业余和 卫星业余 业务 - ITU · 2018-05-29 · 业余和卫星业余业务 iii 前言 此《手册》综合介绍了业余和卫星业余业务,还包括一份涉及业余和卫星业余业务的现
Weiqiang Sun 一些数据 从 1978 年到 2007...
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Transcript of Weiqiang Sun 一些数据 从 1978 年到 2007...
Weiqiang Sun
一些数据• 从 1978 年到 2007 年,通信业年业务收入一直保持两位数增长并一直
领先于 GDP 增幅。业务总量和业务收入年同比增长率均保持了两位数,年收入规模从 7.3 亿元扩张到 7280 亿元,年均增长率达到 26.9%– 78 ~ 87 年,电信业务收入年平均增长率达到 21.1%, 7.3 亿 -> 41.1 亿– 88 ~ 97 年,电信业务收入年复合增长率达到 42.2%, 59.6 亿 1421.3 亿– 98 ~ 07 年,电信业务收入年平均增长率达到 16.6%, 1828.4 亿 7280
亿– 2007 年,电信业务收入增长 11.2%, GDP 增速 13.0%– 2008 年,电信业务收入增长 9.0%, GDP 增速 6.6%– 2009 年上半年,电信业务收入增长 2.3% ,不到 GDP 的 1/3
• 电信业的转型– 话务运营阶段– 转型阶段– 信息运营阶段
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Weiqiang Sun
机会在哪里?• 3G 与宽带!
• 2009 年上半年,电信运营商资本开支投向主要是 3G 、传输网 ( 光传输 ) 、和宽带 (FTTx)– 3G
• 中国移动计划 2009 年底前 3G 覆盖 238 个城市, 2011 年覆盖所有地级市
• 中国联通 3G 网络覆盖城市已由年初计划的 284 个扩大到年内的 335个, 2010 年将近一步扩大覆盖面
– 宽带业务具有高 ARPU 值,现金流稳定的特征• 宽带提速• 有线宽带和无线宽带的融合发展和无缝连接
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Weiqiang Sun
NETWORK LAYER IN PRACTICE: IP AND ATM
Weiqiang Sun
The TCP/IP protocol suite
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• Transmission Control Protocol / Internet Protocol• Developed by DARPA to connect universities and research labs
Applications
Transport
Network
Link
Telnet, FTP, email etc
TCP, UDP
IP, ICMP, IGMP
Device drivers, interface cards
TCP: Transmission Control ProtocolUDP: User Datagram ProtocolIP: Internet Protocol
The Internet Layered model
Weiqiang Sun
Internetworking with TCP/IP
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application
transport
IP
Data link and lower layer
application
transport
IP
Data link and lower layer
IP
Ethernet Token ring
Token ringEthernet
Ethernet
IP protocol
IP protocol
TCP/UDP protocol
FTP, HTTP, SMTP…
Weiqiang Sun
The TCP/IP suite
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PING telnet & rlogin FTP SMTP X Trace
route DNS TFTP BOOTP SNMP RPC
TCP UDP
ICMP IP IGMP
DATA LINKARP RARP
Weiqiang Sun
Internet sub-layer
• A sub-layer between the transport and network layers is required when various incompatible networks are joined together– This sub-layer is used at gateways between the different networks– In the internet this function is accomplished using the Internet Protocol (IP)
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IP
DLC LayerLink 1
DLC LayerLink 1
DLC LayerLink 1
DLC LayerLink 1
DLC LayerLink 1
DLC LayerLink 1
On a gateway connecting different types of networks, IP is the protocol to realize inter-operability
Weiqiang Sun
IP addresses
• 32 bit address written as four decimal numbers– One per byte of address (202.120.39.134)
• IP Address classes
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10 Net ID Host ID
0 Net ID Host ID
8 32
16 32
110 Net ID Host ID
16 32
Class A Address
Class B Address
Class C Address
11100000
16 32Class D Address, (For multicast only)
Weiqiang Sun
IPv4 address classes
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Weiqiang Sun
Routing a packet in the network
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1
2
5
3
6
4
11
22
1122
33
11 33
22
11 22
33
44
11
22 33
11
22 33
Routing table in 5
Dest Next Hop Out Intf
1 3 2
2 2 1
3 3 2
4 3 2
6 6 3
Routing table in 3
Dest Next Hop Out Intf
1 1 1
2 5 4
6 6 3
4 4 2
5 5 4
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Weiqiang Sun
IP router architecture
Weiqiang Sun
3 generations of IP routers
Bus based router
Bus based router with dist. routing
Switch-based router with multi. Forwarding eng.
