TCPIP over Ethernet

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TCP/IP over Ethernet John Mora ltjohn.mora_at_accre.v
anderbilt.edugt
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Ethernet and TCP/IP Timeline

• 1971 - ALOHAnet, also known as ALOHA, was a
  radio-based pioneering computer networking system
  developed at the University of Hawaii.
•  
• 1973 - Researchers at XEROX PARC developed the
  ALOHA radio network concept further (at the time
  used to network XEROX ALTO workstations to
  ARPANET). The new protocol "Ethernet", the "Ether
  Network". The original Ethernet ran at 2.94Mbps.
•  
• 1980 - Digital, Intel and Xerox create the DIX
  Ethernet Standard, version 1.
• 1980 - IEEE creates the 802 working group (Feb.
  1980). 
• 1980 - RFC768 (UDP) is published.
• 1981 - RFC 791 (IP) and RFC 793 (TCP) are
  published.
• 1982 - Digital, Intel and Xerox create the DIX
  Ethernet Standard, version 2.
• 1983 - IEEE 802.3, the third subcommittee
  concentrated on the standardization of a CSMA/CD
  network protocol that was functionally equivalent
  to DIX Ethernet Type II.
• 1985 - Official Standard ANSI/IEEE Std.
  802.3-1985
•  
• Later supplements added to support Ethernet at
  2Mb/s through 10Gb/s and over varied media
  (power, wireless).

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Ethernet and TCP/IP Timeline
Xerox Alto
4
Standards Organizations
Standards are documented in Request For Comment
(RFC)   A complete list of Internet Standards is
available at http//www.rfc-editor.org/rfcxx00.ht
ml
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Ethernet CSMA/CD  
Carrier Sense Multiple Access With Collision
Detection (CSMA/CD)
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Ethernet CSMA/CD  
Carrier Sense Multiple Access With Collision
Detection (CSMA/CD)
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OSI Model, Summary  
8
OSI Model, Summary  
Application
Presentation
Session
Transport
Network
Data Link
Physical
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Ethernet II (DIX) Framing
A frame is the unit of transmission in a link
layer protocol, and consists of a link-layer
header followed by a packet.   MAC Addresses are
48-bit (6 byte) identifiers unique to each
NIC.   EtherType (2 byte/16-bit) describes which
protocol is encapsulated in the frame data
IPv4, IPv6, IBoE, FCoE, etc. (http//standards.iee
e.org/regauth/ethertype/eth.txt)
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MAC Header, Source/Destination addresses

•  MAC Addresses are 48-bit (6 byte) identifiers
  unique to each Network Interface.
•  
• Individual/Group Address Bit
• Universally/Locally administered address bit
• Organizationally unique identifier (OUI, a 22-bit
  field assigned by the IEEE) (bits 3-24) 
• NIC-specific unique address (OUA, a 24-bit number
  assigned by the manufacturer)

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Address Resolution Protocol - RFC 826, STD 37

• The purpose of this RFC is to present a method of
  Converting Protocol Addresses (e.g., IP
  addresses) to Local Network Addresses (e.g., MAC
  addresses).
• Keep in mind host addresses are translated from
  common names like www.google.com to IP addresses
  using the Domain Name System (DNS).
•  
• The Address Resolution module tries to find this
  pair in a table. If it finds the pair, it gives
  the corresponding 48.bit Ethernet address back to
  the caller (hardware driver) which then transmits
  the packet.
• An example of an ARP transaction is explained in
  RFC826 and a diagram of this transaction is
  illustrated at lthttp//eventhelix.com/RealtimeMant
  ra/Networking/Arp.pdfgt.
•  

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Address Resolution Protocol - RFC 826, STD 37
arp a b7n8 (10.0.57.8) at 000D601EC3A6
ether on eth0 vmp035 (10.0.12.15) at
00504502FE83 ether on eth0 vmp171
(10.0.19.11) at 005045BB95D0 ether on
eth0 b10n9 (10.0.60.9) at 000D601EC2F4
ether on eth0 vmp413 (10.0.31.13) at
0050455F1490 ether on eth0 vmp013
(10.0.11.13) at 00504502FEE5 ether on
eth0 b5n24 (10.0.55.24) at 000D601EC264
ether on eth0 vmp416 (10.0.31.16) at
0050455F151C ether on eth0 b1n12
(10.0.51.12) at 000D601EC1E8 ether on
eth0 b4n16 (10.0.54.16) at 000D601EC310
ether on eth0 
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TCP/IP An Overview

