Chapter One Networking basics and trend 1.2 Network trend -networking basics and...
Transcript of Chapter One Networking basics and trend 1.2 Network trend -networking basics and...
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 1
Chapter One
Networking basics and trend
1.1 Networking basics
1.2 Network trend
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2
The network in this course denotes the information
network, since there are a lot of networks that are
different from this one, such as the network of an
organization, postal network , railway network, the
relation network of a family, etc.
Mathematically, a network can be represented as a
graph G=(n , v), where n is the set of nodes and v denotes
a set of links to which nodes are connected.
For an information network, a node can be the device or
equipment that belongs to either users or network
operators.
1. The main components/elements of an
information network
1) Terminal
Terminal could be divided to two types: user terminal
and network terminal (also known as Server)
a) User terminal: It performs the capturing, processing
and transmission of user information, and has the
functions of control and management.
Examples of user terminal
a telephone a notebook
a mobile phone a computer
b) Network terminal (aka Server): It implements the
following functions:
information capturing and/or storage
voice recorder, video camera, data store server
(mixed) processing and transmission of users’ information
video conferencing server
Web Server
Cisco IP/VC 3510
Videoconferencing
Multipoint Control Unit
(MPCU#)
SIP Server
control and management for itself and users
corresponding example are Web server and Session Initiation
Protocol (SIP#, 会话 (/会晤 )发起 /启动协议 ) call processing
server.
2) network node
Traditionally, it mainly performs the switching, exchange,
transfer and multiplexing of user information, and has the
functions of both control and management itself.
Examples of network node:
a router
TPLINK for home and office
Huawei enterprise router
L2/L3 Switch#: it implements the frame or
packet switching according to six-byte MAC
address or IP 4-byte address.
Multiplexor ( 复用器 )#: it can multiplex
several low channels (say 64Kbps) into one
high speed channel (say E1) , and vice versa.
Digital eXchange Cross connect (DXC,数字交叉连接 )#: it performs time slot-, port-,
wavelength-switch by configuring manually.
Concentrator (集中器)#: it usually collects
information from quite a number of users,
and transfers the information captured to a
high-level server, e.g., remote electricity
meters reading (远程电力抄表)
2) network node
As network evolves , except the switching function, it also
performs transforming or mixing of user information, and has
the functions of both control and management for users.
Examples of network node:
an IP telephone gateway could perform:
• Transforming coding between a/μ voice in TDM with
64Kbps and IP voice coding, say G.729A with 8Kbps
• Transforming PSTN signalling and VoIP signaling.
More details in both later slides and Chapter seven of
Access network PPT.
3) transmission link
a) It performs transmit information between adjacent nodes.
Equally, a pair of two nodes or more nodes are connected
physically by it in the forms of either a single channel or a
broadcast one .
b) It usually includes the various transmission facilities (设施),
equipment or devices and their combinations. More specially, it
maybe used by physical transmission network like Synchronous
Digital Hierarch (SDH#,同步数字体系 ) link , or even
Asynchronous Transfer Mode (ATM#,异步转移模式) link .
More details in both Chapter three of Access network and broadband ATM
techniques PPT.
c) In the same network, the transmission rate close to
user sides is lower while transmission rate close to
network provider side is extremely higher with three
orders at least.
Examples of transmission link:
User side Network side
PSTN
TDM-based 64kb/s (digital telephone)
E1: 2M, E2: 8M,
E3: 34M, E4: 140M
(PDH rates only for
European )
broadband
network
2 Mbps,8 Mbps,FE(100M
Ethernet), GE( Gigabit Enet)
STM-0 (51.84Mbps, aka OC-1
means Optical carrier at level
one in SONET ), STM-1
(155.52Mbps)
STM-N# , N=1, 4, 16,
64,256 {SDH 155M,
622M, 2.5G,10G,40G}
xGE, x=1,10,100,200
1/10/100/200 GE
Comments: PDH (Pleisochronous Digital Hierarchy,准同步数字系列/体系) was
widely used in 1980’s. It has three systems with the transmission rates up
to 140Mbps. Its E1 has some applications, especially in PSTN.
SDH#(Synchronous Digital Hierarchy) and Ethernet# have been used
widely in various networks from access, metropolitan to core. SDH’s
transmission rates are abbreviated as STM-N#, meaning Synchronous
Transfer Module at N level, while the later can be denoted as xGE#.
