Post on 07-Nov-2014
description
Telecommunication Services - 3
Contents
Transport and value-added services
Layering
The Internet Value Chain
Business Models
Telecommunication Services - 4
What are networks
Data transport service between
applications
access
Telecommunications network (Logical) circuit services
Packet routing services
ΑΤΜ
Frame Relay
SDH
ISDN
Ethernet
Internet (IP)
Pipe for bits = optical fiber
satellite channel
wireless channel
Telecommunication Services - 5
Connection and connectionless services
Connection-oriented services have the semantics of a
directed virtual pipe (or perhaps a tree)
R bps, delay T, error rate r
Deliver message of size M to A,B with delay T and ber = r
AB
Connectionless services have the semantics of a
datagram service (perhaps to multiple destinations)
Telecommunication Services - 6
Multiplexing
1
2
Fixed TDM
(circuit-switching)
1
2
Statistical TDM
(packet-switching)
Telecommunication Services - 7
Layering in multiplexing
light path
SDH connection
ΑΤΜ VP
IP flow
Application creates flow between Α - Β. What technology will the network choose to support the flow?
Light path: 2.5 GbpsSDH: 155-2.5Gbps (PDH:34Mbps)ATM: 0-2.5GbpsIP: 0-...
pipes of constant size
Fills what it finds! (does not define pipe)
Telecommunication Services - 8
A hierarchy of transport services
guaranteed BW,
Fine - medium granularity
guaranteed BW
Protocol transparency
ATM,
FR
SONET,
SDH
shared+ guaranteed BW
Ethernet
Fiber with DWDM
shared BW
(no QOS)
TCP/IP, UDP/IP
x/IP: short – long lived bursty connections, edges control connection setup,
no BW guarantees, statistical multiplexing
ATM, FR: long lived connections, network controls connection setup, fixed BW
Ethernet: two modes: shared BW (for short lived bursty connections)+ guaranteed
BW (for long lived fixed rate connections)
Fiber using DWDM: long lived connections (for now), protocol transparency
medium – coarse granularity
Telecommunication Services - 10
The Internet Value Chain
Infrastructure Services Layer: simple services that are bought from the other layers
Bit-pipe level connectivity, equipment, call-center services, billing
Internet Services Layer:
End-to-End Connectivity Services: IP connectivity services(unicast, multicast, streaming,…), connection with applications (data centers) and with users
– data center, IP backbone, access, end-user IP network, distribution
Content Providing Services: content services: applications, telecommunication services to the end-user, e-commerce
– Application Service Provider (ASP), Content Provider (CP), Electronic Marketplace Provider (EMP), Communication Service Provider, Internet Retailer
End-User Layer
Telecommunication Services - 11
The Internet Value Chain (cont.)
userApplications
and content
(ASP)
Server farm
Backbone
Access
ISP
Bit pipes
Telecommunication Services - 12
The Internet Value Chain (cont.)
