4507E Port Buffer

[dan.letkeman]

Hello,

From what I have read the 4500E series has a shared buffer for the line cards that are installed in the chassis.  Does anyone know what that buffer size is?  I want to use this switch for esx hosts and iscsi traffic, and buffer size is an important factor to me.

Thanks,

Dan.

[Arumugam Muthaiah]

Hi Dan,

Cisco 4500 switch uses different buffering model. Supervisor provides a certain buffer space (depending on SUP version) for all line cards and ports. Thus that buffer space will be dynamicaly spread among all line cards/ports. So single port can get from few hundreds of bytes up to several MB if no other need it.

Switch Architecture Specifications

• Store-and-forward switching
  
• Functionally transparent line-card architecture
  
• Packet buffering: dynamic, 16 MB shared memory
  

16MB is indeed shared between the entire system and allocation of 16M is purely dependent on the traffic pattern. Each port has the same number of queue entries, but they are used on "as needed" basis.

http://www.cisco.com/en/US/partner/prod/collateral/modules/ps2797/ps5347/product_data_sheet09186a0080197424_ps4324_Products_Data_Sheet.html

Intelligent Network Services with QoS and Sophisticated Traffic Management
The Cisco Catalyst 4500 Series Supervisor Engine II-Plus offers superior per-port QoS features to help ensure that network traffic is optimally classified, prioritized, and scheduled to efficiently handle multimedia, time-sensitive (voice), and mission-critical applications. This supervisor engine can classify, police, and mark incoming packets, allowing the administrator to differentiate between traffic flows and to enforce policies based on granular QoS fields. Sharing, shaping, and strict priority configurations determine scheduling of egress traffic. This supervisor engine also supports Dynamic Buffer Limiting (DBL), a congestion-avoidance feature.

http://www.cisco.com/en/US/partner/prod/collateral/switches/ps5718/ps4324/white_paper_c11-539588.html

Regards,

Aru

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[dan.letkeman]

Thank you for the reply.  I was wondering how it worked. 

Unfortunately those web links are forbidden for me to access.