EoS)
5
0
Metro Core
Global
Internet
Transmisión de Datos Multimedia - Master IC 2007/2008
Servicio Ethernet – Modelo de referencia
Customer Equipment (CE) se conecta a
través de UNI
CE puede ser un
router
Bridge IEEE 802.1Q (switch)
UNI (User Network Interface)
Standard IEEE 802.3 Ethernet PHY and MAC
10Mbps, 100Mbps, 1Gbps or 10Gbps
Soporte de varias clases de servicio (QoS)
Metro Ethernet Network (MEN)
CE
UNI
Metro
Ethernet
Network
(MEN)
Puede usar distintas tecnologías de transporte
CE
y de provisión de servicio
SONET/SDH, WDM, PON, RPR, MAC-in-MAC,
QiQ (VLAN stack), MPLS
5
1
CE
UNI
Transmisión de Datos Multimedia - Master IC 2007/2008
Servicio Ethernet – Modelo (2)
Sobre el anterior modelo, se añade un cuarto ingrediente: una
Ethernet Virtual Connection (EVC)
EVC: es una asociación entre dos o más UNI
Es creada por el proveedor del servicio para un cliente
Una trama enviada en un EVC puede ser enviada a uno o más UNIs del
EVC:
Nunca será enviada de vuelta al UNI de entrada.
Nunca será enviada a un UNI que no pertenezca al EVC.
Las EVC´s pueden ser:
Punto a punto (E-Line)
Multipunto a multipunto (E-LAN)
Cada tipo de servicio ethernet tiene un conjunto de atributos de
servicio y sus correspondientes parámetros que definen las
capacidades del servicio.
5
2
Transmisión de Datos Multimedia - Master IC 2007/2008
Atributos de un servicio en particular Ethernet
Multiplexación de servicios
Asocia una UNI con varias EVC. Puede ser:
Hay varios clientes en una sóla puerta (ej. En un POP UNI)
Hay varias conexiones de servicios distintos para un solo cliente
Transparencia de VLAN
Significa que proveedor del servico no cambia el identificador de la
VLAN ( el MEN aparece como un gran switch)
En el servicio de acceso a Internet tiene poco importancia
“Bundling”
Más de una VLAN de cliente está asociada al EVC en una UNI
Etc.
5
3
Transmisión de Datos Multimedia - Master IC 2007/2008
Atributos
Atributos de UNI:
Atributos de EVC:
5
4
identificador, tipo de medio, velocidad, duplex, etc
Atributo de soporte de VLAN tag
Atributo de multiplexación de servicio
Bundling attribute
Security filters attribute
etc
Parámetros de tráfico (CIR, PIR, in, out, etc)
Parámetros de prestaciones (delay, jitter, etc)
Parámetros de Clase de Servicio (VLAN-ID, valor de .1p, etc)
Atributo de Service frame delivery
Unicast frame delivery
Multicast frame delivery
etc
Transmisión de Datos Multimedia - Master IC 2007/2008
Servicio Ethernet Line (E-Line)
Point-to-Point
Ethernet Virtual Circuits
(EVC)
Servers
UNI
IP Voice
IP PBX
Metro
Ethernet
Network
CE
Data
CE
1 or more
UNIs
IP Voice
UNI
CE
5
5
Data
Video
Transmisión de Datos Multimedia - Master IC 2007/2008
5
6
Servicio Ethernet Line (E-Line)
Una E-Line puede operar con ancho de banda dedicado ó con un
ancho de banda compartido.
EPL: Ethernet Private Line
Es un servicio EVC punto a punto con un ancho de banda dedicado
El cliente siempre dispone del CIR
Normalmente en canales SDH (en NGN) ó en redes MPLS
Es como una línea en TDM, pero con una interfaz ethernet
EVPL:Ethernet Virtual Private Line
En este caso hay un CIR y un EIR y una métrica para el soporte de
SLA´s
Es similar al FR
Se suele implementar con canales TDM compartidos ó con redes de
conmutación de paquetes usando SW´s y/o routers
Transmisión de Datos Multimedia - Master IC 2007/2008
Servicio Ethernet LAN (E-LAN)
Multipoint-to-Multipoint
Ethernet Virtual Circuit
(EVC)
IP Voice
Servers
UNI
UNI
Data
IP PBX
CE
Metro
Ethernet
Network
CE
IP Voice
CE
UNI
UNI
CE
IP Voice
Data
Data
5
7
Transmisión de Datos Multimedia - Master IC 2007/2008
Servicio Ethernet LAN (E-LAN)
Una E-LAN puede operar con ancho de banda dedicado ó con un
ancho de banda compartido.
