Understanding Network Protocols

Different types of protocols are used at different layers of OSI model for providing security to the users. The users need to know if the transactions they perform on the internet are secure or not. The different types of protocols are SLIP (Serial Line Interface Protocol), PPP (Point To Point) protocol, PPTP (Point to Point Tunneling Protocol) and IPSEC (Internet Protocol Security).

SLIP (Serial Line Interface Protocol)

SLIP was designed for Data link protocol used in telephony. It only supported TCP/IP, NetBEUI or IPX network. Any network that uses SLIP required a static IP address as SLIP did not support DHCP. To check for errors SLIP relied on hardware that was used for connection. Another limitation of SLIP was that, all authentication passwords were transmitted as clear text. Even if SLIP had a number of limitations, still it is supported by Remote Access Programs.

PPP (Point to Point Protocol)

PPP addresses all the shortcomings of SLIP. PPP supports IPX and NETBEUI as well as IP. The different services provided by PPP are as follows:
1. Defines the format of frames to be exchanged between devices.
2. Defines how the devices can negotiate for establishment of link and exchange of data.
3. Defines how network layer data is encapsulated in the data link frame.
4. Defines how the devices can authenticate each other.
5. Provides multiple layer services that support different network layer protocols.
6. Provides connection over multiple links.
7. Provides network address configuration which is useful in case a user needs a temporary network address to connect to the internet.

PPTP (Point To Point Tunneling Protocol)

PPTP allows secure transfer of data from a remote client to a server. It creates a Virtual Private Network (VPN) around the TCP/IP network. PPTP provides support for an on-demand multi protocol, virtual private networking over public networks such as internet. The important feature of PPTP is that it provides VPN through the PSTN (Public Switched Telephone Network). PPTP provides secure and encrypted communications over the public telephone lines and the internet reducing the cost. It also provides an easy method of setting up a remote access solution for remote and mobile users. PPTP protocol involves three process: PPP connection and communication, PPTP control connection and PPTP data tunneling.

IP Security (IPSec)

IPSec is a protocol that was developed by IETF (Internet Engineering Task Force) for providing security to a packet at the network level. IPSec helps to create authenticated and confidential packets for the IP layer. The two modes in which IPSec operates are:
Transport Mode: In this mode, IPSec protects packets that are delivered from transport layer to the network layer. It protects the network layer payload that is to be encapsulated in the network layer. Transport mode does not protect the IP header that is it does not protect the whole IP packet. It protects the packet from the transport layer. Transport mode is normally used when the user requires a host to host protection of data. The sending host uses IPSec to authenticate and encrypt the payload delivered from the transport layer. The receiving host uses the IPSec to check the authentication and decryption of IP packet and sends it to the transport layer.

Tunnel Mode

In this mode, IPSec protects the entire packet. It takes an IP packet including the header, applies the IPSec security methods to the entire packet and then adds a new IP header. The new IP header has different information than the earlier IP header. This mode is normally used between two routers or between a host and a router or between a router and a host. Tunnel mode is used when either the sender or receiver is not a host. The entire original packet is protected from intervention when travelling between the sender and the receiver.