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Paul Carmel
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Post by Paul Carmel »

Moliere wrote:So what's a VPN, Paul? :
You did ask...................


A virtual private network (VPN) extends a private network and the resources contained in the network across public networks like the Internet. It enables a host computer to send and receive data across shared or public networks as if it were a private network with all the functionality, security and management policies of the private network. This is done by establishing a virtual point-to-point connection through the use of dedicated connections, encryption, or a combination of the two.

The VPN connection across the Internet is technically a wide area network (WAN) link between the sites but appears to the user as a private network link—hence the name "virtual private network".

Types of VPN

Early data networks allowed VPN-style remote connectivity through dial-up modems or through leased line connections utilizing Frame Relay and Asynchronous Transfer Mode (ATM) virtual circuits provisioned through a network owned and operated by telecommunication carriers such as AT&T or Verizon. These networks are not considered true VPNs because they passively secure the data being transmitted by the creation of logical data streams.They have given way to VPNs based on IP and IP/Multi-protocol Label Switching Networks (MPLS) based VPNs due to significant cost-reductions and increased bandwidth provided by new technologies such as Digital Subscriber Line (DSL)and fiber-optic networks.

VPNs can be either remote-access (connecting an individual computer to a network) or site-to-site (connecting two networks together). In a corporate setting, remote-access VPNs allow employees to access their company's intranet from home or while traveling outside the office, and site-to-site VPNs allow employees in geographically separated offices to share one cohesive virtual network. A VPN can also be used to interconnect two similar networks over a dissimilar middle network; for example, two IPv6 networks over an IPv4 network.

VPN systems can be classified by:
the protocols used to tunnel the traffic
the tunnel's termination point, i.e., customer edge or network-provider edge
whether they offer site-to-site or remote-access connectivity the levels of security provided
the OSI layer they present to the connecting network, such as Layer 2 circuits or Layer 3 network connectivity

Security mechanisms

VPNs typically require remote access to be authenticated and make use of encryption techniques to prevent disclosure of private information.

VPNs provide security through tunneling protocols and security procedures[7] such as encryption. Their security model provides:

Confidentiality such that even if traffic is sniffed, an attacker would only see encrypted data which they cannot understand
Allowing sender authentication to prevent unauthorized users from accessing the VPN
Message integrity to detect any instances of transmitted messages having been tampered with

Secure VPN protocols include the following:

IPSec (Internet Protocol Security) was developed by the Internet Engineering Task Force (IETF), and was initially developed for IPv6, which requires it. This standards-based security protocol is also widely used with IPv4. Layer 2 Tunneling Protocol frequently runs over IPSec. Its design meets most security goals: authentication, integrity, and confidentiality. IPSec functions through encrypting and encapsulating an IP packet inside an IPSec packet. De-encapsulation happens at the end of the tunnel, where the original IP packet is decrypted and forwarded to its intended destination.
Transport Layer Security (SSL/TLS) can tunnel an entire network's traffic, as it does in the OpenVPN project, or secure an individual connection. A number of vendors provide remote access VPN capabilities through SSL. An SSL VPN can connect from locations where IPsec runs into trouble with Network Address Translation and firewall rules.
Datagram Transport Layer Security (DTLS), is used in Cisco AnyConnect VPN, to solve the issues SSL/TLS has with tunneling over UDP.
Microsoft Point-to-Point Encryption (MPPE) works with the Point-to-Point Tunneling Protocol and in several compatible implementations on other platforms.
Microsoft's Secure Socket Tunneling Protocol (SSTP), introduced in Windows Server 2008 and in Windows Vista Service Pack 1. SSTP tunnels Point-to-Point Protocol (PPP) or Layer 2 Tunneling Protocol traffic through an SSL 3.0 channel.
MPVPN (Multi Path Virtual Private Network). Ragula Systems Development Company owns the registered trademark "MPVPN".[8]
Secure Shell (SSH) VPN - OpenSSH offers VPN tunneling (distinct from port forwarding) to secure remote connections to a network or inter-network links. OpenSSH server provides a limited number of concurrent tunnels and the VPN feature itself does not support personal authentication.

Authentication

Tunnel endpoints must authenticate before secure VPN tunnels can be established.

User-created remote access VPNs may use passwords, biometrics, two-factor authentication or other cryptographic methods.

Network-to-network tunnels often use passwords or digital certificates, as they permanently store the key to allow the tunnel to establish automatically and without intervention from the use

Example use of a VPN Tunnel

The following steps [12] illustrate the principles of a VPN client-server interaction in simple terms.