EPLan: Ethernet Private LAN
Suministra una conectividad multipunto entre dos o más UNI´s, con un
ancho de banda dedicado.
EVPLan: Ethernet Virtual Private LAN
Otros nombres:
VPLS: Virtual Private Lan Service
TLS: Transparent Lan Service
VPSN: Virtual Private Switched Network
La separación de clientes vía encapsulación: las etiquetas de VLAN´s
del proveedor no son suficientes (4096)
Es el servicio más rentable desde el punto de vista del proveedor.
5
8
Transmisión de Datos Multimedia - Master IC 2007/2008
5
9
Metro tecnologías...
Los servicios Metro Ethernet services no necesitan que toda la red
de nivel 2 sea ethernet; tambien puede ser:
Ethernet over SONET/SDH (EOS)
Resilient Packet Ring (RPR)
Ethernet Transport
Ethernet sobre MPLS
Transmisión de Datos Multimedia - Master IC 2007/2008
6
0
Implementaciones de los EVC (Ethernet Virtual Conn.)
Virtual Private LAN Services
(VPLS)
Es un tipo de VPN de nivel 2
La red del proveedor emula la
función de un conmutador de
LAN ó bridge, para conectar
todos los UNI del cliente, para
formar una única VLAN
Los requerimientos en el CE
son distintos a los de antes
Cada PE debe actuar como un
bridge de ethernet
Se puede implementar
poniendo ethernet en MPLS ó
bien, haciendo stack de VLAN
usando Q-in-Q
Ver http://vpls.org
Tema 1:
Tecnologías de red.
Estructura de Internet
Redes “core”
SONET
DWDM
Redes de acceso
Redes cableadas: Ethernet et al.
Redes inalámbricas: IEEE 802.11, UMTS et al.
Transmisión de Datos Multimedia –
http://www.grc.upv.es/docencia/tdm
– Master IC 2007/2008
Transmisión de Datos Multimedia - Master IC 2007/2008
Taxonomy
Wireless
Networking
Single
Hop
Infrastructure-based
(hub&spoke)
802.11
802.16
Cellular
Networks
6
2
Multi-hop
Infrastructure-less
(ad-hoc)
802.11
Infrastructure-based
(Hybrid)
Infrastructure-less
(MANET)
Bluetooth
Wireless Sensor
Networks
Wireless Mesh
Networks
Car-to-car
Networks
(VANETs)
Transmisión de Datos Multimedia - Master IC 2007/2008
WLANs, El estándar IEEE 802.11
En el 1997 nace el:
IEEE Working Group for WLAN Standards:
http://grouper.ieee.org/groups/802/11/index.html
Se define el MAC y tres diferentes niveles físicos, que operan a
1Mbps y 2Mbps:
Infrarrojos (IR) en banda base
Frequency hopping spread spectrum (FHSS), banda de 2,4 GHz
Direct sequence spread spectrum (DSSS), banda de 2,4 GHz
IEEE Std 802.11a (diciembre 1999):
Otro estándar de nivel físico: Orthogonal frequency domain multiplexing
(OFDM)
Network
Network
Hasta 54 Mbps
L
IEEE 802.2. LLC
IEEE Std 802.11b (enero 2000):
Extensión de DSSS; hasta 11 Mbps
IEEE Std 802.11g (Junio 2003)
Etc.
