L17. Describe the role and working of BGP Flashcards
What is BGP?
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (ASes) on the internet.
What is the role of BGP in Internet communication?
BGP is crucial for the functioning of the global internet, as it ensures data packets can find efficient paths from source to destination across multiple networks.
What is BGP used for?
Routing between autonomous systems. It manages how packets are routed across different ASes, ensuring that data can travel from one end of the internet to the other.
What is an AS?
Autonomous Systems (AS) are large networks or groups of networks under common administration.
How does BGP allow network administrators to manage traffic?
BGP allows network administrators to implement routing policies based on various criteria like path attributes, network performance, and commercial agreements. This flexibility helps in managing traffic according to business needs and optimizing network efficiency.
What type of routing protocol is BGP?
A Path Vector Protocol
How do BGP routers establish connections?
BGP routers, known as BGP speakers, establish a TCP connection on port 179 to communicate with each other. These connections are called BGP sessions.
What is a BGP session?
A TCP connection between BGP routers
What are the two modes of BGP?
Internal BGP (iBGP) within an AS, and External BGP (eBGP) between different ASes.
What happens after a BGP session is established?
The routers exchange full routing tables. After the initial exchange, only incremental updates are sent as network changes occur. This includes information about reachable networks (prefixes) and the paths to reach them.
How do BGP routers update their tables?
BGP routers propagate routing information throughout the network. When changes occur, BGP updates are sent to inform other routers, allowing the network to converge on a new stable routing state.
When a new BGP session is established between routers, they exchange full routing tables. After the initial exchange, only incremental updates are sent as network changes occur.
What is a policy?
An agreement on how routes should be selected, based on business interests, traffic engineering requirements, and other considerations. Policies can control which routes are advertised and which paths are preferred for incoming and outgoing traffic.
What are some key attributes for path selection in BGP?
- AS Path: A list of ASes that data must traverse to reach the destination. Shorter paths are generally preferred.
- Next Hop: The next router to which data should be forwarded.
- Local Preference: A value used within an AS to prioritize certain paths.
- Multi-Exit Discriminator (MED): Suggests preferred routes when multiple links exist between two ASes.
What are security issues in BGP?
BGP is susceptible to various security issues such as route hijacking, where an AS incorrectly advertises ownership of IP prefixes it doesn’t own. To mitigate these risks, mechanisms like BGP Route Origin Validation (ROV) using Resource Public Key Infrastructure (RPKI) are employed. These mechanisms help validate the authenticity of route advertisements and ensure they originate from legitimate sources.
