Computer Science
Border Gateway Protocol
Border Gateway Protocol (BGP) is a protocol used to exchange routing information between different networks on the internet. It is responsible for directing traffic between autonomous systems (AS) and ensuring that data is routed efficiently and securely. BGP is a critical component of the internet's infrastructure.
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10 Key excerpts on "Border Gateway Protocol"
No longer available |Learn more- (Author)
- 2014(Publication Date)
- The English Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 1 Border Gateway Protocol The Border Gateway Protocol ( BGP ) is the protocol backing the core routing decisions on the Internet. It maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). It is described as a path vector protocol. BGP does not use traditional Interior Gateway Protocol ( IGP ) metrics, but makes routing decisions based on path, network policies and/or rulesets. For this reason, it is more appropriately termed a reachability protocol rather than routing protocol. BGP was created to replace the Exterior Gateway Protocol ( EGP ) routing protocol to allow fully decentralized routing in order to allow the removal of the NSFNet Internet backbone network. This allowed the Internet to become a truly decentralized system. Since 1994, version four of the BGP has been in use on the Internet. All previous versions are now obsolete. The major enhancement in version 4 was support of Classless Inter-Domain Routing and use of route aggregation to decrease the size of routing tables. Since January 2006, version 4 is codified in RFC 4271, which went through more than 20 drafts based on the earlier RFC 1771 version 4. RFC 4271 version corrected a number of errors, clarified ambiguities and brought the RFC much closer to industry practices. Most Internet users do not use BGP directly. Since most Internet service providers must use BGP to establish routing between one another (especially if they are multihomed), it is one of the most important protocols of the Internet. Compare this with Signaling System 7 (SS7), which is the inter-provider core call setup protocol on the PSTN. Very large private IP networks use BGP internally. An example would be the joining of a number of large Open Shortest Path First (OSPF) networks where OSPF by itself would not scale to size.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 1 Border Gateway Protocol The Border Gateway Protocol ( BGP ) is the protocol backing the core routing decisions on the Internet. It maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). It is described as a path vector protocol. BGP does not use traditional Interior Gateway Protocol ( IGP ) metrics, but makes routing decisions based on path, network policies and/or rulesets. For this reason, it is more appropriately termed a reachability protocol rather than routing protocol. BGP was created to replace the Exterior Gateway Protocol ( EGP ) routing protocol to allow fully decentralized routing in order to allow the removal of the NSFNet Internet backbone network. This allowed the Internet to become a truly decentralized system. Since 1994, version four of the BGP has been in use on the Internet. All previous ver-sions are now obsolete. The major enhancement in version 4 was support of Classless Inter-Domain Routing and use of route aggregation to decrease the size of routing tables. Since January 2006, version 4 is codified in RFC 4271, which went through more than 20 drafts based on the earlier RFC 1771 version 4. RFC 4271 version corrected a number of errors, clarified ambiguities and brought the RFC much closer to industry practices. Most Internet users do not use BGP directly. Since most Internet service providers must use BGP to establish routing between one another (especially if they are multihomed), it is one of the most important protocols of the Internet. Compare this with Signaling System 7 (SS7), which is the inter-provider core call setup protocol on the PSTN. Very large private IP networks use BGP internally. An example would be the joining of a number of large Open Shortest Path First (OSPF) networks where OSPF by itself would not scale to size.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 4 Border Gateway Protocol and Character Generator Protocol Border Gateway Protocol The Border Gateway Protocol ( BGP ) is the protocol backing the core routing decisions on the Internet. It maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). It is described as a path vector protocol. BGP does not use traditional Interior Gateway Protocol ( IGP ) metrics, but makes routing decisions based on path, network policies and/or rulesets. For this reason, it is more appropriately termed a reachability protocol rather than routing protocol. BGP was created to replace the Exterior Gateway Protocol ( EGP ) routing protocol to allow fully decentralized routing in order to allow the removal of the NSFNet Internet backbone network. This allowed the Internet to become a truly decentralized system. Since 1994, version four of the BGP has been in use on the Internet. All previous versions are now obsolete. The major enhancement in version 4 was support of Classless Inter-Domain Routing and use of route aggregation to decrease the size of routing tables. Since January 2006, version 4 is codified in RFC 4271, which went through more than 20 drafts based on the earlier RFC 1771 version 4. RFC 4271 version corrected a number of errors, clarified ambiguities and brought the RFC much closer to industry practices. Most Internet users do not use BGP directly. Since most Internet service providers must use BGP to establish routing between one another (especially if they are multihomed), it is one of the most important protocols of the Internet. Compare this with Signaling System 7 (SS7), which is the inter-provider core call setup protocol on the PSTN. Very large private IP networks use BGP internally. An example would be the joining of a number of large Open Shortest Path First (OSPF) networks where OSPF by itself would not scale to size.
