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CS685 Hot Topics in Data Center Networks, Cloud Computing, and Future Internet

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CS685 Hot Topics in Data Center Networks, Cloud Computing, and Future Internet Chen Qian Fall 2013 Introduction CQ (2013) 1-* * * * Layering decomposes a complex ... – PowerPoint PPT presentation

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Title: CS685 Hot Topics in Data Center Networks, Cloud Computing, and Future Internet


1
CS685 Hot Topics in Data Center Networks, Cloud
Computing, and Future Internet
  • Chen Qian
  • Fall 2013

2
What you can learn
  • Basic knowledge of conventional Internet
  • Protocols layers
  • Introduction of current hot topics in networking
    research
  • Data center networking
  • Cloud computing
  • Future Internet
  • Research skills in system and network area
  • Presentation skills

3
Cloud Computing
4
Data centers
5
Data centers
6
Data center networks
7
Future Internet
  • Content-based network? (YouTube, Netflix, etc.)
  • Most devices are mobile? (smartphones, laptops,
    touch pads, etc.)

8
Lecture 1 Introduction
  • 1.1 What is the Internet?
  • 1.2 Network edge
  • end systems, access networks, links
  • 1.3 Network core
  • packet switching, network structure
  • 1.4 Delay, loss and throughput in packet-switched
    networks
  • 1.5 Protocol layers

9
Whats the Internet nuts and bolts view
  • millions of connected computing devices hosts
    end systems
  • running network apps Web browser, YouTube,
    Skype, etc.
  • communication links
  • fiber, copper, radio, satellite
  • transmission rate bandwidth
  • routers forward packets (chunks of data)

10
Whats the Internet nuts and bolts view
  • Internet network of networks
  • loosely hierarchical
  • public Internet versus private intranet
  • protocols control sending, receiving of msgs
  • e.g., TCP, IP, HTTP, DNS, Ethernet

11
Whats the Internet a service view
  • communication services provided to apps
  • reliable data delivery from source to destination
  • File transfer, email, E-bank.
  • best effort (unreliable) data delivery
  • Multimedia (cell phone, video streaming, VoIP)

12
Whats a protocol?
  • human protocols
  • Homework assignment
  • Turn in
  • I have a question
  • Explain
  • specific msgs sent
  • specific actions taken when msgs received, or
    other events
  • network protocols
  • machines rather than humans
  • all communication activity in Internet governed
    by protocols

protocols define format, order of msgs sent and
received among network entities, and actions
taken on msg transmission, receipt
13
Whats a protocol?
  • a human protocol and a computer network protocol

Hi
TCP connection request
Hi
14
Chapter 1 roadmap
  • 1.1 What is the Internet?
  • 1.2 Network edge
  • end systems, access networks, links
  • 1.3 Network core
  • packet switching, network structure
  • 1.4 Delay, loss and throughput in packet-switched
    networks
  • 1.5 Protocol layers

15
A closer look at network structure
  • network edge applications and hosts
  • access networks, physical media wired, wireless
    communication links
  • network core
  • interconnected routers
  • network of networks

16
The network edge
  • end systems (hosts)
  • run application programs
  • e.g. Web, email
  • at edge of network
  • 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

17
Access networks and physical media
  • Q How to connect end systems to edge router?
  • residential access nets
  • institutional access networks (school, company)
  • mobile access networks
  • Keep in mind
  • bandwidth (bits per second) of access network?
  • shared or dedicated?

18
Ethernet Internet access
  • Typically used in companies, universities, etc
  • 10 Mbs, 100Mbps, 1Gbps, 10Gbps Ethernet
  • Today, end systems typically connect into
    Ethernet switch

19
Wireless access networks
  • shared wireless access network connects end
    system to router
  • via base station aka access point
  • wireless LANs
  • 802.11b/g (WiFi) 11 or 54 Mbps
  • wider-area wireless access
  • provided by telco operators
  • 1 Mbps over cellular system (3G)
  • WiMAX promises 10s Mbps over wide area

router
base station
mobile hosts
20
Home networks
  • Typical home network components
  • DSL or cable modem
  • router/firewall/NAT
  • Ethernet
  • wireless access
  • point

wireless laptops
to/from cable headend
cable modem
router/ firewall
wireless access point
Ethernet
21
Chapter 1 roadmap
  • 1.1 What is the Internet?
  • 1.2 Network edge
  • end systems, access networks, links
  • 1.3 Network core
  • packet switching, network structure
  • 1.4 Delay, loss and throughput in packet-switched
    networks
  • 1.5 Protocol layers

