Chapter One Networking basics and trend 1.2 Network trend -networking basics and trend-V2.pdftechnologies in use for it. the networking area is local area, covering from several tens

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


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.


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.


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.



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.



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.


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


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


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.


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.


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.


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.


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


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


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

…


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.


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

https://en.wikipedia.org/wiki/Digital_signal

https://en.wikipedia.org/wiki/Telecommunications_network

https://en.wikipedia.org/wiki/Node_(networking)

https://en.wikipedia.org/wiki/Computing_device

https://en.wikipedia.org/wiki/Computer_network


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


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

https://lecturenotes.in/subject/11/data-communication-and-computer-network-dccn


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.


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


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


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


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


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


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


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


5. Data networks architecture

Planes of a network

PRM –Protocol Reference Model


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.


3. Manage.

Plane

2. Control

Plane

1. Data Plane

4. App Plane


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.


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.


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.


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?

2020/4/23 46

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#

2020/4/23 48

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).

2020/4/23 49

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.


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

https://www.plesk.com/wiki/protocol/

2020/4/23

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.


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


Chapter One

Networking basics and trend

1.1 Networking basics

1.2 Network trend


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


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.


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.


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

https://en.wikipedia.org/wiki/Network_convergence

2020/4/23

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。


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.


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.

2020/4/23 61

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

2020/4/23 62

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）…

2020/4/23 63

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 .

2020/4/23 65

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.


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.

Chapter One Networking basics and trend 1.2 Network trend -networking basics and trend-V2.pdftechnologies in use for it. the networking area is local area, covering from several tens

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