<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: arial,helvetica,sans-serif; font-size: 10pt; color: #000000'><font face="arial, helvetica, sans-serif"><span style="font-size: 10pt;">"</span><span style="font-size: 13.3333px;">It is not economical or even </span></font><span style="font-size: 13.3333px; font-family: arial, helvetica, sans-serif;">physically possible to have an MPLS device next to every DSLAM, hence </span><span style="font-size: 13.3333px; font-family: arial, helvetica, sans-serif;">the aggregation."</span><div><span style="font-size: 13.3333px; font-family: arial, helvetica, sans-serif;"><br></span></div><div><a href="https://mikrotik.com/product/RB750r2">https://mikrotik.com/product/RB750r2</a> MSRP $39.95</div><div><br></div><div>I readily admit that this device isn't large enough for most cases, but you can get cheap and small MPLS routers.<br><br><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; 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font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px;" target="_blank"><img src="http://www.ics-il.com/images/youtubeicon.png" style="border: 0pt none;" src="http://www.ics-il.com/images/youtubeicon.png"></a><span name="x"></span><br></div><hr id="zwchr" style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 10pt;"><div style="color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12pt; font-weight: normal; font-style: normal; text-decoration: none;"><b>From: </b>"Tarko Tikan" <tarko@lanparty.ee><br><b>To: </b>adamv0025@netconsultings.com, nanog@nanog.org<br><b>Sent: </b>Friday, June 21, 2019 2:51:20 AM<br><b>Subject: </b>Re: few big monolithic PEs vs many small PEs<br><br>hey,<br><br>> So what is the primary goal of us using the aggregation/access layer? It's to achieve better utilization of the expensive router ports right? (hence called aggregation)<br><br>I'm in the eyeball business so saving router ports is not a primary concern.<br><br>Aggregation exists to aggregate downstream access devices like DSLAMs, <br>OLTs etc. First of all they have interfaces that are not available in <br>your typical PEs. Secondly they are physically located further <br>downstream, closer to the customers. It is not economical or even <br>physically possible to have an MPLS device next to every DSLAM, hence <br>the aggregation.<br><br>Eyeball network topologies are very much driven by fiber layout that <br>might have been built 10+ years ago following TDM network best practices <br>(rings).<br><br>Ideally (and if your market situation and finances allow this) you want <br>your access device (or in PON case, perhaps even a OLT linecard) to be <br>only SPOF. If you now uplink this access device to a PE, PE linecard <br>becomes a SPOF for many, let's say 40 as this is a typical port count, <br>access devices.<br><br>If you don't want this to happen you can use second fiber pair for <br>second uplink but you typically don't have fiber to second aggregation <br>site. So your only option is to build on same fiber (so thats a SPOF <br>too) to the same site. If you now uplink to same PE, you will still <br>loose both uplinks during software upgrades.<br><br>Two devices will help with that making aggregation upgrades invisible <br>for customers thus improving customer satisfaction. Again, it very much <br>depends on market, in here the customers get nosy if they have more than <br>one or two planned maintenances in a year (and this is not for some <br>premium L3VPN service but just internet).<br><br>-- <br>tarko<br></div><br></div></div></body></html>