The first telecommunication network was a data network - the telegraph
The customer was the Railroads who needed it for safety and control
A digital network with binary signaling and control
Email finally killed all forms of the telegraph network
In 1876, Alexander Graham Bell and Elisha Gray invented the
telephone. Gray lost his patent fight with Bell, setting the stage for
Bell to dominate the telephone industry
AT&T was so worried about network congestion that they
asked early residential customers to use the telephone only for
It took over 100 years until it was possible to telephone from
Canada/USA to Europe without an operator
2.2 Critical innovations for Telecommunication Networks
Step-by-step - Strowger (1892) - 16 years.
Crossbar switching - 1938 (Bell AT&T)
Computer controlled crossbar switch, 1965 (#1-ESS, Bell AT&T)
Fully Digital Switches: Nortel, 1972
A/D (Analogue to Digital) converters on every line card in the CO
This invention and commitment allowed for an
end-to-end digital telephone network (well almost end-to-end)
IIASA (International Institute of Applied Systems Analysis),
Laxenburg, Austria - installed a new step-by-step in 1977.
The last manual Central Office (CO) switchboard, in Bryant Pond, Maine,
ceased operation in 1983.
End/End Line pulses and trunk seizures (copper connections)
Network control using multi-tones (similar to "touchtone")
The separation of signaling and control from the transport of
This allowed advanced phone features such as 800 or "freephone"
198? - Advanced Intelligent Network (AIN) became the world's
largest packet switched network (SS7)
Bandwidth and Signal Quality
Satellite for long distance (Early Bird, 1964)
Use of fibre-optics in the core network and intercontinental traffic
Increasing fibre-optic penetration of the access network
Comment: There has been a continual improvement in quality,
capabilities, and features of the PSTN, but old breakthroughs such as
satellite channels are now considered poor quality compared to current
1957: The Internet really began with the creation of ARPA
(Advanced Research Projects Agency) in response to
the launching of Sputnik.
1969: ARPA asked by US Department of Defense (DOD) to create a
network that would
Survive a nuclear attack
Allow DOD researchers at universities and contractors to collaborate
UCLA, SRI, UCSB, and Utah are the first four nodes
1970: Norm Abramson creates ALOHAnet in Hawaii - a random access
packet radio network
1973: Bob Metcalfe's PhD thesis at Harvard was the invention of Ethernet.
He then moved to Xerox PARC, and and built the first prototype, the
Alto Aloha System. Xerox did not want to commercialise Ethernet so
Metcalfe started 3Com a few years later.
1973/1975: Vint Cerf describes TCP to Bob Kahn and they eventually
refine it to TCP/IP. It took 10 more years (1983) before the
original NCP (Network Control Protocol) of Arpanet was replaced by TCP/IP.
1974/75: Arpanet includes satellite connections to Hawaii and UK
1981: CSNET (Computer Science NETwork) built with seed money by
NSF to get around use restrictions on Arpanet. CSNET was originally
one machine at BBN in Cambridge, Mass. BBN was the original prime
contractor for the Arpanet nodes.
1982: TCP/IP finally becomes the DOD network standard
1986: NSFnet, established with 56kbps lines, connects several
super computer centers. NSF also supports local university networks that
are interconnected through NSFnet.
1988: NSFnet upgraded to T1 lines.
1990: Arpanet retired.
1991: After NSF removed commercial use restrictions on use of
NSFnet, the Commercial Internet eXchange (CIX)
Association formed by CERFnet, PSInet, and AlterNet (UUNET), IXPs become
the key method for interconnecting networks.
1991: NSFnet upgraded to T3 lines.
1995: NSFnet dissolved. This was the critical point in the
Internet evolution and set the stage for the current internet
architecture. At the time NSFnet was dissolved, there
were more than 90 countries connected to it. It was truly the world's
Order preserving routing is preferred for flows (all TCP
connections, RTP, and real time UDP connection.)
Route Flap: a characteristic of BGP4, OSPF - fundamentally due
to routing update synchronisation and the lack of any calculation to
estimate the change in network delay topology by a change in routing -
at this point, one lives with it as a fact of life.
