This is my first posting to the NANOG list. I don't think this is off-topic, but if so, please send replies (or flames) directly to me (rather than to the list) and I will issue a detailed summary. We are in the process of implementing an OC-12 SONET ring connection between two sites in New Jersey that span a distance of 15 miles. The SONET ring will be provided by Bell Atlantic and is composed of fully redundant hardware (there are no single points of within the telecom equipment) and redundant rings. We are splitting the OC-12 into pairs of OC-3's on two routers in each location (running ATM on the WAN). This interface is extremely mission critical to the point that a 99.9% uptime will not be acceptable. I have the following questions: 1) Bell Atlantic assures us that, because of the redundancy, we can expect 100% uptime from the OC-12. I would like feedback as to whether this is a realistic portrayal of the SONET environment. 2) We have the option of using either single-mode or multi-mode fiber OC-3 connections - what factors should be considered in selecting the fiber media type. 3) Which routers should be used. The options are 3com NB-II's DPE+ (dual CPU), Cisco 7200 series, or Cisco 7500 (each router will have at least two 100Base-T LAN ports). OK, I know the 3com suggestion is a loaded question for this list, but has anybody used the 3com's in this capacity? We are a 3com shop that is considering switching to Cisco - this is a significant decision because switching will require us to continue to maintain the existing 3com environment (~500 routers) and the new Cisco routers. Thanks, Peter Polasek
1) Bell Atlantic assures us that, because of the redundancy, we can expect 100% uptime from the OC-12. I would like feedback as to whether this is a realistic portrayal of the SONET environment.
Don't just buy from one carrier. Even if they give you dig plans, and diversity warranties, they are likely to reroute things without telling you. Even if you get around this one, and all the other problems, and are satisfied you have permanent, true, diversity which will protect you against any one fiber break, it doesn't protect you against a procedure break, like someone terminating the wrong circuit on misreading a circuit ID. The above is certainly true in the UK, and from my experience in the US I'd think it's doubly or quadruply true. Also, use the lowest level routing redundancy you can find. I may get flamed for this, but if bandwidth is not an issue, you might consider ATM switches instead especially if cutover time is critical. -- Alex Bligh GX Networks (formerly Xara Networks)
At 10:55 AM 10/16/98 +0100, Alex Bligh wrote:
1) Bell Atlantic assures us that, because of the redundancy, we can expect 100% uptime from the OC-12. I would like feedback as to whether this is a realistic portrayal of the SONET environment.
Don't just buy from one carrier. Even if they give you dig plans, and diversity warranties, they are likely to reroute things without telling you. Even if you get around this one, and all the other problems, and are satisfied you have permanent, true, diversity which will protect you against any one fiber break, it doesn't protect you against a procedure break, like someone terminating the wrong circuit on misreading a circuit ID.
In addition to what Alex has stated, if you are purchasing this OC-12c or OC-3c from a single carrier, you might want to check that the carrier has a 'dual-entrance' into your building. Although the "main" fiber backbone may be truly ringed and redundant, it is common practice for RBOCs and CLECs to spur off the backbone and bring the fibers into the building via SINGLE sheath. This subjects the spur to backhoes or augers that might be digging up the sidewalks in front of your building. Most large data centers require the telco/clec to enter the facility (via fiber) from two diverse entry points. This literally brings their main backbone "through" the facility, thereby, truly preventing a fiber-cut that will take down your OC-12/OC-48 Sonet gear. Good dual-entries will even land the two diverse fiber runs on two seperate FODUs in the event that someone is moving fibers or reterminating. (However, this kind of fiber build usually requires a revenue commitment from the customer since it costs three times as much as a standard spur build.) Might be a good thing to check out if your applications are very mission critical. Dave Cooper Electric Lightwave, Inc.
The above is certainly true in the UK, and from my experience in the US I'd think it's doubly or quadruply true.
Also, use the lowest level routing redundancy you can find. I may get flamed for this, but if bandwidth is not an issue, you might consider ATM switches instead especially if cutover time is critical.
-- Alex Bligh GX Networks (formerly Xara Networks)
participants (3)
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Alex Bligh -
Dave Cooper -
Peter Polasek