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QoS and MetroEthernet core


I just need some clarification regarding QoS in Ethernet core network.

My network is constituted of  Cisco7600 routers with mostly Ethernet LAN modules.

It is MPLS network and transport technology is ethernet,

Between cities there are SIP or ES WAN modules (for 1Gbps links) but now there is a demand for higher speeds ( 10Gbps).

Inside city (MAN) I only have LAN 10Gbps modules.

I still didn't introduce QoS in network but I always make sure that there is at least 20% of bandwidth free on every link (intercity or MAN).

I know that this can't be substitution for QoS in regards to delay and jitter of real time traffic. But also I can't say that I receive complaints from users about bad voice or video service.

My questions are

1) Can I use for intercity links Ethernet modules (i.e. WS-X6704-10GE)  which are few times cheaper than SIP or ES+ modules?

Since I don't have QoS enabled in network,  SIP and ES linecards shouldn't make a difference (or I am wrong here)?

2) If I use WAN linecards (SIP, ES+) for intercity links should I also need to have WAN linecards toward the MAN network?

It seems to me that these intercity WAN linecards have no use in scenario where one side of router (toward WAN links) have SIP/ES linecards and other side of the router toward MAN have ethernet linecards.

3) If I enable QoS on routers I can also enable it on WS-X6704-10GE linecards. It has 7 hardware queues per port - 1P7Q - one priority queue and 6 other queues. If I have only 5 QoS classes in netwrok shouldn't it be sufficient? (Aren't 10Gb/s ports capable to sustain 10Gbps traffic so there shouldn't be drops for prioritized traffic, or this is not so true?)

4) Isn't now with metroethernet networks different situation than in earlier netowrks with serial links in regards to QoS? I.e Cisco 7600 is non-blocking switch and if all ports are medium utilazed there shouldn't be drops. Also priority queue takes care of voice and video traffic which are delay and jitter sensitive,

We don't have situation anymore where WAN link is much smaller than LAN and MAN links and thus serialization problem occured. Can it be compared to huge LAN and accordingly there is a only need for LAN QoS?

5) where can be useful to have linecards with 128000, 512000 or even more queues per port? (per user policing on BBRAS maybe)?

Thank you,



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