Introduction to Networking Concepts Lesson 1

TCP/IP Protocol Suite Network protocols provide the logical “language” for communication over the network. The most common networking protocol in use today is Transmission Control Protocol/Internet Protocol (TCP/IP).

IP Addressing For any computer or host to communicate on a TCP/IP network, it must be configured with a valid IP address. Each IP address consists of two components: – network address — This portion of the IP address is shared by all TCP/IP hosts on a particular network or subnet. – host address — This comprises the portion of the IP address that is unique to a particular computer or host. Both combined form a unique IP address across an entire TCP/IP network.

IP Addressing In addition to the IP address, each TCP/IP host must be configured with the following: – subnet mask — Used to identify which network the TCP/IP host resides on by defining where the network address stops and the host address begins. – default gateway — Allows a host to communicate with devices that reside on a remote network or location. You don’t need a default gateway if it is does not need to communicate outside of the host’s own subnet.

IPv4 Addressing

The most commonly used version used today. Based on 32-bits (four bytes, or octets) (4,294,967,296) possible addresses. Some of the possible addresses are reserved IPv4 addresses are commonly represented using what is called dotted-decimal notation, in which the decimal value of each byte is shown, using periods to separate the bytes:   

Classful Addressing The field for the network number was a different length for different classes of network, and the remaining bits were used for the host number. Each network class had a different maximum number of nodes. The first one to four bits identified the network class, and the remaining bits comprised the network and host address fields.

Classful Addressing

Class A Networks Had the most significant bit as “0” and used the remainder of the first octet for the network number. There were 126 Class A networks, with a maximum of 16,777,214 hosts in each. Note that the number of valid networks and hosts available is always 2 N – 2 (where N is the number of bits used and the 2 adjusts for the special function of the first and last address in each network).

Class B Network Class B networks had the two most significant bits as “10,” with the remainder of the first two octets, or fourteen bits, representing the network number. There were 16,384 Class B networks, with a maximum of 65,534 hosts in each.

Class C Networks Class C networks had the three most significant bits as “110,” with the remainder of the first three octets as the network number and the last octet as the host number. There were 2,097,152 Class C networks, each with a maximum of 254 host addresses.

Classful Addressing Examples – Default subnet mask is – Network address is – Host address is – Default subnet mask is – Network address is – Host address is

Class D and Class E Networks Network addresses with the four most significant bits “1110” (Class D, multicast). – Multicast addressing is used to deliver to multiple host simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split. “1111” (Class E, reserved) were also defined.

Classless Inter-Domain Routing (CIDR) When classful network addresses started became scarce, public Internet Service Providers (ISPs) started to allocate many small networks to their customers. Breaks the network address space into CIDR blocks The number of masked bits is specified with the CIDR notation. Example: – /8 would describe 8 bits masked and 24 bits for host numbering.

Classless Addressing Examples /24 – Subnet mask is – Network address is – Host address is /16 – Subnet mask is – Network address is – Host address is

Subnetting Logical partitioning of an organization’s network address range into smaller blocks.

Subnetting Example Network Address (Enteprise/corporation): /16 – Default Subnet mask is Site 1 has network address of: – With subnetting, the subnet mask becomes Site 2 has network address of: – With subnetting, the subnet mask becomes

Private Addresses For convenience, several network address blocks were reserved for private networks. Defined as non-routable outside of the private network.

Network Address Translation (NAT) Hosts using private network addresses can communicate with public networks only by using network address translation (NAT), Enables routing by mapping their private network address to a different, routable network address.

Loopback Address Specifies itself at address

IPv6 Addressing Near exhaustion of the 4-billion-plus IP addresses available through IPv4. While the use of private IP networks and NAT have alleviated the problem somewhat, a long- term solution is still required. IPv6, the next generation of the TCP/IP protocol, was developed to provide a significantly larger address space for current and future implementations of TCP/IP networks.

IPv6 Addressing IPv6 uses 128 bits, or 16 bytes, for addressing. – Providing (about 340 billion) unique addresses. Uses eight groups of four hexadecimal digits, separated by colons. IPv6 includes a few other enhancements for performance and security. – IPSec.

