1. Intro to Service Providers

7/24/2019 1. Intro to Service Providers

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2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-1

Service Provider Network Architecture


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A service provider is an entitythat provides different kinds ofservicesto other entities. Five types exist:

Communications service provider (CSP)

Telecommunications service provider (TSP)

Network service provider (NSP)

Internet service provider (ISP)

Application service provider (ASP)


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ISP provides access to common network called Internet

ISP provides service to:

- Home user subscribers

ADSL, cable internet, and FTTH

Internet access, VoIP, and IPTV

- Businesssubscribers

ADSL, SDSL, and leased lines

Internet access, private VPNs, and VoIP


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Three entities in service provider relationship model:

- Customers

Pay ISP for providing Internet access to them

- Peers

Exchange traffic for free, which is a mutual benefit

- Transit partners You pay your partner to access a certain range of networks

Relationships are defined in settlements between partners.

The Internet is based on the principle of global reachability.

Each network has to do one of two things:- Pay another network for transit

- Peer with every other network


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The IXP is the physical infrastructure that service providers use to

exchange traffic.

IXPs reduce traffic to upstream providers.

- Per-bit delivery cost reduction

Routing efficiency and fault tolerance is improved.

BGP is used for traffic routing.

IXP

ISP 5 Internet

ISP 3

ISP 1ISP 2

ISP 4

Peering

Transit


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Tier 3 ISP Tier 3 ISP

Internet Users

Tier 1 ISPs

Tier 2 ISP

Tier 2 ISP

Tier 2 ISP


7/19 2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-7

Purchase transit links from Tier 1 or Tier 2 ISPs

Peer with regional partners for cutting costs

Provide Internet access to end customers

- Focused on specific region

- Usually low price access

- Usually lower access speeds

Customers are usually home user subscribers



Purchase transit links from Tier 1 ISPs

Peer with other ISPs for cutting costs (using IXP)

Provide Internet access to:

- End customers (home and business)

Focus on business customers

Charge higher prices

Offer higher speeds

- Tier 3 ISPs



Large national or international ISPs

- Reach every other network on the Internet without purchasing IP transit linksor paying settlements

Transit-free network

- Peers with (every) other Tier 1 ISP

- Highest-speed connections- Very reliable networks

- Usually expensive

Customers

- Lower-tiered ISPs

- Large companies



Internet Assigned Numbers Authority (IANA)

- Responsible for allocation of globally unique:

IP addresses

AS number allocation

DNS root zone management

Protocol parameters- IANA is operated by Internet Corporation for Assigned Names and Numbers

(ICANN)

IANA NIR/LIR/ISPRIR ISPallocate allocate allocate

assign assign assign

End user End user End user



Five Regional Internet Registries (RIRs)

- Manage and distribute Internet parameters within their respective regions

- IANA delegates Internet resources to RIRs

IANA

AfriNIC APNIC RIPE LACNIC ARIN

RIR

ISPNIR LIRISP

End user End user End user End user

End user End user

End user

ISP

End user

ISP



Local Internet Registry (LIR)

- Assigns address space to its users (that is, end users or other ISPs)

- RIR delegates Internet resources to LIR

- LIR can be:

ISP

Enterprise Academic institution

National Internet Registry (NIR)

- Works within a country or economic unit

End Users- Customers that need Internet access

IP address

AS number



End user requests IP address by its ISP

- IPv4 address or block of addresses

- IPv6 block of addresses

/64 address space (network) for end users

/48, /52, and /56 address spaces (networks) for business users

ISP distributes addresses from its assigned address space

IP address space can be:

- Provider Independent (PI)

Assigned by RIR from its special address space

A way to make your network multihomed

End user keeps address space Results in big routing tables

- Provider Assigned (PA)

Assigned by ISP from ISP address space

End user needs to renumber when changing ISP



Routing is used to forward traffic from the source network to the

destination network

Routers pass traffic between networks based on a routing table.

- The routing table is built by a routing algorithm.

BGP (used for route distribution on the Internet)

OSPF (used internally in the service provider core network)

The RIR has only an indirect role in the routing process.

- The RIR helps to keep the routing table at manageable sizes.

Distribute larger blocks of address space



AS represents a group of routing prefixes (that is, list of IP addresses)

- Group of devices under a single administrative control

- Represented as a 2-Byte number

AS information is used in the routing process

Three types of autonomous systems

- Stub AS

Connected to only one AS (and ISP)

Only one connection to the Internet

- Multihomed AS

Connected to two or more autonomous systems

Redundant connection to the Internet

- Transit AS

Provide connection through itself to other networks

ISPs use transit autonomous systems



BGP Routing Protocol

- Basic routing protocol on the Internet

- Exchange prefix information between BGP peers

Between autonomous systemsEBGP

Inside one ASIBGP

- Is multiprotocol Carry information for multiple protocols

Size of routing table grows very fast

- Need more memory and CPU load for processing routing table

- Route aggregation and route summarization is used



Multihoming is used to increase the reliability of the Internet connection

for an IP network.

Multihoming customer site can have:

- Multiple connections to the same ISP

- Multiple connections to multiple ISPs

Customer

ISP

Internet

ISP 1 ISP 2

Internet

Customer



A network must have its own

- IP address space

- AS number

BGP is used for routing.

Redundant gateway routers are suggested.

Prefixes smaller than /24 usually are filtered by the ISP.


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Documents

1. Intro to Service Providers