eBook - PDFAdministering Cisco QoS in IP Networks
Including CallManager 3.0, QoS, and uOne
- Syngress(Author)
- 2001(Publication Date)
- Syngress(Publisher)
BGP was introduced as an inter-autonomous system (AS) routing protocol. An AS is defined as a collection of routers under a common administration. Furthermore, within the AS you can have multiple Interior Gateway Protocols Overview: Border Gateway Protocol (BGP) • Chapter 10 377 378 Chapter 10 • Overview: Border Gateway Protocol (BGP) (IGPs) that are used to exchange network routing information. A BGP speaker’s primary function is to exchange network reachability information with other BGP systems. Since the BGP speaker sees the Internet as a collection of autonomous systems (AS), the network reachability information includes the full AS path that traffic must travel to reach these networks.This information allows the BGP system to construct a graph of AS connectivity.This graph is used to prune routing loops, and it permits policy decisions by the system.Thus, BGP is best described as a hop-by-hop protocol in which each system advertises only the network reachability information that it uses. The implementation of BGP 3 introduced the foundation elements that are still in use today. First of all, BGP systems establish a connection upon initializa-tion over TCP using port 179. Next, the systems exchange the complete routing table and send incremental updates only as necessary. Since there is no provision to periodically refresh the complete BGP database, all systems keep track of a ver-sion of one another’s table. Once the BGP speakers enter the established state, the BGP scanner process on each system ensures consistency among the BGP database, the IGP database, and the IP routing table. If you issue the exec command show process cpu, you will see this process in the list identified as BGP Scanner. It is important to note that this process is different from the BGP Router process, which is used to establish and maintain the BGP session.
eBook - PDF- Laura DeNardis(Author)
- 2014(Publication Date)
- Yale University Press(Publisher)
Each router within the AS uses this interior protocol to calculate how to route packets to the next best router (sometimes called a “hop”) to forward packets to their destination within the autonomous system. An exterior routing protocol dictates how routing occurs between autonomous systems. All Internet interconnections among autonomous systems occur via a standard called Border Gateway Protocol (BGP). In this sense, BGP, like the Internet Protocol, is one of the core technolo-gies keeping the Internet operational. BGP is the de facto standard for routing information between autonomous systems. BGP is not as well known a protocol as IP and HTTP, probably because it is not directly used by end users but is used by the networks that interconnect to form the global Internet. The important function BGP performs is sometimes referred to as inter-AS routing. Neighboring autonomous systems typi-cally exchange a complete accounting of routing information under their respective control when first connected. After that, updates are usually sent only when a route has changed. BGP’s basic function is to allow networks to exchange information about “reachability”—meaning which systems each autonomous system (or network of routers under common administration) can reach. In this sense, BGP is an inter-AS routing standard. The current version, called BGP-4, has been in effect since 2006 and is well documented in RFC 4271, titled “A Border Gateway Protocol 4 (BGP-4).” The Evolution of Internet Exchange Points Interconnected networks physically conjoin at bilateral connection points housed in a network operator’s facility or, increasingly, at shared Internet exchange points. IXPs are the physical junctures where different compa-nies’ backbone trunks interconnect, exchange packets, and route them governance at the internet’s core 115 toward their appropriate destinations.
