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A MAC layer address look like this: 08:00:05:81:79:66.
and it should not be confused with an
IP address
that look like this: 121.006.62.06
they are not the same and perform
different functions. How do I broadcast email through a firewall? - Page 1
A router or gateway are hardware devices that |
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Local IP Address When 2 computers try to communicate, an ARP request is initiated--if the IP address is on the local network, it (the source host) checks its ARP cache to see if it has the hardware MAC address of the receiving host--if not, a broadcast is sent to all local hosts. If the receiving host finds that the IP address of the source host matches its own--it sends a reply to the source host with its hardware address. When received by the source host, its ARP cache is updated to include it--if no hosts respond to the broadcast then the request is discarded. ARP - Address Resolution Protocol, translates an IP packet address into a MAC layer address-(below) so that frames can be delivered to a LAN destination workstation (LAN does not use IP addresses but MAC layer address). ARP are dynamic or can be static and if a dynamic entry is not used within 2 minutes, it gets deleted--if used it remains for 10 minutes, whereas, a static entry will remains until the machine is rebooted or a dynamic entry is received to overwrite it.
Remote
IP address Basically, the router follows the same pattern--by checking its cache for a path to the receiving host--if one is found, the packet is forwarded--if not, it sends a broadcast and waits for a reply from the host. It may again determine that it is a remote host and then the process repeats with a broadcast to the next router and so on--once the receiving host gets the request, it sends an ICMP echo request.
ICMP -
Internet Control Message Protocol are used by routers and
nodes to perform error reporting for Internet Protocol. It report errors such as invalid
IP address, invalid port address, and the packet has
hops too many times. |
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A router or gateway are hardware devices that forwards packets from one network to another. IP uses a routing table to determine which networks that packets can be forwarded to and will only forward them to networks that it has been configured to do so. When a packet is to be sent, IP determines whether or not the IP address is local or remote. If it is local, it forwards the packet. If it is remote, it consults the routing table to determine the path to the remote host. If there is no entry in the routing table, then the default gateway is used instead. IP - Internet Protocol prepares a packet (datagram) for transmission across the Internet with the IP header encapsulated. The IP packet is then passed to the next layer where further network information is encapsulated onto it. Internet traffic travel in bursts of segments (packets or datagram) of around 536 bytes (4,288 bits). The routing table is checked at the router and the process repeats. A packet can be forwarded from router to router. Each one of these steps is called a hops --if a route to the remote host is never found then an error message will return. Routing can be either static or dynamic. Static routing involves manually programming the routing table into the router. <><><><><><> MAC (Media Access Control) manages one of the sublayers handles access to shared media. MAC address (are 6 bytes long and are controlled by the IEEE). It is a standardized data link layer address that is required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures. MAC address are also known as;
A MAC layer address look like this: 08:00:05:81:79:66. and it should not be confused with an IP address that look like this: 121.006.62.06 they are not the same and perform different functions. MAC address can be displayed for Windows NT users by opening a command shell (DOS prompt) and entering ipconfig /all -- to display a text list of PCs network info. Win95 users can get the MAC address by opening a command shell (DOS prompt) and entering net diag /s and you will be asked for the computer Netbios name and enter key--the MAC address displayed next Permanent Node Name
Win95 users can
get the MAC address by opening a command shell (DOS prompt) and entering winipcfg if TCP/IP protocols
are already installed. <><><><><><> MTU Maximum Transmission Unit - is the default packet Windows uses to negotiate when a connection is opened between two computers, they must agree on an MTU by comparing MTU and selecting the smaller of the two. If it is set too large for routers, it is then fragmented into packet size and can take double the amount of time it takes to send a single packet. UART Universal Asynchronous Receiver Transmitter Data flow between the serial port and the modem is governed by a UART chip, which can contain no data buffers, single-byte data buffers or 16-byte data buffers. All data flows between the serial port and the modem via the UART RWIN (TCP Receive Window) determines how much data the receiving computer is prepared to receive. RWIN value that is set too high will result in greater data loss if the packet is lost or damaged in transit. RWIN value that is set too low will produce poor throughput. MSS (Maximum Segment Size) is the largest segment of TCP data that Winsock is prepared to receive on a particular connection. When the TCP connection is initially established, both uses the minimum of each other's MSS value. If the MSS is too low, the data/header ratio will be low. If the MSS is too high, will lead to large IP packets or datagram will tend to fragment in transit where other networks may be having smaller MTU. Hence, performance can be increase by reducing MSS value. Since packet headers are normally 40 bytes in length, your MSS value should always be set to MTU value minus 40 (i.e. if your MTU is 1500 the set MSS to 1460) at least 40 less than the value of the MTU
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