From: Devi Mallampalli (Devi.Mallampalli@chubb.com.au)
Date: Tue Sep 07 2004 - 08:22:56 GMT-3
Hi Group,
Got a real world scenario at hand and would like to gather your thoughts
on this :-)
I am seriously planning to replace our Internet Router/2651 and its
expensive 2MB Frame circuit with that of Layer 3 switch (either 3550 or
3750) and with lesser expensive 2 MB BDSL (Business DSL) WAN circuit
which is delivered on to "Ethernet" port on layer 3 switch directly.
The primary reason of doing this design is to not only to derive direct
cost savings to the tune of around US$20k per annum (Yes, 4MB HSSI
installation cost and per annum usage cost are too high when compared to
a 2 MB BDSL Ethernet circuit) to our corporation , but also to try out
alternative WAN protocols which can delivered on to an Ethernet/RJ45
interface rather than on x25 or v35 interfaces (with a long term view to
replace all Routers on our WAN with that of Layer 3 switches with an
MPLS core and BDSL combination at remote sites so that we can move away
with our current HUB and SPOKE Frame relay WAN and instead can have one
flat , one hop away WAN. Any way that is different story)
But before I proceed I just want to have a second opinion on whether or
not it is a good idea to assign Internet periphery responsibility to a
Layer 3 switch , rather than a decent Router such as 2651 XM , primarily
from both Qos and required Redundancy point of view.
Qos , because I am not 100% on whether or not I can do Shaping ,
Policing , Policy Routing and IP Routing on Ethernet interfaces of
3550/3750 to the same "Degree" as that of Routers/2651XM serial
interfaces ? And more over , I was wondering with this Layer 3 design ,
I will be loosing congestion indicators such as DEs, BECNs and FECNs on
the wire and so from what features I can take help on Ethernet WAN
interfaces(well in my case it is BDSL which is being delivered on to a
RJ 45 interface at customer premises) to the similar effect ?
Redundancy , since our Internet infrastructure need to support critical
Ecommerce apps, originally I thought of deploying a back up 2651 as well
and then run BGP between them and our ISP's Internet edge routers.
Unlike our current static routing , I was planning to extract more
effective dynamic fail over between two Routers from L3 protocol/BGP. In
addition , from L3 protocol I am hoping to do some traffic engineering
in terms of preferred "outbound" and "inbound" in to our AS. And I am
not 100% on whether I can do the same things on Layer 3 switches ?
I have seen 3550s operating happily on our N/W in doing roles such as
"Campus Vlan router" and "switch block aggregator" for 20 odd 7960 IP
phones ...etc. But I have not seen them in the role of perimeter Routing
device in doing both Routing functions as well as advanced Qos.
I am inclined towards Layer 3 switching design because 1) we can
eliminate routers costs 2) it will save us Telco circuit costs as well
since we are not using expensive WAN protocols such as Frame/HSSI.
But I appreciate any feed back on the intended solution.
Cheers
Devi.
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