Weiqiang Sun
Host name
• Each host has a unique name• Domain name system (DNS): a distributed
database that provides a mapping between IP addresses and host names
• E.g., 202.120.39.134 FRONT.SJTU.EDU.CN
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Weiqiang Sun
Internet standards
• Internet Engineering Task Force (IETF)– Development on near term internet standards– Open body– Meets 3 times a year
• Request For Comments (RFCs)– Official internet standards– Available from IETF web page: http://www.ietf.org/
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Weiqiang Sun
The Internet protocol (IP)
• Routing packets across the network• Unreliable service
– Best effort delivery– Recovery from lost packet must be done at higher layers
• Connectionless– Packets are delivered independently– Can arrive out of order– Re-ordering must be done at higher layers
• Current version V4, IPv4• Future IPv6
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Weiqiang Sun
IP header
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0 bit Version Header length Type of Service Total Length
32 bit Identification Flags Fragment Offset
64 bit Time To Live Protocol Header Checksum
96 bit Source IP Address
128 bit Destination IP Address
160 bit Options
160or192+ Data
Note that the minimum header size is 20 bytes, or 160 bits
Weiqiang Sun
IP header
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Weiqiang Sun
Dynamic Host Configuration (DHCP)
• Automated method for assigning network numbers– IP addresses, default routers
• Computer contact DHCP server at Boot-up time• Server assigns IP address• Allows sharing of address space
– More efficient use of address space– Adds scalability
• Addresses are “leased” for some time– Not permanently assigned
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Weiqiang Sun
Address Resolution Protocol (ARP)
• The role of the IP routing is to deliver the packet to its destination subnet– To the last hop router
• Addressing inside a subnet, or a LAN, is based on local addresses, such as Ethernet addresses
• ARP provides a mapping between IP addresses and LAN addresses• RARP provides mapping from LAN addresses to IP addresses• Both accomplished by sending out a broadcast message• An ARP cache is maintained at each node with recent mappings to avoid
frequent address resolution (for better performance)
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Weiqiang Sun
ARP at source subnet
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R1
S
(4) I am here at 00-01-21-32-32-32
(3) Hi all~ Where is my lovely router R1?
(1) Computer S is configured to have a default router R1(2) S wants to send a message to D, and D is outside of the same LAN(3) S sends an ARP request for Ethernet Address of R1(4) R1 sends ARP responds to S(5) S sends the message to R1 with Ethernet addressing(6) R1 routes the packet to the next hop in the internet and the message
will be subsequently routed further toward D
Weiqiang Sun
ARP at destination subnet
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R2
D
(3) Hi all~ I got a message for 202.120.39.134. Where is
he?
(4) Hi R2~ I am here at 00-01-01-11-AB-
ED
(1) An IP packet is delivered by the network from its source subnet to router R2.
(2) Router R2 realizes that the packet has reached its destination subnet by comparing the destination address in the IP packet and its local interface configurations (subnet address and mask)
(3) Router R2 sends an ARP request on the interface to the subnet(4) Destination node D responses to the request(5) Packet is delivered to D with Ethernet addressing
Weiqiang Sun
Routing in the multi-AS Internet
• The Internet is divided into sub-networks, each under the control of a single authority known as an Autonomous Systems (AS)
• Routing algorithms are divided into two categories– Interior protocols (within an AS)– Exterior protocols (between ASs)
• Interior protocols use shortest path algorithms– Distance vector proto. Based on Bellman-Ford– Link state proto. Based on Dijkstra’s algorithm
• Exterior protocols route packets across ASs– Issue: no single cost metric, policy routing, etc– Hierarchical routing based on “peering” agreements– Example: Exterior Gateway Protocol (EGP) and Border Gateway Protocols
(BGP)
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Weiqiang Sun
Border Gateway Protocol (BGP)
• Routing between Autonomous systems– Find a path (no optimality) to destination (AS)– Path must satisfy policy criteria
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AS corporation
AS Large service
provider
AS Large service
provider
AS Small ISP
AS corporation
AS corporation
AS Small ISP
AS Small ISP
Transit AS
Multi-homed AS(No transit traffic)
Stub AS
Weiqiang Sun
BGP overview• BGP speaker – one per AS
– Establishes (TCP) sessions with other “speakers” to exchange reachability information
• Border “gateways” – routers that interface between AS’s• BGP advertises complete paths to destination AS
– Avoid loop problems– Enable policy decisions (e.g. avoid certain ASs)– AS numbers – centrally assigned 16 bit numbers for transit ASs
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128.64.3128.61.2
192.12.2Path to 128.64.2: (AS-144, AS-367)
AS - 12 AS - 144
AS - 367
AS - 298
Weiqiang Sun
Relationship between ASs
• ISP “tiers”– Tier-1 ISPs – provide global reachability– Tier-2 ISPs – regional/country– Tier-3 ISPs – local
• Provider-customer relationship (transit)– Smaller ASs purchase internet access from
larger ones
• Peering– ISPs of similar size are “peers” and
forward each other’s traffic at no charge– Paid peering: a small ISP may purchase
the right to peer with a larger provider
• Policy issue– Which route would an ISP advertise?