Comments (continued):
As its name suggests, SDH has following advantages:a) In SDH network, all network elements are synchronous;
b) The transmission rate at each level is four times to that of its
adjacent lower level, and N=1,4,16,64,256, which explains the
“hierarchy”;
c) It is suitable for optical transmission of high speed with up to
40Gbps;
d) The powerful network management makes it easy for network
operators to configure and maintain, which satisfies partly
the requirements of NGN# (New/Next Generation Network)
with reprogrammable, reconfigurable and reconstruction-
enabled features ;
e) It has the pointer adjustment mechanism that allows the
“load ” to vary within some limited ranges, which means the
“load” may be faster or lower than the standard rate.
More details in Chapter three of Access network techniques PPT.
Comments (continued): Contrary to the synchronous transmission techniques like SDH,
Ethernet has been using widely in both transmission link and
switching techniques.
a) The transmission rate at each level m, mGE, is ten times to
that of its adjacent lower level, and m=0.1,1,10,100, which has
also the “hierarchy”;
b) It is suitable for optical transmission of high speed with up to
100Gbps at one carrier or wavelength 𝛌 ; It is reported that
Huawei has launched its optical module with 800Gbps, the
highest rate in the world.
c) It is the simpleness or “simplification” that makes it to be
used widely in transmission link and networking.
More details in both Chapter five of Access network techniques PPT.
ConclusionAs the representatives of synchronous- and
asynchronous-transmission & switching, SDH and
Ethernet are significantly important, and have been
using widely and extensively in Access, Metropolitan,
Core networks.
It is mandatory that students have the firm basic
knowledge about the both.
More details in Data and computer communication
authored by William Stallings, and Chapters three and five
of Access network techniques PPT.
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2. The sorts and definitions of networks
There are many ways to sort various networks.
• Geography
• Transmission medium
• Technique used
• Services provision
• Functionality
• …
Here, we introduce some ones that are based on
different features and have been recognized
professionally.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 15
1) Geography
Name Definition Main features
Body area
networking
(BAN), a.k.a.
wireless body
area network
(WBAN)
A body area network (BAN), also referred
to as a body sensor network (BSN) or a
medical body area network (MBAN), is a
wireless network of wearable computing
devices. Through gateway devices, it is
possible to connect the wearable devices
on the human body to the Internet.
the networking
area is human
body, covering
2M range.
Home and
small office
networking
A home network is a group of devices,such as computers, game systems,
printers, and mobile devices, that are
located at a home area and connected
together and able to access to the
Internet via a home network gateway.
the networking
area is home or
small office
, covering
several tens
meters.
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Name Definition Main features
Local area
network(LA
N# 局域网,局部区域网络in1980’))
A local area network (LAN) is a
computer network that
interconnects computers within
a limited area such as a
residence, school, laboratory,
university campus or office
building. Ethernet and Wi-Fi
are the two most commontechnologies in use for it.
the networking area
is local area
, covering from
several tens of
meters to several
kilometers.
Metropolitan
Area
Network
(MAN#, 城域网)
MAN provides the networking
facilities that interconnects
local area networks (LANs) in a
city into a single larger one.
the networking area
is a city, covering
from several to
several tens, even a
hundred kilometers.
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Name Definition Main features
Wide
area
network(
WAN#
广域网)
It is a long-distance network
connecting computer
communication of LANs and/or
MANs in different areas. It
usually spans a large physical
range, covering from tens of
kilometers to thousands of
kilometers. It can connect
multiple regions, cities and
countries, or across several
continents via sea optical
fibers ,and provide long-distance
communication, forming an
international long-distancenetwork.
the networking
area is a nation,
across several
continents,
covering from
hundreds to
thousands
kilometers.
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2) Transmission medium
Medium types Main features
Twisted Pair xDSL (digital subscriber Line), 2M~54 Mbps,
let telephone user to access to Internet
Cable (coaxial cable,electricity line)
It usually refers to the former, typical
application is HFC (Hybrid Fiber Coax), which
uses fiber between the service provider and
residential zone, while employs coax within
old residential buildings.
Optical fiber
It has been using widely in the form of EPON
(Ethernet Passive Optical Network) in
residential zone, connecting various routers
or switches together.