6
3
Data
Link
L
C
M
A
C
ISO 8802.2
Data Link
Ethernet
v2.0
Physical
http://standards.ieee.org/getieee802/802.11.html
IEEE
802.3
IEEE
802.11
ISO
8802.3
ISO
8802.11
Transmisión de Datos Multimedia - Master IC 2007/2008
Arquitectura 802.11
Estructura descentralizada
Flexible:
Redes pequeñas y grandes,
Redes transitorias y
permanentes
Control del consumo de
potencia
Componentes:
Estación (STA)
Access Point (AP)
6
4
Independent Basic Service Set (IBSS)
Basic Service Set (BSS)
Extended Service Set (ESS)
infrastructure Basic Service Set (BSS)
CSMA/CA con binary
Servicios sin contienda
exponential backoff
El protocolo mínimo consiste de
dos tramas: DATOS+ACK
El standard propone RTS-CTSDATOS-ACK
Point
Coordination
Function (PCF)
Distributed Coordination
Function (DCF)
Los 5 valores de timing:
• Slot time
• SIFS: short interframe space
• PIFS: PCF interframe space (=SIFS+1slot)
• DIFS: DCF interframe space (=SIFS+2slots)
• EIFS: extended interframe space
DIFS
DIFS
ventana de contienda
PIFS
SIFS
defer access
slot
busy medium
6
5
MAC
Transmisión de Datos Multimedia - Master IC 2007/2008
El MAC: entrega de datos fiable
Servicios
con contienda
Transmisión de Datos Multimedia - Master IC 2007/2008
Mecanismo de detección de portadora
Se basa en el network allocation vector (NAV)
DIFS
fuente
data
RTS
SIFS
destino
SIFS
SIFS
ACK
CTS
DIFS
otro STA
NAV (RTS)
NAV (CTS)
defer access
6
6
ventana de contienda
Transmisión de Datos Multimedia - Master IC 2007/2008
6
7
QoS: 802.11e and WMM™
QoS needed for audio, voice, video
Original Wi-Fi® didn’t have QoS
IEEE 802.11e is new QoS standard
Still in process after more than 4 years
Both “prioritized” and “guaranteed” QoS
WMM (Wi-Fi Multimedia)
Prioritized QoS subset of 802.11e draft
Widely accepted by 802.11e members
Added to Wi-Fi certification in September 2004
Already included in some products
6
8
Transmisión de Datos Multimedia - Master IC 2007/2008
WMM™ for Video
Source: Wi-Fi Alliance
Transmisión de Datos Multimedia - Master IC 2007/2008
Bluetooth Specifications
Bluetooth is a system solution comprising hardware, software and
interoperability requirements. The Bluetooth specifications specify
the complete system.
De facto standard - open specifications.
Two part document - Volume 1:Core and Volume 2:Profiles.
Bluetooth specs developed by Bluetooth SIG.
February 1998: The Bluetooth SIG is formed
promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba
May 1998: The Bluetooth SIG goes “public”
July 1999: 1.0A spec (>1,500 pages) is published
December 1999: ver. 1.0B is released
December 1999: The promoter group increases to 9
3Com, Lucent, Microsoft, Motorola
February 2000: There are 1,500+ adopters
0.7 ---> 0.9 ---> 1.0A ---> 1.0B ---> 1.1 -->
November 2003: release 1.2
Currently (November 2004), release 2.0
6
9
(aka EDR or Extended Data Rate) triples the data rate up to about 2
Mb/s
7
0
Transmisión de Datos Multimedia - Master IC 2007/2008
release 2.0: the new partitioning
Transmisión de Datos Multimedia - Master IC 2007/2008
7
1
Bluetooth usage
Low-cost, low-power, short range radio a cable replacement
technology
Common (File transfer, synchronisation, internet bridge, conference
table)
Hidden computing (background synchronisation, audio/video player)
Future (PC login, remote control)
Why not use Wireless LANs?
power
cost
Transmisión de Datos Multimedia - Master IC 2007/2008
7
2
Bluetooth RF
1 Mb/s symbol rate
Normal range
10m (0dBm)
Optional range
100m (+20dBm)
Normal transmission power 0dBm (1mW)
Optional transmission power
-30 to +20dBm (100mW)
Receiver sensitivity
-70dBm
Frequency band
2.4Ghz ISM band
Gross data rate
1Mbit/s
Max data transfer
721+56kbps/3 voice channels
Power consumption 30uA(max), 300uA(standby), ~50uA(hold/park)
Packet switching protocol based on frequency hop scheme with
1600 hops/s
Transmisión de Datos Multimedia - Master IC 2007/2008
7
3
Bluetooth Power Class Table
Power Class
Max Output Power
Max Output Power
Expected Range
Range in
Free Space
Class 1
100mW
20dBm
42m
300m
Class 2
2.5mW
4dBm
16m
50m
Class 3
1mW
0dBm
10m
30m
Transmisión de Datos Multimedia - Master IC 2007/2008
Bluetooth Network Topology
Bluetooth devices have the ability to work as a slave or a master in
an ad hoc network. The types of network configurations for
Bluetooth devices can be three.
