SIP (Session Initiation Protocol)
SIP (Session Initiation Protocol)
SIP is an application layer protocol designed to be independent of the underlying transport layer; it can run on transmission control protocol (TCP), UDP, or SCTP. It is a text based protocol, incorporating many elements of the HTTP and the SMTP.The session Initiation Protocol is a signaling communication protocol, widely used for controlling multimedia communication sessions such as voice and video calls over IP.
The protocol defines the messages that are sent between peers which govern establishment, terminations and other essential element of call. SIP can be used for creating, modifying, and terminating two party (unicast) or multiparty (multicast) sessions consisting one or several media streams. Other SIP applications include video conferencing, streaming multimedia distribution, instant messaging, presence information, file transfer and online games.
SIP work in conjunction with several other application layer protocols that identify and carry the session media identification and negotiation is achieved with session description protocol (SDP). For the transmission of media stream a(voice, video) SIP typically employs the Real-Time transport protocol (RTP), which many be secured with the secure Real-Time transport protocol (RTP). For secure transmissions of SIP message the protocol may be encrypted with transport layer security TLS.
NNTP (Network News Transport Protocol)
NNTP (Network News Transfer Protocol)
The News Transport Protocol (NNTP) is an application protocol used for
transporting Usenet news articles (net news) between news server and for
reading and posting articles by end client application.
Usenet was originally designed based on the UUCP network, with most
article transfer taking place over direct point to point telephone link between
news sever and which were powerful time sharing systems. Readers and posters logged
into this computer reading the article directly from the local disc.
As local area network and internet participation it became describe to
allow news readers to be run on personal computers connected to local networks.
Because distributed files system were not yet widely available, a news protocol
was developed based on the client server model. It resembled the simple Mail Transfer
Protocol (SMTP), but was tailored for exchanging news group article.
A news reader, also known as a news client, is a software application
that reads article on Usenet, either directly from the news server's disks or
via the NNTP. The well-known TCP port 119 is reserved for NNTP. When client
connect to a news server with transport layer security (TLS), TCP port 563 is
used. This is sometimes referred to as NNTPS.
In October 2006, the IETF released RFC 3977 which updates the NNTP protocol
and codifies many of the additions over the years since RFC977.
Domain Name System
DNS (Domain Name System)
The
Domain Name System is a hierarchical distributed naming system for computers,
services, or any resource connected to internet or a private network. It
associates various information with domain names assigned to each of the
participating entities. Most prominently, it translates easily memorized domain
name to the numerical IP addresses needs for the purpose of locating computer
services and devices worldwide. By providing a worldwide, distributed
keyword-based redirection service, the Domain Name System is an essential component
of the functionality of the internet.
An
often-used analogy to explain the Domain Name System is that it serves as the
phone book for the internet by translating human-friendly computer hostnames
into IP addresses. For example the domain name www.example.com
translates to the addresses 192.163.0.10 (IPv4) and 2001:500:88:200::10 (IPv6).
Unlike a phonebook the DNS can be quick updated, allowing a service's location
on the network to change without effecting the end users, who continue to use
the same hostname. Users take advantage of this when they use meaningful
uniform resource locator (URL) and E-mail addresses without having to known how
the computer actually locates the services.
The
Domain Name System distributes the responsibility of assigning domain names and
mapping those names to IP addresses by designating authoritative name serves
for each domain. Authoritative name servers are assigned to be responsible for
their particular domain and in turn can assign other authoritative name servers
for their sub-domains. This mechanism has made the DNS distributed and fault
tolerant and has held avoid the need for a single central register to be
continually consulted and updated. Additionally the responsibility for
maintaining and updating the master record for the domain is spread among many
domain name registers, who compete for the end-user's (the domain-owner's)
business. Domain can be moved from one registrar to other registrar at any time.
The
Domain Name System also specifies the technical functionality of this data base
service. It defines the DNS protocol, a detailed specification of the data
structures and data communication exchanges used in DNS, as part of the
internet protocol suit.
What is Protocol?
Protocols
A
communication protocol is (Networking protocol) is a system of digital message
formats and rules for exchanging messages in or between computing system and in
telecommunications. A protocol may have a formal description. Protocol may include
signaling, authentication and error detection and correction capability.