Transmission medium can be categorized two kinds: wired and
wireless
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Classification Band Initials Frequency Range Characteristics
Extremely Low Freq. ELF < 300 Hz
Ground waveInfra Low Freq. ILF 300 Hz - 3 kHz
Very Low Freq. VLF 3 kHz - 30 kHz
Low Freq. LF 30 kHz - 300 kHz
Medium Freq. MF 300 kHz - 3 MHz Ground/Sky wave
High Freq. HF 3 MHz - 30 MHz Sky wave
Very High Freq. VHF 30 MHz - 300 MHz
Space waveUltra High Freq. UHF 300 MHz - 3 GHz
Super High Freq. SHF 3 GHz - 30 GHz
Extremely High Freq. EHF 30 GHz - 300 GHz
Tremendously High Freq. THF 300 GHz - 3000 GHz
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3) Technique used
network
types
Data/Ctrl
Plane Main features
Ethernet Data
It finds wide applications in various levels networking,
covering from home, office, LAN, to MAN. The speed
could be 1G,10G, 100G, 200G, 400G, 800G.
The line rates of optical networks are rapidly moving from
100 Gbps to 200/400 Gbps. Huawei released this 800G
module to help operators cope with the bandwidth
challenges of 5G networks.
SDH/SONET(OTN: optical
transport
network,
光传送网) is
SDH
successor(后继者)
Data
It provides transmission capabilities for different networks,
and is fundamentally and really a physical network since it
performs the function of OSI/PRM# (Open Sys.
Interconnection/ Protocol Reference Model开放系统互连-协
议参考模型) layer one.
It carries TDM slot, frames, packets. The highest rate
commonly deployed is STM-256 circuit, which operates at
rate of just under 40 Gbps. However, its highest rate of
STM-1024 with 160G is defined.
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continued
network
types
Data/Ctrl.
Plane Main features
IP Data
It uses absolute 4 or 16 bytes to identify the endpoints of
various types, such as router port, host, terminal.
It has outstanding advantage in simpleness and flexibility
without a connection between source and destination.
However, its disadvantages are service quality of “best
effort#” (尽力而为), and network security.
ATM Data/Ctrl
Oppositely, ATM uses 28 or 32 bits to identify the virtual
link (VL#, 虚链路) between two endpoints, and these are
misadvised to be referred to as “address”.
It implements the hardware switching of a constant-length
packet or an ATM frame entitled as Cell, while still guarantees
the quality of service (QoS#, 服务质量) for different user
services, such as voice, video, data.
However, its significant drawback is it needs to set up a
virtual connection between endpoints before the data delivery.
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continued
network
types
Data/Ctrl.
Plane Main features
MPLS Data/Ctrl
Multiprotocol Label Switching (MPLS# 多协议标签/标交换) is
a routing technique in telecommunications networks that
directs data from one node to the next based on short path
labels (similar to ATM virtual channel/path identifier,VCI/VPI#, 虚通路标识符/虚通道标识符) rather than long
network addresses, thus avoiding complex lookups in a
routing table and speeding up traffic flows. ---Wikipedia
GMPLS Data/Ctrl
Generalized Multi-Protocol Label Switching (GMPLS# 通用多协议标签/标交换 ) is a protocol suite extending MPLS to
manage further classes of interfaces and switching
technologies other than packet interfaces and switching,
such as time division multiplexing (TDM# 时分复用 ) , layer-2
switching, wavelength switching and fiber-switching. In other
words, the labels of time slots (TSs# 时隙), wavelength
𝝀 , fiber and interface are used in GMPLS to extend the
concepts of label in MPLS.
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4) Services provision Service time Network Main features
Voice
traditio
nal
The public switched telephone network
(PSTN#, usually refers to fixed
telephone network ) is the aggregate of
the world's circuit-switched telephone
networks that are operated by national,
regional, or local telephony operators,
providing infrastructure and services
for public telecommunication.
It uses the 64Kbps circuit-
switching.
traditio
nal
Mobile telephone network uses a fixed
location station to connect a mobile user
to the network. Such networks are also
referred to as cellular networks, such as
2G, 3G an 4G.
In the early period, it employed
the circuit switching. Then , it
evolves to circuit/packet hybrid
switching. Last, it evolves to
packet switching.
nowad
ays
Besides the above techniques, it can be
transferred by the Voice over IP (VoIP#,网络电话) in various access techniques.