Internet Service Layer
Financial
Service Provider
Connectivity Provider
Information Provider
End-User
Billing
Service Provider
Infrastructure Layer
Network Component
Service Provider
(Dark fiber, , SONET
Ethernet, Satellite,…)
Telecommunication Services - 13
Internet Retailer
Internet Service Provider
Information ProviderConnectivity Provider
End-User
Access Provider
Backbone Provider
Data Center Application Service Provider
Content Provider
Internet Retailer
Communication Service Provider
End-User Network Provider Market Place Provider
ISP Reference Business Model
Telecommunication Services - 14
End- user
Backbone
Provider
Generic
ISP
Internet
Retailer
Business Relationship
Backbone
Provider
Communication
Service provider
Access
Provider
Stakeholder
Business Model: typical ISP
Telecommunication Services - 15
Data Center Provider
End User Information Provider
Access and Backbone Provider
Money flow
Physical Line
Connection
Value Chain Example
Telecommunication Services - 16
Examples of ISP Business Models
XXCommunication
XXRetailer
XContent
XApplication
XXData Center
XBackbone
XXXXAccess
AkamaiExodusCovadMindspring/Ear
thlinkAOLService
Telecommunication Services - 17
AOL Mindspring
/EarthlinkCovad Exodus Akamai
Customer Residential
End-Users
Residential
End-Users
Business
Customers
Business
Customers
Business
End-Users
Addressed
Needs of
Customers
Backbone
Connectivity
and Content
Broadband
and
Narrowband
and Hosting
Broadband
Access and
VPN
Reliable
Information
Delivery
Fast Content
and Streaming
Media
Delivery
Owned
Services
Content Hosting Access and
Backbone
Backbone and
Data Centers
Data Centers
Bundled in
Services
Access and
Backbone
Access, Data
Center, and
Backbone
--- Broadband
Access
---
ISPs market segmentation
Telecommunication Services - 18
Backbone
Provider
Access
Provider
Internet
Retailer
Content
Provider
AOLInternet
Retailer
Content
ProviderCommunication
Service
Provider
End User
Stakeholder
Business Relationship
AOL Business Model
Telecommunication Services - 20
Contents
Service contracts
Best-effort and guaranteed services
Policing
Telecommunication Services - 21
Service contracts
Services = packet/cell transport service (1->1, 1->M)
Traffic contract = connection’s (or flow’s) performance +
traffic profile user must conform to
Unicast: usually sender initiates service establishment
Multicast: might be receiver initiated, more flavours
Network
Service
Interface
Service contract
Telecommunication Services - 22
Guaranteed and best-effort services
Guaranteed services (contracts):
network provides some form of performance guarantees in terms of loss, delay, and delay jitter
users request some amount of resources
subject to admission control
Best-effort services (contracts):
no specific performance guarantees
performance deteriorates during overload periods
no specific bandwidth request
intended for applications that can adapt sending rate
– elastic applications
Telecommunication Services - 23
Guaranteed services
Performance guarantees
Quality of Service (QoS): loss, delay, and delay jitter
statistical (e.g., loss < 10-7) or deterministic (delay < 30 ms)
Required mechanisms:
Connection Admission Control (CAC)
Policing
User-network traffic contract: connection’s QoS and traffic description:
Network promises to support the specified QoS,
provided the user’s traffic is within his traffic contract
Telecommunication Services - 24
Best-effort services
No specific performance guarantees, but can provide some form of fair treatment to different connections
Feedback mechanisms inform source of congestion
Explicit (binary, rate), implicit (packet loss)
Mechanisms in routers/switches to share bandwidth, enforce fairness, etc.
Example of source behaviour
increase (additive) when there is no congestion
decrease (multiplicative) when there is congestion
Examples:
ABR: rate-based flow control (EFCI, Explicit Rate)
Internet: TCP flow control
Telecommunication Services - 25
Policing: leaky buckets
r = leak rate (cells/s) , b = bucket size (cells)
Real cell arriving
Virtual cell
b cells
r cells/s
Arriving cell = conforming : there is space in token bucket
= non-conforming : no space for complete cell
Case of variable size cells (packets): measure r in bytes/s
Telecommunication Services - 26
The Leaky Bucket
copier
1/s 100/s
.1
100 same connections
10
Properties:
• the central buffer never
overflows
• maximum delay = .1s
In time t the source can transfer
maximum volume of liquidt1.
t1.
Telecommunication Services - 28
What is interconnection
Technologies: circuit switched, packet switched
Circuit switched: leased lines, ISDN (based on PSTN)
Packet switched: ATM, Frame Relay, IP VPNs
Dark fiber, light paths
LAN 1 LAN 2
Router A Router B
WAN service
Telecommunication Services - 29
Service contracts
The network service is described by a contract (Service Level Agreement, SLA)
The contract includes
the responsibilities of the network
– maximum delay, losses, jitter, …
the responsibilities of the client
– maximum rate, burstiness, ...
SLA
Telecommunication Services - 30
Multiplexing
1
2
Fixed TDM
(circuit-switching)
1
2
Statistical TDM
(packet-switching)
Telecommunication Services - 31
The economics of multiplexing
multiplexing is driven by economics
Different technologies suited for different customer traffic
needs
Telecommunication Services - 32
A simple model
Α
Β
C
D
Post offices Α, Β, C,...