eBook - ePub- Ben Piper(Author)
- 2020(Publication Date)
- Sybex(Publisher)
Chapter 7 The Border Gateway Protocol (BGP)THE CCNP ENCOR EXAM OBJECTIVES COVERED IN THIS CHAPTER INCLUDE THE FOLLOWING:- Domain 3 Infrastructure
- ✓ 3.2 Layer 3
In this chapter you'll learn about Border Gateway Protocol (BGP), defined in RFC 4271. BGP was designed as the successor to the Internet's early distance-vector routing protocols, the Exterior Gateway Protocol (EGP). BGP has held the Internet together for over 30 years, a testament to its scalability and flexibility. In addition to its ubiquity on the Internet, many organizations use BGP internally. BGP is a huge topic, so we're going to focus on the aspects of it that you're most likely to encounter on the job and those most relevant to the ENCOR exam, including the following:- Differences between BGP and IGPs
- BGP AS numbers
- BGP session establishment
- Prefix advertisement
- Path selection algorithm
- Route redistribution between BGP and IGPs
- Route summarization and filtering
BGP Fundamentals
You're familiar with how IGPs make routing decisions. The limitation of IGPs is that they don't scale in very large networks, such as the Internet. Recall from Chapter 5, Open Shortest Path First (OSPF), and Chapter 6, Enhanced Interior Gateway Routing Protocol (EIGRP), that both of these protocols require propagating updates throughout the network, one hop at a time. And if a link goes down, the routers may have to perform new route computations, potentially causing packet loss. Another potential problem with trying to use an IGP in a large network is that if you ever need to merge two networks running different IGPs—such as in the case of an acquisition—you'll have the additional administrative burden of configuring mutual route redistribution, not to mention the potential for redistribution loops and routing loops.BGP was designed to allow different ASs to connect to one another over the Internet or through private networks without the risk and hassle inherent in using IGPs. According to RFC 1930, a BGP autonomous system is “a connected group of one or more IP prefixes run by one or more network operators which has a single and clearly defined routing policy.” In contrast to IGPs, BGP errs on the side of route stability and scalability, with the tradeoff being that new routes and routing updates take longer to propagate. BGP doesn't periodically send route updates at least every 30 minutes the way OSPF does.
eBook - PDF- Jerry FitzGerald, Alan Dennis, Alexandra Durcikova(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
Border Gateway Protocol (BGP) is a dynamic distance vector exterior routing protocol used on the Internet to exchange routing information between autonomous systems—that is, large sections of the Internet. Although BGP is the preferred routing protocol between Internet sections, it is seldom used inside companies because it is large, complex, and often hard to administer. Internet Control Message Protocol (ICMP) is the simplest interior routing protocol on the Internet. ICMP is simply an error-reporting protocol that enables computers to report routing errors to message senders. ICMP also has a very limited ability to update routing tables. 136 Chapter 5 Network and Transport Layers Routing Information Protocol (RIP) is a dynamic distance vector interior routing protocol that is commonly used in smaller networks, such as those operated by one organization. The net- work manager uses RIP to develop the routing table. When new computers are added, RIP simply counts the number of computers in the possible routes to the destination and selects the route with the least number. Computers using RIP send broadcast messages every minute or so (the timing is set by the network manager) announcing their routing status to all other computers. RIP is used by both TCP/IP and IPX/SPX. Intermediate System to Intermediate System (IS-IS) is a link state interior routing protocol that is commonly used in large networks. IS-IS is an ISO protocol that has been added to many TCP/IP networks. Open Shortest Path First (OSPF) is a dynamic hybrid interior routing protocol that is com- monly used on the Internet. It uses the number of computers in a route as well as network traffic and error rates to select the best route. OSPF is more efficient than RIP because it normally doesn’t use broadcast messages. Instead, it selectively sends status update messages directly to selected computers or routers. OSPF is the preferred interior routing protocol used by TCP/IP.
eBook - PDFThe Internet and Its Protocols
A Comparative Approach
- Adrian Farrel(Author)
- 2004(Publication Date)
- Morgan Kaufmann(Publisher)
The route has been distributed through three ASs: 1962, 15, and 10. 5.8.5 Interior BGP Although the introduction to this section on BGP concentrated on BGP as an Exterior Gateway Protocol, it can also be used as an Interior Gateway Protocol for route exchange between routers within an autonomous system or for transporting exterior routes across an AS to advertise them into the next AS. This second use has clear benefits because it significantly simplifies the interactions between the IGP and BGP and removes any requirement for the IGP to transport information across the AS on behalf of BGP. Run as an IGP, BGP is referred to as Interior BGP (I-BGP). In fact, the previous BGP examples have been somewhat simplistic, and have treated each AS as though it had just one ASBR providing connectivity to other ASs. In practice, many ASs at the core of the Internet carry transit traffic from one AS to another, and have many ASBRs each providing connectivity to other ASs. Figure 5.71 shows five autonomous systems joined together to form a larger network. AS D and AS E are able to communicate directly and would use BGP (that is, E-BGP) to exchange routing information, but traffic to and from ASs A and B must traverse AS C. Each of the ASs runs an IGP internally, but this only provides routing information within the AS. The question must be asked: How does a router at the core of an AS know how to forward packets out of the AS? For the routers in the peripheral ASs, this is not a significant issue because they 218 Chapter5 Routing Figure 5.71 A transit autonomoussystem links together several other autonomoussystems. 5.8 Border Gateway Protocol 4 (BGP-4) 219 have only one ASBR and this is obviously the gateway out of the AS. But for routers in AS C the choice is more difficult. Routers that only have one other adjacent router can handle the problem using default routes, but routers with more than one adjacent router (transit touters) must make an informed routing decision.