Load balancing: intentionally spreading packets amongst equally
good (bad?) routes
RED: Rapid Early Detection - random discarding of packets by a
router during periods of congestion. Intent is to prevent all the TCP
connections from retransmitting at the same time and causing a
"blizzard" of additional packets. UDP ignores this action.
For IPv4, special cases are bumped out of the fast-track
processing for slower, special treatment. It remains to be seen whether
the IPv6 header design is sufficient to allow unprejudiced use
7.5 Requirements for Real Time Flows On The Internet
Sequencing: reordering in real time at reception, and
compensation for loss without retransmission;
Intra-Media synchronization, for proper restitution, including
silence periods (not transmitted);
RSVP was supposed to be the protocol of choice to handle QoS, but it is
now viewed as being unnecessarily complex, which has made it unappealing
for the community at large and even its working group has disbanded.
Reserves resources for multicast conferences
Receiver based - the receiver builds a multicast tree from itself
to all the senders in the conference, reserving resources as it is
built. Since there is, usually, only one sender active at time,
reservations for the same resource may be shared.
Basic assumption is that receivers will have widely differing
capabilities and only the receivers know what they are. This precludes
sender resource reservation
Both receivers and senders in a conference are undisciplined
coming and going at will.
The key idea is to annotate IP packets with a small, easily read field,
and have the Internet router/switches handle them differently. This
appears to be a proposal that could, eventually and radically, change
the basic communication infrastructure of the Internet. The
diffserv working group is developing the rules that compliant IP
routers/switches should/must follow:
IP switching - Tag, Label (ATM?)
QoS based routing
Separation of Route calculation and Packet forwarding
Question: ATM and IP: When does a long lasting IP packet/flow
based route become equivalent to a virtual circuit - or does it ever?
"Define and promote implementation agreements for voice and voiceband
data traffic over an IP network that ensures seamless product
interoperability and a high quality of service" (Objective of the
Voice over IP Forum of the International Multimedia
Teleconferencing Consortium (IMTC) http://www.imtc.org)
Ecumenical Approach - support all existing (standardised?) voice
Little activity in improving the infrastructure for carrying real
time interactive traffic.
Incorporate and be compatible with telephony signaling
Video conferencing, from conferencing centers, is the first, and
simplest, application on an Intranet.
Desk to Desk conferencing is next.
Incorporation of "ordinary" internal telephony.
QoS requirements are higher than commodity Internet
Intranet architecture is conventional, with few, if any QoS or CoS
(Class of Service) guarantees.
Standards are not necessary but helpful to allow connection to the
outside world, such as your suppliers and customers.
8.4 Voice On A Packet Switched Infrastructure (Packet Voice)
Voice and other real time interactive traffic on a new packet
The network will be dimensioned and engineered (if possible) to
carry real time interactive traffic with acceptable delay and jitter.
New infrastructure must interconnect and interwork with the
existing PSTN and Internet.
Standards are important - eg. H323+
It is still far from certain that a packet network can deliver
satisfactory delay/jitter performance.
QWEST and LEVEL3: The QWEST/LEVEL3 networks appeared to commit
themselves to a packet-switched network that carries all
traffic. Their networks are important datapoints for a potential
evolutionary path for Telco survival, and both are in deep trouble
9 A Bottom Line - Internet Architecture for the New Infrastructure?
IPv6, or something resembling it, will replace IPv4. IPv4 is not
sufficient for universal access
Variability in all performance measures is reality
Internet architecture resembles telephone architecture at the turn
of the century, with the world being the village, and many outlying
"farms" still not having service
The "near term" communications infrastructure will be a melange
of current switching techniques
The current Internet will be "current", for only a few days
10 A Potential Architecture for the New Telecommunication
10.1 IP based packet network communications infrastructure
New IP-based networks for integrated services are being proposed for
small, medium and large size corporations.
Will they work? As long as the end-to-end network is small enough ...
Will it be cost effective? Switching packets may be cheaper, on a small
scale. On the WAN side, the infrastructures are similar.