Stephen Kingston

So who has the class A network addresses? Well it turns out that many of these have been recovered from their original allocations, and handed back to IANA (Internet Assigned Numbers Authority). Many of these have then been allocated to registries such as the American Registry for Internet Numbers (ARIN), and are being carved up into smaller blocks and allocated out. We will discuss how that works in lecture 3.

But there are still a good number of class A networks allocated to organisations that really don’t need blocks that large (although giving up their blocks would be an expensive process). The list below shows the current allocations of all class A networks on the Internet.

1 IANA – Reserved
2 IANA – Reserved
3 General Electric Company
4 Level3/Genuity-BBN (IANA INFO: Bolt Beranek and Newman Inc.)
5 IANA – Reserved
6 Army Information Systems Center
7 IANA – Reserved
8 Level3/Genuity-BBN (IANA INFO: Bolt Beranek and Newman Inc.)
9 IBM
10 IANA – Private Use. See RFC 1918
11 DoD Intel Information Systems
12 AT&T Bell Laboratories
13 Xerox Corporation
14 IANA – Public Data Network
15 Hewlett-Packard Company
16 Digital Equipment Corporation
17 Apple Computer Inc.
18 MIT
19 Ford Motor Company
20 Computer Sciences Corporation
21 DDN-RVN
22 Defense Information Systems Agency
23 IANA – Reserved
24 ARIN – Cable Block (Formerly IANA – Jul 95)
25 Royal Signals and Radar Establishment
26 Defense Information Systems Agency
27 IANA – Reserved
28 DSI-North
29 Defense Information Systems Agency
30 Defense Information Systems Agency
31 IANA – Reserved
32 AT&T (IANA INFO: Norsk Informasjonsteknologi)
33 DLA Systems Automation Center
34 Halliburton Company
35 MERIT Computer Network
36 IANA – Reserved (Formerly Stanford University – Apr 93 to
37 IANA – Reserved
38 COGENT/PSI (IANA INFO: Performance Systems International)
39 IANA – Reserved
40 Eli Lily and Company
41 AFRINIC
42 IANA – Reserved
43 V6NIC
44 Amateur Radio Digital Communications
45 Interop Show Network
46 Level3/Genuity-BBN (IANA INFO: Bolt Beranek and Newman Inc.)
47 Nortel (IANA INFO: Bell-Northern Research)
48 Prudential Securities Inc.
49 IANA (Formerly DoD – Joint Technical Command. Used: May 94
50 IANA (Formerly DoD – Joint Technical Command. Used: May 94
51 Deparment of Social Security of UK (EU territory should be
52 E.I. duPont de Nemours and Co., Inc.
53 Cap Debis CCS (EU territory should be in RIPE database)
54 Merck and Co., Inc.
55 Naval Ocean Systems Center (IANA INFO: Boeing Computer Services)
56 U.S. Postal Service
57 SITA (Equant.Net routable. EU territory should be in RIPE database)
58 APNIC
59 APNIC
60 APNIC
61 APNIC
62 RIPE
63 ARIN
64 ARIN
65 ARIN
66 ARIN
67 ARIN
68 ARIN
69 ARIN
70 ARIN
71 ARIN
72 ARIN
73 ARIN
74 ARIN
75 ARIN
76 ARIN
77 IANA – Reserved
78 IANA – Reserved
79 IANA – Reserved
80 RIPE
81 RIPE
82 RIPE
83 RIPE
84 RIPE
85 RIPE
86 RIPE
87 RIPE
88 RIPE
89 RIPE
90 RIPE
91 RIPE
92 IANA – Reserved
93 IANA – Reserved
94 IANA – Reserved
95 IANA – Reserved
96 IANA – Reserved
97 IANA – Reserved
98 IANA – Reserved
99 IANA – Reserved
100 IANA – Reserved
101 IANA – Reserved
102 IANA – Reserved
103 IANA – Reserved
104 IANA – Reserved
105 IANA – Reserved
106 IANA – Reserved
107 IANA – Reserved
108 IANA – Reserved
109 IANA – Reserved
110 IANA – Reserved
111 IANA – Reserved
112 IANA – Reserved
113 IANA – Reserved
114 IANA – Reserved
115 IANA – Reserved
116 IANA – Reserved
117 IANA – Reserved
118 IANA – Reserved
119 IANA – Reserved
120 IANA – Reserved
121 IANA – Reserved
122 IANA – Reserved
123 IANA – Reserved
124 APNIC
125 APNIC
126 APNIC

