2-1 Protocols and Standards
Posted February 27th, 2007 by admin
TCP/IP model
2.1 Identify a MAC (Media Access Control) address and its parts.
Every device on the network must have a unique MAC address to ensure proper receiving and transmission of data. The MAC address is a device's actual physical address, which is usually designated by the manufacturer of the device
Medium Access Control sublayer Operations The purpose of the MAC sublayer is to determine when each frame should be passed on to the physical layer to be transmitted as a data signal over the network. The MAC sublayer governs which devices have permission to transmit data over the network and when. There are four basic methods for controlling access to the network, polling, contention, token passing, and switching.
The data link layer is divided into two sublayers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking.
2.2 Identify the seven layers of the OSI (Open Systems Interconnect) model and their functions.
| APPLICATION layer 7 |
Gives user applications access to network. This layer represents the services, that directly support the user applications such as software for file transfers, database access, and E-mail |
| PRESENTATION layer 6 |
The presentation layer, usually part of an operating system, converts incoming and outgoing data from one presentation format to another. Presentation layer services include data encryption and text compression. |
| SESSION layer 5 |
Opens manages, and closes conversations between two computers. It performs name recognition and the functions such as security, needed to allow two applications to communicate over the network, also provides error handling. |
| TRANSPORT layer 4 |
This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer. Sequences data packets, and requests retransmission of missing packets. It also repackages messages for more efficient transmission over the network. |
| NETWORK layer 3 |
Establishes, maintains and terminates network connections. Routes data packets across network segments. Translates logical addresses and names into physical addresses. |
| DATA LINK layer 2 |
Transmits frames of data from computer to computer on the same network segment. Ensures the reliability of the physical link established at layer 1. Standards define how data frames are recognized and provide the necessary flow control and error handling at the frame set. The data link layer is divided into two sublayers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking. |
| PHYSICAL layer 1 |
The Physical layer defines all the electrical and physical specifications for devices. This includes the layout of pins, voltages, and cable specifications. Hubs, repeaters and network adapters are physical-layer devices. Defines cabling and connections. Transmits data over the physical media. |
2.3 Identify the OSI (Open Systems Interconnect) layers at which the following network components operate:
> Hubs, Switches, Bridges, Routers, NICs (Network Interface Card), WAPs (Wireless Access Point)
| APPLICATION layer 7 |
|
| PRESENTATION layer 6 |
|
| SESSION layer 5 |
|
| TRANSPORT layer 4 |
|
| NETWORK layer 3 |
Routers - Switches - Bridges
|
| DATA LINK layer 2 |
|
| PHYSICAL layer 1 |
Network adapters - Repeaters - Ethernet hubs - Modems - Wireless 802.11x
|
2.4 Differentiate between the following network protocols in terms of routing, addressing schemes, interoperability and naming conventions:
> TCP/IP
Transmission Control Protocol, A connection based Internet protocol responsible for breaking data into packets, which the IP protocol sends over the network. IP is located at the TCP/IP Internet layer which corresponds to the network layer of the OSI Model. IP is responsible for routing packets by their IP address.
IP is a connectionless protocol. which means, IP does not establish a connection between source and destination before transmitting data, thus packet delivery is not guaranteed by IP. Instead, this must be provided by TCP. TCP is a connection based protocol and, is designed to guarantee delivery by monitoring the connection between source and destination before data is transmitted. TCP places packets in sequential order and requires acknowledgment from the receiving node that they arrived properly before any new data is sent.
TCP/IP model
| Application layer |
| DHCP - DNS - FTP - HTTP - IMAP4 - IRC - NNTP - XMPP - MIME - POP3 - SIP - SMTP - SNMP - SSH - TELNET - BGP - RPC - RTP - RTCP - TLS/SSL - SDP - SOAP - L2TP - PPTP |
| Transport layer |
| This layer deals with opening and maintaining connections, ensuring that packets are in fact received. This is where flow-control and connection protocols exist, such as: TCP - UDP - DCCP - SCTP - GTP |
| Network layer |
| IP (IPv4 - IPv6) - ARP - RARP - ICMP - IGMP - RSVP - IPSec |
| Data link layer |
| ATM - DTM - Ethernet - FDDI - Frame Relay - GPRS - PPP |
| Physical layer |
| Ethernet physical layer - ISDN - Modems - PLC - RS232 - SONET/SDH - G.709 - Wi-Fi |
Internetwork Packet Exchange/Sequenced Packet Exchange developed by Novell and is used primarily on networks that use the Novell NetWare network operating system. The IPX and SPX protocols provide services similar to those offered by IP and TCP. Like IP, IPX is a connectionless network layer protocol. SPX runs on top of IPX at the transport layer and, like TCP, provides connection oriented, guaranteed delivery.
IPX nodes do not have to be configured with a unique node identifier; instead, they copy the MAC address of the network interface card into the IPX node address field. The IPX header contains information about which transport layer protocol receives a particular packet. With IPX, this information is contained in the destination socket field. Servers have pre specified destination socket numbers, so workstations always know what value to use to send information to the server. In contrast, these workstations assign source socket numbers dynamically for their own protocols outside the server socket number's range.
IPX routing protocols require each logical network to have a different network number in order to forward IPX packets correctly. But, unlike IP, with IPX only servers and routers must be configured with a network number. New network stations first use dynamic Routing Information Protocol (RIP) routing packets to learn network topography and configuration from servers and routers and then configure themselves accordingly.
Because IPX is a connectionless protocol, NetWare servers are unable to tell if a station's connection to the server is currently active. To avoid reserving resources for inactive users, the NetWare server sends a watchdog packet to a client after a predetermined length of inactivity. The packet asks if the client is still connected and, if the client does not respond, the server terminates the connection.
SPX is connection oriented and, thus, does not require the use of watchdog packets. However, network devices will keep an SPX session open by sending keep alive packets to verify the connection.
> NetBEUI
NetBIOS Enhanced User Interface was designed as a small, efficient protocol for use in department-sized LANs of 20-200 computers that do not need to be routed to other subnets. NetBEUI is used almost exclusively on small, non-routed networks.
As an extension of NetBIOS, NetBEUI is not routable, therefore networks supporting NetBEUI must be connected with bridges, rather than routers, like NetBIOS, the NetBEUI interface must be adapted to routable protocols like TCP/IP for communication over WANs.
AppleTalk is a LAN architecture built into all Apple Macintosh computers. While AppleTalk is a proprietary network, many companies now market AppleTalk based products, including Novell and Microsoft. Similarly, designed to be link layer independent, AppleTalk supports Apple's LocalTalk cabling scheme, but also runs over Ethernet (EtherTalk), Token Ring (TokenTalk), and Fiber Distributed Data Interface, or FDDI (FDDITalk).
AppleTalk node addresses are assigned dynamically to ensure minimal network administration overhead. When a node running AppleTalk starts up, it generates a random network layer protocol address and then sends out a broadcast to determine whether that particular address is already in use. If it is, the node with the conflicting address responds and the broadcasting node selects a new address and repeats the inquiry process.