Computer Networking Lesson 6

Longest prefix matching of destination IP addresses is a sufficient method of packet forwarding.

• True

• False

We need to handle packets based on multiple criteria such as TCP flags, source addresses, and so on. We refer to this finer packet handling as packet _______. 

What are considered to be variants of packet classification? (Select all that apply)

• Firewalls

• Resource reservation protocol

• Resource usage protocol

• Routing based on traffic type

Firewall is an example of an implementation of a simple solution the packet classification because it uses the concept of caching as a result so that future search can run faster.

• True

• False

Answer explanation

Firewall implementations perform a linear search of the rules database and keep track of the best-match rule. This solution can be reasonable for a few rules, but the time to search through a large database that may have thousands of rules can be prohibitive.

 DiffServe and MultiProtocol Label Switching (MPLS) are examples of Passing Labels for packet classification.

• True

• False

The implementation of Set-Pruning Tries is to build a trie on the destination prefixes in the database and then for every leaf-node at the destination trie to hang source tries. Thus, for every destination prefix D in the destination trie, we prune the set of rules to those compatible with D.

• True

• False

When using Tries for packet classification, the difference between Set Pruning and Backtracking is that Set Pruning has a high cost in ​ (a)   to reduce cost in ​ (b)   . Backtracking reduces ​cost in ​ (c)   at the expense of increased cost in ​ (d)   .

• memory
• time

Set-Pruning Tries can result in ​ (a)   since a source prefix can occur in multiple destination tries.

• memory explosion
• memory reduction
• memory expansion
• memory overflow

What is true of the Grid of Tries approach to packet classification?

• Susceptible to memory explosion

• Uses precomputed switch pointers to avoid backtracking

• Starts the search in the source trie

• Reduces time complexity associated with backtracking

• Keeps track of our current best source match and skips source tries that are shorter than that match

In Set-Pruning, what actually gets pruned?

• The set of rules compatible with a destination

• The set of rules compatible with a source