Hitchhikers Guide to the Internet | Page 6

address. If a system does allow this choice, care should be taken that the all ones format is chosen. (This is explained in RFC-1009 and RFC-1010).
Internet Problems
There are a number of problems with the Internet. Solutions to the problems range from software changes to long term research projects. Some of the major ones are detailed below:
Number of Networks
When the Internet was designed it was to have about 50 connected networks. With the explosion of networking, the number is now approaching 300. The software in a group of critical gateways (called the core gateways of the ARPAnet) are not able to pass or store much more than that number. In the short term, core reallocation and recoding has raised the number slightly. By the summer of '88 the current PDP-11 core gateways will be replaced with BBN Butterfly gateways which will solve the problem.
Routing Issues
Along with sheer mass of the data necessary to route packets to a large number of networks, there are many problems with the updating, stability, and optimality of the routing algorithms. Much research is being done in the area, but the optimal solution to these routing problems is still years away. In most cases the the routing we have today works, but sub-optimally and sometimes unpredictably.
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Trust Issues
Gateways exchange network routing information. Currently, most gateways accept on faith that the information provided about the state of the network is correct. In the past this was not a big problem since most of the gateways belonged to a single administrative entity (DARPA). Now with multiple wide area networks under different administrations, a rogue gateway somewhere in the net could cripple the Internet. There is design work going on to solve both the problem of a gateway doing unreasonable things and providing enough information to reasonably route data between multiply connected networks (multi-homed networks).
Capacity & Congestion
Many portions of the ARPAnet are very congested during the busy part of the day. Additional links are planned to alleviate this congestion, but the implementation will take a few months.
These problems and the future direction of the Internet are determined by the Internet Architect (Dave Clark of MIT) being advised by the Internet Activities Board (IAB). This board is composed of chairmen of a number of committees with responsibility for various specialized areas of the Internet. The committees composing the IAB and their chairmen are:
Committee Chair Autonomous Networks Deborah Estrin End-to-End Services Bob Braden Internet Architecture Dave Mills Internet Engineering Phil Gross EGP2 Mike Petry Name Domain Planning Doug Kingston Gateway Monitoring Craig Partridge Internic Jake Feinler Performance & Congestion ControlRobert Stine NSF Routing Chuck Hedrick Misc. MilSup Issues Mike St. Johns Privacy Steve Kent IRINET Requirements Vint Cerf Robustness & Survivability Jim Mathis Scientific Requirements Barry Leiner
Note that under Internet Engineering, there are a set of task forces and chairs to look at short term concerns. The chairs of these task forces are not part of the IAB.
-9- Routing
Routing is the algorithm by which a network directs a packet from its source to its destination. To appreciate the problem, watch a small child trying to find a table in a restaurant. From the adult point of view the structure of the dining room is seen and an optimal route easily chosen. The child, however, is presented with a set of paths between tables where a good path, let alone the optimal one to the goal is not discernible.***
A little more background might be appropriate. IP gateways (more correctly routers) are boxes which have connections to multiple networks and pass traffic between these nets. They decide how the packet is to be sent based on the information in the IP header of the packet and the state of the network. Each interface on a router has an unique address appropriate to the network to which it is connected. The information in the IP header which is used is primarily the destination address. Other information (e.g. type of service) is largely ignored at this time. The state of the network is determined by the routers passing information among themselves. The distribution of the database (what each node knows), the form of the updates, and metrics used to measure the value of a connection, are the parameters which determine the characteristics of a routing protocol.
Under some algorithms each node in the network has complete knowledge of the state of the network (the adult algorithm). This implies the nodes must have larger amounts of local storage and enough CPU to search the large tables in a short enough time (remember this must be done for each packet). Also, routing updates usually contain only changes to the existing information (or you spend a large amount of the network capacity passing around megabyte routing updates). This type of algorithm has several problems. Since the only way the routing information