User Guide
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gateways, and even root name servers. One common method of attack involves saturating the target
machine with external communication requests, such that it cannot respond to legitimate traffic, or
responds so slowly as to be rendered effectively unavailable.
IGMP
The Internet Group Management Protocol (IGMP) is a communications protocol used by hosts and
adjacent routers on IP networks to establish multicast group memberships. IGMP can be used for online
streaming video and gaming, and allows more efficient use of resources when supporting these types of
applications.
IP
The Internet Protocol (IP) is the principal communications protocol used for relaying datagrams (also
known as network packets) across an internetwork using the Internet Protocol Suite. Responsible for
routing packets across network boundaries, it is the primary protocol that establishes the Internet. The
Internet Protocol only provides best effort delivery and its service is characterized as unreliable. Each
network device attached to LAN or WAN is assigned with an IP address. This IP address is used for
unique identifier of a network device on the network.
The dominant internet working protocol in the Internet Layer in use today is IPv4; IPv4 uses 32-bit
addresses, which indicates 4 billion, or 4.3×109, available addresses. Thus IPv6 is brought into use for
addressing rapid exhaustion of IP addresses. The IPv6 uses 128-bit addresses, which indicates 340
undecillion, or 3.4×1038 available addresses. Yet, IPv4 is still the dominant protocol of the internet. Its
successor of IPv6 is increasing in use though slow.
MAC Table
An Ethernet device uses a MAC address table for forwarding frames. When forwarding a frame, the
device first looks up the MAC address of the frame in the MAC address table for a match. A switch
maintains a MAC address table for frame forwarding. Each entry in this table maps the MAC address to
associated interface. It tells the switch from which port a MAC address (or host) can be reached. A MAC
address table consists of two types of entries: static and dynamic. Static entries are manually configured
by administrators and never age out.
A frame also carries a source MAC address which indicates the sender. The device can automatically
populate its
MAC address table by obtaining the source MAC addresses (known as “MAC address
learning”) of incoming frames on each port. If a dynamic entry has not updated when the aging timer
expires, the device deletes the entry.
PING
Ping is a computer network administration utility used to test the reachability of a host on an Internet
Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a
destination computer. Ping operates by sending Internet Control Message Protocol (ICMP) echo request
packets to the target host and waiting for an ICMP response. In the process it measures the time from
transmission to reception (round-trip time) and records any packet loss. The results of the test are printed
in the form of a statistical summary of the response packets received, including the minimum, maximum,
and the mean round-trip times, and sometimes the standard deviation of the mean.
