<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Sep 13, 2010, at 3:49 PM, Alan Batie wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>On 9/13/10 11:32 AM, <a href="mailto:michael.dillon@bt.com">michael.dillon@bt.com</a> wrote:<br><br><blockquote type="cite">Anyone in this position should simply assign a /48 to every customer site<br></blockquote><blockquote type="cite">no matter how big or small. A one bedroom apartment gets a /48. A<br></blockquote>manufacturing<br><blockquote type="cite">plant with 5 buildings including a 4-story office block, gets a /48.<br></blockquote><blockquote type="cite">No exceptions.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">Later, when you have learned more, you might want to shift to only give<br></blockquote><blockquote type="cite">a /56 to residential customers if there is a good business reason, but<br></blockquote><blockquote type="cite">you are more likely to conclude that there is only a reason for large<br></blockquote><blockquote type="cite">ISPs to introduce this complexity.<br></blockquote><br>I like to have my cake and eat it to: if you give /48, it's gone. If<br>you give /56, using 1 bits from the left (reserving the first 4 bits: 1<br>customer block, 1 us block, 14 in reserve), you have a sparse allocation<br>that, if the customer needs /48, you can easily expand them into by<br>shrinking the netmask. Eventually the bits from the left will run into<br>the bits from the right, but by that time, we'll have a lot more<br>experience with the subject. If we need more /56's, we'll have them. Up<br>until that point, if people turn out to need /48's (or more!), no problem.<br><br></div></blockquote>This is a really horrible approach... Yes, if you give a /48, it's gone.</div><div>So what?</div><div><br></div><div>If you need more /48s, then, get another /32 or even a shorter than /32</div><div>prefix.</div><div><br></div><div>Really... There's plenty of space to do this for quite a while and still not</div><div>even use 0.2% of the first 1/8th of the IPv6 address space.</div><div><br></div><div>For sparse allocation, allocate your /48s by bisection...</div><div><br></div><div><font class="Apple-style-span" face="Monaco">Customers (in order of allocation):</font></div><div><font class="Apple-style-span" face="Monaco"><br></font></div><div><font class="Apple-style-span" face="Monaco">Internal:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:0000::/48</font></div><div><font class="Apple-style-span" face="Monaco">First:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:8000::/48</font></div><font class="Apple-style-span" face="Monaco">Second:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:4000::/48</font><div><font class="Apple-style-span" face="Monaco">Third:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:C000::/48</font></div><div><font class="Apple-style-span" face="Monaco">Fourth:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:2000::/48</font></div><div><font class="Apple-style-span" face="Monaco">Fifth:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:6000::/48</font></div><div><font class="Apple-style-span" face="Monaco">Sixth:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:A000::/48</font></div><div><font class="Apple-style-span" face="Monaco">Seventh:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:E000::/48</font></div><div><font class="Apple-style-span" face="Monaco">Eighth:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:1000::/48</font></div><div><font class="Apple-style-span" face="Monaco">Ninth:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:3000::/48</font></div><div><font class="Apple-style-span" face="Monaco">...</font></div><div><font class="Apple-style-span" face="Monaco">Fifteenth:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:f000::/48</font></div><div><font class="Apple-style-span" face="Monaco">16th:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:0800::/48</font></div><div><font class="Apple-style-span" face="Monaco">17th:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span><font class="Apple-style-span" face="Monaco">XXXX:XXXX:1800::/48</font></div><div><font class="Apple-style-span" face="Monaco">...</font></div><div><font class="Apple-style-span" face="Monaco">31st:</font><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> <span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:f800::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">32nd:<span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:0400::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">33rd:<span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:0C00::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">34th:<span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:1400::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">35th:<span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:1C00::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">...</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">63rd:<span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:fC00::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">64th:<span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:0200::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">65th:<span class="Apple-tab-span" style="white-space:pre"> </span>XXXX:XXXX:0600::/48</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco">...</font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Monaco"> </font></span></div><div><span class="Apple-tab-span" style="white-space:pre"><br></span></div><div><span class="Apple-tab-span" style="white-space:pre">A</span>s you can see, you get lots and lots and lots of customers installed</div><div>before they get packed with any level of density. Specifically, you</div><div>get 255 customers installed before you have to put any of them</div><div>close enough that they can't all be expanded to 256 /48s (a /40).</div><div>You get 4095 customers installed before you have to worry</div><div>about any of them not being able to expand to a /44.</div><div><br></div><div>You can have your cake and eat it too without complicating your network as you describe.</div><div><br></div><div>Owen</div><div><br></div><div><br></div></body></html>