The voice in VoIP is encoded by
VoIP encoding standard like
G.729A at 8Kbps, and the
resulting voice is encapsulated
by VoIP protocols suites.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 24
Service
Name
Network Main features
television
A “cable channel” (sometimes known as a
“cable network”) is a
television network available via cable
television. The abbreviation CATV# (闭路电视系统) is often used for cable television. It
originally stood for Community Access
Television (社区接入电视) or Community
Antenna Television ( 社 区 天 线 电 视 ),
from cable television's origins in 1948.
In the early period, it
employed the analog
system. Each channel
covered 6.5 or 8.0MHz.
In the digital TV era, the TV service can be
transferred by one or the combination of the
many techniques, such as Cable, Hybrid
Fiber coaxial Cable (HFC,混合同), Fiber in
Ethernet passive optical network (EPON#,以太无源光网络), xDSL, WiFi, wireless
Mobile phone, etc.
The TV screen video
resolution is determined
by video player or the
user side device.
continued
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 25
Service
Name
Network Main features
Data
In the 1960’s to 1980’s, data was usually
transferred in LANs except the early network
like ARPNET.
In the 1990’s, the telephone line MODEM#
(modulation +Demodulation,调制解调) was
used at from 600 to 1200 bauds , up to 56k
bauds in 2000’s.
The transmission
speed is very low.
In the digital era, the data service can be
transferred by one or the combination of the
many techniques, such as Cable, Hybrid Fiber
coaxial Cable (HFC), Fiber in Ethernet passive
optical network (EPON), xDSL, WiFi, and
wireless Mobile phone .
It is
transported in
an
asynchronous
packed-based
way.
continued
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 26
3. Some definitions of networks
There are many networks that make us confused
Here, we introduce some ones that have been
recognized professionally.
Data communication networks
Computer networks
Information networks
…
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 27
Data communication networks consist of such endpoints ordevices as terminal, host, transmission- and switching-equipment, and implement information capturing,processing, transport and switching with open standardprotocols.
1) Data communication networks
Comments for transmission and transport:
Transmission usually denotes the physical transmission between a
transmitter/sender and a receiver (an acceptor), which belongs to the
function of OSI/RM# layer 1. However, the former does not know whether
the receiver has gotten the information sent.
However, transport# (传送 ), the later, usually means the function of
transmission and switching, the sender does know (确实知晓) the delivery
state due to using the protocol in OSI/RM layers 1 to 4. Here are
corresponding examples, SDH in L1 (in which the data delivery is ensured
implicitly (含蓄地保证) by SDH network management instead of an explicit
mechanism in L1), HDLC in L2, X.25 in L3, TCP in L4.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 28
Computer networks: from Wikipedia
A computer network is a digital telecommunications network for
sharing resources between nodes, which are computing
devices that use a common telecommunications technology. Do
you know how the meanings of telecommunications are evolved ?
https://en.wikipedia.org/wiki/Computer_network
CNs are a set of the dependable or undependable computers,
which are connected together by communication facilities via
standard protocols, and usually located at different geographies,
sharing the resources of hardware, software and data. --
Viewpoint of the instructor
2) Computer networks
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Information networks:
a) consist of such endpoints as user terminal, network
terminal (Sever), transmission- and switching-
equipment;
b) implement the information of capturing, processing,
transport and switching, as well as applications with
open standard protocols.
3) Information networks
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 30
Relations among three networks:
a) Both data communication networks and computer
networks are often called by professionals of
communication engineering and computer, respectively.
It is a bit hard to distinguish a network whether belongs
either one or the both.
b) In fact, it is recognized that the emphasis of the former is
on the network infrastructure (网络基础设施) including
data processing, transport and switching, while on the
various applications like QQ and Microletter for the later.
More lecture notes at https://lecturenotes.in/subject/11/data-
communication-and-computer-network-dccn
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4. Controls of data comm. networks
The controls of data communication networks
(abbreviated as network control ) mean how to control
them and to make them work normally. The first
question is “ what are to be controlled? ”
We discuss this issues in two aspects: control sorts and
control modes.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 32
network control could be divided into two types: user
terminal control and network node control.
For the first one, it implements:
a) Sets up a “transport channel” between source and destination
for transferring user data, which can be regarded as a physical
connection or virtual connection. Corresponding examples are
physical TDM# ( Time Division Multiplexing, 时分复用)
connection in PSTN and ATM virtual channel/path;
b) Performs a session association or constructs a session
connection between source and destination before user data is
transferred, whose function is similar to TCP/IP protocols
stock or to negotiate some parameters.
