4 ms·

The real debate is between OSPF and QSFP-DD as they are the only ones with a shot at high density. QSFP-DD is backwards compatible so that you can run your 400

The real debate is between OSPF and QSFP-DD as they are the only ones with a shot at high density. QSFP-DD is backwards compatible so that you can run your 400G port as a 100G or 40G with 4 lanes at 25G/10G. OSFP will be able to do the same thing but with an adapter from OSFP to QSFP But what this article fails to mention is that OSFP is the connector of the future that will support 8 lanes of 100G to support 800G ethernet with good signal integrity and capability to support high power optics for longer distances. ( This looks to be in 2020 ) So QSFP-DD is a 1 generation connector... OSFP will see us through 400G and 800G. Disclaimer I work at Arista Networks who is bullish on OSFP. For more info see Andy Bechtolsheim's talk on 400G optics at OCP https://www.youtube.com/watch?v=Kotu6B7AQpk https://www.youtube.com/watch?v=Kotu6B7AQpk

mmmBacon 8y ago
There is no real debate between QSFP-DD and OSFP. OSFP will exist at Google but nearly everyone else is going to use QSFP-DD. The main reason is backwards compatibility for data center upgrades. The only reason to use OSFP might be because you want to use a 400G-ZR plug. But with the advent of 7nm DSP, vendors will be able to fit the ZR into the DD plug. So if the above is true OSFP is not needed now. Honestly, 800G is only incremental at best and frankly it’s not clear that An 800G pluggable is the way to go. The 800G presumes 32 radix and that breaks down power-wise in the datacenter when we get to spine switches where we need 128 radix. The reason being that we need so many power hungry chips to make a high radix switch fully non-blocking (eg Clos topology). 112G SERDES will have limited reach and hence require many retimers which eat power too. So the OSFP is in my view is A solution looking for a problem.
walrus01 8y ago
I am also optimistic about OSFP as compared to the QSFP size for 400G. I'm not a laser engineer but I do have a pretty good understanding of how 400G will be achieved through two strands of singlemode. For medium reach optics it's actually an 8-channel CWDM with prism built into each optic, so the optic body needs to be large enough to dissipate the heat from eight separate 25 Gbps lasers. CFP size will obviously handle that but is a true first generation solution and is huge. The only bad thing about OSFP is that its highly similar name will confuse the hell out of network engineers who never see the OSI layer 1 of a network, and deal with things at OSI layer 3. OSFP != OSPF (the routing protocol).
- agoodthrowaway 8y ago
  100G/wave device will be the norm moving forward and 8 lane devices for 400G won’t be around much except in niche applications.
  - walrus01 8y ago
    for long reach, yes, but not for ISP-to-ISP interconnection... the cost of coherent (QPSK, 8PSK, 16QAM) 100G SerDes and modulation/demodulation is considerably higher and only justified if going a great many km. For intra-peering-facility connections I don't see coherent 100G (or multiples of coherent 100G bundled by CWDM into 200G, 400G interfaces) becoming the norm anytime soon.
    - wmf 8y ago
      I was looking at this the other day; it sounds like 100G-DR1 and 400G-DR4 are not coherent and vendors are aiming to make it commodity. Coherent is more like 200-600G per lambda.
      - walrus01 8y ago
        At present 100G-LR4 is the defacto standard for ISP peering interconnections (such as to an IX switch in the same building, or for PNIs between big players within the same carrier hotel). Because it is very low cost. The cheap 25 Gbps x 4 approach and low cost cwdm prism are a big part of that. Since 100G will soon move from qsfp format down to the same size as SFP and SFP+ (fitting 48 in a 1RU height, 17.5" wide line card in a chassis based Arista), I don't foresee them becoming any less popular... Not when the optics are so affordable.
    - agoodthrowaway 8y ago
      We aren’t talking about long distance and coherent here but direct detect. Coherent is not cost or power competitive with direct detect for short reaches yet. When I talk about SERDES I’m talking about the electrical signal interface to the optic. Also it’s worth noting that the majority of coherent DWDM interfaces are some kind of embedded optic already.
agoodthrowaway 8y ago
Sorry but OSFP has at most a life of 2 generations and likely only useful for a single generation. 112G SERDES is not going to scale well and will require repeaters all over the place. Moreover doubling the signaling rate to 224 Gb/s is wholly impractical. The future is embedded devices and not legacy pluggables.
djrogers 8y ago
I get the attraction of OSFP, but in early days backward compatibility usually trumps future potential. If I'm buying an high density switch/router tomorrow (figuratively speaking), I'd greatly prefer the flexibility to use the density it provides for some existing lower speed connections. As long as QSFP-DD 'works', as a customer I'm not really concerned with which technology is more elegant or technically 'better'. The problem this presents for OSFP going forward is that it encourages early adoption to steer toward QSFP-DD, which will tend to drive follow-on purchase decisions as well.
- agoodthrowaway 8y ago
  I see any criticism of OSFP is getting downvoted but your points are correct. OSFP is not needed for 400GE.