• When data is requested from a remote host, the
  TCP module of the host takes the data and divides
  it into individually numbered segments to be
  forwarded to the requesting host.
• The IP module encapsulates the TCP segment into
  an IP packet by adding the appropriate protocol
  headers, which include the destination IP
  address.
• Distinct packets from the same source host may
  take distinct and seperate routes to reach the
  requesting host.
• The requesting host receives the packets, where
  the TCP module then reassembles the segments,
  which are then passed to the Application Layer.

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Transmission Control ProtocolRFC 793, STD 7
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Internet Protocol - RFC 791, STD 5

• Summary
• The internet protocol implements two basic
  functions  addressing and fragmentation.
• IP does not provide a reliable communication
  facility.
• No error control for data, only a header
  checksum.
• No retransmissions or flow control.
• No connections or logical circuits (virtual or
  otherwise).

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Internet Protocol - RFC 791, STD 5
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Transmission Control ProtocolRFC 793, STD 7

• The primary purpose of the TCP is to provide
  reliable, securable logical circuit or connection
  service between pairs of processes.
• Basic Data Transfer TCP is able to handle data
  in streams
• Reliability Each octet is assigned a Sequence
  Number and 16-bit Checksum, which must be ACK'd
  by the receiving end
• Flow Control The receiver can govern the
  sender's behavior by issuing a range of sequence
  numbers.
• Multiplexing TCP provides a series of ports by
  which multiple sockets can be created.
• Connections Sockets, Sequence Numbers and Window
  Sizes are together referred to as a Connection.
• Precedence and Security The user may specify the
  security and precedence of their connections.

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OSI Model, Summary  
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Internet Protocol - RFC 791, STD 5

• Internet Datagram Header Fields
• Total Length (in octets)
• Identification (reassembly info.)
• Flags (Fragment Status)
• Fragment Offset
• Time to Live, Protocol (IANA)
• Header Checksum
• Source Address (32-bit)
• Destination Address (32-bit)
• And more!

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Internet Protocol - RFC 791, STD 5
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Transmission Control ProtocolServices

• Common Services
• SSH, tcp/22
• Telnet, tcp/23
• SMTP, tcp/25
• DNS (zone transfers), tcp/53
• HTTP, tcp/80
• POP3, tcp/110
• IMAP, tcp/143
• HTTPS, tcp/443
• Secure IMAP, tcp/993

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Internet Protocol - RFC 791, STD 5

• There are three Classes of internet addresses
• Class C (CIDR /24, netmask 255.255.255.0, 256
  Hosts)
• Class B (CIDR /16, netmask 255.255.0.0, 65k
  Hosts)
• Class A (CIDR /8, netmask 255.0.0.0, 16M Hosts)

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Internet Protocol - RFC 791, STD 5

• Subnetting - RFC 1878
•  Addresses are fixed length of four octets (32
  bits).  An address begins with a network number,
  followed by local address (called the "rest"
  field).
• For example,
• 11000000.10101000.01111011.10000100 -- IP address
  (192.168.123.132)
• 11111111.11111111.11111111.00000000 -- Subnet
  mask (255.255.255.0)
•  

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Internet Protocol - RFC 791, STD 5
An example of subnetting The subnet mask
255.255.255.192 gives you four networks of 62
hosts each. This works because in binary
notation, 255.255.255.192 is the same as
1111111.11111111.1111111.11000000. The first
two digits of the last octet become network
addresses, so you get the additional networks
00000000 (0), 01000000 (64), 10000000 (128) and
11000000 (192). 192.168.123.1-62 /
192.168.123.65-126 / 192.168.123.129-190 /
192.168.123.193-254
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ICMP - RFC 792, STD 5