1) what are to be controlled
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 33
Comments:
In VoIP, some parameters are to be negotiated mandatorily
(强制协商), such as voice coding, voice packetized length,
UDP port number, silence detecting, etc. However, these
parameters are either unnecessary to negotiate or inexistent
(不存在的), since traditional PSTN used the assigned a/μ
voice coding in advance, while it does not need the
parameters of voice packetized length and UDP port
number.
-continued
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 34
For the network node, it implements:a) For transferring user data, it implements followings
alternatively:① In the connection oriented network (面向连接网络), it sets
up a “mapping table” of (Port number, packet identifier)between input port and output port, such as ATM virtualchannel/path switching table ;
② Or, in the connectionless network ( 无连接网络 ), itnegotiates some network performance parameters like IProuting protocol with neighbors , then transfers a packetaccordingly.
b) Performs a session association or constructs a callsession between source and destination users before userdata is transferred, whose function is similar to TCP/IPprotocols stock or to negotiate some parameters, which isused for data transport control (data plane) and call
session control (signaling in control plane).
-continued
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 35
network control modes could be categorized into
three : central, distributed, and hybrid.
a) Central control
To provide the data transfer between source and
destination, network allocates the “dedicated” or “private”
transmission link and switching node resources physically
or statistically, and one by one. Here “one” denotes link or
node. We name such two types of resources as physical
private resource and statistical private resource,
respectively.
2) Control modes
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 36
A network working in this control mode is referred to as
“connection oriented” network.
“physical private resource” means all allocated resources
in related links and nodes are used solely (独占地) by this
users pair, e.g., PSTN.
“statistical private resource” represents all allocated
resources in related links and nodes are not used solely by
this users pair while shared by other related users on a
link or in a node, e.g., Ethernet Tunnel, ATM network.
-continued
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 37
b) distributed
To transfer a packet between a source-destination pair,
network switches a packet according to the packet
identifier and path selection mode (e.g., Routing
algorithm, OSPF#- open shortest path first), which may
result in different paths for packets transport of a
specific source-destination pair.
A network working in this control mode is referred to
as “connectionless network ”, e.g., IP network.
-continued
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 38
c) hybrid
A network working in this control mode has both the
central and distributed controls.
Such a typical network is VoIP network, it sets up a
session for both endpoints in central mode, which is
regarded as the signalling function. While the user data
packets are transferred by IP in distributed mode.
More details in Chapter seven of Access network techniques
PPT.
-continued
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 39
5. Data networks architecture
Planes of a network
PRM –Protocol Reference Model
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1) Planes ( functional architecture) of a network
We use planes to describe the function of network in higher
(even highest) level compared to protocol reference model
(PRM#) used widely.
Usually, the function of networks consists of three planes,
namely, data (a.k.a. transport, user) plane, control (signaling)
plane, and management plane.
In stead, I suggest an application plane should be added to
make the “Planes of network” perfect, since each element is
dedicated to providing a specific function, such as a web
server or video conferencing server.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 41
3. Manage.
Plane
2. Control
Plane
1. Data Plane
4. App Plane
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Data (transport, user) Plane
It is responsible for data transport either unreliably or reliably
( Layer one implements bit or (physical) frame transmission ,
while layers two and four guarantee reliable transfer if needed)
Comments: most text books said that layer one implements bit
transmission , which is irrelevant (不恰当) or inappropriate and
imperfect at least. In the Ethernet frame structure, there are 7 bytes
for bit recovery and one byte for frame delimiter (帧定界) as shown
below.
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additional functions for reliable transfer as used in TCP or
HDLC, such as error correction , traffic control, etc.
Control (signaling) Plane
Performs call and connection controls, i.e., all capabilities
of signaling processing for setup, supervision, and release
of a connection. The example is signaling system in
traditional telephone system, and extra parameters
negotiation is needed in VoIP. Concisely, such a connection
is used for providing either transport “channel ” of an IP
packet in IP/ATM or of user service in VoIP voice.
Controls the network element itself, e.g., initiation, status
exchange with neighbor using OSPF routing protocol.
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Management Plane
Performs system management and interaction among
different planes, referring to as Planes management.
