2 COMP 431 Internet Services & Protocols A Whirlwind Introduction to the Internet ( “Networking Nouns and Verbs ”) Jasleen Kaur January 14, 2019 3 A Whirlwind Introduction to the Internet Overview ◆ What’s the Internet ◆ Network core ◆ Network edge ◆ Access nets, physical media ◆ Internet Structure & ISPs ◆ Performance: loss, delay ◆ Security ◆ Protocol layers, service models Introduce the major nouns and verbs of networking! *Internet Service Provider mobile network global ISP regional ISP* home network Institutional network
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COMP 431Internet Services & Protocols
A Whirlwind Introduction to the Internet(“Networking Nouns and Verbs”)
Jasleen Kaur
January 14, 2019
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A Whirlwind Introduction to the InternetOverview
◆ What’s the Internet◆ Network core◆ Network edge
◆ Access nets, physical media◆ Internet Structure & ISPs◆ Performance: loss, delay◆ Security◆ Protocol layers, service models
◆ Forwarding:» The process of moving packets among
routers from source to destination
◆ Datagram network: » Each packet carries a destination address» Destination address used to look up next hop» Route (next hop) may change at any time
◆ Virtual circuit (path) network: » Packets carry a “tag” (virtual circuit ID) that determines the next hop» Path determined at call setup time & remains fixed throughout call» Routers maintain per-call path state
mobile network
global ISP
regional ISP
home network
Institutional network
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Forwarding in Packet Switched NetworksVirtual circuit forwarding
◆ A (static) route is computed before any data is sent
◆ Packets contain a VC identifier» Identifier replaced at every hop
a b
c
aab
InboundInterface
...
bbc...
OutboundInterface
VCNumber
1273284...
New VCNumber
19863...
◆ Routers maintain per-connection state » And perform set-up/tear-
down operations
(Why not choose a single VC identifier for the entire path and avoid replacing it at each hop?)
//////
//////
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Forwarding in Packet Switched NetworksDatagram forwarding
◆ Packets contain complete destination address» Address specifies both a network and a host
◆ Each router examines the destination address» And forwards packet to the next router closest to the destination network
❖ Routers maintain a table of “next hops” to all destination networks◆ Routers maintain no per-connection state
a b
c
xxx.yyy.uuu.vvv.sss.ttt.
bbc
NetworkID
NextHop
... ...
//////
//////
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The Structure of the InternetThe physical makeup of the Internet
◆ Network core: » Routers» Network of networks
◆ Network edge:» Applications and hosts
◆ In between: Access networks» Physical media: communication links
mobile network
global ISP
regional ISP
home network
Institutional network
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Network StructureThe network edge
◆ End systems (hosts)» Live at the “edge of network”» Run applications
◆ Applications using UDP:» DNS (name to address mapping),» Streaming media (some), » Teleconferencing, » Internet telephony (VoIP)
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Network TaxonomyTelecommunication
networks
Circuit-switchednetworks
FDM TDM
Packet-switchednetworks
Networkswith VCs
DatagramNetworks
◆ The Internet» Is a Datagram network» Provides two types of services to applications:
❖ Connectionless (UDP)❖ Connection-oriented (TCP)
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The Structure of the InternetThe physical makeup of the Internet
◆ Network core: » Routers» Network of networks
◆ Network edge:» Applications and hosts
◆ In between: Access networks» Physical media: communication links
mobile network
global ISP
regional ISP
home network
Institutional network
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Network StructureAccess networks and physical media
◆ How to connect end-systems to the Internet (edge router)?» Residential access nets» Institutional/enterprise access
networks» Mobile access networks
◆ Differences/Issues: » Transmission speed (bits per second)
of access network?» Shared or dedicated?
mobile network
global ISP
regional ISP
home network
Institutional network
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Access Networks Example: Digital subscriber line (DSL)
◆ Uses the existing telephone line to connect to the “central office” DSLAM» Data sent over DSL phone line goes to Internet» Voice sent over DSL phone line goes to telephone net
◆ Lots of flavors of DSL but common data rates are:» A max of 2.5 Mbps upstream (typically < 1 Mbps)» ~24 Mbps downstream (possibly up to 50 Mbps)
central office telephonenetwork
DSLAM
voice, data transmitted at different frequencies over dedicated line to central office
DSLmodem
splitter
DSL access multiplexer
ISP
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Access Networks Example: Cable networks
◆ Cable relies on frequency division multiplexing (FDM)» Different communication “channels” are transmitted in different frequency