Flashcards
SCC 203 - Lecture 9 - Internet Forwarding
Cards in this deck (30)
- 1How do routers conspire to deliver packets to destination?Each routers push packets closer to their destination.
- 2Define the two distinct parts to process?Routing - Application level process to determine routes.
Forwarding - System level process directing packets according to learned routes. - 3What is a routing table?A routing table is a set of rules, often viewed in table format, that is used to determine where data packets traveling over an Internet Protocol (IP) network will be directed. All IP-enabled devices, including routers and switches, use routing tables.
- 4What do routing processes exchange?Routing processes exchange route updates
– Details later inform forwarding decisions - 5What does IP forwarding involve?Involves
– Selecting best of known path to destination
– Updating IP header - 6What layer does IP forwarding operate on?Kernel function operating at Network layer
- 7What is IP forwarding independent of?• Independent of Link-layer
– Can forward between different types of network - 8What is the format of IPV4 addresses?• 32 bit address
• Typically represented in dotted-quad form
– 194.80.37.5
– Each part represents 8 bit (byte), thus 0 – 255 - 9Properties of IP addresses?Hierarchical
Topological
-Reflects network structure
-Not geographic - 10Who allocates Network Addresses?Network addresses are allocated to organisations by their Internet Service Provider (ISP)
- 11What do network addresses allow?– Used to correctly forward traffic – how we know destination
– Fixed and cannot be changed by organisation - 12Who do host addresses belong to?• Host addresses ‘belong’ to organisation
– Allocate/ change them at will - 13Why do subnet addresses only make sense within organisation?because we can no longer determine network-host boundary by knowing address class
- 14Why are subnet masks used?Subnet mask is used to split (sub-)net and host parts.
- 15What must masks have?Mask must have set of ones followed by set of zeros
- 16For a subnet of n bits Number of available host addresses is?2n-2
- 17Why do we minus 2 for the number of avaialable host addresses?Two reserved addresses per subnet :
– All zeros is reserved (it’s the network number)
– All ones is subnet broadcast address - 18What is super netting?Grouping of multiple contiguous address ranges?
- 19What could be done if there were allocated adjacent Class C blocks?– Organisation could ‘merge’ them
• Simplifies management of allocated addresses
• Allows more flexibility when structuring internal subnets - 20How do ISP's treat merge blocks? What must a super-netted address not span?• ISP will continue to treat them as independent
– A super-netted address MUST NOT span network addresses not subject to same routing path - 21Two mains aims of classless inter domain routing?– Reduce number of routing table entries
– Slow IPv4 address depletion (Note: now all allocated) - 22What is the logical step after variable length Subnet Masks?– Allowed registries to allocate on any bit boundary
– Can better reflect size of requesting organisation - 23State the /prefix length notation?address / prefix-length
- 24What do addresses belong to?Addresses belong to interfaces not machines
- 25Each network interface needs to be configured with what parameters?Network address, subnet masks, Subnet Broadcast Address
- 26What does IP depend on?IP depends on underlying data-link protocol
- 27What address devices can Data-link protocol store?Data-link protocol can only address devices
on same physical link/ network segment. - 28What address does IP header hold?IP header holds endpoint addresses
– Original source and final destination - 29How are data link holding packets sent?Data-link frames ‘holding’ packet sent hop-by-hop
– Always sent to next-hop router, until last subnet - 30Many nodes have default route? What is this?– Route of last resort, when no other route available
– Default route typically toward our ISP’s router
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- Flashcards on SCC 203 - Lecture 9 - Internet Forwarding, created by Ayo Olutobi on 03/04/2017.
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- Ayo Olutobi
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