Conclusions and project presentation - comp
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Transcript Conclusions and project presentation - comp
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A COURSE-END
CONCLUSIONS
Dr. Rocky K. C. Chang
The internetworking problem
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The internetworking problem
Different
data-link protocols
Different MAC address spaces
Different MTUs
An hour-glass model (end-to-end argument)
IP
as the glue
IP addresses
IP fragmentation and reassembly
IP over anything and everything
All boil down to the design goals
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Best effort IP service
Reliability
requirement: trusting states to the end hosts
Requirement for supporting a variety of TOS
Requirement for accommodating a variety of networks
End-to-end argument
Keep
the network simple: IP packets go in and IP
packets come out.
Implement applications at the network edge.
The forwarding problem
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Main issues of concerns
Who knows what
Speed (forwarding table size and lookup)
Not responsible for the correctness of the routes
Hop-by-hop forwarding as a result of the best-effort
approach.
Source routing and tunnels
Virtual circuit switching
IP switching
From classful to classless routing
The routing problem
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THE intelligence of the IP layer
Use a hop-by-hop protocol to deliver packets end-toend.
Main issues of concerns
Speed of convergence
Prone to routing loops
Efficiency
Two main approaches (in midst of many other
differences and variations)
Distance vector and link state
A tale of two routing problems
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All routing protocols concern delivering packets
from one point to another.
An
intradomain routing additionally concerns optimizing
certain costs of a route.
An interdomain routing additionally concerns satisfying
certain policies of an AS.
Current Internet characteristics
Asymmetric
routes
Packet reordering
Packet losses
Nonfriendly intermediaries
The end-to-end problems
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TCP adds the following services to IP:
Multiplexing
(through the port number)
Inordering (through the TCP SN)
At-most-one-copy (through the TCP SN)
Arbitrarily large application messages (through the
wraparound TCP SN space)
Flow control (through advertised window)
End-to-end reliability (through the sliding window
protocol and retransmission)
Congestion control (through ACK clocking, congestion
window, slow start, etc)
The congestion control problem
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Congestion control and/or resource allocation hold one of the
keys to the Internet stability.
A TCP sender interprets packet losses (without receiving ACKs)
as a sign of congestion.
Slow starting to trigger packet losses (reaching the network capacity)
Next time, perform congestion avoidance when approaching to the
congestion point.
Other approaches do not induce packet losses.
TCP/Vegas, Explicit Congestion Notification
Two Internet applications
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DNS provides
a distributed database for domain names and
protocols to obtain their resource records.
Web provides
A global naming system to identify resources
A text-based language to facilitate a navigation across
various related resources, and
A protocol for requesting and responding
Interaction between TCP and HTTP
Web proxies: not longer end-to-end
Coverage in terms of protocols
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Application
Transport
Network
BGP
FTP
Telnet
RIP-I/II
SMTP
DNS
TLS
RTP
TCP
UDP
IPSec
IGMP
PIM
OSPF
DVMRP
ICMPv4
IPv4
IPv6
ICMPv6
ARP
HTTP1.0
/1.1
IKE
DHCP
RSVP
Mobile
IPv4
Mobile
IPv6
RTSP
SIP