Implements OAM# (Operation, Administration,
Maintenance) of each layer, referring to as Layers
management .
Application (service) Plane -my viewpoint
Performs application specific functions, such as conference
videos mixer, different severs of (cloud, banking,
emails,…), transcoding like between G.729A and G.723.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 45
2) PRM
There are two protocol reference models (PRMs) used
widely, OSI and TCP/IP.
As techniques and human’s understanding of PRM
evolve, some concepts become clearer while others still
keep ambiguous (模糊的).
The former examples are service data unit (SDU#),
protocol data unit (PDU#), etc. One of the later instance
is functions of session layer, which can be viewed in
different ways, such as, does such a function belong data
plane or control plane, or the both?
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The seven Layers
Presentation
Application
Session
Transport
Network
Data Link
Physical
Network
Data Link
Physical
End system End systemIntermediate sys.
Presentation
Application
Session
Transport
Network
Data Link
Physical
Web ServerNote book
2020/4/23 47
Presentation
Application
Session
Transport
Network
Data Link
Physical
destination endpoint
Presentation
Application
Session
Transport
Network
Data Link
Physical
tSDU
aSDU
pDUp
sSDU
AH
PH
SH
TH
nSDU NH
nSDU NHDT
NHDT
source endpoint
nSDU
Presentation
Application
Session
Transport
Network
Data Link
Physical
Dest. endpoint
Presentation
Application
Session
Transport
Network
Data Link
Physical
tSDU
aSDU
pDUp
sSDU
AH
PH
SH
TH
nSDU NH
dSDU DHDT
PhHDT
source endpoint
phSDU
data
H-header#(标头), T-Tailer(尾部) , SDU-service data unit
a/H through ph/Ph placed before SDU or H denote the each corresponding layer.
Top-to-bottomEncapsulation#封装#
Bottom upDeencapsulation#拆封#
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Comments: We refer a physical link as real connection#, since the information is
really transmitted or sent via it, and do not care whatever the transmission medium, wired or wireless, is used. Some notes say this connection is virtual connection when wireless medium is employed, which is fundamentally wrong.
Even for the intermediate sys, the information or corresponding PDUs exchange can take place in each of the three layers:
Presentation
Application
Session
Transport
Network
Data Link
Physical
Network
Data Link
n1 L1 n1’
Presentation
Application
Session
Transport
Network
Data Link
Physical
Switching occurs in n1 and n1’ nodes of layer one, examples are switching like time slot, wavelength λ and fiber, which are called circuit-based switching, or physical tunnel#(隧道).
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Comments continued :
Switching occurs in layer two, typical examples are ATM
switching, MPLS, which are referred as link circuit
switching, or link tunnel#.
Presentation
Application
Session
Transport
Network
Data Link
Physical
n3 L3 n3’
n2 L2 n2’
L1
Presentation
Application
Session
Transport
Network
Data Link
Physical
Switching happens in layer three, typical example is IP
switching, in which IPv4 switching or IPv6 in packet
switching models can not be referred as network circuit-
based switching. However, IPv6 in flow switching model
can be referred as network circuit-based switching.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 50
RS-x: RS-232, a specification for serialinterface
ISDN: Integrated Service Digital Network: a digitalized user network interface instead of analog one in PSTN
ADSL: one of xDSL, x=Asymmetric, High speed, Symmetric
ATM: Asynchronous Transfer Mode
FDDI: Fiber Distributed Data Interface
Category: CAT-5 twisted pair line (双绞线) is widely used as Ethernet connection line
Subnetwork Access Protocol (SNAP) is a mechanism for multiplexing on networks by using IEEE 802.2 LLC
SMTP: Simple Mail Transfer Protocol
POP: Point of Presence, a demarcation point, access point, or physical location at which two or more networksdevices communicates
POP 3 is the most up to date version of the Post Office Protocol, and it lets email applications retrieve (获取)email messages from email servers
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Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 51
ATM L3
ATM L2 (IP/ATM)
ATM L2.5(IP/ATM)
ATM uses its own protocol architecture supporting voice, data, …
ATM is used as a “channel” or “tunnel” to transfer IP packet service, while IP switching is not needed, such as 163 net in the middle of 1990’s .
ATM is used as a “channel” or “tunnel” to transfer IP packet service, while ATM switching and IP switching are both needed to maximize the network utilization.
