ESE 572 Lectures on Addresses in Networks Addresses

ESE 572 Lectures on Addresses in Networks

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

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

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).

Example of Hierarchical Addressing: Telephone 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) -N 11 service code (e. g. , 411 for directory assistant, 611 for repair) -Suffix (e. g. , # for end of digit transmission) 10 digit addressing (legend: N=2 -9, X=0 -9, 0/1=0 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? ).

-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 N 0/1 X NXX XXXX”)

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.

Hierarchical Network Layer Address There are too many addresses. Partitioning into smaller pieces is required. (Postal delivery example below. ) -Get to to the the correct country. state or province. city. 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.

IP Network Layer Address 4 octet address Address=link ID + host ID Masking technique is used to distinguish link ID from host ID. 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. 0. Host ID Link ID 01001111 11010110 11000000 01010011 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.

Link ID can be further decomposed into subnets. Link ID=net ID+subnet ID Masking allows aggregation of links, creating hierarchy of subnets. . * 4. * 12 * 5. R R . 12 1 4. 1 2. * 1. * R 12. 9 R 4. 19. *

IP Address Convention 000… 0=“this” and 111… 1=“all” First octet. second octet. third octet. fourth octet(e. g. , 13. 222. 13. 2) Multicast address=“ 1110”+class D address The current version of IP address is called IP V 4. Now the addressing is going towards 128 bit convention to accommodate the rapidly increasing ID devices. (IP V 6)

Requirements for Communication 1. R 1 and R 2 need to know the network layer addresses of E 1 and E 2, for announcing to the world. 2. R 1 and R 2 need to know the data link layer addresses of E 1 and E 2, for packet routing. 3. E 1 and E 2 need to know the date link layer address pf either R 1 or R 2 or both. 4. E 1 should be able to send a packet directly to E 2 without routers. 5. E 1 to E 3 communication should use R 2 not R 1. 6. E 1 should be able to find the date link layer address of E 2 without R 1 or R 2. E 4 Rest of network R 1 E 3 R 2 E 2

Solutions If End node is attached via point to point link: Use Neighborhood Greeting -Use of End-System-Hello (ESH) E R 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