IPv6 Addressing IPv6 addresses are 128 bits in length and expressed in hexadecimal notation. For example, – 2001:0db8:85a3:08d3:1319:8a2e:0370:7334 If an IPv6 address contains a series of sequential zeroes, the address can be shortened to use a single zero in each group, or else the entire grouping can be represented using a double colon (::). – 2001:0000:0000:0000:0000:0000:0000:7334 – 2001:0:0:0:0:0:0:7334 – 2001::7334

IPv6 Addressing IPv6 networks can be expressed using CIDR notation such as 2001:0db8:1234::/48 to represent the 2001:0db8:1234 network configured with a 48-bit subnet mask.

Domain Name System (DNS) Domain Name System (DNS) used for name resolution. It translates from Host name to IP addresses. HOSTS files also translate from Host name to IP addresses. Prevents you from remembering addresses. – Instead, remember meaningful logical names.

Domain Name System (DNS)

Traditional Top-Level Domain Names.com – Commercial.edu – Education.gov – Agencies of U.S. federal government.net – Computers of network providers and ISPs.org – nongovernmental and nonprofit organizations

Fully Qualified Domain Name (FQDN) Describes the exact relationship between a host and its DNS domain. Example: computer1.sales.adatum.com – Host name is computer1 – In the sales domain, which is in the adatum second- level domain, which is in the.com top-level domain, which is under the “.” root domain.

Dynamic Host Configuration Protocol (DHCP) Simplifies the problem of static IP address by automating the assigning, tracking, and reassigning of IP addresses. Also to provide other important settings such as the default gateway, subnet mask, DNS, and so on.

DHCP Relay Agent DHCP relies heavily on broadcast messages. Broadcast messages are generally limited to the subnet in which they originate and are not forwarded to other subnets. A DHCP relay agent is either a host or an IP router that listens for DHCP (and BOOTP) client messages being broadcast on a subnet and then forwards those DHCP messages to a DHCP server on a remote subnet. The DHCP server sends DHCP response messages back.

Dynamic Host Configuration Protocol (DHCP)

Remote Access A Windows Server 2008 computer can act as a remote access server, which can allow remote network clients to access resources on a network as though they were physically connected to the LAN. The Windows Server 2008 remote access server can provide remote access using either dial-up connections via a modem or else through a Virtual Private Network (VPN) connection over the Internet or another public network.

Routing The process of transferring data across a network from one LAN to another, provides the basis for TCP/IP communications on the Internet and nearly all other corporate networks. By configuring two network interface cards (NICs) within a Windows Server 2008 server, the server can provide a means of transmitting data from one network to another. For larger networks, the processing demands of network routing are typically handled by dedicated hardware- based routers.

Network Access Protection (NAP) One of the principal challenges in corporate networks is the ability to secure networks against unwarranted access. Network administrators also need to protect the network against “inside threats,” laptop computers that are physically brought inside the corporate network or that gain access to the company network through remote access technologies such as Virtual Private Networks (VPNs.) Windows Server 2008 provides the Network Access Protection platform, which provides a policy enforcement mechanism to control access to a 2008 network.

Summary Network protocols create a logical language that allows computers to communicate. The most commonly used network protocol on modern networks is the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. There are currently two implementations of TCP/IP: TCP/IP version 4, or IPv4, and TCP/IP version 6, or IPv6.

Summary Each host on a TCP/IP network needs to be configured with a unique IP address. TCP/IP networks use the Domain Name System (DNS) to map human-readable machine names to IP addresses and vice versa, such as mapping the host name to the IP address.

Summary Network administrators can use the Dynamic Host Configuration Protocol (DHCP) to automatically assign IP addresses to multiple client computers. The Routing and Remote Access service provides the ability to use a Windows Server 2008 computer as a router, which passes network traffic from one TCP/IP network to another, as well as remote access capabilities using either dial-up or VPN technology.

Summary To allow administrators to enforce network security policies, such as mandatory anti-virus or firewall configurations, Windows Server 2008 has introduced the Network Access Protection (NAP) enforcement platform. Network addressing is fundamental to successful communication between systems.

Summary DNS provides name resolution to allow meaningful names to be used to refer to network addresses. DHCP is a simple, standard protocol that makes TCP/IP network configuration much easier for the administrator by dynamically assigning IP addresses and providing additional configuration information to DHCP clients automatically.

Summary Clients may be configured to use APIPA or an alternate static IP address configuration if DHCP is unavailable.