We present this paradox (悖论) as an assignment.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 52
Layer i
Layer i+1
Top-to-bottomEncapsulation#封装
Bottom upDeencapsulation#拆封
The information exchange between adjacent layers i+1 and i is
implemented via SAP# (Service Access Point,服务接入点), which
includes but not limited to information about SDUi (or PDUi+1) :
a) Length and location for relevant information reading or
writing
b) Type of the SDU, data or control command
c) Identifier and other information of the SDU, e.g., MAC
address, if needed
Except the top and bottom layers, layer i provides the service for
the adjacent (邻接的 )upper layer i+1 based on the service
supported by adjacent layer i-1.
Layer i-1
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Chapter One
Networking basics and trend
1.1 Networking basics
1.2 Network trend
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1. the main trends in networking
There are many predictions about the networking
trends from different aspects:
Coming from techniques, economics, sociality, …
Coming from large companies, such as google,
Microsoft, Huawei, …
From time scale, 2020, 2019, 2018,…
Maybe from famous advising companies like Gartner
(高德纳)
From academic organizations, associations,
funding,…
Here are some my opinions
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 55
Some general trends in networking are as follows:
Higher or ultra-high transmission speed: Huawei
company announced that it developed an optical module
working at up to 800Gbps with a single optical carrier,
which is the highest transmission rate worldwide.
Larger or huger switching volume: It is reported that an
NE5000E router developed by Huawei company could
perform switching as much as 256 to 819.2 Tbps with
2560 100GE ports and 289920 MPPS# (Million packets per
second) .
Integration: more functions are embedded network
elements, which keeps true at least for user terminal like
mobile phone.
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Packet-based transfer: Most information exchanges
will be packet-based, and may not be dominated by IP
switching.
(Virtual) channel-based transfer: To guarantee the
Quality of Service/Experience (QoS#, QoE#体验质
量,…) at most, channel or virtual channel will be used
to minimize switching/transfer time delay. The
corresponding examples are circuit (DXC), MPLS ,
ATM and Tunnel.
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 57
Convergence: It refers to providing more different types of services by
one network element, such as mobile phone, which is similar to
Integration just introduced. The second point is network convergence,
which denotes one type of network could provide the service that is
traditionally supported by other network being different kind. For
example, in the convergence era of PSTN, computers and Cable TV
network, PSTN could provide Internet and TV services besides typical
voice service. Such an action is also named as triple-paly or triple
plyers, which is mistranslated or misinterpreted into Chinese “三重播
放”, instead, the correct one should be triple-network convergence
“三网融合”.
More details at: https://en.wikipedia.org/wiki/Network_convergence
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Dr. Zhanqi XU, National Key Lab on ISN, Xidian University
58
Ubiquity(泛在性) : It means networking is everywhere, letting you
access to Internet via any feasible ways, such as WiFi, Mobile phone,
wired Ethernet, xDSL, EPON and HFC. Ubiquitous computing is the
concept of using small internet connected and inexpensive computers to
help with everyday functions in an automated fashion.
Comments: (internet connected互连网络连接,internet不是指Internet
(前者指多个网络连接,不一定采用TCP/IP; 后者大众译为互联网,我认为译为因特网 )) ,否则,容易导致概念混乱,例如,战术互联网指战场上多个网络互联,它不一定采用TCP/IP协议,也不一定提供WWW,email等。
2020/4/23 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 59
Integrated space-air-ground-sea network, it connects four
types of networks together, specifically:
Space network includes satellites locating at geostationary-,
middle- and low-orbit, from 36000 Kms to several hundreds Kms
Air network includes aerial nodes, such as, airplane, High Altitude
Platform Stations (临近平台17 ~ 20 Kms), aeroboat(飞艇),
Unmanned Aerial Vehicle (UAV无人航空器)
Ground network is one used by human at most, such as WAN,
MAN, LAN,…
Sea network may include the connected nodes that are either over
the water surface or underwater.
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Function separation in networking and/or network element
exists among data transfer (transport) , control (session
control, data transfer control like routing protocol, element
control), and service/application provision. The advantages
of such an action are:
One network element will implement only one dominated function
(专业人做专业特长之事), such as Media Gateway (MG#媒体网
关,指语音、视频等,不可译为媒质,与传输媒质无关 ) for
source coding translation, Media Gateway Controller (MGC#,
MG#媒体网关控制器) for session control.