• Internet Control Message Protocol
• ICMP travels directly within the IP datagram, so
  like UDP is unreliable
• ICMP is used by TCP/IP to relay connectivity
  information
• As packets travel through the network, the TTL is
  decreased on every hop. When the TTL reaches 0, a
  TTL exceeded message is sent to the sending
  host.
• Ping is an ICMP echo and ICMP reply
• Traceroute can be either be UDP-based or
  ICMP-based both look for TTL expired or
  Destination Unreachable messages
•  

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IPv6 - RFC 2460, Draft Standard

• IPv6
• IPv6 over Ethernet described in RFC 2464.
•  
• 128-bit IP addressing, vs. 32-bit
• New unicast and broadcasting methods
• Allows for hex in IP addresses
• Built-in QoS (Flow Label)
• Default MTU of 1280 bytes vs. 576 bytes
• MTU Size Error Feedback from routing hosts
• MTU Discovery

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IPv6 - RFC 2460, Draft Standard
IPv6 Header

• Version  IPv6 version number.
• Priority 4-bit  Internet traffic priority
  delivery value
• Flow Label 24-bit field, special router handling
  
• Payload Length 16-bit unsigned integer. Length
  of payload, i.e., the rest of the packet
  following the IPv6 header, in octets.
• Next Header 8-bit selector. Identifies the type
  of header immediately following the IPv6 header.
  Uses the same values as the IPv4 Protocol field.
• Hop Limit 8-bit unsigned integer (TTL)
• Source Address 128 bits. The address of the
  initial sender of the packet.
• Destination Address 128 bits. The address of the
  intended recipient of the packet (possibly not
  the ultimate recipient, if an optional Routing
  Header is present).

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IPv6 - RFC 2460, Draft Standard

• Addressing Architecture - RFC 2373
• IPv6 Unicast - a single address identifying a
  single interface
•  
• Global unicast - publicly routable address
  (2000/3)
• Link-local  - private, non-routable addresses
  (FE80/10)
• Unique local - private addressing, with the
  addition of being unique. Analogous to 192.x,
  etc. (FC00/7)
• Multicast - similar to the IPv4 broadcast address
  (FF00/8)
• Anycast - single address assigned to multiple
  nodes
•  
• RFC 4291 describes the Addressing specification

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IPv6 Unicast Address Format - RFC 3587
For example, the following addresses 2001DB800
8800200C417A - unicast addressFF0100000
0101 - multicast address00000001 -
loopback address00000000 - unspecified
addressmay be represented as2001DB8880020
0C417A - unicast addressFF01101 - multicast
address1 - loopback address - unspecified
address
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Interior Gateway Protocols

• Interior Gateway Protocols are used within larger
  Autonomous Systems.
• Distance-vector routing protocol RIP
• RIP (Routing Information Protocol) is a
  widely-used protocol for managing router
  information within a self-contained network such
  as a LAN.
• Link-state routing protocol OSPF
• Using OSPF,
• Changes are immediately multicast
• OSPF bases its path descriptions on "link states"
  
• OSPF also lets the user assign weights
• OSPF supports a variable network subnet mask
• With RIP, the routing table is sent to a neighbor
  host every 30 seconds. OSPF multicasts only when
  a change has taken place.

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Border Gateway Protocol (RFC 4271)

• The primary function of a BGP speaking system is
  to exchange network reachability information with
  other BGP systems. This network reachability
  information includes information on the list of
  Autonomous Systems (ASes) that reachability
  information traverses.
• Routing information exchanged via BGP supports
  only the destination-based forwarding paradigm,
  which assumes that a router forwards a packet
  based solely on the destination address carried
  in the IP header of the packet.
• BGP uses TCP

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Border Gateway Protocol (RFC 4271)
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Border Gateway Protocol (RFC 4271)
http//www.isoc.org/tools/blogs/ispcolumn/?p67
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Border Gateway Protocol (RFC 4271)
http//www.isoc.org/tools/blogs/ispcolumn/?p67
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Border Gateway Protocol (RFC 4271)
One potential explanation of this data is that
the underlying inter-AS topology of the Internet
in IPv4 is very stable, and much of the churn in
routing may be attributable to the effects of
other measures, such as traffic engineering or
local efforts to optimise certain aspects of
routing policies.
http//www.isoc.org/tools/blogs/ispcolumn/?p67
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Conclusion