Single point-to-point (Piconet): In this topology the network consists of
one master and one slave device.
Multipoint (Piconet): Such a topology combines one master device and
up to seven slave devices in an ad hoc network.
o Scatternet: A Scatternet is a group of Piconets linked via a slave device
in one Piconet which plays master role in other Piconet. The Bluetooth standard
M
M
M
Master/Slave
S
M
S
S
7
4
S
S
S
i) Piconet (Pointto-Point)
S
S
ii) Piconet (Multipoint)
S
S
iii) Scatternet
does not describe any
routing protocol for
scatternets and most of
the hardware available
today has no capability
of forming scatternets.
Some even lack the
ability to communicate
between slaves of one
piconet or to be a
member of two piconets
at the same time.
Transmisión de Datos Multimedia - Master IC 2007/2008
Bluetooth stack: short version
Applications
RFCOMM
SDP
L2CAP
HCI
Link Manager
Baseband
RF
7
5
Transmisión de Datos Multimedia - Master IC 2007/2008
Transport Protocol Group (contd.)
Radio Frequency (RF)
Sending and receiving
modulated bit streams
Baseband
Defines the timing, framing
Flow control on the link.
The Radio, Baseband and Link Manager
are on firmware.
The higher layers could be in software.
The interface is then through the Host
Controller (firmware and driver).
The HCI interfaces defined for Bluetooth
are UART, RS232 and USB.
Link Manager
Managing the connection
states.
Enforcing Fairness among
slaves.
Power Management
Logical Link Control & Adaptation Protocol
Handles multiplexing of higher
level protocols
Segmentation & reassembly of
large packets
Device discovery & QoS
7
6
BLUETOOTH SPECIFICATION, Core Version 1.1 page 543
Source: Farinaz Edalat, Ganesh Gopal, Saswat Misra, Deepti Rao
Transmisión de Datos Multimedia - Master IC 2007/2008
7
7
Physical Link Definition
Synchronous Connection-Oriented (SCO) Link
circuit switching
symmetric, synchronous services
slot reservation at fixed intervals
Asynchronous Connection-Less (ACL) Link
packet switching
(a)symmetric,
asynchronous services
polling access scheme
Transmisión de Datos Multimedia - Master IC 2007/2008
7
8
ACL data rates
P
a
c
k
e
tt
y
p
e
N
a
m
e
S
y
m
m
e
t
r
ic
(
k
b
p
s
)
A
s
y
m
m
e
t
r
ic
(
k
b
p
s
)
1s
lo
t+
F
E
C
D
M
1
1
0
8
.8
1
0
8
.8
1
0
8
.8
1s
lo
t
D
H
1
1
7
2
.8
1
7
2
.8
1
7
2
.8
3s
lo
t+
F
E
C
D
M
3
2
5
6
.0
3
8
4
.0
5
4
.4
3s
lo
t
D
H
3
3
8
4
.0
5
7
6
.0
8
6
.4
5s
lo
t+
F
E
C
D
M
5
2
8
6
.7
4
7
7
.8
3
6
.3
5s
lo
t
D
H
5
4
3
2
.6
7
2
1
.0
5
7
.6
Transmisión de Datos Multimedia - Master IC 2007/2008
Multi-slot packets
fn
Single slot
Three slot
Five slot
7
9
fn+1
fn+2
fn+3
fn+4
fn+5
Transmisión de Datos Multimedia - Master IC 2007/2008
Symmetric single slot
fn
Master
Slave
8
0
fn+1
fn+2
fn+3
fn+4
fn+5 fn+6
fn+7
fn+8
fn+9
fn+10 fn+11 fn+12
Transmisión de Datos Multimedia - Master IC 2007/2008
Mixed Link Example
MASTER
SLAVE 1
SLAVE 2
SLAVE 3
8
1
SCO
ACL
SCO
ACL
ACL SCO
SCO
ACL
Transmisión de Datos Multimedia - Master IC 2007/2008
Bluetooth Connection States
There are four Connection states on
Bluetooth Radio:
Active: Both master and slave participate
actively on the channel by transmitting or
receiving the packets (A,B,E,F,H)
Sniff: In this mode slave rather than
listening on every slot for master's
message for that slave, sniffs on
specified time slots for its messages.
