1 02/07/06 1 Internet and Intranet Protocols and Applications Lecture 1a: Introduction to Internet and Intranet Protocols and Applications January 17, 2006 Arthur Goldberg Computer Science Department New York University [email protected]02/07/06 2 Why Study “Internet and Intranet Protocols and Applications”? – Same systems used in the two major types of networks, the public Internet and internal (corporate) Intranets – Accessible for study, because protocol standards are published and their design is publicly debated 02/07/06 3 Growth of the Internet Source: Internet Software Consortium ; available at http://www.isc.org/ds/hosts.html Survey data obtained: 87-97: walking the DNS Tree(s). See RFC1296 for details 97-present: checking which IP addresses are valid; see http://www.isc.org/ds/new-survey.html 02/07/06 4 Log Growth of the Internet Source: Internet Software Consortium ; available at http://www.isc.org/ds/hosts.html Note exponential growth; recent slowing. 100 1,000 10,000 100,000 1,000,000 10,000,000 100,000,000 1,000,000,000 1980 1985 1990 1995 2000 2005 host table DNS/domain survey Adjusted IP active domain survey
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Why Study “Internet and Intranet Protocols and Applications”?
– Same systems used in the two major types of networks, the public Internet and internal (corporate) Intranets
– Accessible for study, because protocol standards are published and their design is publicly debated
02/07/06 3
Growth of the Internet
Source: Internet Software Consortium ; available at http://www.isc.org/ds/hosts.htmlSurvey data obtained: 87-97: walking the DNS Tree(s). See RFC1296 for details97-present: checking which IP addresses are valid; see http://www.isc.org/ds/new-survey.html
02/07/06 4
Log Growth of the Internet
Source: Internet Software Consortium ; available at http://www.isc.org/ds/hosts.htmlNote exponential growth; recent slowing.
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000
1980 1985 1990 1995 2000 2005
host tableDNS/domain surveyAdjustedIP active domain survey
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Systems to study• Protocols
– Web (HTTP, SSL)– Email (SMTP, POP3, IMAP)
– File Transfer (FTP)
– Reliable Multicast (PGM)
• Client and server software (and intermediate systems, like caching proxies, gateways and firewalls)
• Object formats for documents and programs (embedded in protocols)
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Challenges
• Heterogeneity• Client and server system architecture• Performance (in protocols and
given notion of “network”, let’s examine IP addresses:
“class-full” addressing:
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Classes And Network Sizes
• Maximum network size determined by class of address– Class A large– Class B medium– Class C small
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IP Addressing Example
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IP addressing: CIDR• classful addressing:
– inefficient use of address space, address space exhaustion– e.g., class B net allocated enough addresses for 65K hosts, even if
only 2K hosts in that network• CIDR: Classless InterDomain Routing
– network portion of address of arbitrary length– address format: a.b.c.d/x, where x is # bits in network portion of
address
11001000 00010111 0001000 000000000
networkpart
hostpart
200.23.16.0/23
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Internet Packets• Contains sender and destination addresses• Size depends on data being carried• Called IP datagram• Two Parts Of An IP Datagram
• Header– Contains source and destination address– Fixed-size fields
• Data Area (Payload)– Variable size up to 64K– No minimum size
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IP V4 Datagram format
ver length
32 bits
data (variable length,typically a TCP
or UDP segment)
16-bit identifierInternet
checksumtime to
live32 bit source IP address
IP protocol versionnumber
header length (bytes)
max numberremaining hops
(decremented at each router)
forfragmentation/reassembly
total datagramlength (bytes)
upper layer protocolto deliver payload to
head.len
type ofservice
“type” of data flgs fragment offsetupper
layer
32 bit destination IP address
Options (if any) E.g. timestamp,record routetaken, specifylist of routers to visit.
From Computer Networking: A Top-Down Approach Featuring the Internet by Kurose & Ross 02/07/06 34
IP Semantics
• IP is connectionless– Datagram contains identity of destination– Each datagram sent/handled independently
• Routes can change at any time
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IP Semantics (continued)
• IP allows datagrams to be– Delayed– Duplicated– Delivered out-of-order– Lost
• Called best effort delivery• Motivation: accommodate all possible networks
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Requests For Comment (RFC)
• Describe formally (and sometimes not so formally) everything about the Internet.
• Actually, RFCs are really a form of Memo.• For amusement, try RFC 968 (“‘Twas the Night Before
Startup”)• All are available on-line: www.ietf.org/rfc.html• We use RFCs to learn about SMTP (2821), HTTP (2616) ,
for example.
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RFC Characteristics
• RFC Statuses (2026)– Standard track
• PS - proposed standard• DS - draft standard• S - standard
– Non-standards track• E - experimental• I - information only• H - Historic• BC - Best current practices
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ExampleNetwork Working Group D. Waitzman Request for Comments: 1149 BBN STC 1 April 1990 A Standard for the Transmission of IP Datagrams on Avian Carriers Status of this Memo
This memo describes an experimental method for the encapsulation of IP datagrams in avian carriers. This specification is primarily useful in Metropolitan Area Networks. This is an experimental, not recommended standard. …
Overview and Rational Avian carriers can provide high delay, low throughput, and low altitude service. The connection topology is limited to a single point-to-point path for each carrier, used with standard carriers, but many carriers can be used without significant interference with each other, outside of early spring. This is because of the 3D ether space available to the carriers, in contrast to the 1D ether used by IEEE802.3. The carriers have an intrinsic collision avoidance system, which increases Frame Format The IP datagram is printed, on a small scroll of paper, in hexadecimal, with each octet separated by whitestuff and blackstuff. The scroll of paper is wrapped around one leg of the avian carrier. A band of duct tape is used to secure the datagram's edges. The bandwidth is limited to the leg length.
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RFC citations
• RFC citations appear in this format: – #### Title of RFC. Author 1, Author 2,