K packets/sA B
Interconnection service
< K/3 p/s
K/3 p/s
Smart management of container space:
overbooking
Container for K packets
1 s
New interconnection
service
Container service
Telecommunication Services - 33
Multiplexing technologies
ATM
SONET
IP packets
IP router
Optical fiber
Light paths
622 Mbps35 Mbps
54Kbps
Telecommunication Services - 34
ATM και SDH
SDH
ATM
switch
ATM networkrouter
virtual path
ATM
switch
Telecommunication Services - 35
The hierarchy of multiplexing services
guaranteed BW,
Fine - medium granularity
guaranteed BW
Protocol transparency
ATM,
FR
SONET,
SDH
shared+ guaranteed BW
Ethernet
Fiber with DWDM
shared BW
(no QOS)
TCP/IP, UDP/IP
x/IP: short – long lived bursty connections, edges control connection setup,
no BW guarantees, statistical multiplexing
ATM, FR: long lived connections, network controls connection setup, fixed BW
Ethernet: two modes: shared BW (for short lived bursty connections)+ guaranteed
BW (for long lived fixed rate connections)
Fiber using DWDM: long lived connections (for now), protocol transparency
medium – coarse granularity
Telecommunication Services - 36
Circuit-switched WAN services
Dark fiber and light paths
Leased lines
ISDN TDM
Telecommunication Services - 37
Dark fiber and light paths
With dark fiber, the customer leases the fiber itself and buys the necessary
equipment to actually activate the fiber
The customer pays for the physical media, not for bandwidth
As the customer adds equipment that can either pulse more bits per
second or extract more wavelengths out of the underlying fiber, the
bandwidth essentially becomes cheaper and cheaper
Light paths: customer buys an optical network service: end-to-end transport
of light of a particular colour, with transparency w.r.t. to network technology
Telecommunication Services - 38
Leased lines
Point-to-point, multipoint, managed, fractional services, offered by PSTN
infrastructure, PDH (E1,E3,T1,T3, FE1,..), SDH (OC3..)
Single-purpose leased-line networks
Telecommunication Services - 39
ISDN
One of the ideas behind narrowband ISDN (N-ISDN) was to give customers
one access into the network, from which they could then engage in circuit-
switched, leased-line, or packet-switched options
Although all these options were available before ISDN, each one generally
required its own special access line and device, which meant extra costs
and administrative responsibilities because of the large number of options
The goal of ISDN was to provide one plug into the network, from which you
could then go out over multiple alternatives.
Telecommunication Services - 40
Packet-switched WAN services
Based on virtual-circuits (provide QoS)
ATM
Frame Relay
MPLS
Based on packet switching
Ethernet
IP (Internet) connectivity
Telecommunication Services - 41
Virtual Circuits
a
b
c
b
c
d
c
d
S1
S2
S3
d
a
a
b
e
1
1
1
1
1
a,1: d,1
a,1: e,1 and c,1
a,1: b,1
12
1
c,1: d,2
a,2: b,11
2
1
d,1: e,2
a,2: c,1
VC data
ATM cell
12
1
Telecommunication Services - 42
ATM: cell switching
25 25 25
34
30
ATM switchCell
Header
(VPI/VCI)
Payload
30 49
input
port 1
output
port1
output
port 2input
port 2
Input Port VPI/VCI Output Port VPI/VCI
1 25 2 341 30 1 49
Internal Routing Table
Telecommunication Services - 43
Multi Protocol Label Switching (MPLS)
IP is a connectionless protocol, it cannot guarantee that network resources
will be available
MPLS allows to define network connections (like VCs) with QoS for specific
IP packet flows which bypass intermediate routers
Provide differential treatment for the above IP flows
MPLS offers the advantages of circuit-switching technology—including
bandwidth reservation and minimized delay variations, which are very
important for voice and video
It enables service providers to create VPNs that have the flexibility of IP
and the QoS of ATM