2. Syllabus Distribution (online)
• LIU Rules
In class behavior
• My rules
– On time, honesty, hard working, reading
3. Course outcomes
• Identify the current approaches to design and
implement broadband packet networks.
• Outline the evolution of broadband networks
• Design a cost-effective network that meet the
requirements of emerging technologies.
• Explain the importance of broadband networks for
modern communication systems.
• Learn the foundation and theory of the quality of
service in modern networks.
4. Textbook and handouts
• Required text:
– Connection-Oriented Networks: SONET/SDH,
ATM, MPLS, OPTICAL NETWORKS Harry
G. Perros, Wiley 2005
– QoS in Packet Networks, K. Park, Springer
– Will be delivered when needed
Overview of the Internet structure
Overview of the current networks implementation
Classification of communication systems
Examples of connections
1st generation of transport networks
9. Example of AT&T (Tier 1)
- Connects virtually every country and territory around the world.
- More than 3,800 service nodes supporting MPLS-based services in 143 countries.
T&T manages more than 200,000 MPLS customer ports.
- A global carrier of IP and data traffic, carrying over 14,000 terabytes of traffic per average business day.
T&T has one of the world's most powerful and advanced IP backbone networks, encompassing over 540,000 worldwide
fiber-route miles - enough to circle the Earth at the equator more than 20 times.
13. Current Evolution in Cellular Networks
Migration to the all-IP cellular networks
In 4G, there will be no circuit swiching
All data (voice, video, web, ftp, etc.) will use IP IP convergence
Source Alcatel-lucent 2008
14. Classification of Communication Networks
Broadcast communication networks
Switched communication networks
Packet radio network
Wavelength routing network
18. Circuit-switched networks
In order for two users to communicate a
circuit or a connection has to be first
established by the network. Specifically, the
following three phases are involved:
– circuit establishment,
– data transfer,
– circuit disconnect.
20. Connection-oriented packet-switched
networks imitate circuit-switched network.
In order for two users to communicate a
virtual circuit or a connection has to be first
established by the network. The following
three phases are involved:
– connection establishment,
– data transfer, and
– connection disconnect.
• In an IP network, a user can send packets to a
destination without having to set up a connection
first, i.e., without informing the network prior to
• This simplifies the network, as there is no need for
a special signaling protocol.
22. Routing in IP
The routing of a packet through the network is done
on a hop-per-hop basis based on the destination IP
address carried in the IP packet’s header.
23. Quality of Service (QoS) in IP
• Typically, an IP router does not offer QoS.
• It cannot distinguish packets belonging to
different service classes based on their destination
• IP is almost ubiquitous. There has been a lot of
interest in introducing QoS in the IP network, and
MPLS seems to be the architecture of choice for
24. Examples of connections
Probably the oldest connection-oriented
circuit-switched network is the plain old
telephone system (POTS).
25. An ATM connection
A bi-directional connection is established using signaling.
The connection is associated with an id number.
26. • The switching of a cell through an ATM switch is
done based on its connection ID number.
• A connection is associated with a specific class of
• An ATM switch can distinguish cells belonging to
different service classes, and serve them
accordingly so that to provide them with the
27. An MPLS connection
• The procedure is similar to ATM.
• An MPLS-enabled IP router switches IP
packets not on a hop-by-hop basis using the
packet’s IP address. Rather, it forwards them
using a label which identifies the connection
that the packet has to follow.
28. A wavelength routing optical network
A three-node wavelength routing network
29. • An important feature of a wavelength
routing optical network is that it is a circuitswitched network.
• A connection is an optical path through the
optical network (called a lightpath) and it is
established using a wavelength on each hop
along the connection’s path.
Packet switched with
connectionless (IP network)
Dedicated physical path
Packets follow the same path
Packets arrive in sequence
Breakdown in core equipment is fatal
On call establishment
On every packet
Bandwidth is fully utilized
Availabilty in bandwidth
When the congestion can occur
31. Standards Committees
ITU : International Telecommunication Union
ISO: International Organization for Standardization
ANSI: American National Standards Institute
IEEE: Institute of Electrical and Electronics
IETF: Internet Engineering Task Force
32. First Generation of Transport
– History of the multiplexing in circuit switched
– The PDH hierarchy
33. PSTN History
• PSTN is the first telecommunication
– Based on circuit switched.
• The subscriber is connected to the central
office using a dedicated twisted pair (local
• Multiplexing is done between two central
offices to transport the calls of many users
• FDM (Frequency Division Multiplexing)
used for analog signals.
• TDM (Time division Multiplexing) used for
digital signals PDH (Plesiochronous
– How to digitize an analog signal (voice)?
• WDM (Wavelength Division Multiplexing)
used for optical signals
36. First Step towards TDM
Digitize the analog signal PCM (Pulse Code Modulation)
By sampling: take a sample every125 µsec.
Then by quantification: represent the taken sample on 8 bits coding
8000 samples per seconde 8000 * 8 = 64 000 bits per second.
DS0 is the basic digital signal of 64 000 bits/sec
• Time division multiplexing allows a link to be utilized
simultaneously by many users
• The transmission is organized into frames.
• Each frame contains a fixed number of time slots.
• Each time slot is pre-assigned to a specific input link. The
duration of a time slot is either a bit or a byte.
• If the buffer of an input link has no data, then its associated
time slot is transmitted empty.
• A time slot dedicated to an input link repeats continuously
frame after frame, thus forming a channel or a trunk.
38. Hierarchical Multiplexing in TDM
• Two approaches:
– PDH (Plesiochronous Digital Hierarchy)
• Plesion means “nearly the same”, and chronos means
“time” in Greek)..
• Frame Format (Ex: European standard, Tx: North
– SONET/SDH (will be explained next week)
• SONET: Synchronous Optical NETwork (North
• SDH: Synchronous Digital Hierarchy (European).
39. Synchronous vs Plesiochronous
• Synchronous Digital Multiplexers have tributaries with the
same clock frequency, and they are all synchronized to a
master clock SONET/SDH
• Plesiochronous Digital Multiplexers have tributaries that
have the same nominal frequency (that means there can be
small difference from one to another), but they are not
synchronized to each other PDH
• For synchronous case, the pulses in each tributary all rise
and fall during the same time interval
• For the PDH, the rise and fall time of the pulses in each
tributaries do not coincide with each other
40. PDH: T carrier / E carrier
• The DS signal is carried over a carrier system
known as the T carrier.
– T1 carries the DS1 signal,
– T2 carries the DS2 signal etc…
• The ITU-T signal is carried over a carrier
system known as the E carrier.
• The DS and ITU-T hierarchy is known as the
plesiochronous digital hierarchy (PDH).
41. The DS1 signal in T1
• 24 (8-bit time slots)/frame
– Each time slot carries 8 bits/ 125 µsec, or the
channel carries a 64 Kbps voice.
– Every 6th successive time slot (i.e, 6th, 12th,
18th, 24th, etc), the 8th bit is robbed and it is
used for signaling.
• F bit: Used for synchronization. It transmits
the pattern: 101010110…
42. The DS1 signal in E1
– 30 voice time slots plus 2 time slots for synchronization
– Total transmission rate: 32x8 = 256 bits per 125 sec,
or 2.048 Mbps
43. T1 frame for voice
24 time intervals, each one is composed of 8 bits (192 bits)
8 bits per « timeslot »
1 « Framing bit »
per DS1 frame
44. T1 frame for data (fractional T1)
• It is possible to have a partial or an entire DS1
• A partial DS1 allows to have multiple throughputs