22
The Network Core
  • mesh of interconnected routers
  • the fundamental question how is data transferred
    through net?
  • circuit switching dedicated circuit per call
    telephone net
  • packet-switching data sent thru net in discrete
    chunks

23
Packet Switching
100 Mb/s Ethernet
C
A
statistical multiplexing
1.5 Mb/s
B
queue of packets waiting for output link
  • Sequence of A B packets does not have fixed
    pattern
  • bandwidth shared on demand
  • queueing delay, packet loss

24
store-and-forward
L
R
R
R
  • store and forward entire packet must arrive at
    router before it can be transmitted on next link
  • A file/message larger than maximum packet size is
    transmitted as multiple packets

25
Network Core Packet Switching
  • each end-end data stream divided into packets
  • packets of different users share network
    resources
  • each packet uses full link bandwidth
  • resources used as needed
  • resource contention
  • aggregate resource demand can exceed amount
    available
  • congestion packets queue, wait for link use

26
Packet Switching versus Message Switching
Advantages of packet switching
  • Smaller end-to-end delay from pipelining
  • Less data loss from transmission errors

Disadvantages of packet switching
  • More header bits
  • Additional work to do segmentation and reassembly

27
Packet switching versus circuit switching
  • Packet switching allows more users to use network!
  • 1 Mb/s link
  • each user
  • 100 kb/s when active
  • active 10 of time (a bursty user)
  • circuit-switching
  • 10 users
  • packet switching
  • with 35 users, probability gt 10 active at same
    time is less than .0004

N users
1 Mbps link
Q how did we get value 0.0004?
28
Packet switching versus circuit switching
  • Is packet switching a slam dunk winner?
  • great for bursty data
  • resource sharing
  • simpler, no call setup
  • excessive congestion packet delay and loss
  • protocols needed for reliable data transfer,
    congestion control
  • Q How to provide circuit-like behavior?
  • bandwidth guarantees needed for audio/video apps
  • solution may impact network neutrality

29
Internet structure network of networks
  • roughly hierarchical
  • at center tier-1 ISPs (e.g., Verizon, Sprint,
    ATT, Cable and Wireless), national/international
    coverage
  • treat each other as equals

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
30
Tier-1 ISP e.g., Sprint
31
Internet structure network of networks
  • Tier-2 ISPs smaller (often regional) ISPs
  • Connect to one or more tier-1 ISPs, possibly
    other tier-2 ISPs

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
32
Internet structure network of networks
  • Tier-3 ISPs and local ISPs
  • last hop (access) network (closest to end
    systems)

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
33
Internet structure network of networks
  • a packet passes through many networks!

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
34
Chapter 1 roadmap
  • 1.1 What is the Internet?
  • 1.2 Network edge
  • end systems, access networks, links
  • 1.3 Network core
  • packet switching, network structure
  • 1.4 Delay, loss and throughput in packet-switched
    networks
  • 1.5 Protocol layers

35
How do loss and delay occur?
  • packets queue in router buffers
  • packet arrival rate to link exceeds output link
    capacity
  • packets queue, wait for turn

A
B
36
Four sources of packet delay
  • 1. nodal processing
  • check bit errors
  • determine output link
  • 2. queueing
  • time waiting at output link for transmission
  • depends on congestion level of router

37
Delay in packet-switched networks
  • 4. Propagation delay
  • d length of physical link
  • s propagation speed in medium (2x108 m/sec)
  • propagation delay d/s
  • 3. Transmission delay
  • Rlink bandwidth (bps)
  • Lpacket length (bits)
  • time to send bits into link L/R

