incoming traffic flooding

[tedauction]

Hello, I have the following QoS policy-map applied outbound on my 100Mbps WAN uplink:

interface GigabitEthernet1/0/1
description WAN_PRI
switchport access vlan 83
switchport mode access
load-interval 30
speed 100
duplex full
service-policy output QUEUE -------------- preventing saturation of outgoing traffic by one particular class of traffic

Policy Map QUEUES
Class Multi-Media
priority
Class DataTrans
bandwidth remaining 70 (%)
Class IA-High
bandwidth remaining 15 (%)
Class class-default
bandwidth remaining 15 (%)

This is fine in that it limits the amount of bandwidth a class of traffic can use when being sent outgoing. So the link is never saturated by one class of traffic.

However, my question is, what happens if an external client is sending a large file transfer IN TO the WAN uplink. Will this potentially saturate the full 100Mbps of bandwidth ? If so, how do I prevent that from happening ?

Thank you.

[Joseph W. Doherty · Accepted solution]

So the link is never saturated by one class of traffic.

Normally, for the policy you've posted that's not exactly true.

What yuor policy should do is preclude any one class from precluding other classes from obtaining their minimum bandwidth guarantees.

However, my question is, what happens if an external client is sending a large file transfer IN TO the WAN uplink. Will this potentially saturate the full 100Mbps of bandwidth ?

Yes, it may.

If so, how do I prevent that from happening ?

Short answer - you cannot totally guarantee it doesn't happen.

Longer answer, if you're working with adaptive rate traffic, for example TCP, you can often "signal" it, in some manner, to slow its transmission rate.  To do this at its best, you need an appliance designed for it.

You might try policing ingress traffic and/or shaping "feedback" (e.g. TCP ACKs) traffic.