No longer available |Learn moreCompTIA Network+ Study Guide
Exam N10-008
- Todd Lammle(Author)
- 2021(Publication Date)
- Sybex(Publisher)
Introduction to IP Routing THE FOLLOWING COMPTIA NETWORK+ EXAM OBJECTIVES ARE COVERED IN THIS CHAPTER: ✓ ✓ 2.2 Compare and contrast routing technologies and band-width management concepts. ✓ ■ Dynamic routing ✓ ■ Routing Information Protocol (RIP), Open Shortest ✓ ■ Path First (OSPF), Enhanced ✓ ■ Interior Gateway Routing Protocol ✓ ■ (EIGRP), Border Gateway Protocol (BGP) ✓ ■ Link state vs. distance vector vs. hybrid ✓ ■ Static routing ✓ ■ Default route ✓ ■ Administrative distance ✓ ■ Exterior vs. interior ✓ ■ Time to live Chapter 9 IP routing is the process of moving packets from one network to another network using routers. The IP routing process is a super-important subject to understand because it pertains to all routers and configurations that use IP. Before you read this chapter, you need to understand the difference between a routing protocol and a routed protocol. A routing protocol is a tool used by routers to dynamically find all the networks in the internetwork as well as to ensure that all routers have the same routing table. Basically, a routing protocol determines the path of a packet through an inter-network. Examples of routing protocols are Routing Information Protocol (RIP), Routing Information Protocol version 2 (RIPv2), Enhanced Interior Gateway Routing Protocol (EIGRP), Open Shortest Path First (OSPF), and Broder Gateway Protocol (BGP). Once all routers know about all networks, a routed protocol can be used to send user data (packets) through the established internetwork. Routed protocols are assigned to an interface and determine the method of packet delivery. Examples of routed protocols are Internet Protocol (IP) and Internet Protocol version 6 (IPv6). In this chapter, I’m going to describe IP routing with routers. I will explain, in a step-by-step fashion, the IP routing process.
eBook - PDFNetwork Routing
Algorithms, Protocols, and Architectures
- (Author)
- 2010(Publication Date)
- Morgan Kaufmann(Publisher)
Part II: Routing in IP Networks In this part, we focus on routing in IP networks. It is divided into five chapters. In Chapter 5, we first present the basic background on IP routing in the presence of IP addressing, and how the routing table is organized and used by routers for packet forward-ing. We then present protocols for Internet that falls into the distance vector protocol family. Specifically, we discuss three well-known protocols RIP, IGRP, and EIGRP. The connection is also drawn between a protocol specification such as RIP and and the basic concept of a distance vector protocol. Chapter 6 covers OSPF and integrated IS-IS. In discussing OSPF, we point out why dif-ferent types of link statement advertisements are required to cater to the needs in different operational configuration scenarios. For the integrated IS-IS protocol, we show its similarities and subtle differences with OSPF, although as of now there are no fundamental differences. An important aspect of efficient routing in an operational network is proper traffic engi-neering. In Chapter 7, we show how network flow modeling can be applied to determine link weights for IP traffic engineering. In doing so, we also discuss how traffic demands are taken into account in the traffic engineering decision process. Next, we present Border Gateway Protocol (BGP) in Chapter 8. The role of BGP in the Internet is critical as it allows exchange of reachable IP prefixes and in determinating AS-paths. There are, however, several attributes to consider in the path selection process; more importantly, policy constraints are also taken into account. Thus, many facets of BGP are covered in this chapter. Finally, in Chapter 9, we present Internet routing architectures. This brings together how BGP is used, interaction between different domains either through public or private peering, and how points of presence are architected. Furthermore, we discuss growth in routing table entries.
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