mmmBacon 8y ago

There is no real debate between QSFP-DD and OSFP. OSFP will exist at Google but nearly everyone else is going to use QSFP-DD. The main reason is backwards compatibility for data center upgrades. The only reason to use OSFP might be because you want to use a 400G-ZR plug. But with the advent of 7nm DSP, vendors will be able to fit the ZR into the DD plug. So if the above is true OSFP is not needed now. Honestly, 800G is only incremental at best and frankly it’s not clear that An 800G pluggable is the way to go. The 800G presumes 32 radix and that breaks down power-wise in the datacenter when we get to spine switches where we need 128 radix. The reason being that we need so many power hungry chips to make a high radix switch fully non-blocking (eg Clos topology). 112G SERDES will have limited reach and hence require many retimers which eat power too. So the OSFP is in my view is A solution looking for a problem.

walrus01 8y ago

I am also optimistic about OSFP as compared to the QSFP size for 400G. I'm not a laser engineer but I do have a pretty good understanding of how 400G will be achieved through two strands of singlemode. For medium reach optics it's actually an 8-channel CWDM with prism built into each optic, so the optic body needs to be large enough to dissipate the heat from eight separate 25 Gbps lasers. CFP size will obviously handle that but is a true first generation solution and is huge. The only bad thing about OSFP is that its highly similar name will confuse the hell out of network engineers who never see the OSI layer 1 of a network, and deal with things at OSI layer 3. OSFP != OSPF (the routing protocol).

agoodthrowaway 8y ago
100G/wave device will be the norm moving forward and 8 lane devices for 400G won’t be around much except in niche applications.
- walrus01 8y ago
  for long reach, yes, but not for ISP-to-ISP interconnection... the cost of coherent (QPSK, 8PSK, 16QAM) 100G SerDes and modulation/demodulation is considerably higher and only justified if going a great many km. For intra-peering-facility connections I don't see coherent 100G (or multiples of coherent 100G bundled by CWDM into 200G, 400G interfaces) becoming the norm anytime soon.
  - wmf 8y ago
    I was looking at this the other day; it sounds like 100G-DR1 and 400G-DR4 are not coherent and vendors are aiming to make it commodity. Coherent is more like 200-600G per lambda.
    - walrus01 8y ago
      At present 100G-LR4 is the defacto standard for ISP peering interconnections (such as to an IX switch in the same building, or for PNIs between big players within the same carrier hotel). Because it is very low cost. The cheap 25 Gbps x 4 approach and low cost cwdm prism are a big part of that. Since 100G will soon move from qsfp format down to the same size as SFP and SFP+ (fitting 48 in a 1RU height, 17.5" wide line card in a chassis based Arista), I don't foresee them becoming any less popular... Not when the optics are so affordable.
  - agoodthrowaway 8y ago
    We aren’t talking about long distance and coherent here but direct detect. Coherent is not cost or power competitive with direct detect for short reaches yet. When I talk about SERDES I’m talking about the electrical signal interface to the optic. Also it’s worth noting that the majority of coherent DWDM interfaces are some kind of embedded optic already.

agoodthrowaway 8y ago

Sorry but OSFP has at most a life of 2 generations and likely only useful for a single generation. 112G SERDES is not going to scale well and will require repeaters all over the place. Moreover doubling the signaling rate to 224 Gb/s is wholly impractical. The future is embedded devices and not legacy pluggables.

djrogers 8y ago

I get the attraction of OSFP, but in early days backward compatibility usually trumps future potential. If I'm buying an high density switch/router tomorrow (figuratively speaking), I'd greatly prefer the flexibility to use the density it provides for some existing lower speed connections. As long as QSFP-DD 'works', as a customer I'm not really concerned with which technology is more elegant or technically 'better'. The problem this presents for OSFP going forward is that it encourages early adoption to steer toward QSFP-DD, which will tend to drive follow-on purchase decisions as well.

agoodthrowaway 8y ago
I see any criticism of OSFP is getting downvoted but your points are correct. OSFP is not needed for 400GE.