[armd] review of draft-ietf-armd-problem-statement-02
Lucy yong <lucy.yong@huawei.com> Thu, 10 May 2012 19:31 UTC
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From: Lucy yong <lucy.yong@huawei.com>
To: "armd@ietf.org" <armd@ietf.org>
Thread-Topic: [armd] review of draft-ietf-armd-problem-statement-02
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Date: Thu, 10 May 2012 19:29:24 +0000
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Subject: [armd] review of draft-ietf-armd-problem-statement-02
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Hi, I read this draft and think it describes clearly. I support it. Here are some editing suggestion and comments. Notation: > for original text, < suggested text. >the issue is complicated by routers having many interfaces on which address resolution must be performed or with IEEE 802.1Q domains, where individual VLANs form their own broadcast domains. < the issue is complicated by routers having many interfaces on which address resolution must be performed or within IEEE 802.1Q domains where individual VLANs form their own broadcast domains. >This document is a product of the ARMD WG and identifies potential issues associated with address resolution in datacenters with massive number of hosts. <This document identifies potential issues associated with address resolution in datacenters with massive number of hosts. > Broadcast Domain: The set of all links, repeaters, and switches that are traversed in order to reach all nodes that are members of a given L2 domain. For example, when sending a broadcast packet on a VLAN, the domain would include all the links and switches that the packet traverses when broadcast traffic is sent. Comment: in DC, will a link or switch be physical link or virtual link, physical switch or virtual switch? It is better to state explicitly. > As the size of an L2 network increases, the level of broadcast traffic from protocols like ARP increases. < As the size of an L2 broadcast domain increases, the level of broadcast traffic from protocols like ARP increases. > That is, split large L2 networks into multiple smaller L2 networks, each operating as its own L3/IP subnet. Numerous data center networks have been designed with this principle, e.g., with each rack placed within its own L3 IP subnet. By doing so, the broadcast domain (and address resolution) is confined to one Top of Rack switch, which works well from a scaling perspective. Unfortunately, this conflicts in some ways with the current trend towards dynamic work load shifting in data centers and increased virtualization as discussed below. Comment: In DC, split large L2 network into multiple smaller L2 network is for security trust design. Multiple L2 networks are on the same L3 subnetwork so they all can support the same application, but they are isolated by L2 network for security reason, which also reduces ARP issue. > First, it uses broadcast, and any network with a large number of attached hosts will see a correspondingly large amount of broadcast ARP traffic. Comment: it is not necessary true. A lot of trust designs prevent from host-to-host communications. > Additionally, If no response is received, the router has to send the ARP/ND query multiple times. < Additionally, if no response is received, the router has to send the ARP/ND query multiple times. > Although address-resolution traffic remains local to one L2 network, some data center designs terminate L2 subnets at individual aggregation switches/routers (e.g., see Section 4.4.2). < Although address-resolution traffic remains local to one L2 network, some data center designs terminate L2 domain at individual aggregation switches/routers (e.g., see Section 4.4.2). Regards, Lucy
- [armd] review of draft-ietf-armd-problem-statemen… Anoop Ghanwani
- [armd] review of draft-ietf-armd-problem-statemen… Lucy yong
- [armd] review of draft-ietf-armd-problem-statemen… Donald Eastlake
- Re: [armd] review of draft-ietf-armd-problem-stat… Thomas Narten