ESE 572 Lectures on Addresses in Networks

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ESE 572Lectures on Addresses in Networks
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Addresses in Communication Networks

• What is network address?
• Unique identifier for a network destination that
  enables correct delivery of information from any
  source to this destination.
• Examples of address that a person can have.
• -Postal address
• -Phone number (home, office, cellular)
• -Pager of beeper number
• -Fax number
• -Email address
• -Social Security Number
• -Drivers ID number
• -Student ID number
• -Account number (bank, credit card)
• -Finger prints
• -Corneal scan

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Some Terminologies

• Link
• Node
• Network
• Local area network (LAN)
• Wide area network(WAN)
• Router
• Network Layer
• Data Link Layer

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Network Layer Addresses

• Term
• A unique global address that enables routing of
  information from any source to any destination(s)
  in the network. As opposed to this term, the Data
  Link Addresses are defined on a point-to-point
  basis, i.e., not necessarily globally.
• Address Types
• -Hierarchical There is some structure in the
  addressing scheme that indicates the location of
  destination form the address itself (e.g., Postal
  Address, telephone number, IP address for
  workstation). Wide area networks with a large
  number of subscribers traditionally have a
  hierarchical address structure to deal with the
  complexity. However, this is changing to
  accommodate the mobility.
• -Unstructured or flat An address is nothing more
  than an identifier. The location of the
  destination must be advertised (frequently) to
  let others to know how to get to you (e.g.,
  Ethernet). This type of address is typical for
  small networks.
• -Combination Some structure complemented by
  advisement (e.g., wireless telephone).

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Example of Hierarchical Addressing Telephone
Number

• Numbering plan established for North America in
  1947
• Designed for
• -Subscriber to subscriber call
• -Subscriber to telco service (e.g.,directory
  service)
• -Operator to subscriber (e.g.,prearranged call)
• -Operator to operator (when direct dialing is
  unavailable)
• Special numbers
• -Prefix (e.g.,011 for international, 01 for
  person to person)
• -N11 service code (e.g.,411 for directory
  assistant, 611 for repair)
• -Suffix (e.g., for end of digit transmission)
• 10 digit addressing (legend N2-9, X0-9, 0/10
  or 1)
• - It used to be that 3 digit area code must be in
  the form of N 0/1 X. This resulted in 152
  possibilities (why?).

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• -3 digit central office code (NXX) 800
  possibilities
• -4 digit line number (XXXX) 10,000 possibilities
• Digits are transmitted by
• -Dual Tone Multi Frequency (DTMF)
• -Dialed Pulse
• Call processing
• -NXX XXXX calls are processed immediately
• -Prefix 0 is used for operator access. 1 is
  reserved for the toll calls.
• -Critical timing issue When is the dialing
  completed? E.g., 0 versus 0 N0/1X NXX XXXX)

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Example of Flat Addressing Ethernet

• One of the IEEE 802 Standard for LANs.
• Each device is given a permanent hardware
  configured address by a manufacturer
• Manufacturers obtain a block of Ethernet
  addresses and use it consecutively to ensure
• that no two devices have the same address.
• Ethernet device can move to another location
  without changing its data link layer
• address.
• Ethernet address is a 48 bit binary number
• Ethernet device listens on the link it is
  attached to and filters out the messages that are
• not directed to it.
• Non typical addresses - Broadcast address
• - Multicast address
• Non typical addresses are configured in
  firmware. To recognize these addresses, at the
• start up, additional addresses must be down
  loaded to the Ethernet interface to allow
• these other types of addresses to be filtered
  in.

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Hierarchical Network Layer Address

• There are too many addresses. Partitioning into
  smaller pieces is required.
• (Postal delivery example below.)
• -Get to the correct country.
• -Get to the correct state or province.
• -Get to the correct city.
• -Get to the correct destination.
• IP (Internet Protocol) Network Layer Address is
  the best example of this.
• However, due to the mobility (via wireless IP
  devices), the hierarchical nature of the IP
  addresses are being modified.

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IP Network Layer Address

• 4 octet address
• Addresslink ID host ID
• Masking technique is used to distinguish link ID
  from host ID.
• Each node must know the mask for the link it is
  attached to and its own host ID.? Every node
  attached to the same link must share the same
  link portion of the address.

Example IP Address of a computer is
79.214.192.83. Suppose the 79.214.192.X is the
link ID. Then the mask is 255.255.255.0.
Host ID
Link ID
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• Link ID can be further decomposed into subnets.
  Link IDnet IDsubnet ID
• Masking allows aggregation of links, creating
  hierarchy of subnets.

12.
4.
4.12.
4.15.
12.12.
4.19.
12.91.
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IP Address Convention

• 0000this and 1111all
• First octet.second octet.third octet.fourth
  octet(e.g., 13.222.13.2)
• Multicast address1110class D address
• The current version of IP address is called IP
  V4.
• Now the addressing is going towards 128 bit
  convention to accommodate the rapidly increasing
  ID devices. (IP V6)

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• End node attached via LANs Requirements for
  Communication
• 1.R1 and R2 need to know the network layer
  addresses of E1 and E2, for announcing to the
  world.
• 2.R1 and R2 need to know the data link layer
  addresses of E1 and E2, for packet routing.
• 3.E1 and E2 need to know the date link layer
  address pf either R1 or R2 or both.
• 4.E1 should be able to send a packet directly to
  E2 without routers.
• 5.E1 to E3 communication should use R2 not R1.
• 6.E1 should be able to find the date link layer
  address of E2 without R1 or R2.

E4
Rest of network
E3
E1
E2
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Solutions

• If End node is attached via point to point link
  Use Neighborhood Greeting
• -Use of End-System-Hello (ESH)

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Rest of network

• For general network topology
• All devices in the same link share the same
  mask. By design, routers know their end nodes
  data link addresses.
• Use of three messages
• - Address Resolution Protocol (ARP) query
  broadcast from an end node to all other end
  nodes.
• - ARP response response to ARP query
• - Redirect from a router to end node