In yesterday’s lecture we looked at the network layer, and introduced some concepts. I have added some diagrams to the slides on the course website to make things a little clearer, including this one:

This diagram describes the data encapsulation involved in transmitting packets of data across the network. First the application data is broken up into small units, and then it is passed to the transport layer. The transport layer will add a header to the data unit and pass the protocol data unit (PDU) to the network layer. Now an IP header is added an the packet is passed to the link layer, where an frame header and usually a trailer is added to create a complete frame which is now transmitted across the network.

Encapsulation of these layers means that you can change what is happening at a layer without affecting the other layers. You can transmit frames over Ethernet, or WiFi or some other technology, without changing the upper layers at all. You can move from IPv4 to IPv6 without changing your link layer or ttansport leyer, and you can use any of a variety of transport layer protocols over the same network layer.

The IPv4 header looks like this:

The meaning of the fields in the header is fully described in RFC 791. There is also a good article on IPv4 including a description of the header on Wikipedia. The Wikipedia article also discusses IPv4 address exhaustion, which we mentioned in yesterday’s lecture.

The following diagram describes three of the IPv4 address classes – the “unicast” classes A, B and C. It shows how the first bits of the address can be used to determine the address class.

The Internet is not something you just dump something on. It’s not a truck.

It’s a series of tubes.

American Senator Ted Stevens (Alaska)

Full story.

In CS35110 lecture one today, we briefly looked at the network stack. Particularly this diagram:

At each level the protocol module at that level communicates only with the layer above and the layer below. Thus the network layer may received data from the transport layer that it must enclose in a network packet (like an envelope) before passing that packet down to the link layer.

the protocol layers are thus stacked on top of each other in the protocol suite.

Bear in mind that packets are really just sequences of data, and all that is really transmitted over the physical medium (the wires or wireless medium of the internet) are long strings of binary data.

Next lecture we will look particularly at issues such as why packets are used, and we will look at the network layer in more detail. However, if there are specific issues you want to raise, add comments here and we can discuss those issues in the next lecture.

We have Sky satellite at home. Sky like to monitor their satellite boxes through the telephone line using a clever little feature that BT developed called “silent signalling”.

The idea is that any piece of data terminal equipment (DTE) can be plugged into the phone line and called up from a central system from where it can be interrogated over the phone network. The signalling is silent, so the phone does not ring and the householder need not be aware a call is in progress. As I understand it, taking a phone off the hook immediately interrupts this process, and no calling line identification (CLI) is ever presented, so it is as if the call did not happen.

Except that theory is not always the reality. It seems that some lines are configured (or misconfigured) in such a way as to cause a telephone to “chirp” briefly when the silent signalling takes place.

Caller line identification is also presented by silent signalling, so it is possible the phone will chipr briefly before all calls for users who have CLI presented on their lines.

Phones will also ring if the BT exchange is carrying out routine testing to your line. This may present as a regular short ring at about the same time each night.

So solutions?

We tried raising a fault with BT. As usual, BT faults told us that they had never heard of such a thing, they could book an engineer for us, but they would charge us if they decided our equipment was at fault. (But the problem is at the exchange, I told them – to no avail).

We tried asking Sky to stop calling us. They suggested unplugging our box from the wall (but the problem is your equipment raising the call, I told them – to no avail. Apparently Sky cannot stop their equipment from contacting you).

Next we tried the BT nuisance call bureau. They tried to convince us to sign up for a service that stops calls from a given number. (But hey – this is silent signalling. No number is presented!)

Finally we found someone at the nuisance call bureau who passed us onto someone at the exchange who knew what was what. He took our line off the regular testing schedule. Hooray!

And then that very night, Sky called and the phones chirped just as my daughter was falling asleep. Grrr.

Last attempt with Sky – I shall tell them we have changed telephones and give them a new number to call. Now if I knew Rupert Murdoch’s number, I would give them his. But I don’t, so I’ll just have to send the chirping phone to work!

If anyone else has found a way to convince BT to fix the line to stop this happening, please let me know. In the meantime, I offer my solutions above as the best way to avoid those annoying calls at 5 AM and the children’s bed time.