lecture 2 1-1 internet overview: roadmap 1.1 what is the internet? (a simple overview last week)...
Post on 21-Dec-2015
217 views
TRANSCRIPT
![Page 1: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/1.jpg)
Lecture 2 1-1
Internet Overview: roadmap
1.1 What is the Internet? (A simple overview last week)
Today, A closer look at the Internet structure!1.2 Network edge
end systems, access networks, links
1.3 Network core circuit switching, packet switching
1.4 Delay, loss and throughput in Internet
1.5 Protocol layers, service models1.6 Networks under attack: security
![Page 2: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/2.jpg)
Lecture 2
Recap: What are the components of Internet?
End-users (Hosts) e.g. computers
access networks, physical media: wired, wireless
communication links
network core: interconnected
routers network of networks
1-2
![Page 3: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/3.jpg)
Lecture 2
End-users (Hosts) End-users (hosts):
run application programs e.g. Web, email
Hosts further divided into Client Hosts Server Hosts
Two different models of networking client/server model
• client host requests, receives service from always-on server
• e.g. Web browser/server; email client/server
peer-peer model:• minimal (or no) use of dedicated servers• e.g. Skype, BitTorrent
client/server
peer-peer
1-3
![Page 4: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/4.jpg)
Client/server model is the dominant design for Internet applications server - is the information provider client - is the information consumer
example web server and a client running web browser a CNN web server simultaneously serves
thousands of clients.
Lecture 2
The Client/Server Model
1-4
![Page 5: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/5.jpg)
Lecture 2
Hosts are not sufficient for networking!
End-users (hosts): run application programs e.g. Web, email
But, hosts alone would not be enough We need to connect the
hosts
HOW?
1-5
![Page 6: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/6.jpg)
Lecture 2
Access networks and physical media
Q: How to connect end systems to edge router?
1. residential access nets
2. institutional access networks (school, company)
3. mobile access networks
1-6
![Page 7: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/7.jpg)
Lecture 2
Residential access: point to point access
Dialup via modem up to 56Kbps direct access
to router (conceptually)
ADSL: asymmetric digital subscriber line up to 1 Mbps home-to-router up to 8 Mbps router-to-home ADSL deployment:
happening
1-7
![Page 8: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/8.jpg)
Lecture 2
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
deployment: available via cable companies, e.g., MediaOne, CableVision
1-8
![Page 9: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/9.jpg)
Lecture 2
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 Mbps, 100Mbps, Gigabit Ethernet
deployment: institutions, home LANs happening now
1-9
![Page 10: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/10.jpg)
Lecture 2
Wireless access networks
shared wireless access network connects end system to router
wireless LANs: radio spectrum replaces
wire e.g., 802.11b/g (WiFi):
11 or 54 Mbps
wider-area wireless access next up (?): WiMAX
(10’s Mbps) over wide area
basestation
mobilehosts
router
1-10
![Page 11: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/11.jpg)
Lecture 2 1-11
Internet Overview: roadmap
1.1 What is the Internet? (A simple overview last week)
Today, A closer look at the Internet structure!1.2 Network edge
end systems, access networks, links
1.3 Network core circuit switching, packet switching
1.4 Delay, loss and throughput in Internet
1.5 Protocol layers, service models1.6 Networks under attack: security
![Page 12: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/12.jpg)
Lecture 2 1-12
The Network Core
Internet: mesh of interconnected routers
How is data transferred through net? circuit switching:
dedicated circuit per call: telephone net
packet-switching: data sent thru net in discrete “chunks”
![Page 13: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/13.jpg)
Lecture 2 1-13
Network Core: Circuit Switching
Telephone call like mechanism End-end resources
reserved for “call”
dedicated resources: no sharing (link bandwidth)
circuit-like (guaranteed) performance
call setup required
![Page 14: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/14.jpg)
Lecture 2 1-14
Network Core: Circuit Switching
Total network resources (e.g., bandwidth) divided into “pieces” pieces allocated to calls resource piece idle if not used by owning call
(no sharing)
dividing link bandwidth into “pieces”…HOW? frequency division multiplexing (FDM)
• Users use different frequency channels time division multiplexing (TDM)
• Users use different time slots
![Page 15: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/15.jpg)
Lecture 2 1-15
Circuit Switching: FDM and TDM
FDM
frequency
time
TDM
frequency
time
4 users
Example:
![Page 16: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/16.jpg)
Lecture 2 1-16
Numerical example 1
You need to send a file of size 640,000 bits to your friend. You are using a circuit-switched network with TDM. Suppose, the circuit-switch network link has a bit rate of 1.536 Mbps (1Mb = 106 bits) and uses TDM with 24 slots. How long does it take you to send the file to your friend?