Assume a remote host with public IP address 1.2.3.4 wishes to connect to a server found inside a company network. The server has internal address 192.168.1.10 and is not reachable publicly. Before the client can reach this server, it needs to go through a VPN server / firewall device that has public IP address 5.6.7.8 and an internal address of 192.168.1.1. All data between the client and the server will need to be kept confidential, hence a secure VPN is used.

The VPN client connects to a VPN server via an external network interface.
The VPN server assigns an IP address to the VPN client from the VPN server's subnet. The client gets internal IP address 192.168.1.50, for example, and creates a virtual network interface through which it will send encrypted packets to the other tunnel endpoint (the device at the other end of the tunnel).[13] (This interface also gets the address 192.168.1.50.)
When the VPN client wishes to communicate with the company server, it prepares a packet addressed to 192.168.1.10, encrypts it and encapsulates it in an outer VPN packet, say an IPSec packet. This packet is then sent to the VPN server at IP address 5.6.7.8 over the public Internet. The inner packet is encrypted so that even if someone intercepts the packet over the Internet, they cannot get any information from it. They can see that the remote host is communicating with a server/firewall, but none of the contents of the communication. The inner encrypted packet has source address 192.168.1.50 and destination address 192.168.1.10. The outer packet has source address 1.2.3.4 and destination address 5.6.7.8.
When the packet reaches the VPN server from the Internet, the VPN server decapsulates the inner packet, decrypts it, finds the destination address to be 192.168.1.10, and forwards it to the intended server at 192.168.1.10.
After some time, the VPN server receives a reply packet from 192.168.1.10, intended for 192.168.1.50. The VPN server consults its routing table, and sees this packet is intended for a remote host that must go through VPN.
The VPN server encrypts this reply packet, encapsulates it in a VPN packet and sends it out over the Internet. The inner encrypted packet has source address 192.168.1.10 and destination address 192.168.1.50. The outer VPN packet has source address 5.6.7.8 and destination address 1.2.3.4.
The remote host receives the packet. The VPN client unencapsulates the inner packet, decrypts it, and passes it to the appropriate software at upper layers.

Overall, it is as if the remote computer and company server are on the same 192.168.1.0/24 network.
Routing

Tunneling protocols can operate in a point-to-point network topology that would theoretically not be considered a VPN, because a VPN by definition is expected to support arbitrary and changing sets of network nodes. But since most router implementations support a software-defined tunnel interface, customer-provisioned VPNs often are simply defined tunnels running conventional routing protocols.
PPVPN building-blocks

Depending on whether the PPVPN (Provider Provisioned VPN) runs in layer 2 or layer 3, the building blocks described below may be L2 only, L3 only, or combine them both. Multiprotocol label switching (MPLS) functionality blurs the L2-L3 identity.

RFC 4026 generalized the following terms to cover L2 and L3 VPNs, but they were introduced in RFC 2547.[14] More information on the devices below can also be found in Lewis, Cisco Press.[15]

Customer (C) devices

A device that is within a customer's network and not directly connected to the service provider's network. C devices are not aware of the VPN.

Customer Edge device (CE)

A device at the edge of the customer's network which provides access to the PPVPN. Sometimes it's just a demarcation point between provider and customer responsibility. Other providers allow customers to configure it.

Provider edge device (PE)

A PE is a device, or set of devices, at the edge of the provider network which connects to customer networks through CE devices and present the provider's view of the customer site. PEs are aware of the VPNs that connect through them, and maintain VPN state.

Provider device (P)

A P device operates inside the provider's core network and does not directly interface to any customer endpoint. It might, for example, provide routing for many provider-operated tunnels that belong to different customers' PPVPNs. While the P device is a key part of implementing PPVPNs, it is not itself VPN-aware and does not maintain VPN state. Its principal role is allowing the service provider to scale its PPVPN offerings, for example, by acting as an aggregation point for multiple PEs. P-to-P connections, in such a role, often are high-capacity optical links between major locations of providers.

ser-visible PPVPN services

This section deals with the types of VPN considered in the IETF; some historical names were replaced by these terms.
OSI Layer 1 services
Virtual private wire and private line services (VPWS and VPLS)

In both of these services, the service provider does not offer a full routed or bridged network, but provides components to build customer-administered networks. VPWS are point-to-point while VPLS can be point-to-multipoint. They can be Layer 1 emulated circuits with no data link .