Different network elements that are either small or large, low or
high price, are used to constructed together, and to accommodate
with varied needs perfectly.
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NG Optical Net:
ASON/ASTN
NG Optical Net:
ASON/ASTN
NG InternetNG Internet
NG Switching /
Networking:Softswitch, IMS, SDN
,NFV
NG Switching /
Networking:Softswitch, IMS, SDN
,NFV
NGN umbrella
App Layer
Ctrl Layer
Transport Layer
Access Layer
NG Transport Net
IPV6, MSTP ,…
NG Transport Net
IPV6, MSTP ,…
NG Ctrl Net:
MPLS,GMPLS
NG Ctrl Net:
MPLS,GMPLS
NG Mobile
Net:
4G,5G,
6G
…
NG Mobile
Net:
4G,5G,
6G
…NG Access Net:xPON,FTTx ,EoC, WiFi 6, …
NG Access Net:xPON,FTTx ,EoC, WiFi 6, …
ASON/ASTN: Automatic Switching Optical/Transport Net
GMPLS: General Multi-Protocol Label Switching
IMS: IP Multimedia Subsystem
EoC: Ethernet over Cable
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2. A separation example in PSTN connecting with VoIP
A gateway could connect the traditional PSTN with VoIP
system, it performs: Translation of call signaling, translates signallings between PSTN
and VoIP, which is not easy since the former has common channel
signaling and different in-band signallings being one hundred types;
PSTN
Client
IP
Backbone
IP
Backbone
Client
Gateway implementation:1. Computer-based (computer + VoIP card)
2. Telecommunication grade (Chassis 机架)
Translates media formats between PSTN and VoIP;
AAA# (Authentication, Authorization, Accounting,认证 授权 记帐)…
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We could break one gateway into three connected networkelements, which is referred to as a decomposed gateway (拆分式网关):MGs# (Media Gateways)
–Conversion of media streams between circuit format and packet format
–Processing of in-band signaling in CSN, off-hook(摘机?挂机?), ringing,..
MGCs #(Media Gateway Controllers) or Softswitch# or CA (Call Agents)
–Manages connections (or processes call session ) in packet network
–Signaling conversion: CSN (电路交换网) PSN (分组网)SGs #(Signaling Gateways): constitute the interface to the CSN’s
out-of-band signaling, SS7.
MGC MG
SG
Gateway
64
IP
Backbone
SG
MGC
MGMG
PST
N
PST
N
PCMSS7 CAS,Q.931,…
Client
SIP /MEGACO
VoIP signalling: SIP, MEGACO
CCSS# common channel signaling sys: SS7
In-band signaling: CAS (channel associated
signalling), Q931
–Advantages Keeping the gateways simple,
different module has specific
functionality;
MG is dedicated to media
conversion, increasing the capability
of media processing;
Easy to meet various requirements
by combining different types of
SG/MGC/MG, so optimized the
performance-cost-ratio or agility of a
Gateway .
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3. Seminar for novel networking technologies
Each group of three students could select one issue, all
followings are all in English.
Each group performs a tutorial or overview related to
the selected issue, includes but not limited to :
background, motivation, system or networking
architecture, protocols, application scenario#(场景),…
Each group prepares a PPT related to the selected issue,
the selected PPTs will be presented in the course time
about 21 May (seventh course time). After each group
presentation is given, the comments will be given by
the other group and me.
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1. Home Networking
2. 10GE/100GE and networking
3. network slicing
4. SDx (x=almost everything, Networking, Access network, transceiver, satellite,
Modulator, …) 5. Network function virtualization application
6. Centric-y (Driven-y, y= application, content, data, name, …)
7. 5G access
8. 5G networking
9. 6G 10. Integrated or converged resource assignment of storage, computing and
transport
11. space-air-ground-sea networks
12. Network softwarization or softwarized network (网络软件化,there is an
international conference discussing annually, Netsoft.)
13. Intelligent clouding network (智慧云网络)14. AI-empowered (AI赋能)application in aspects of point (information
processing ,device), Line (communication sys), plane (access network,
optical net, core network, wireless net,…) and service (cloud, …)
15. Cognitive networking and application
16. IoT (Internet of thing) and application
17. Edge (Fog) computing
18. Block Chains and networking applications
19. Other issues make sense and novel.