Networking, Python, BigData and Linux

http://www.certificationzone.com/newsletter/SL/IE-RIP-WP1-F03_RLP.html http://searchnetworking.techtarget.com/definition/split-horizon

How Relay Agents Work The following figure shows how Client C on Subnet 2 obtains a DHCP address lease from DHCP Server 1 on Subnet 1. Using a Relay Agent DHCP Client C broadcasts a DHCPDiscover message on Subnet 2 as a UDP datagram over well-known UDP port 67, which is the port reserved and shared for BOOTP and DHCP server communication. The relay agent, in this case a DHCP relay-enabled router, examines the Gateway IP Address field (also known as the giaddr field) in the DHCP message header. If the field has an IP address of 0.0.0.0, the agent fills the Gateway IP Address field with the IP address assigned to the interface on which the DHCPDiscover was received, and forwards the DHCPDiscover message as a unicast message to the DHCP server on Subnet 1. When DHCP Server 1 receives the DHCPDiscover message, it examines the Gateway IP Address field to determine if the packet was relayed. The DHCP server then determines whether it can supply an IP address lease to clients o

There are basically two ways to assign the IP addresses to any network device. One is Static IP address allocation and the other is dynamic IP address allocation.  Incase of static configuration of IP address we have following disadvantages: There is chance of assigning duplicate IP address to the clients is very high when the network is having so many devices. For every new device that is connected to network, user has to manually assign the IP address. DHCP (dynamic host configuration protocol) is a protocol which is used to assign the IP addresses to clients dynamically. Using DHCP protocol we can overcome the problems faced above due to static IP address assignment. DHCP is a application layer protocol which uses UDP as transport layer. In DHCP configuration, we need to configure one device in a subnet as DHCP server so that all the clients in that subnet receive the IP address from that server dynamically. As DHCP uses broadcast messages (which will be by

Suppose I am a service provider, and providing internet service to a network of 1000 end users. Now, I want to provide another new service lets say IPTV to the users on the same network. How could I do that? Shall I use broadcast so that all the users get IPTV service? How do I provide IPTV service to the only users who are interested for it? Shall I use unicasting to send to the interested receivers?      Well, broadcasting would be a good idea if all the users are interested to use the service and pay for that. What if all the users are not interested and ready to pay for it? Hence I won’t use broadcasting. What about the unicasting? Yes I can provide the IPTV service to interested receivers using unicasting.In this case what I have to do is i  need to send the traffic on one by one basis. If there are 100 users out of 1000 then I have to send a same packet 100 times.oops! Network congestion, bandwidth bottleneck!! So let me not use unicasting for this. What next? Is there any

Well, MTU(maximum transmission unit) for ethernet is limited to 1500 only.That is because of following main two reasons: 1. When the frame size is too high then chances of signal at physical media being corrupted will be high.And, if there is even a single byte, entire frame needs to be re transmitted which aids overhead significantly.Also, large frame size delays the signal follow. 2. As per the Ethernet frame standard 802.3 there is 2 byte Length field and Ethernet frame standard II there is 2 byte Type field.Based on that numerical 2 byte field Ethernet standard being used will be distinguished.If numerical value is more than 1500 in decimal then it signifies Ethernet standard -II else it signifies  Ethernet standard 802.3. In case the packet size is such that it exceeds the MTU then fragmentation needs to be done.