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These are the Lecture Slides of Computer Networks which includes Specific Protocols, Socket Programming, Network Application Protocols, Service Models, Client Server Paradigm, Distributed Processes, Interprocess Communication etc. Key important points are: v
Typology: Slides
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1: Introduction 1
Chapter goal:
get context, overview, “feel” of networking
more depth, detail
approach:
descriptive use Internet as example
Overview: what’s the Internet what’s a protocol? network edge network core access net, physical media performance: loss, delay protocol layers, service models backbones, NAPs, ISPs history ATM network
1: Introduction 2
What’s the Internet
backbone ISPs
regional ISPs
local ISPs
1: Introduction 4
A closer look at network structure:
network edge:
applications and hosts
network core:
routers network of networks
access networks,
physical media: communication links
1: Introduction 5
end systems (hosts):
run application programs e.g., WWW, email at “edge of network”
client/server model
client host requests, receives service from server e.g., WWW client (browser)/ server; email client/server
peer-peer model:
host interaction symmetric e.g.: teleconferencing
1: Introduction 7
Network edge: connectionless service
Goal: data transfer between end systems same as before! UDP - User Datagram Protocol [RFC 768]: Internet’s connectionless service unreliable data transfer no flow control no congestion control
App’s using TCP: HTTP (WWW), FTP (file transfer), Telnet (remote login), SMTP (email)
App’s using UDP: streaming media, teleconferencing, Internet telephony
1: Introduction 8
mesh of interconnected routers
question: how is data transferred through net? circuit switching: dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete “chunks”
1: Introduction 10
Network Core: Circuit Switching
network resources
(e.g., bandwidth) divided into “pieces”
pieces allocated to calls
not used by owning call
dividing link bandwidth into “pieces” frequency division time division
1: Introduction 11
Network Core: Packet Switching
each end-end data stream
network resources
each packet uses full link bandwidth
resource contention: aggregate resource demand can exceed amount available congestion: packets queue, wait for link use store and forward: packets move one hop at a time transmit over link wait turn at next link
Bandwidth division into “pieces” Dedicated allocation Resource reservation
1: Introduction 13
Network Core: Packet Switching
Packet-switching: store and forward behavior
1: Introduction 14
Packet switching versus circuit switching
1 Mbit link
each user: 100Kbps when “active” active 10% of time
circuit-switching: 10 users
packet switching: with 35 users, probability > 10 active less that.
Packet switching allows more users to use network!
N users 1 Mbps link
1: Introduction 16
Packet-switched networks: routing
destination we’ll study several path selection algorithms (chapter 4)
datagram network: destination address determines next hop routes may change during session analogy: driving, asking directions
virtual circuit network: each packet carries tag (virtual circuit ID), tag determines next hop fixed path determined at call setup time, remains fixed thru call routers maintain per-call state
1: Introduction 17
Access networks and physical media
residential access nets institutional access networks (school, company) mobile access networks
bandwidth (bits per second) of access network? shared or dedicated?
1: Introduction 19
Residential access: cable modems
HFC: hybrid fiber coax asymmetric: up to 10Mbps upstream, 1 Mbps downstream network of cable and fiber attaches homes to ISP router shared access to router among home issues: congestion, dimensioning deployment: available via cable companies, e.g., MediaOne
1: Introduction 20
Institutional access: local area networks
company/univ local area network (LAN) connects end system to edge router Ethernet: shared or dedicated cable connects end system and router 10 Mbs, 100Mbps, Gigabit Ethernet deployment: institutions, home LANs soon LANs: chapter 5
