Network basics lecture 16: Internet routing and peer-to-peer networking

What is Internet? This article will explain some concepts required to understand the Border Gateway Protocol (BGP is the topic of the next knowledge Lecture ). To send packets over the Internet, organizations on the Internet need to cooperate. Therefore, it is not as simple as learning the Internal Gateway Routing (IGP) principle.

Let's take a local ISP with a small scale as an example, starting from the service provider's perspective.

JoeBob, the ISP, needs another ISP to transmit customers' data streams to the Internet. Therefore, it should first establish a definite relationship with two different level-1 ISPs, which are big players, such as Level 3, AT&T, Cogent, And XO. JoeBob ISP will establish a peering relationship with these ISPs through the BGP protocol, which means they need to establish a BGP session and exchange routing information with them. A large ISP sends all Internet routes to JoeBob. Currently, there are nearly 200,000 Internet routes. The detailed working principles will be elaborated in the next lecture on BGP.

JoeBob ISP will pay a certain amount for the data streams sent to the two connected ISPs in MB. Because it is connected to two ISPs, there may be two different prices. If so, you can choose the cheapest link through BGP settings. The key to the problem is that JoeBob ISP obtains the route from another ISP, so it can use the route information to do what it wants. Some data streams are sent to a superior ISP, and some can be sent to another ISP.

This Peering relationship is not only applicable to BGP sessions between the ISP and the ISP, but also can be used to negotiate data traffic between the company and the company. Even small-scale ISPs may sometimes connect to local exchange nodes to establish peering relationships with other companies, schools, or ISPs in the region. A switching node is a network connection point. Each city has at least one switching node. All major ISPs in a region are connected to this node and maintain their own routers. If they decide to establish a peering connection with a peer, they only need to have the switch node operator connect some optical fiber cables to the device bracket of the peer, and get free data traffic. Port fees are usually charged for connecting to the switch node, and I have not mentioned how to connect your site to the switch node. It also requires optical fiber (money.

For small-scale local ISPs, establishing peer-to-peer relationships with other ISPs is not very common, but it is indeed a large-scale ISP (or even a school) operation method. Sometimes the ISP even provides its peer route to the customer, and allows the data stream to be free of charge. The ISP's capabilities in this regard depend on the details in the peer-to-peer protocol.

There are currently two types of peer-to-peer nodes: public and private ).

The public exchange node allows almost anyone to become a member of the peer-to-peer relationship. Publicpeering does not mean that you can suddenly obtain the route of each ISP in the exchange node for free. Instead, it only means that you can connect to this switching node, and sometimes it is free. Currently, a popular Exchange node is SIX, namely, the Seattle Internet Exchange. If you have rented a house at the Westin building in Seattle (where SIX is located, you can spend some money to add yourself to the SIX chassis. Once you get the IP address from the SIX operator, you are ready, but then you must sign a peer-to-peer agreement with other BGP service providers in the Exchange Center.

SIX and PAIX are two of the most popular exchange nodes on the west coast of the United States. SIX is operated by several employees through several Cisco switches. Currently, basically all major carriers and service providers are connected to SIX, including Google, XO, and AT&T Broadband companies. PAIX, founded in Palo Alto, is currently operated by Switch and Data. It is also a public exchange node and operates private peering while providing public peer-to-peer services) business.

Next, let's talk about dedicated peer-to-peer interconnection.

Most public exchange centers have MB or 1 GB links for customers to use. If you are a large ISP, you need one or more 10 Gbit/s links to process all your data streams. The problem is, public exchange centers usually do not have sufficient funds to provide reliable such services. Dedicated peer-to-peer interconnection defines service level agreements (SLAs) under which better hardware devices can be used to process data traffic. The debate between the public and private peer-to-peer networks has never come to any conclusion. If you need a customized solution, such as binding two links (trunk) together, dedicated peer-to-peer interconnection will be your final choice.

What is opposite to the peering connection is the channel connection (transit ). A channel interconnection service provider, such as a level-1 ISP, will provide you with all the Internet routes you have paid for and be responsible for all other transactions. The ISP that provides services for the company is generally a provider of access interconnection services. Similarly, a small ISP that provides services for a smaller ISP is also a provider of access interconnection services. Generally, the ISP that provides both the peering and VPC services will send all data that can be directly routed through the peer-to-peer service provider, and then send the remaining data packets to the channel service provider.

A default router is a router that can obtain the entire Internet route table. If your channel interconnection service provider does not send routes to some networks, and you cannot understand the situation through other peer-to-peer interconnection relationships, then this part of the network does not arrive. If you send all the information to the router, you expect it to do the right thing. Such a "default router" does not exist.

If an ISP is large enough to allow other level-1 ISPs to send a large amount of data traffic to it, the two sides generally sign a peer-to-peer protocol. There are two real motivations for establishing peer-to-peer relationships: profit and transmission efficiency. The two ISPs often find that there are frequent conversations between them, but data must be around the Earth to reach each other. If the ever-growing ISP is geographically isolated, they can establish peering relationships in multiple different exchange centers, and soon their data will no longer be transmitted through the Internet provider. As long as an ISP can establish a peering connection with a large ISP and its own infrastructure is in place, it may already be a major service provider.

The above provides a very concise description of the working principle of the Internet. There are actually more layers than we mentioned, but what we mentioned above is the key to Internet operations. The next basic knowledge lecture will discuss how routes run between independent organizations. It is quite attractive.

Summary

There is no so-called default route on the Internet.

Vrouters are placed in the Exchange Center, which are connected to vrouters in other places by contract to establish a peering relationship.

Public peer-to-peer interconnection is mostly free of charge, but may suffer from resource shortage. Dedicated peer-to-peer interconnection is expensive but necessary.

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Network basics Lecture 14: OSPF routing protocol preliminary
Network basics lecture 13: routing information protocol (RIP)
Network basics lecture 12: Basic knowledge of routing protocols
Lecture 11 on basic network knowledge: Internet management architecture
Lecture 10 on basic network knowledge: TCP protocol understanding (advanced tutorial)
Lecture 9 on basic network knowledge: a preliminary understanding of the TCP protocol
Lecture 8 on basic network knowledge: a preliminary understanding of the IP protocol
Lecture 7: understanding and using ICMP protocol
Lecture 6 on basic network knowledge: Implementing subnets, including IPv6)
Lecture 5: Learning Spanning Tree Protocol
Lecture 4: understanding the data link layer
Network basics Lecture 3: Understanding OSI network layering
Network basics Lecture 2: Understanding subnet and CIDR
One of the basic network knowledge lectures: understanding the meaning of IPv4 addresses