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7/24/2019 1. Intro to Service Providers
1/19
2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-1
Service Provider Network Architecture
7/24/2019 1. Intro to Service Providers
2/19
2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-2
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)
7/24/2019 1. Intro to Service Providers
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2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-3
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
7/24/2019 1. Intro to Service Providers
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2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-4
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
7/24/2019 1. Intro to Service Providers
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2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-5
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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2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-6
Tier 3 ISP Tier 3 ISP
Internet Users
Tier 1 ISPs
Tier 2 ISP
Tier 2 ISP
Tier 2 ISP
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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
7/24/2019 1. Intro to Service Providers
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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
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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
7/24/2019 1. Intro to Service Providers
10/19 2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-10
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
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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
7/24/2019 1. Intro to Service Providers
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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
7/24/2019 1. Intro to Service Providers
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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
7/24/2019 1. Intro to Service Providers
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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
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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
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16/19 2012 Cisco and/or its affiliates. All rights reserved. SPNGN2 v1.011-16
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
7/24/2019 1. Intro to Service Providers
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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
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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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