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Tier-1 ISP
Tier-2 ISP Tier-1 ISP
Tier-2 ISP
Tier-3 ISP
Weiqiang Sun
IPv6
• Effort started in 1991 as IPng• Motivation
– Need to increase IP address space– Support for real-time applications – QoS– Security, mobility and auto-configuration
• Major changes– Increased address space (128bit)– Support for QoS via Flow Label field– Simplified header– Security
• Transition to IPv6– Cannot be done at once; must support co-existance– Dual-stack: routers run both IPv4 and IPv6– Tunneling: IPv6 packets carried in payload of IPv4 packets, or vice versa
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Weiqiang Sun
QoS in the Internet
• Quality of Service parameters– Dropped packets– Delay– Jitter– Out-of-order delivery– Error
• Applications that require QoS– Multimedia streaming – IPTV– IP telephony, or VoIP– Video conferencing– Online game– Remote control– …
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Weiqiang Sun
QoS mechanisms
• IntServ: integrated services– best-effort service, real-time service, and
controlled link sharing– Resource reserved prior to data transfer– Resource released after transfer completes
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request
grant
Weiqiang Sun
QoS mechanisms (cont.)
• DiffServ: differentiated services– Tagging on ingress edge node– Un-tagging on egress edge node– Routed/processed in network according to the tag/label– Realizes service differentiation through per-hop behavior (PHB)
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Weiqiang Sun
DiffServ and MPLS
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• MPLS: Multi-Protocol Label Switching
Weiqiang Sun
ATM - Asynchronous Transfer Mode
• 1980’s effort by the phone companies to develop an integrated network standard (B-ISDN) that can support voice, data, video, etc.
• ATM uses small (53 Bytes) fixed size packets called “cells” – Why cells?
• Cell switching has properties of both packet and circuit switching Easier to implement high speed switches
– Why 53 bytes? • Small cells are good for voice traffic (limit sampling delays) For 64Kbps voice it takes 6 ms to fill
a cell with data
• ATM networks are connection oriented – Virtual circuits
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Weiqiang Sun
ATM Reference Architecture
• Upper layers – Applications – TCP/IP
• ATM adaptation layer – Similar to transport layer – Provides interface between upper layers
and ATM – Break messages into cells and
reassemble • ATM layer
– Cell switching – Congestion control
• Physical layer – ATM designed for SONET – Synchronous optical network – TDMA transmission scheme with 125 μs
frames
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Weiqiang Sun
ATM Cell format
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Weiqiang Sun
VPI/VCI
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Weiqiang Sun
ATM cell switches
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Weiqiang Sun
ATM summary
• ATM is mostly used as a “core” network technology • ATM Advantages
– Ability to provide QoS – Ability to do traffic management – Fast cell switching using relatively short VC numbers
• ATM disadvantages – It not IP -most everything was design for TCP/IP – It’s not naturally an end-to-end protocol
• Does not work well in heterogeneous environment • Was not design to inter-operate with other protocols • Not a good match for certain physical media (e.g., wireless)
• Many of the benefits of ATM can be “borrowed” by IP– Cell switching core routers – Label switching mechanisms
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Weiqiang Sun
Project #1
• Try to identify at least 3 applications that use plaint text password/identification method– Use Wireshark to capture the plaint text password– Write a report to describe the problem
– Due date: Oct. 28
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