38
End-to-End Delay
  • Nodal delay (from when last bit of packet arrives
    at this node to when last bit arrives at next
    node)
  • dnodal dproc dqueue dtrans dprop
  • End-to-end delay over N identical nodes/links
    from client c to server s (from when last bit of
    packet leaves client to when last bit arrives at
    server)
  • dc-s dprop Ndnodal
  • Round trip time (RTT)
  • RTT dc-s ds-c tserver
  • where tserver is server processing time

39
Implications of end-to-end delay
  • Relative importance of bandwidth and distance
  • for a small message (e.g. 1 byte), distance (1 ms
    vs. 100 ms propagation time) is more important
    than bandwidth (1 Mbps vs. 100 Mbps)
  • for a large message (e.g., 25 Mbyte), bandwidth
    is more important than distance
  • Delay x Bandwidth product
  • Example for 100 ms end to end delay and 45 Mbps
    bandwidth, there can be up to 560 Kbyte of data
    in flight

40
Throughput
  • throughput rate (bits/time unit) at which bits
    transferred between sender/receiver
  • instantaneous rate at given point in time
  • average rate over longer period of time

link capacity Rs bits/sec
link capacity Rc bits/sec
server, with file of F bits to send to client
server sends bits (fluid) into pipe
41
Throughput (more)
  • Rs lt Rc What is average end-end throughput?

Rs bits/sec
42
Throughput Internet scenario
Rs
  • per-connection end-end throughput
    min(Rc,Rs,R/10)
  • in practice Rc or Rs is often bottleneck
  • Or the server is the bottleneck

Rs
Rs
R
Rc
Rc
Rc
10 connections (fairly) share backbone bottleneck
link R bits/sec
43
Chapter 1 roadmap
  • 1.1 What is the Internet?
  • 1.2 Network edge
  • end systems, access networks, links
  • 1.3 Network core
  • packet switching, network structure
  • 1.4 Delay, loss and throughput in packet-switched
    networks
  • 1.5 Protocol layers

44
Protocol Layers
  • Networks are complex!
  • many pieces
  • hosts
  • routers
  • links of various media
  • applications
  • protocols
  • hardware, software
  • Question
  • Is there any hope of organizing structure of
    network?
  • Or at least our discussion of networks?

45
Layered architecture
  • Use abstraction to hide complexity
  • Each layer
  • provides a service via its own internal actions
    as well as relying on service provided by layer
    below
  • is a network of processes
  • Can have alternative abstractions at each layer
    (resulting in protocol graph rather than protocol
    stack)

46
Each protocol
  • involves two or more peers
  • two interfaces defined
  • service interface operations a local user can
    perform on a protocol entity and get results
  • peer-peer interface form and meaning of messages
    exchanged by protocol entities (also called
    peers) to provide protocol service
  • term protocol generally used to refer to
    peer-peer spec

Host 1
Host 2
High-level entity
Service interface
Protocol entity
Peer-to-peer interface
47
Internet protocol stack
  • application supporting network applications
  • FTP, SMTP, HTTP
  • transport process-process data transfer
  • TCP, UDP
  • network routing of datagrams from source to
    destination
  • IP, routing protocols
  • link data transfer between neighboring network
    elements
  • PPP, Ethernet
  • physical bits on the wire

48
ISO/OSI reference model
  • presentation allow applications to interpret
    meaning of data, e.g., encryption, compression,
    machine-specific conventions
  • session synchronization, checkpointing, recovery
    of data exchange
  • Internet stack missing these layers!
  • these services, if needed, must be implemented in
    application

49
Logical communication between peers
data
  • E.g. transport
  • accept data from application
  • add addressing, reliability check info to form a
    message
  • send message to peer via a delivery service
  • wait for peers reply (ack)

transport
ack
data
data
transport
50
Physical path of data
  • Each layer takes data (service data unit) from
    above
  • adds header to create its own protocol data unit
  • passes protocol data unit to layer below

More terminology A switch is a relay with two
layers (physical and link). A repeater is a
relay with only the physical layer.
51
Introduction Summary
  • Covered a ton of material!
  • Internet components hosts, links, routers,
    Internet
  • whats a protocol?
  • network edge, core, access network
  • packet-switching versus circuit-switching
  • Internet structure ISPs
  • performance loss, delay, throughput
  • layering

52
End of Lecture01
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