INTERNET ARCHITECTURE & PROTOCOLS Set # 01 Delivered By: Engr Tahir Niazi
What is Internet? Basically it is called Network of networks Nuts and Bolts (Pieces of internet) Services description (applications) What is Protocol? (agreement)
Nuts & Bolts Internet composed of million of devices attached Hosts or end systems Communication links Routers and switches Transmission rate Packets/datagram Route and path Internet service provider
Nuts & Bolts
Services Description: Multiple end systems that exchange data with each other called distributed application Electronic mail Web surfing Social networks Instant messaging VoIP Video streaming Gaming file sharing
Protocols: A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event. Human analogy concept Networks analogy concept
Humans & Computer Network Protocol:
The Network Edge: End systems or Hosts that are connected to internet are located at the edge of the network
Access Networks: The Network that physically connects an end systems to first router (also known as edge router)
Home Access: DSL,Cable, FTTH DSL and Cable normally deployed for residential broadband access
Ethernet & Wi-Fi Access:
Communication media: Twisted pair Coaxial cable Optical fibre Terrestrial radio channels Satellite radio channel
The Core Network: Switching (Circuit & packet) take place long messages into smaller chunks of data known as packets. packet travels through communication links and packet switches. Packets are transmitted over each communication link at a rate equal to the full transmission rate of the link. So, if a source end system or a packet switch is sending a packet of L bits over a link with transmission rate R bits/sec, then the time to transmit the packet is L/R seconds.
Core Network:
Packet Switching: Store and forward means that the packet switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link
Queuing delays and Packet loss: arriving packet needs to be transmitted onto a link but finds the link busy with the transmission of another packet, the arriving packet must wait in the output buffer this is known as Queuing delay amount of buffer space is finite, an arriving packet may find that the buffer is completely full with other packets waiting for transmission. In this case, packet loss will occur
Forwarding table & Routing protocols: When a packet arrives at a router, the router examines the address and searches its forwarding table, using this destination address, to find the appropriate outbound link routing protocol may, for example, determine the shortest path from each router to each destination and use the shortest path results to configure the forwarding tables in the routers
Packet Switching: Store & forward Delays & packet loss Forwarding table
Circuit switching: Circuits (dedicated end to end) Resources reserved (FDM,TDM) Traditional telephone networks
Circuit Vs Packet switching: Circuit switching: carry bit streams a. establishes a dedicated circuit b. links reserved for use by communication channel c. send/receive bit stream at constant rate d. example: original telephone network Packet switching: storeand-forward messages a. No dedicated circuit is established b. utilizes resources according to traffic demand c. send/receive messages at variable rate d. example: Internet
Network Taxonomy: Telecom/Computer networks Circuit-switched networks Packet-switched networks FDM TDM Networks with VCs Datagram Networks
Internet Architecture: Tier 1, Tier 2, Tier 3 ISPs End system to the internet through access ISP Access ISP can provide guided or un guided connection Provider & Customers CPE, PoP, IXP, Content providers
Interconnection of ISPs
Delays in packet switched networks: The most important of these delays are the nodal processing delay, queuing delay, transmission delay, and propagation delay Nodal Processing: - time required to examine the packet s header - determine where to direct the packet - check for bit-level error - typically on the order of microseconds or less
Delays in packet switched networks: Queuing delay: - Time taken at queue - Heavy traffic more delay, less traffic low delay - Microsecond to millisecond Transmission delay: - Time required to send all of the packet s bits onto the link - Transmission Delay = L/R,Where L is the length of the packet and R is the bandwidth of the link - Microsecond to millisecond
Delays in packet switched networks: Propagation delay: - Once a bit is pushed into the link, it needs to propagate onto the link. The time required to propagate from the beginning of the link to the end - Depend on physical medium used
Protocols Layered Architecture: Why layered architecture? Take human analogy
Internet & OSI Model:
Operation: Internet Model Encapsulation (headers & control info) Message- Segment-Packets-Frames-Bits Multilevel addressing
Layered Hierarchy: Example
What is an IP Address? An IP address is a 32-bit address. The IP addresses are unique.
Address space rule The address space in a protocol.. That uses addr1 N-bits.. to define an Address is: addr15 addr2...... 2 N addr41 addr226 addr31.... The address space of IPv4 is 2 32 or 4,294,967,296.
Binary Notation 01110101 10010101 00011101 11101010 Dotted-decimal notation
Hexadecimal Notation 0111 0101 1001 0101 0001 1101 1110 1010 75 95 1D EA
Example 1 Change the following IP address from binary notation to dotted-decimal notation. 10000001 00001011 00001011 11101111 Solution 129.11.11.239
Example 2 Change the following IP address from dotted-decimal notation to binary notation: 111.56.45.78 Solution 01101111 00111000 00101101 01001110
Example 3 Find the error in the following IP Address 111.56.045.78 Solution There are no leading zeroes in Dotted-decimal notation (045)
Example 3 (continued) Find the error in the following IP Address 75.45.301.14 Solution In decimal notation each number <= 255 301 is out of the range
Example 4 Change the following binary IP address Hexadecimal notation 10000001 00001011 00001011 11101111 Solution 810B0BEF16
CLASSFUL ADDRESSING
In classful addressing the address space is divided into 5 classes: A, B, C, D, and E.