The customer determines the overall customer VPN service, which also can involve routing, bridging, or host network elements. An unfortunate acronym confusion can occur between Virtual Private Line Service and Virtual Private LAN Service; the context should make it clear whether "VPLS" means the layer 1 virtual private line or the layer 2
OSI Layer 2 services

Virtual LAN

A Layer 2 technique that allows for the coexistence of multiple LAN broadcast domains, interconnected via trunks using the IEEE 802.1Q trunking protocol. Other trunking protocols have been used but have become obsolete, including Inter-Switch Link (ISL), IEEE 802.10 (originally a security protocol but a subset was introduced for trunking), and ATM LAN Emulation (LANE).

Virtual private LAN service (VPLS)

Developed by IEEE, VLANs allow multiple tagged LANs to share common trunking. VLANs frequently comprise only customer-owned facilities. Whereas VPLS as described in the above section (OSI Layer 1 services) supports emulation of both point-to-point and point-to-multipoint topologies, the method discussed here extends Layer 2 technologies such as 802.1d and 802.1q LAN trunking to run over transports such as Metro Ethernet.

As used in this context, a VPLS is a Layer 2 PPVPN, rather than a private line, emulating the full functionality of a traditional local area network (LAN). From a user standpoint, a VPLS makes it possible to interconnect several LAN segments over a packet-switched, or optical, provider core; a core transparent to the user, making the remote LAN segments behave as one single LAN.[16]

In a VPLS, the provider network emulates a learning bridge, which optionally may include VLAN service.

Pseudo wire (PW)

PW is similar to VPWS, but it can provide different L2 protocols at both ends. Typically, its interface is a WAN protocol such as Asynchronous Transfer Mode or Frame Relay. In contrast, when aiming to provide the appearance of a LAN contiguous between two or more locations, the Virtual Private LAN service or IPLS would be appropriate.

IP-only LAN-like service (IPLS)

A subset of VPLS, the CE devices must have L3 capabilities; the IPLS presents packets rather than frames. It may support IPv4 or IPv6.
OSI Layer 3 PPVPN architectures

This section discusses the main architectures for PPVPNs, one where the PE disambiguates duplicate addresses in a single routing instance, and the other, virtual router, in which the PE contains a virtual router instance per VPN. The former approach, and its variants, have gained the most attention.

One of the challenges of PPVPNs involves different customers using the same address space, especially the IPv4 private address space.[17] The provider must be able to disambiguate overlapping addresses in the multiple customers' PPVPNs.

BGP/MPLS PPVPN

In the method defined by RFC 2547, BGP extensions advertise routes in the IPv4 VPN address family, which are of the form of 12-byte strings, beginning with an 8-byte Route Distinguisher (RD) and ending with a 4-byte IPv4 address. RDs disambiguate otherwise duplicate addresses in the same PE.

PEs understand the topology of each VPN, which are interconnected with MPLS tunnels, either directly or via P routers. In MPLS terminology, the P routers are Label Switch Routers without awareness of VPNs.

Virtual router PPVPN

The Virtual Router architecture,[18][19] as opposed to BGP/MPLS techniques, requires no modification to existing routing protocols such as BGP. By the provisioning of logically independent routing domains, the customer operating a VPN is completely responsible for the address space. In the various MPLS tunnels, the different PPVPNs are disambiguated by their label, but do not need routing distinguishers.
Plaintext tunnels
Main article: Tunneling protocol

Some virtual networks may not use encryption to protect the data contents. While VPNs often provide security, an unencrypted overlay network does not neatly fit within the secure or trusted categorization. For example a tunnel set up between two hosts that used Generic Routing Encapsulation (GRE) would in fact be a virtual private network, but neither secure nor trusted.

Besides the GRE example above, native plaintext tunneling protocols include Layer 2 Tunneling Protocol (L2TP) when it is set up without IPsec and Point-to-Point Tunneling Protocol (PPTP) or Microsoft Point-to-Point Encryption (MPPE).
Trusted delivery networks

Trusted VPNs do not use cryptographic tunneling, and instead rely on the security of a single provider's network to protect the traffic.

Multi-Protocol Label Switching (MPLS) is often used to overlay VPNs, often with quality-of-service control over a trusted delivery network.