Hence the slave can go to sleep in the
free slots thus saving power (C)
Hold: In this mode, a device can
temporarily not support ACL packets and
go to low power sleep mode to make the
channel available for things like paging,
scanning etc (G)
Park: Slave stays synchronized but not
participating in the Piconet, then the
device is given a Parking Member
Address (PMA) and it loses its Active
Member Address (AMA) (D,I)
A
H
B
C
Master
H
D
E
I
G
Bluetooth Connection States
8
2
C
F
Transmisión de Datos Multimedia - Master IC 2007/2008
Bluetooth Forming a Piconet
Inquiry: Inquiry is used to find the
identity of the Bluetooth devices in the
close range.
Inquiry Scan: In this state, devices are
listening for inquiries from other devices.
Inquiry Response: The slave responds
with a packet that contains the slave's
device access code, native clock and
some other slave information.
Page: Master sends page messages by
transmitting slave's device access code
(DAC) in different hop channels.
Page Scan: The slave listens at a single
hop frequency (derived from its page
hopping sequence) in this scan window.
Slave Response: Slave responds to
master's page message
Master Response: Master reaches this
substate after it receives slave's response
to its page message for it.
Master
Inquiry
Slave
1
Inquiry Scan
2
3
Page
Inquiry
Response
4
5
Page Scan
Slave Response
6
Master
Response
7
Connection
Connection
Forming a Piconet Procedures
8
3
Tema 1:
Tecnologías de red.
Estructura de Internet
Redes “core”
SONET
DWDM
Redes de acceso
Redes cableadas: Ethernet et al.
Redes inalámbricas: IEEE 802.11, UMTS et al.
Transmisión de Datos Multimedia –
http://www.grc.upv.es/docencia/tdm
– Master IC 2007/2008
Transmisión de Datos Multimedia - Master IC 2007/2008
2G: Technology Summary
TDMA: Time Division Multiple Access
Standardized in 1990 as IS-54
Provides 3-6 times capacity increase over AMPS (1G)
Peak data rate of 14.4kpbs (can bundle up to 8 channels)
Introduced authentication and encryption for security
GSM: Global System of Mobile communications
Standardized in 1992, based on TMDA technology
Improved battery life over TDMA
GPRS peak data rates of 140 kbps; EDGE data rates of 180kbps
CDMA: Code Division Multiple Access
Standardized in 1993 as IS-95
Provides 1.5-2 times capacity increase over TDMA
Peak data rate of 14.4kpbs (can bundle up to 8 channels)
8
5
Transmisión de Datos Multimedia - Master IC 2007/2008
8
6
2G: Winners & Losers
TDMA
Marginally better capacity than GSM, marginally worse battery life
No evolution path beyond 2G – DEAD END !!
CDMA
Lots of hype on capacity, delivered on upwards of 2x capacity
improvement over TDMA/GSM
Clear evolution to 3G
GSM
International Roaming and Compatibility
Clear evolution to 3G
Defacto Global Standard
Transmisión de Datos Multimedia - Master IC 2007/2008
Evolution to 3G
Drivers: Capacity, Data Speed, Cost
Expected market share
TDMA
GSM
GPRS
2G
CDMA2000
1x
First Step into 3G
EDGE
Evolution
3GPP Core
Network
WCDMA
PDC
cdmaOne
8
7
EDGE
CDMA2000
1x EV/DO
3G phase 1
90%
HSDPA/HSUPA
CDMA2000
EV/DO Rev A
Evolved 3G
10%
Transmisión de Datos Multimedia - Master IC 2007/2008
Mobile Networks Evolution
Download
Speed
HSDPA
1-10 Mbps
250-384 kbps
UMTS
90-180 kbps
40 kbps
1995
8
8
EDGE
GPRS
2005
2015
Transmisión de Datos Multimedia - Master IC 2007/2008
3G = new network
GSM/GPRS
Radio network
2G SGSN
Packet switched
Core network
3G SGSN
GGSN
External IP
network
PCU
BSC
GSM
GPRS
UMTS/
HSDPA
HLR
UMTS/HSDPA
Radio network
RNC
2G MSC
3G MSC
GMSC
External
voice
network
8
9
Circuit switched
Core network
Transmisión de Datos Multimedia - Master IC 2007/2008
3G Network = The Future
New network
No voice overload
Increased capacity by Spectrum efficiency
Better performances