Let’s work it out!
![Page 17: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/17.jpg)
Lecture 2 1-17
Disadvantages of Circuit-Switching
Only static number of users This number must be fixed before the actual
operation Each user gets only a “piece of the pie” even if the
other users are possibly idle Prev. example: I get only 1/24th of the entire time
Resource wastage Impossible to admit new user in the middle of the
operation
![Page 18: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/18.jpg)
Lecture 2 1-18
Packet Switching
A
B
C100 Mb/sEthernet
1.5 Mb/s
D E
queue of packetswaiting for output
link
![Page 19: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/19.jpg)
Lecture 2 1-19
Network Core: Packet Switching
each end-end data stream divided into packets
user A, B packets share network resources
each packet uses full link bandwidth
resources used as needed
Bandwidth division into “pieces”
Dedicated allocationResource reservation
![Page 20: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/20.jpg)
Lecture 2 1-20
Packet switching versus circuit switching Adv: Packet switching allows users to use the
network dynamically! resource sharing simpler, no call setup New user can enter or leave inside the
operation
Is there any downside of packet switching? With excessive number of users packet delay and loss Efficiency of the system (measured in throughput)
drops!
![Page 21: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/21.jpg)
Lecture 2 1-21
How do delay and loss occur?packets queue in router buffers store and forward: packets move one hop at a
time Router receives complete packet before forwarding
packets queue, wait for turn…DELAY
A
B
packet being transmitted (delay)
packets queueing (delay)
![Page 22: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/22.jpg)
Lecture 2 1-22
Four sources of packet delay
1. nodal processing: check bit errors determine output link
A
B
propagation
transmission
nodalprocessing queueing
2. queueing time waiting at output
link for transmission depends on
congestion level of router
![Page 23: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/23.jpg)
Lecture 2 1-23
Delay in packet-switched networks3. Transmission delay: R=link bandwidth
(bps) L=packet length (bits) time to send bits into
link = L/R
4. Propagation delay: d = length of physical
link s = propagation speed in
medium (~2x108 m/sec) propagation delay = d/s
A
B
propagation
transmission
nodalprocessing queueing
Note: s and R are very different quantities!
![Page 24: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/24.jpg)
Lecture 2 1-24
Total delay
dproc = processing delay typically a few microsecs or less
dqueue = queuing delay depends on congestion
dtrans = transmission delay = L/R, significant for low-speed links
dprop = propagation delay a few microsecs to hundreds of msecs
proptransqueueproctotal ddddd
![Page 25: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/25.jpg)
Lecture 2 1-25
Numerical example 2
Example: A wants to send a packet to B. The packet size is, L = 7.5 Mb (1 Mb = 106 bits). The link speed is, R = 1.5 Mbps. How long does it take to send the packet from A to B? Assume zero propagation delay.
Let’s work it out!
R R R
L
A B
![Page 26: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/26.jpg)
Lecture 2 1-26
Packet loss
queue (aka buffer) preceding link in buffer has finite capacity
packet arriving to full queue dropped (aka lost)
lost packet may be retransmitted by previous node, by source end system, or not at allA
B
packet being transmitted
packet arriving tofull buffer is lost
buffer (waiting area)
![Page 27: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/27.jpg)
Lecture 2 1-27
Throughput throughput: rate at which information
bits transferred between sender/receiver
Rs
Rs
Rs
Rc
Rc
Rc
R
![Page 28: Lecture 2 1-1 Internet Overview: roadmap 1.1 What is the Internet? (A simple overview last week) Today, A closer look at the Internet structure! 1.2 Network](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649d5e5503460f94a3d890/html5/thumbnails/28.jpg)
Lecture 2 1-28
Numerical example 3: Throughput
Rs
Rs
Rs
Rc
Rc
Rc
A
B Example: A has requested for
a packet (size 640,000 bits) from server B. The packet will come through an intermediate router C. It takes 0.1 second for the packet from B to C and 0.4 seconds from C to A. (Note: 1Mb=106 bits). Assume zero propagation delay. What is the throughput from
B to C? What is the throughput from
C to A? What is the average
throughput from B to A?
Let’s work it out!
C