Why Tunnelling Is Utilised

Published Date: 02 Nov 2017

This report will outline the reasons why tunnelling is utilised, critically compare and contrast a number of standard protocols, explain why they have been developed and the situation in which they may be preferred over one another.

What it tunnelling in regards to computing:

The process of encapsulation, transmission and de capsulation of packets is known as tunnelling. It allows the transmission of the packet through the internetwork via a logical pathway and it is also a technology that allows one to deliver a payload via the use of a protocol. Typically the payload is the packets/frames of another protocol. The payload is not sent as it was produced; rather it is encapsulated with an additional header. The transmission process of private network traffic to public network i.e. internet is known as encapsulation. The encapsulation header is beneficial as it supplies routing information allowing the payload to navigate intermediate internetwork. This is also known as transit internetwork. On arrival of the encapsulated payload packets, the frame is de-capsulated and then directed to its specified destination.

To summarise; encapsulation, transmission and de capsulation of packets over same or different networks is known as tunnelling

Why tunnelling is utilised

The use of tunnelling allows one to transfer data over an incompatible delivery network or make available a secure path via an untrusted network. It provides the means for a remote access user to connect to a different variety of network resources such as internet services or corporate home gateways etc. One of the most momentous benefits of tunnelling is that it allows for the construction of VPN’s (virtual private networks) over public data networks which in turn allows for cost saving for both end users as then the creation of dedicated networks is not required. It is also beneficial for service providers as they may influence their network investments through to many VPN customers.

Another reason why tunnelling is utilised is that it provides the means to connect discontiguous subnets. An example of a discontiguous subnet is having two major networks that are divided by another major network. Because the two major networks are divided by another major network; administrators utilise tunnels rather than VLSM to resolve the communication problem between the networks. The following diagram is an illustration of this

Networks that have limited hop counts due to the protocols they use are provided with a workaround by utilising tunnels as shown in the diagram below. Tunnelling also facilitates multiprotocol local networks over a single protocol backbone

http://www.cisco.com/en/US/i/100001-200000/110001-120000/117001-118000/117459.jpg

references

http://www.cisco.com/en/US/docs/ios/12_4/interface/configuration/guide/inb_tun.html#wp1045731

http://docstore.mik.ua/cisco/CCNP-CCDP/CID-Sybex/ch03/03-07.html

http://www.cisco.com/en/US/products/ps6625/products_ios_protocol_option_home.html

Protocols (PPTP)

Point to point tunnelling protocol (PPTP), is a protocol established by Microsoft. Amongst the majority of windows clients, it is the most widely supported virtual private network technique. Through the use of PPTP one is able to encrypted multiprotocol traffic, encapsulate it within an IP header and send it to private or public IP networks i.e. the internet. PPTP is also used as a means for remote access and site to site VPN connections.

It is important to note that PPTP establishes the tunnel but does not provide encryption, rather uses the Microsoft point to point encryption (MPPE) protocol to create a protected VPN.

Advantages

PPTP makes use of very low overheads thus making it faster than some other VPN techniques.

The utilisation of the internet as a connection rather than using long distance telephone number or 0800 services greatly decreases transmission costs.

Hard ware costs are also reduced as PPTP allows modems and ISDN cards to be separated.

Using PPTP, networking administrators can centrally manage and safe guard remote access networks at the remote access server. They do not have to support convoluted hardware configurations rather only have to manage user accounts instead. This in turn reduces administrative overheads

Disadvantages

The main disadvantage of PPTP is the lack of security as it does not encrypt the control message traffic thus making the connection susceptible to attack or hijacking during the transmission of the information.

Applications of PPTP

Any type of packet can be sent over a network as PPTP permits multiprotocol encapsulation for example sending IPX packets over the internet.

Utilising PPTP, current corporate networks are treated as PSTN, ISDN or X.25 networks. The virtual wireless area network is then assisted through public carriers i.e. the internet.

When comparing PPTP to different WAN protocols:

When utilising as PSTN, ISDN or X.25. Over a switched network, a remote access client initiates a PPP connection with a RAS server. Once the connection is initiated PPP packets are routed to the destination LAN over the switched network via the RAS server.

In contrast, rather than utilising a switched connection, PPTP uses TCP/IP to send PPP packets to the RAS server over the virtual WAN.

In conclusion, using the internet instead of long distance dial up connection allows one to save money as long distance dial up connections cost more than the internet.

Sources

http://vpnblog.info/pptp-vs-l2tp.html

http://technet.microsoft.com/en-us/library/cc771298(v=WS.10).aspx

http://technet.microsoft.com/en-us/library/cc751470.aspx

http://www.worldnet-long-distance.com/advantages-pptp/

http://www.your-freedom.net/index.php?id=242&L=7

Protocols (L2TP)

Layer two tunnelling protocol (L2TP) was developed in collaboration between Cisco and Microsoft. Cisco’s L2F protocol and Microsoft’s PPTP protocol was combined to produce L2TP. The protocol is used by ISP’s to permit VPN operations over the internet. It can be utilised as a tunnelling protocol over private intranets or over the internet. The mergence of both, L2F and PPTP’s best features have resulted in a reliable and secure protocol.

L2TP operates by allowing endpoints to be discovered on different machines by utilising packet switched network connections. It encapsulates PPP frames that are sent over IP, X.25, frame Relay or ATM networks. When transmitted over an IP internetwork the frames are encapsulated as UDP messages.

The pros are:

It is a standard protocol that provides vendor interoperability

For enterprise users it provides flexibility for remote access solution, guaranteed priority and security.

For service providers: management for VPN’s and a wide range of VPN services

The cons are

L2TP encapsulated data twice which results in slower speed than PPTP. The main disadvantage is the amount of configuration required in the setting up of L2TP. This includes PKI and computer certificates. Server 2008 and windows vista may need registry changes prior to using L2TP being configured successfully with them. This is dependent on how the network is constructed with network address translation.