Higher throughput Faster download (Max 384kbps)
Lower latency Faster browsing
Better Services
Seamless hand-over to GPRS (service continuity)
New way to design applications
Video
Future proof technology : HSDPA
9
0
Transmisión de Datos Multimedia - Master IC 2007/2008
3G/HSDPA for business innovation
text picture video
Text messaging
Voice
Push email
Photo & Picture
Messaging
Customized
infotainment
Video Telephony
Mobile TV
Full track music
Enhanced email
2G/EDGE
3G / HSDPA
SPEED
9
1
High speed internet access
High speed LAN access
Transmisión de Datos Multimedia - Master IC 2007/2008
…and Beyond
Technology Convergence on OFDM (Orthogonal Frequency Division
Multiple Access)
WIMAX
Standardized by IEEE 802.16, evolution of 802.11 (Wi-Fi)
Improved bandwidth, encryption and coverage over WiFi
Theoretical peak data rates of 70Mbps (practical peak ~2Mbps)
Improved QoS better enables applications such as VoIP or IPTV
Ideal application is for “last mile” connectivity to the home or business
Intel plans to embed WiMAX chips as part of ‘Intel Inside’
L3GTE/HSOPA
Early standardization work starts in 3GPP R8
Improved bandwidth, latency over UMTS/HSxPA
Radio technology based on MIMO-OFDM, peak data rates of up to
70Mbps
Network simplification
9
2
Transmisión de Datos Multimedia - Master IC 2007/2008
Market Segments
Voice
Cellular
Broadband
Mobile
2.5G
WiMAX 16e
HSDPA to OFDM
EV-DO to OFDM
Local
WiFi
Cordless
802.11a/b/g
802.11n MIMO
Mesh
Fixed
POTS
9
3
Dialup
WiMAX 16d
DSL / Cable
Transmisión de Datos Multimedia - Master IC 2007/2008
Network Convergence - IMS
Unlicensed Mobile Access (UMA) and the IP Multimedia Subsystem (IMS) -- two standard architectures under the 3GPP
umbrella -- both support fixed-mobile convergence (FMC). But their approaches to FMC have little in common. UMA is a
highly constrained approach to a single service -- dual-mode access to GSM networks -- while IMS is an open platform for
all types of services and all types of networks. UMA offers mobile network operators (MNOs) a quick fix, but IMS promises
profitable new services and sustainable growth for all service providers.
Access
Network
PDG
WLAN
Media
Resources
Applications
Multimedia
Services
Messaging
Services
Web / WAP
Services
Audio/
Video
Streaming
Services
GGSN
Service Control
GPRS
UMTS
ASN
CSN
WiMAX
MRF
HSS/
AAA
ASN
ASGW
EASGW
Presence / GLMS
TDM & Packet
Interworking
Call
Session
Controller
R4
CDMA
PSTN
MGCF
(CS2000)
PDF
MG15000
HSOPA
OFDM/MIMO
ASG
IP/MPLS Core
BRAS
9
4
Peer IP
Network
Transmisión de Datos Multimedia - Master IC 2007/2008
Market Trends
Media Convergence – Multiple Play
Dual Play: High-Speed Internet & Fixed Line
Triple Play: Dual Play + TV
Quadruple Play: Triple Play + Wireless
Challenge: Consolidated Invoice and Price Points
Fixed Mobile Convergence
Dual Mode connectivity
Cellular / Cordless (DECT, ADSL/Bluetooth)
WLAN / WWAN
Challenge: Technology standardization
MVNO – Mobile Virtual Network Operator
9
5
Wireless Service Reseller, wholesales access from wireless operators
Discount & Lifestyle MVNO’s
Segment, Product, Utilization Driven
Challenge: Market Saturation & Service Differentiation
Transmisión de Datos Multimedia - Master IC 2007/2008
9
6
Market Trends (continued)
Multimedia – use of several media types to convey information
Effective information delivery across many disciplines: art, education,
telecommunications, medicine
IMS enables multimedia services for mobile users
VoIP
Challenge: User Interface, Form Factor, lack of “killer app”
Presence – Always on, always connected
Combine Mobility & Reachability
Effectively bring Popularity of IM to mobile phones (AOL, Yahoo!, MSN,
Skype)
Opportunity for standardization & interworking based on SIP/SIMPLE
Challenge: Standardization & always on connectivity