Finding the class in binary notation
Finding the address class
Example 6 Find the class of the following IP addresses 00000001 00001011 00001011 11101111 11000001 00001011 00001011 11101111 Solution 00000001 00001011 00001011 11101111 1 st is 0, hence it is Class A 11000001 00001011 00001011 11101111 1 st and 2 nd bits are 1, and 3 rd bit is 0 hence, Class C
Finding the class in decimal notation
Example 7 Find the class of the following addresses 158.223.1.108 227.13.14.88 Solution 158.223.1.108 1 st byte = 158 (128<158<191) class B 227.13.14.88 1 st byte = 227 (224<227<239) class D
Netid and hostid
Network Addresses The network address is the first address. The network address defines the network to the rest of the Internet. Given the network address, we can find the class of the address, the block, and the range of the addresses in the block
Example 8 Given the network address 132.21.0.0, find the class, the block, and the range of the addresses Solution The 1 st byte is between 128 and 191. Hence, Class B The block has a netid of 132.21. The addresses range from 132.21.0.0 to 132.21.255.255.
Mask A mask is a 32-bit binary number. The mask is ANDeD with IP address to get The block address (Network address) Mask And IP address = Block Address
Masking concept
AND operation
The network address is the beginning address of each block. It can be found by applying the default mask to any of the addresses in the block (including itself). It retains the netid of the block and sets the hostid to zero.
Default Mask Class A default mask is 255.0.0.0 /8 Class B default mask is 255.255.0.0 /16 Class C Default mask 255.255.255.0 /24
Find Network ID & Broadcast Address Broadcast Address: An IP Address that allows information to be sent to all machines on a given subnet rather than a specific machine Example: 192.168.1.15/24
Exercise: Find the Network and Broadcast Addresses for each of the following 1. 10.10.1.97/23 2. 192.168.0.3/25 3. 172.16.5.34/26 4. 192.168.11.17/28
Exercise Answers: 1. The network Address is 10.10.0.0 and the Broadcast Address is 10.10.1.255 2. The network Address is 192.168.0.0 and the Broadcast Address is 192.168.0.127 3. The network Address is 172.16.5.0 and the Broadcast Address is 172.16.5.63 4. The network Address is 192.168.11.16 and the Broadcast Address is 192.168.11.31
Internetworking Devices: Hub/Repeater Bridge Switches Router Hub/Repeater: Repeat the signal with greater power 1 collision domain 1 broadcast domain Layer 1
Internetworking Devices: Bridge: Main function (learning, forwarding, filtering) 2 collision domain 1 broadcast domain Layer 2 Switch: Each port separate collision domain 1 broadcast domain Full duplex Layer 2
Internetworking Devices: Router: Works on IP address No broadcast domain Routing Layer 3
DHCP Dynamic Host Configuration Protocol Allow IP Address / Netmask / Gateway Information to be allocated dynamically - At random, OR - Predetermine for specific MAC address Typically given for a period of time DHCP server can be server based or router based
DHCP Process: Four steps - DHCP discover (broadcast) - DHCP offer (unicast) - DHCP request (broadcast/unicast) - DHCP Ack (unicast)
DHCP on window server:
ARP: Address Resolution Protocol Interaction between IP and MAC Host 138.37.35.215 want to send a packet to 138.37.35.74 IP packet needs to be put in an Ethernet frame with MAC address Need to find MAC address for 138.37.35.74 ARP sends broadcast asking for the MAC address Usually the destination host will reply with it s own MAC address Cached in arp table
ARP: different Subnet Host 138.37.35.215 wants to send a packet to 138.37.32.214 (different subnet) IP packet needs to be put in an Ethernet frame with MAC address as before Different subnet so will need to go through a router Routing table (see later) provides address of router - (138.37.35.254 here) arp will find the MAC address of the router
ARP Process:
Two Address concept:
DNS: Domain name system Applications refer to hosts etc by name Need to map these to IP addresses Reverse look up Originally a file, hosts.txt, that listed all the hosts and their IP addresses - flat structure; every night all the hosts would collect this file from the host that maintained it - not scalable DNS ( Domain Name System) distributed database now used
Domain Name System: DNS is a hierarchical, domain-based naming scheme and a distributed database system for implementing this naming scheme using Delegation of Authority concept Hierarchically structured distributed database Each element of the hierarchy is referred to as a domain Mainly used for mapping host names and email destinations to IP addresses
Domain Name System: At the top of the hierarchy is the root domain, known as. Sub domains directly underneath the root domain are called top level domains Domains directly underneath top-level domains are called second-level domains, and so on Any domain in the name space can be referred to by the domain names in its hierarchical path separated by dots e.g.
Example: abcdefg@uos.edu.pk Host name, domain name, fully qualified domain name Consider another example:
Nameservers: Information on the root domain resides on a select number of root nameservers around the Internet The root nameservers hold data for all the top-level domains Top-level domains - two-letter abbreviations for each country, such as uk and us - special domains such as edu, com, net, gov etc These root nameservers make it possible for every host on the Internet to have access to the complete DNS database
DNS Principle: Each domain has one or more Resource Records (RRs) Computers query the nameservers to find out information about domains in the DNS Each nameserver handles a specific part of the DNS referred to as a zone. A zone is a collection of domains Since no single server in the Internet knows the addresses of all other hosts, the responsibility of resolving addresses to IP mapping is then delegated to the authority servers of that zone
DNS Resolver: Clients use resolvers - resolvers are the nameservers clients The resolver's function is to resolve queries from the user s terminal. To do that, it queries a nameserver, which then returns either the requested information or a referral to another server This can be done in two ways: - Recursively - iteratively
Recursive Query: The resolver asks the DNS server within its own domain for the IP address of the named destination. If this is not known, the query is escalated to the next higher nameserver, responsible for a higher domain. This may escalate the query higher etc.
Iterative Query:
SUMMARY: What is Internet? Different parts of Network Network Taxonomy Delay, types of delay and Packet loss Layered & Internet Architecture IP addressing Network and Broadcast address Internetworking devices DHCP, ARP & DNS
Q & A IAP, University of Sargodha, CS & IT Dept