In
a routing protocol, it specifies that how routers communicate with each other
and with the other types of machines. Protocols are determines and enable the
routes between the nodes on a computer network. Algorithms determine the
specific choice of routing. A router has knowledge only the direct attached
networks and a protocol shares information about the neighbors immediate and
then throughout the network. A router can understand the network topology
through the protocol. So we can say that a protocol is playing very important
role in a network. Although, there are many types of protocols.
Types of protocols
There
are many types of protocols for different purpose in networking.
Routing protocols
IS-IS,
OSPF, IGRP and EIGRP, RIP, BGP,
Internet protocols
Application Layer
DHCP,
DHCPv6, DNS, FTP, HTTP, IMAP, IRC, LDAP, MGCP, NNTP, BGP, NTP, POP, RPC, RTP,
RTSP, RIP, SIP, SMTP, SNMP, SOCKS, SSH, Telnet, TLS/SSL, XMPP.
Transport Layer
TCP, UDP, DCCP, SCTP, RSVP, TP-TCP, NC, MTP
Network Layer
IP(IPv4,IPv6),
ICMP, ICMPv6, ECN, IGMP, IPSec, GGP.
Link Layer
What is subnet mask?
Subnet mask
A network mask is used when a network is not sub netted. The
subnet mask is used to find the first address in the block. However when a mask
is sub netted, the situation is different. We must have a subnet mask. The
subnet has more 1s.
Subnetting increases the length of the netid and decrease
the length of hostid. When we divide a network to s number of subnetworks, each
of number of hosts, we can calculate the subnetid for each subnetwork as in
which n is the length of netid,.
Subnet Address
When a network is subnetted, the first address in the subnet
is the identifier of the subnet and is used by the router to route the packets
destined for that subnet works. Given any address in the subnet, the router can
find the subnet mask using the same procedure we discussed to find the
subnetwork mask. ANDing the given address with the subnet mask.
Super netting
Subnetting couldn’t completely solve address depletion problems
in classful addreeing, because most organization did not want to share their
granted blocks with others. since class C blocks were still available but the
size of block did not meet the requirement of new organization that wanted to
join the internet, one solution was super
netting . in super netting, an organization can combine several class C block
to create a larger range of addresses. In other, words several networks are
combined to create a supernet work. By doing this, an organizarion can apply
for several class C blocks instead of just one. For example, an organization
that needs 1000 addresses can be granted four class C blocks.
What is subnetmask?
Subnetting
In subnetting, a network divides into several smaller
networks with each subnetwork having its
own subnetworks. A portion of IP address is indicating the network (netid), and
a portion indicates the network hostid. This means that there is a sense of hierarchy
in IP addressing. To each a host on the internet, we must first reach the
network using the first portion of the address. Then we must reach the host
itself using the second portion. In the other word, IP address is designed with
two level of hierarchy. However in many cases two levels of hierarchy are not
enough. For example, imagine an organization with the network address
141.14.0.0 (a class B address). The organization has two hierarchical addressing,
but cannot have more than one physical network. One solution of this problem is
subnetting. Further division of a network into smaller networks is called
subnetting.
Three level of hierarchy
Adding subnetworks an intermediate level of hierarchy in the
IP addressing system. Now we have three levels; site, subnet and host. The site
is the first level. The second level is subnet and the tird level is host of
hierarchy, it defines the connection of the host to the subnetwork.
The
routing of an IP datagram now involves steps: delivery to site, delivery to subnet
work and delivery to the hostWhat is subnetmask?
Mask
If the network address is given, we can find the block and
the range of addresses in the block. What
about the reserves? If an address is given, can we find the given address (the
beginning address in the block). This is important because to route a packet to
the correct network, a router needs to extract a network address from the
destination address (a host address) in the packet header.
One way we can find the network address to first find the
class of the address and the net ID. We then set the host ID to zero to find
the network address. For example, if the address is 134.45.78.2 is given, we
can immediately say that the address belong to class B. the net ID is 134.45 (2
bytes) and the network address is
134.45.0.0.
The above method is feasible if we not subnetted the
network; that is, if we have not divided the network into subnetworks. A
general procedure that can be used involves a mask to find the network address
from a given address.
A mask is a 32 bits binary number that gives first address
in the block (the network address). When bit-wise ANDed with an address in the
block.
AND
Operation
Masking uses the bit-wise AND operation defined in computer
science. The operation is applied bit by bit to the address and the mask.
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