Layer 2 Tunneling Protocol (L2TP)[20] which is a standards-based replacement, and a compromise taking the good features from each, for two proprietary VPN protocols: Cisco's Layer 2 Forwarding (L2F)[21] (obsolete as of 2009) and Microsoft's Point-to-Point Tunneling Protocol (PPTP).[22]

From the security standpoint, VPNs either trust the underlying delivery network, or must enforce security with mechanisms in the VPN itself. Unless the trusted delivery network runs among physically secure sites only, both trusted and secure models need an authentication mechanism for users to gain access to the VPN.
VPNs in mobile environments
Main article: Mobile virtual private network

Mobile VPNs are used in a setting where an endpoint of the VPN is not fixed to a single IP address, but instead roams across various networks such as data networks from cellular carriers or between multiple Wi-Fi access points.[23] Mobile VPNs have been widely used in public safety, where they give law enforcement officers access to mission-critical applications, such as computer-assisted dispatch and criminal databases, while they travel between different subnets of a mobile network.[24] They are also used in field service management and by healthcare organizations,[25] among other industries.

Increasingly, mobile VPNs are being adopted by mobile professionals and white-collar workers who need reliable connections.[25] They are used for roaming seamlessly across networks and in and out of wireless-coverage areas without losing application sessions or dropping the secure VPN session. A conventional VPN cannot survive such events because the network tunnel is disrupted, causing applications to disconnect, time out,[23] or fail, or even cause the computing device itself to crash.[25]

Instead of logically tying the endpoint of the network tunnel to the physical IP address, each tunnel is bound to a permanently associated IP address at the device. The mobile VPN software handles the necessary network authentication and maintains the network sessions in a manner transparent to the application and the user.[23] The Host Identity Protocol (HIP), under study by the Internet Engineering Task Force, is designed to support mobility of hosts by separating the role of IP addresses for host identification from their locator functionality in an IP network. With HIP a mobile host maintains its logical connections established via the host identity identifier while associating with different IP addresses when roaming between access networks.

Did you know Max Clifford has been nicked?
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e-richard
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Post by e-richard »

I'm so glad I read that post all the way through to the last sentence. :lol:
** Richard
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Paul Carmel
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Post by Paul Carmel »

e-richard wrote:I'm so glad I read that post all the way through to the last sentence. :lol:
Who got nicked then............... :lol:
Cheers
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e-richard
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Post by e-richard »

That is one helluva publicity stunt :shock:
** Richard
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Post by paolo »

That is a very thorough post, Paul. Don't forget to post the footnotes you refer to in the square brackets.
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Moliere
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Post by Moliere »

Thank you so much for that, Paul, it makes me feel warm all over. I think maybe I shall live without iplayer, and stick with (k)nickers for entertainment! Oops, better watch out for the Old Bill.

Max Clifford now, Oh god, when will this nausea ever end?

It makes the Autumn Budget Statement look positively riveting.

Mols :cry:
Jumping is just dressage with speed-bumps.
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Post by Paul Carmel »

Hi Paolo, what happed to that littel critter who used to be on your shoulders?
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Post by paolo »

He will soon be 11 so I thought it was time to let him get off.
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Moliere
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Post by Moliere »

Time to let a horse take over, Paolo (Xmas is approaching!) :lol:

Mols
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Post by paolo »

My wife would like to exchange me for a horse, so it might happen.
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Post by greenbarn »

Very interesting post PC, and many thanks for the simplified explanation.
One thing puzzling me is the omission of SSL VPN, and indeed any related mention of OSI Layer 4 - do you not think this is relevant to the discussion? I was thinking that if Max had implemented it he might not have been rumbled.
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Post by Moliere »

Clifford does not strike me as the type (I could be wrong of course) - I suspect it's about what he might have known, not what he did.

Mols
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tavi
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Post by tavi »

my mind BOGGLES, not just at the VPN definition, but also at the Clifford news. Honestly where will it all end?
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Post by lorca »

tavi wrote: Honestly where will it all end?
....well there´s that 82 year old bloke who "cannot be named for legal reasons"....

No idea if I´ve got VPN or not PC ...so I guess I better give filmon a miss. No point in risking my laptop crashing in a tunnel like poor old Will´s mum.
If not now, when?
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Post by CSE »

tavi wrote: Honestly where will it all end?
Amazon paying is due taxes: Osborne resigning his post: The Spanish finally believing their politicians are corrupt: The Greeks leaving the Euro?....you name it!

Just to keep this on subject:
I use to use a Firefox add on, but over the last week it has gone very slow, UK IPs do not exist and they want money for the service... :shock:
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