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Chapter 8: Transport layer systems - Pg. 141

CHAPTER Transport layer systems 8 TRANSPORT LAYER The transport layer is responsible for providing connectivity between end-system applications. When looking at the transport layer, packets can be grouped into "connections" or "flows" that are used by end-system applications. This grouping is finer-grained than the grouping by IP prefixes that we have seen in the network layer, as each end system may have numerous active connections in parallel. Using this finer granularity, network systems can perform operations that are connection- specific. For example, network address translation translates the address infor- mation for a connection from a local network to the global Internet. In another example, packet schedulers can provide different levels of quality of service to packets that belong to different connections (as discussed in Chapter 10).