Superb Router Operation Summary & a Rant on the State of Technical Writing in Text Books

Like most students of networking and router operation, I know the personal frustration of trawling the pages of countless text books and link-after-link on the web in search of those rare gems of information that clarify a difficult concept and give rise to one of those Eureka moments. Those gems rarely come in a form longer than a sentence or two, but here is one that did. It made such an impact on my understanding of router operation that I felt I had to share it. In a single paragraph, this author achieves what most authors fail to achieve in an entire book. It is a rare piece of superb technical writing.

This is a test question solution that appears on the web site of Ken Christensen, an Associate Professor in the Department of Computer Science and Engineering at the University of South Florida. I don't know if he penned it or not since I have no affiliation with him or with that University. I was simply lucky enough to have come across the site while searching for some good info.

I would be curious to know if the paragraph below "illuminates" anyone else's "light bulb," as it were. Is anyone else as pissed off as I am with the standard of technical writing in networking books? It galls me to fork out the lion's share of $100 for a book whose text doesn't even appear to have been spell-checked, let alone revised for accuracy and clear, concise expression.

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IP Router Operation

An IP router uses a routing table consisting of net_ids and port numbers to forward IP datagrams, or packets, to the destination net_id through the "best" port. A port is a physical connection to a network (typically, a network is a LAN). The best port is the one that leads to the shortest path. The routing table must contain all the net_ids in the autonomous system. A packet intended for a net_id not in the routing table is sent out on a default gateway (e.g., it sent to the Internet). The routing table is generated via a distributed routing protocol such as RIP or OSPF that constantly computes least-cost paths between networks. A least-cost path can be lowest delay (i.e., adaptive routing) or simply lowest hop count. An incoming packet to a router has its MAC addresses swapped to the destination address of the next router, or the host if routing to a target network. The ARP cache at each port resolves host_id to MAC address for target hosts or resolves net_id for routers proxying for other networks. Thus, routing tables consist only of net_ids and port numbers reducing the overall size (i.e., compared to if the routing tables contained host_id information in addition to net_id information).

John WA, USA

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johnduggan
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John, I like you! This is one of the better post on the board. Your spot on here, that ip router description is something worth commit to long term memory.

Thanks

Paul

Reply to
testo

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