Confusion regarding Leased Lines

[edwinn999]

Hello I'm Edwin.

I have some questions regarding Leased Lines . and how they work.

When company XYZ  from branch A , wants to connect to Branch B that is at a distance of over 500 km, then yes we use leased lines.

But does the branch A need to use the dedicated line from the same ISP , that Branch B uses ?.  If No, how is it going to be a Point to Point connection. Does the ISP give a separate path though its network to connect to Branch B.  How is this possible if different ISP's are used ?.

Moreover , over this line will I be able to connect to my Branch office B only ?. Or will I be able to connect to other branch offices also.

If I want to access the internet from the ISP , would I be able to access the web from this same link ?

What are the types of leased lines that are available and widely used by companies ?.

Please read and answer my questions. 

Thanks and regards,

Edwin

[Bilal Nawaz · Accepted solution]

A leased line is a service contract between a single provider and customer, where the provider agrees to deliver a symmetric or at least bidirectional telecommunications line - connecting two or more locations in exchange for a monthly rent. In the UK its also called a private circuit or data line. 

Typically they are used to connect one site to another, but can provide internet also known as "internet leased lines"

If you want to access the internet from the same link used to connect to a branch office, then no. Often providers offer services like MPLS where they can offer multiple services, internet, telephony, site connectivity, all from the same link.

When we look at fiber connectivity itself, sometimes its not possible for one provider to have fiber everywhere, so fairly frequently we see providers using other providers' fiber at some POP (or else where) provides for them a mechanism to join fiber together, for some of the distance, albeit the beginning / middle / end. The main provider, charges you for the overall circuit, and the main provider pays the agreement terms with the transit provider of that fiber.

Some organisations have chosen to go with "MPLS" solution as soon as the distance between their  offices goes beyond 50KM + as it becomes more cost effective and beneficial.

[edwinn999]

Suppose I'm taking a lease from an ISP that has his network only in my State . But I want to connect to my branch office that is outside my State. What if the destination branch network is not reachable by the ISP and is outside its network.

And the entire 400 km link passing from location A to B is only for my company ?

[Joseph W. Doherty]

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Posting

Some of you confusion might be thinking an ISP and leased lines always go together (alone); they do not.

A traditional leased line is a Telco line that's been "nailed up" (i.e. always connected/hot/active) between two end points.  It's generally used for data.  (In US, such Telco links might be called DS0, DS1 or T1, DS3 or T3, OC1, OC3, etc.)

You mention using a leased line if the distance is over 500 KM, but distance, alone, isn't always a principle factor.  Today, long distance leased lines, at least in the US, are becoming pretty rare as there's usually more cost effective solutions.  Generally, today in US, leased lines are only used, locally, to get you to a MAN/WAN service provider's, or ISP's, network.

The leased line's endpoints might be between the same organization's sites, your example of two of your branches, or it might be between two different organizations' sites.  The leased line, itself, might be only within one Telco's circuits, or it might interconnect between Telco's.

If a leased line, from your site, goes to a MAN/WAN service provider's local POP (point of presence), generally the "cloud" portion will stay within the logical network of that provider, until it gets to a leased line on the other side of the "cloud", which might be a different Telco.  (Also, circuits within the data provider's "cloud" might use different Telco leased lines.)

MAN/WAN provider "clouds" might use frame-relay, ATM, MPLS, Ethernet, etc.

If a leased line, from your site, goes to an ISP's local POP, you have access to the Internet.

Some examples of leased line usage:

Your branch A <leased line> your branch B

Your branch A <leased line> your branch C (add this, and you have: hub A and spokes B and C)

Your branch C <leased line> your branch B (add this, and you have: full mesh between A, B and C)

Your company <leased line> another company A

Your company <leased line> another company B

Your branch A <leased line> MAN/WAN provider

Your branch B <leased line> MAN/WAN provider

Your branch C <leased line> MAN/WAN provider

(in above, you layer on logical paths across the provider's network)

Your company <leased line> MAN/WAN provider <leased line> another company

Your company <leased line> ISP A

ISP A <leased line> ISP B

Another company B <leased line> ISP A

Another company C <leased line> ISP B

(Generally, everyone connected to Internet has a path to everyone else)

Lastly, one company may be just a Telco, MAN/WAN provider or ISP, or some combination; possibly all.