Network Certification Preparation

Module - 1 Communication methods OSI reference model and layered communication TCP/IP model TCP and UDP IP addressing and subnetting MAC addressing

Todays’s networks Service Provider Job to connect all these different networks together Design and other rules are different and more intense Mission critical more than any other networks More complex and more issues Enterprise There are hundreds and thousands of users Policies in place Speed and efficiency is important Need connectivity to remote sites or home users Residential Small Local area networks Evolving networks i.e. wireless, fiber, fax machines etc

OSI Model and Layered approach Why we need layered approach OSI Model Seven layers of OSI model TCP/IP Model Four layers in TCP/IP model

TCP/IP Model

TCP/IP Model - continued

OSI Model

OSI Model - Layered communication

OSI Model – layer communication

TCP TCP - Transmission Control Protocol Most commonly used protocol on the Internet. Reliable - It is connection oriented hence guaranteed delivery TCP uses flow control which determines when data needs to be re- sent, and stops the flow of data until previous packets are successfully transferred. This works because if a packet of data is sent, a collision may occur. When this happens, the client re-requests the packet from the server until the whole packet is complete and is identical to its original, hence it is slow protocol. Ordered Delivery Offers error correction Examples: World Wide Web (Apache TCP port 80), (SMTP TCP port 25), File Transfer Protocol (FTP port 21) and Secure Shell (OpenSSH port 22) etc.

TCP – 3 way handshake Host A sends a TCP SYNchronize packet to Host B Host B receives A's SYN Host B sends a SYNchronize-ACKnowledgement Host A receives B's SYN-ACK Host A sends ACKnowledge Host B receives ACK. TCP socket connection is ESTABLISHED. TCP Three Way Handshake (SYN,SYN-ACK,ACK) SYNchronize and ACKnowledge messages are indicated by a bit inside the header of the TCP segment.

TCP – 3 way handshake

UDP UDP - User Datagram Protocol – connectionless protocol UDP is never used to send important data such as webpages, database information, etc; UDP is commonly used for streaming audio and video, because it offers speed! The reason UDP is faster than TCP is because there is no form of flow control or error correction. The data sent over the Internet is affected by collisions, and errors will be present. Remember that UDP is only concerned with speed. This is the main reason why streaming media is not high quality. Not reliable Not ordered delivery Example :Domain Name System (DNS UDP port 53), streaming media applications such as IPTV or movies, Voice over IP (VoIP), Trivial File Transfer Protocol (TFTP) and online multiplayer games etc

TCP Frame

UDP Frame

MAC Address A Media Access Control address (MAC address) is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used in the Media Access Control protocol sub- layer of the OSI reference model. MAC addresses assigned by the manufacturer of a network interface card (NIC) and are stored in its hardware. MAC address also referred to as the burned-in address, Ethernet hardware address (EHA), hardware address or physical address. 6 bytes of address. 3 bytes are for Manufacturer identifier and 3 bytes are NIC specific.

IP addressing IP address is a unique identifier which distinguishes a node from other in a network. An IPv4 address is 4 bytes/32 bites long IP address has a format of a.b.c.d, where a,b,c,d are octets in binary. Each ip address has two portions, network and host Different classes of IP address schemes. Class A, Class B, Class C, Class D, and Class E

IP addressing Class A Binary address start with 0 i.e. most significant bit of first byte is always 0. Hence the decimal number can be anywhere from 1 to 126. The first 8 bits (the first octet) identify the network and the remaining 24 bits indicate the host within the network. An example of a Class A IP address is , where "102" identifies the network and " " identifies the host on that network.

IP addressing Class B Binary addresses start with 10 i.e. two most significant bits of first bytes are always 10. Hence the decimal number can be anywhere from 128 to 191. (The number 127 is reserved for local machine and loopback interfaces). The first 16 bits (the first two octets) identify the network and the remaining 16 bits indicate the host within the network. An example of a Class B IP address is where " " identifies the network and " " identifies the host on that network.

IP addressing Class C Binary addresses start with 110 i.e. three most significant bits of first octet is always 110. Hence the decimal number can be anywhere from 192 to 223. The first 24 bits (the first three octets) identify the network and the remaining 8 bits indicate the host within the network. An example of a Class C IP address is where " " identifies the network and "226" identifies the host on that network.

IP addressing Class D Binary addresses start with 1110 i.e. four most significant bits are always Hence the decimal number can be anywhere from 224 to 239. Class D networks are used to support multicasting. Local Subnet: Addresses in the range to are individually assigned by IANA and designated for multicasting on the local subnetwork only. Routing Information Protocol (RIPv2) uses , Open Shortest Path First (OSPF) uses & , etc. Routers must not forward these messages outside the subnet in which the originate.

IP addressing Internetwork control block Addresses in the range to are individually assigned by IANA and designated the Internetwork Control Block. It is used for traffic that must be routed through the public Internet, such as for applications of the Network Time Protocol ( ). AD-HOC block Addresses in the ranges to , to and to are individually assigned by IANA and designated the AD-HOC block. These addresses are globally routed and are used for applications that don't fit either of the previously described purposes.

BACKUP SLIDES

Access methods An access method is a set of rules on how the network nodes share the transmission media. Rule could be Either first come first served or take turns Contention methods CSMA/CD (Carrier Sense Multiple Access with Collision Detection) CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Token Passing Demand Priority

Access methods Contention Methods: IEEE Ethernet LAN use CSMA/CD method. WLAN uses CSMA/CA protocol and have mechanism of explicit packet acknowledgment. Token Ring : Uses a token-passing method. Demand Priority : 100VG-AnyLAN uses this method. Networks are connected to hubs and hubs are connected to other hubs. Contention occurs at hub level. Demand Priority provides mechanism for prioritizing data types. If contention happens, data with highest priority takes precedence.